Structure and Infrastructure Engineering Maintenance, Management, Life-Cycle Design and Performance ISSN: 1573-2479 (Print) 1744-8980 (Online) Journal homepage: https://www.tandfonline.com/loi/nsie20 Toward life-cycle reliability-, risk- and resiliencebased design and assessment of bridges and bridge networks under independent and interacting hazards: emphasis on earthquake, tsunami and corrosion Mitsuyoshi Akiyama, Dan M. Frangopol & Hiroki Ishibashi To cite this article: Mitsuyoshi Akiyama, Dan M. Frangopol & Hiroki Ishibashi (2020) Toward lifecycle reliability-, risk- and resilience-based design and assessment of bridges and bridge networks under independent and interacting hazards: emphasis on earthquake, tsunami and corrosion, Structure and Infrastructure Engineering, 16:1, 26-50, DOI: 10.1080/15732479.2019.1604770 To link to this article: https://doi.org/10.1080/15732479.2019.1604770 Published online: 11 May 2019. Submit your article to this journal Article views: 409 View related articles View Crossmark data Citing articles: 1 View citing articles Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=nsie20 STRUCTURE AND INFRASTRUCTURE ENGINEERING 2020, VOL. 16, NO. 1, 26–50 https://doi.org/10.1080/15732479.2019.1604770 Toward life-cycle reliability-, risk- and resilience-based design and assessment of bridges and bridge networks under independent and interacting hazards: emphasis on earthquake, tsunami and corrosion Mitsuyoshi Akiyamaa, Dan M. Frangopolb and Hiroki Ishibashia a Department of Civil and Environmental Engineering, Waseda University, Tokyo, Japan; bDepartment of Civil and Environmental Engineering, Engineering Research Center for Advanced Technology for Large Structural Systems (ATLSS Center), Lehigh University, Bethlehem, PA, USA ABSTRACT ARTICLE HISTORY After recent large earthquakes, field investigations confirmed that several bridges were severely damaged and collapsed not only due to the earthquake, as an independent hazard, but also to the subsequent tsunami, landslide or fault displacement. In addition, long-term material deterioration might have an important impact on seismic damage to bridges. Therefore, it is important to study both independent and interacting hazards and their effects on the reliability and risk of bridges and bridge networks. Although earthquake is still a dominant hazard to bridges in many earthquake-prone countries, a life-cycle reliability and risk approach has to consider both independent and interrelated hazards causing bridge failure. Such an approach is presented in this paper. In addition, issues related to lifecycle analysis, design, risk, resilience and management of bridges under earthquake and other hazards are discussed. Finally, the concepts and methods presented are illustrated on both single bridges and bridge networks. Received 23 September 2018 Revised 5 December 2018 Accepted 9 January 2019 1. Introduction Bridges may be susceptible to damage during an earthquake event, particularly if they were designed without adequate seismic detailing. Bridge columns built using earlier design codes (i.e. without proper seismic detailing) often lack adequate flexural strength and ductility capacity, and/or shear strength. When subjected to strong ground motions, they have the potential to exhibit brittle failure. Several destructive earthquakes in Japan inflicted various levels of damage on the structures and infrastructure systems. The investigation of these negative consequences gave rise to serious discussions about performance indicators and seismic design philosophy, and to extensive research activity on the retrofit of as-built bridges (Akiyama, Frangopol, & Mizuno, 2014). There are several performance indicators that can be related to the possible occurrence of local and global failures, including system ductility, failure times, redundancy, robustness and resilience (Biondini & Frangopol, 2016). These performance indicators need to be included into the practical design and assessment for bridges (Biondini & Frangopol, 2018). A review of performance indicators and metrics is available in Barone and Frangopol (2014), Frangopol and Saydam (2014), Ghosn et al. (2016), Saydam and Frangopol (2011) and Zhu and Frangopol (2012). Reliability-based performance indicators, which account for the uncertainty in both resistance and load, have been the basis for establishing the safety levels of structural CONTACT Mitsuyoshi Akiyama akiyama617@waseda.jp ß 2019 Informa UK Limited, trading as Taylor & Francis Group KEYWORDS Life-cycle; reliability; risk; resilience; hazard; earthquakes; bridge; bridge network design codes. Although reliability-based performance indicators can provide adequate information on the safety of bridge components and individual bridges, they lack the ability to reflect the outcome of a failure event in terms of economic losses. On the other hand, risk and risk-based performance indicators offer additional information on the performance of structural systems under various hazards. Risk allows combining the probability of component or system failure with the consequence of the event. As observed in recent disasters (e.g. 2011 Great East Japan earthquake and 2016 Kumamoto earthquake in Japan), because the transportation networks, including bridges, play a crucial role in the evacuation of affected people and the transportation of emergency goods and materials, the functionality of the network after a disaster must be investigated (Unjoh, 2012). A significant amount of research efforts has shifted the focus from the investigation of the performance of individual components of the infrastructure to that of entire distributed civil infrastructure systems and networks (Frangopol & Estes, 1997; Akg€ ul & Frangopol, 2003; Biondini, Frangopol, & Restelli, 2008; Ghosn, Moses, & Frangopol, 2010; Bocchini, Frangopol, & Deodatis, 2011; Dong & Frangopol, 2017; Saydam, Bocchini, & Frangopol, 2013; Stergiou & Kiremidjian, 2010; Torbol & Shinozuka, 2014). The prompt restoration of critical infrastructure facilities after an extreme event is always a goal of paramount importance (Bocchini & Frangopol, 2012a, 2012b). To STRUCTURE AND INFRASTRUCTURE ENGINEERING 27 Figure 1. Recent large earthquakes in Japan after the 1995 Hogoken-Nanbu (Kobe) earthquake. quantify the promptness of the restoration, it has become customary to use the concept of resilience. Even though there are several definitions of resilience in the literature, the most widely accepted definition is provided by Bruneau et al. (2003): ‘resilience is defined as the ability of social units (e.g. organisations, communities) to mitigate hazards, contain the effects of disasters when they occur, and carry out recovery activities in ways that minimise social disruption and mitigate the effects of future earthquake’. Resilience emphasises the impact of infrastructure damage, failure and societal recovery under hazards with a low probability of occurrence and high consequences. On the other hand, sustainability concentrates on current and future resource management, and addresses the impacts of planning and development on the economy, society and the environment. A sustainable infrastructure system needs to include resilient and adaptive capabilities for ensuring its long-term sustainability. Some of the most promising solutions for resilience are actually also sustainable in nature (Mackie, Kucukvar, Tatari, & Elgamal, 2016). Meanwhile, Bocchini, Frangopol, Ummenhofer and Zinke (2014) proposed a unified approach by combining resilience and sustainability and concluded that a systematic unification of resilience and sustainability is mandatory. Design and assessment of structures have been geared towards addressing the most dominant hazard at the location of interest. However, the possibility of structures experiencing multiple hazards of different types during their lifetime needs to be considered. The design methodology of bridges must shift towards a more comprehensive approach of addressing multiple hazards to ensure adequate performance under different mechanical and environmental scenarios (Chulahwat & Mahmoud, 2017; Gidaris et al., 2017). Quantification of the reliability and risk associated with damage to each bridge under multiple hazards can help in prioritising retrofit activities for bridges in a network. Significant advances have been accomplished in the field of earthquake engineering. However, there is a need to promote further research for developing concepts and methods in order to design and assess resilient and sustainable bridges and bridge networks in a life-cycle context. This paper provides an overview of life-cycle design and assessment methodologies of bridges under multiple hazards with an emphasis on earthquake, tsunami and continuous deterioration based on the lessons from recent large earthquakes in Japan. Several performance indicators necessary to be implemented into the practical design and assessment are introduced. Finally, the concepts and methods presented are illustrated in two case studies on bridges under independent hazards and bridge networks under interacting hazards. 2. Lessons from recent large earthquakes in Japan Figure 1 shows several recent destructive earthquakes in Japan after the 1995 Hyogoken-Nanbu (Kobe) earthquake. Lessons from these earthquakes have demonstrated that not only seismic safety, but also other performance indicators for both individual bridges and bridge networks have to be taken into consideration. Based on the field investigations conducted after the recent large earthquakes in Japan, important lessons are introduced herein. 2.1. Typical failure modes of as-build RC columns designed before 1990 In Japan, seismic design specifications for structures and civil infrastructure systems have been significantly revised. The first seismic design code for road bridges, which included the seismic analysis considering the inelastic bridge behaviour and seismic design actions for the verification of the no-collapse requirement (i.e. Level 2 Ground Motion), 28 M. AKIYAMA ET AL. Figure 2. Typical failure mode of RC columns designed before the 1990s: shear failure of RC columns of Shinkansen viaducts [photographs (a) and (b) taken by the first author and photograph (c) courtesy of Dr. Takahashi at Kyoto University]. Figure 3. Typical failure mode of RC columns designed before the 1990s: damage to RC columns with the cut-off of the rebars [photographs (a) and (b) taken by the first author and photograph (c) courtesy of East Japan Railway Company]. was issued in Japan in 1990 (Japan Road Association, 1990). Before 1990, the designers did not predict the whole behavior of bridges under seismic excitation and did not identify the most probable failure modes of these bridges (Akiyama, Matsuzaki, Dang, & Suzuki, 2012). Also, there was a lack of proper knowledge on structural details. Figures 2 and 3 illustrate typical failure modes of RC columns designed according to the old design code. RC bridge piers had insufficient shear reinforcement and/or have cutoffs of longitudinal rebars without adequate anchorage length at the midpoint of bridge pier. These deficiencies caused several damages to RC columns during the past large eartquakes. 2.2. Ductility design and seismic retrofit Based on the experience of seismic damage to bridges and research progress on earthquake resistance, shear and ductility design methodologies of RC components were modified. Figure 4 depicts the relationship between horizontal load and displacement of a bridge pier. According to the revisions of seismic design codes, lateral strength and displacement ductility have been improved (Kawashima, 2000). In addition, several seismic retrofitting methods have been developed. Figure 5 presents the damaged states of the Shinkansen viaducts taken after the 2003 Sanriku-Minami earthquake and the 2011 Great East Japan earthquake. The retrofitted columns of the viaducts performed well, with almost no damage during the 2011 Great East Japan earthquake (Akiyama & Frangopol, 2012b). There have been no reports on the damage of retrofitted RC columns or on the undesirable consequences elsewhere in the retrofitted bridge. 2.3. Effect of damage to bridge on the network functionality An example of post-disaster functionality deterioration of a road network is shown in Figure 6. Figure 6(a) displays the collapse of as-build bridges over the Kyushu Expressway preventing traffic passage after the 2016 Kumamoto earthquake. Since the old overpass bridge did not have a substantial daily traffic, this bridge was not retrofitted to meet the current seismic design requirements. Seismic retrofit strategy must be established considering the consequences associated with the bridge failure. In Figure 6(b), the damage of the embankment is shown. Although the nearby bridge did not have any damage, the functionality of the post-disaster road network deteriorated severely. Reliable and efficient frameworks for quantifying the functionality loss of road networks involving bridges and other road structures (e.g. tunnels and embankments), and for identifying the most vulnerable structure in the network are needed. 2.4. Bridge damages due to independent hazards (seismic damages of corroded bridges) The effect of corrosion on the deterioration of the capacity of bridges under seismic hazard has to be considered. Field investigation conducted after the 2011 Great East Japan earthquake confirmed that some of RC structures and steel bearings were severely deteriorated due to chloride-induced corrosion as shown in Figure 7. It is important to understand that the seismic demand depends on the results of seismic hazard assessment, whereas the seismic capacity STRUCTURE AND INFRASTRUCTURE ENGINEERING 29 Figure 4. Improvement of seismic capacities associated with horizontal strength and displacement. Figure 5. No. 5 Inohana viaduct taken after the 2003 Sanriku-Minami earthquake and after the 2011 Great East Japan earthquake (Note: the viaduct was retrofitted before the 2011 Great East Japan earthquake) (both photographs taken by the first author). Figure 6. Example of post-disaster functionality deterioration of road network [photograph (a) courtesy of Mr. Matsunaga at Kyodo Engineering Consultant Co. Ltd. and photograph (b) taken by the first author]. Figure 7. Material deterioration observed in the field investigation after the 2011 Great East Japan earthquake (all photographs taken by the first author). depends on the other hazard, such as hazard associated with airborne chlorides. The seismic performance of existing bridges in a harsh environment cannot be expected to be the same as that at the time of construction. 2.5. Bridge damages due to interacting hazards Several bridges were severely damaged and collapsed not only due to the strong ground motion, but also to the 30 M. AKIYAMA ET AL. Figure 8. Matsurube bridge collapsed due to the land slide during the 2008 Iwate-Miyagi earthquake (both photographs taken by the first author). Figure 9. Koizumi bridge collapsed due to the tsunami during the 2011 Great East Japan earthquake (both photographs taken by the first author). Figure 10. Utatsu bridge collapsed due to the tsunami during the 2011 Great East Japan earthquake (all photographs taken by the first author). subsequent tsunami, landslide or fault displacement. Figure 8 shows the collapse of Matsurube bridge during the 2008 Iwate-Miyagi Nairiku earthquake. The abutment was displaced by the landslide due to the strong ground motion. Figures 9 and 10 present the photographs of Koizumi bridge and Utatsu bridge, respectively, taken after the 2011 Great East Japan earthquake. Koizumi bridge had the superstructure supported by five RC bridge piers. The superstructure was displaced more than 400 m from the original position. The concrete superstructure of Utatsu bridge was washed away. Koizumi bridge has been retrofitted by a seismic damper to prevent the excessive superstructure response under strong excitations. Also, RC bridge piers of the Utatsu bridge were retrofitted by jacketing to improve their capacity against the strong ground motions (Akiyama, Frangopol, Arai, & Koshimura, 2013). Retrofitted bridges could prevent failures from a strong ground motion; however, they could not prevent the washout of superstructure due to a giant tsunami. For these bridges, tsunami was the dominant hazard. Figure 11 presents the photograph of the Aso bridge taken before and after the 2016 Kumamoto earthquake. This bridge was constructed in 1970. The central part of this bridge is an arch with a simple span and continuous threespan girders on both sides. The Aso bridge was seismically STRUCTURE AND INFRASTRUCTURE ENGINEERING 31 Figure 11. Aso bridge collapse due to the ground motion, land slide and/or fault displacement during the 2016 Kumamoto earthquake [photograph (a) taken before the bridge collapse (courtesy of Dr. Yabe at Chodai Co. Ltd.) and photograph (b) taken after the bridge collapse by the first author]. Figure 12. Okirihata bridge damaged due the ground motion and/or land slide (all photographs taken by the first author). retrofitted before the 2016 Kumamoto earthquake; however, for this bridge, the ground motion was not the dominant hazard. In fact, this bridge was completely destroyed due to a huge landslide or fault displacement caused by the 2016 Kumamoto earthquake. Figure 12 shows the photograph of the Okirihata bridge taken after the 2016 Kumamoto earthquake. This bridge was designed based on the design code revised after the 1995 Hyogoken-Nanbu earthquake. Rubber bearings, including elastomeric bearings and seismic isolators, had been installed to improve the seismic performance. All rubber bearings at the abutments and three piers were ruptured. Since the landslide occurred in the mountains directly beside the bridge, this damage might have been caused by not only the ground motion but by landslide effects. Please note that the causes of the collapses of the Aso bridge and Okirihata bridge are still under investigation. 2.6. Examples of robust and resilient bridges against unexpected actions Compared with the conventional girder bridges, a rigid frame bridge under seismic action has less damage due to the effect of tsunami or landslide as presented in Figures 13 and 14. The rigid frame structure could be appropriate for the bridge under the hazards associated with tsunami and landslide. As shown in Figure 13, since the rigid frame structures do not have bearings between the superstructure and substructure, they could prevent the washout of superstructure due to the tsunami attack compared with the conventional girder bridge. Figure 14 depicts that the abutment of Aso-Choyo bridge could not support the PC box girder after it was transversely displaced by the landslide. However, since both the superstructure and the substructure were rigidly connected and behaved as a continuous unit, the severe damage to the Aso-Choyo bridge due to this landslide was not observed. 2.7. Sustainability issues (debris caused by tsunami) In Japan, following the tsunami due to the 2011 Great East Japan earthquake, large areas of farmland were flooded with salty water and contaminated by sea sediments, which led to long-term soil contamination of high fertile agricultural land by metal and metalloid compounds (Portugal-Pereira & Lee, 2016). As a result of the earthquake and subsequent tsunami, approximately 23 million tons of disaster debris was generated (Figure 15), with more than 12 million m3 of tsunami deposits left in the flooded area. The structural and geotechnical utilisation of the concrete and soil fraction in the disaster debris and tsunami deposits has presented a huge challenge to engineers since: (a) the clearance of debris and tsunami deposits is an urgent task which must be completed within a few years and (b) although a large amount of waste-mixed concrete and soil can be recycled and used in the reconstruction, their properties have temporal and spatial variations (Inui, Yasutaka, Endo, & Katsumi, 2012). If poorly managed, the waste can have significant environmental and public health impacts and can affect the overall recovery process (Brown, Milke, & Seville, 2011). 32 M. AKIYAMA ET AL. Figure 13. Rigid frame in the tsunami affected region taken after the 2011 Great East Japan earthquake (all photographs taken by the first author). Figure 14. Rigid frame in the landslide affected region taken after the 2016 Kumamoto earthquake (both photographs taken by the first author). Figure 15. Debris generated by the tsunami due to the 2011 Great East Japan earthquake [photograph (a) taken by the first author and photograph (b) courtesy of Dr. Takahashi at Kyoto University]. Figure 16. Progress of structural design methodology: from the classical allowable stress design method toward the life-cycle-based design and assessment of network involving bridges under multiple hazards. 3. Toward life-cycle-based design and assessment of bridges and bridge networks under independent and interacting hazards Figure 16 illustrates the progress of structural design methodology from the deterministic allowable stress design (ASD) toward the life-cycle-based design and assessment of transportation networks involving bridges. The structural safety in design is traditionary quantified by comparing the structural capacity, R, with the load, L. In the ASD method, the designer must size the structural components such that their service loads do not exceed a certain fraction of elastic STRUCTURE AND INFRASTRUCTURE ENGINEERING limit. Static and linear elastic analysis are performed to estimate R at the component-level. With the development of computer technology and computer simulation capability, and with the lessons from the disasters as described in Section 2, structural design methodology has progressed so that consequences caused by the structural failure, several performance indicators, and lifecycle concepts of bridges and bridge networks under multiple hazards are being developed. These progresses are overviewed herein. 3.1. Progress of structural design methodology 3.1.1. Reliability-based design In current semi-probabilistic load resistance-factored design, the concept of the reliability index is introduced in code calibration. The uncertainties in R and L are considered separately by assigning different load factors and resistance factors through rational calibration procedures, where the target reliability index for each type of structural element is assigned to maintain an acceptable probability of failure (Liu, Frangopol, & Kim, 2009). The structural components are designed based on ultimate limit states, or serviceability limit states, or both (Estes & Frangopol, 2001). Evolution of structural design methodologies from allowable structural design (ASD) method to load and resistancefactored design (LRFD) method has revealed the importance of uncertainty consideration in balancing economical and safety aspects of structural designs (Liu et al., 2009). Along with the improvement of computer performance, R and L at the structure-level could be evaluated by the nonlinear and dynamic analysis considering uncertainties and correlations. A reliability-based capacity design procedure was proposed to obtain the hierarchy of resistance of the various structural components and failure modes necessary to ensure a suitable plastic mechanism and avoid brittle modes (Akiyama et al., 2012). Although the capacity design method has been developed to maximise post-event operability and minimise the cost of repairing bridges after a severe earthquake, consequences associated with functionality and recovery cannot be explicitly incorporated in the reliability-based design method. 3.1.2. Risk-, reslience- and sustainablity issues Performance-based engineering has gained significant attention and is being used in many areas of structural engineering. Performance-based earthquake engineering has been at the frontier among natural hazards (Attary et al., 2017). This framework is based on the total probability theorem and can be disaggregated into different analysis phases that include hazard analysis, structural analysis, fragility analysis and loss analysis. When the limit states of the structure are mutually exclusive, the probability of losses due to failure can be determined by multiplying the probability of failure by the probability of losses (Ellingwood, 2006a, 2006b): XX P½Loss > LjLSP½LSjH P½H (1) P½Loss>L ¼ LS H P½Loss>L ¼ X P½Loss > LjLSP½LSjHs 33 (2) LS where P [H] is the probability of occurrence of hazard H, P [LS | H] is the conditional probability of the limit state LS given the occurrence of H, P [Loss > L | LS] is the probability of loss exceeding L given the limit state LS and P [LS | Hs] is the conditional probability of the limit state LS given the postulated hazard scenario Hs. Consequences have been quantified in terms of several measures, e.g. monetary loss, human fatalities and environmental damage (ISO13824, 2009). Lounis and McAllister (2016) reported that the consequences associated with sustainability can be grouped as follows: Social consequences: fatalities, injuries, and reduction/ loss of service. Economic consequences: loss of income, loss of productivity, delays in service delivery and user’s costs. Environmental consequences: irreversible and reversible environmental damages. With regard to resilience, there may be similar social and economic consequences of failure. Additional consequences associated with resilience may include (Lounis & McAllister, 2016): Functionality consequences: loss of other systems or services due to dependence on damages system. Recovery consequences: time to restore system functionality causing delays and losses in restoration of other systems. In addition to studies investigating the risk, resilience and sustainability through quantitative approaches and application to case studies to bridge structures, studies on the contribution to risk reduction and resiliency coming from structural control have been provided. For example, enhancing the robustness of bridge can improve the resiliency of not only the bridge itself but also the surrounding community by reducing repair costs and downtime after an extreme event. Several interesting structures, and their design methodologies have been developed experimentally and computationally (Akiyama, Abe, Aoki, & Suzuki, 2012b; Brito, Ishibashi, & Akiyama, 2018; Domaneschi & Martinelli 2016; Eatherton & Hajjar, 2011; Echevarria, Zaghi, Christenson, & Accorsi, 2016; Iqbal, Fragiacomo, Pampanin, & Buchanan, 2018; Lehman et al., 2015; Loli, Knappett, Brown, Anastasopoulos, & Gazetas, 2014; Mitoulis & Rodriguez, 2017; Rodgers, Mander, Chase, & Dhakal, 2016). 3.1.3. Life-cycle perspective A life-cycle approach is needed in the risk assessment, mitigation procedure, and quantification of resilience and sustainability, because the effect of aging and environmental aggressiveness can reduce the structural performance and functionality, and it depends on the time of occurrence of the event (Biondini, Camnasio, & Titi, 2015; Frangopol, 2011; Frangopol & Soliman, 2016). The classical time-invariant structural design and 34 M. AKIYAMA ET AL. hazards is useful for identifying significant threat scenarios. A discussion on various design and analysis aspects for bridges under multiple hazards in a life-cycle context is provided herein. Figure 17. Bridges belonging to a network under independent and interacting hazards. assessment methods need to be revised to account for a proper modelling of the structural system over its entire life-cycle by taking into account the effects of deterioration process, timevariant loadings, and maintenance and repair interventions, among others (Liu & Frangopol, 2005; Sanchez-Silva, Frangopol, Padgett & Soliman, 2016; Yang & Frangopol 2019a; Biondini & Frangopol, 2016; Frangopol, 2011). It is crucial to implement rational management strategies that maintain performance of bridges within acceptable levels through their life-cycle. As shown in Figure 16, life-cycle design and assessment methodology can encompass all the key concepts such as risk, resilience and sustainability. However, there is still a need to fill the gap between theory and practice by incorporating life-cycle concepts in structural design and assessment codes (Sabatino, Frangopol, & Dong, 2016; Yang & Frangopol, 2019b; Biondini & Frangopol, 2018; Frangopol & Kim, 2014; Frangopol & Soliman, 2016). Moreover, as provided in the lessons learnt from the past seismic disasters, more comprehensive multiple hazards have to be taken into consideration in the life-cycle design and assessment for ensuring the adequate life-cycle performance. 3.2. Life-cycle design and assessment of bridges under multiple hazards As mentioned in Sections 2.4 and 2.5, a strong earthquake could cause multiple disasters, including damage to structures due to strong ground motions and/or liquefaction and the washout of structures due to subsequent tsunamis and landslides. In addition, seismic capacity would deteriorate due to the material corrosion, fatigue and scour caused by the flood, among others. Figure 17 presents an example of an individual bridge and road network near a coast line. Comparing life-cycle reliabilities and risks among structures belonging to a network under independent and interacting 3.2.1. Literature review on multi-hazard analysis Different types of hazard such as independent hazards, correlated hazards, concurrent hazards and cascading hazards have been investigated in the literature (Akiyama & Frangopol, 2012b, 2013; Asprone, Jalayer, Prota, & Manfredi, 2010; Kameshwar & Padgett, 2014). Life-cycle performance approaches of RC structures exposed continuously to the chloride ions in earthquake-prone regions were proposed in several studies (Akiyama, Frangopol, & Matsuzaki, 2011; Alipour, Shafei, & Shinozuka, 2011;Biondini, Camnasio, & Palermo, 2014; Rao, Lepech, & Kiremidjian, 2017a, 2017b, among others). Several researchers estimated the seismic risk or resilience of road network taking into consideration the effect of corrosion on the bridge performance deterioration (Alipour & Shafei, 2016; Biondini et al., 2015; Kurtz, Song, & Gardoni, 2016; Rokneddin, Ghosh, Duenas-Osorio, & Padgett, 2013; Zanini, Faleschini, & Pellegrino, 2017). The influence of the climatic changes, and in particular of the temperature and humidity on the corrosion rate has been reported in the literature (e.g. Andrade, Alonso & Sarrıa, 2002). Recently, several advanced simulations for investigating the effect of the temperature and humidity, and the concentration of CO2 in the atmosphere due to the climate change on the probability of reinforcement corrosion of RC structures have been performed (Bastidas-Arteaga & Stewart, 2015; Stewart, Wang, & Nguyen, 2011, 2012; Yooh, Çopuroglu & Park, 2007). Zhang, Cai and Pan (2013) presented a framework for fatigue reliability analysis of long-span bridges under combined dynamic loads from vehicles and wind. Even though the stresses from either the vehicle loads or wind loads may not be able to induce serious fatigue problems alone, the superposed dynamic stress ranges cannot be ignored for fatigue reliability assessment of long-span bridges. A multi-hazard optimisation framework for wind and seismic loading for two suspended floor slab isolation system was proposed by Chulahwat and Mahmoud (2017). Their results highlighted the effectiveness of tuning the suspended slab system to meet the wind and seismic performance objectives. Scour plays an important role in the seismic response of bridges since it weakens the lateral strength of the foundation. A multi-hazard reliability-based or risk-based framework for evaluating the structural response of bridge under the combined effects of scour and earthquake events has been investigated (Alipour, Shafei, & Shinozuka, 2013; Banerjee & Prasad, 2013; Chandrasekaran & Banerjee, 2016; Dong, Frangopol, & Saydam, 2013; Yilmaz, Banerjee, & Johnson, 2016). Structural damage accumulation resulting from the action of sequences of seismic excitations has been investigated in the assessment of life-cycle system reliability and performance optimization (e.g. Esteva, Campos, & Dıaz-Lopez, STRUCTURE AND INFRASTRUCTURE ENGINEERING 2011; Esteva, Dıaz-L opez, Vasquez, & Le on, 2016). Meanwhile, the aftershocks have the potential to cause more severe damage to bridges, since the bridges damaged due to a mainshock cannot be repaired under high aftershock hazard. Seismic hazards associated with aftershocks are not explicitly accounted for in modern bridge design codes, nor in emerging methodologies such as performance-based seismic design. Nazari, van de Lindt and Li (2015) developed a methodology that can quantify the changes that would be needed in the structural design of a building to account for aftershock hazards and illustrate it by using a basic nonlinear model of a building. Probabilistic risk and resilience of highway bridges under mainshock and aftershock sequences were estimated for implementing risk mitigation strategies and equipping decision makers with a better understanding of structural performance (Dong & Frangopol, 2015). 3.2.2. Life-cycle performance of bridges under independent hazards For bridges under independent hazards, the effect of material corrosion due to mechanical and/or environmental stressors on the structural performance deterioration needs to be taken into consideration. As mentioned in Section 3.2.1, seismic reliabilities of corroded bridges or bridges damaged by the scour due to flood are examples of independent hazards. Structural capacity larger than structural demand has to be ensured for a whole lifetime. However, further research is needed to develop the numerical model of the structural fragility of corroded or damaged bridges. Structural reliability can be evaluated based on the multiple independent hazard curves and fragility curves. For new bridges, it could be possible to provide higher structural performance and durability. For example, RC structures designed with high quality concrete and adequate concrete cover prevent the steel corrosion causing the deterioration of structural performance during whole lifetime of these structures. An alternative approach is to use corrosion-resistant stainless steel or epoxy-coated reinforcement. In this case, even when a bridge using durable materials is located in an earthquake prone region and marine environment, it’s not necessary to consider the effect of material corrosion on the seismic capacity in the fragility analysis. Life-cycle reliability can be estimated only considering a dominant hazard. Although the initial cost of a bridge designed with high durability would be expensive, this can be justified on a life-cycle cost basis. For existing bridges, visual inspections, field test data regarding structural performance and/or monitoring play an important role in the bridge performance assessment. This information helps engineers to update the variables associated with prediction of current and future structural capacity, and to confirm whether the structural capacity deteriorates and it’s necessary to be repaired. Maintenance strategy of existing bridges under independent hazards has to be developed considering which hazard is dominant on the basis of the significance and how the structural capacity could deteriorate before the occurrence of the identified 35 dominant hazard. A case study of bridges under independent hazards is illustrated in Section 4. 3.2.3. Life-cycle performance of bridges under interacting hazards It is not feasible to design a bridge that will remain intact under all hazards that might impact its performance (Ellingwood, 2006a, 2006b). Under excessive interacting hazards on bridges such as seismic and tsunami hazards, and seismic and landslide hazards, it is quite difficult to identify the solution in terms of structural control for preventing the failure of bridges with damage due to the strong ground motion under the cascading giant tsunami or huge landslide shown in Figures 8–12. Damaged structures are more vulnerable, since the damage cannot be repaired before the occurrence of the cascading hazard. The technology may not exist for enhancing the structural ductility and integrity of bridge against damage and collapse even if additional requirements beyond those provided in the current structural codes are required. For new bridges under excessive interacting hazards, conceptual design plays an important role in reducing the risk and in enhancing the resilience of bridge and bridge network. When determining the structural form (e.g. girder bridge versus rigid frame) and alignment of roads and structures, various circumstantial conditions such as geological and geographical conditions, environmental conditions, disaster history, and specific characteristics of the expected disasters have to be investigated. Additionally, attention should be paid to a wider spectrum of factors such as the regional disaster management plan, and expected recovery process of structures (Honda et al., 2017). For existing bridges under excessive interacting hazards, it is quite difficult to reduce the probability of bridge failure and the associated risk with a limited budget. As observed in 2011 Great East Japan earthquake and 2016 Kumamoto earthquake, large-scale hazards can damage many bridges in an existing transportation system simultaneously. It is of vital importance to develop a management plan to recover structures and civil infrastructure systems in terms of resilience and sustainability. Accelerated bridge construction (ABC) technology and disaster waste management system have to be established for the networks under the excessive interacting hazards. Prefabrication of structural component using ABC technology is a resilient solution that decreases on-site construction time and help roads and road structures reopen soon after a disaster. The environmental impacts of a disaster is substantial as mentioned in Section 2.7. For example, Hurricane Katrina in 2005 resulted in debris management costs exceeding USD 4 billion, accounting for more than a quarter of the total cost associated with disaster response and recovery according to Lorca, Çelik, Ergun, & Keskinocak (2017). They presented a decision-support tool employing analytical models to assist disaster and waste management with decisions regarding collection, trasportation, reduction, recycling and disposal of debris. It is very important before the occurrence 36 M. AKIYAMA ET AL. Figure 18. Flowchart for evaluating the deterioration process of RC structures in a marine environment (adapted from Miyamoto et al., 2015). Figure 19. Cracked area patterns of RC slabs in Niigata City. Figure 20. Cracked area patterns of RC slabs in Uwajima City. of the disaster to develop the tool for optimising and balancing the financial and environmental costs, duration of the collection, and disposal operations, landfill usage, and the amount of recycled materials (FEMA, 2007; Kim, Deshmukh, & Hastak, 2018). A case study of bridges and bridge networks under interacting hazards is illustrated in Section 5. 4. Life-cycle reliability of bridges under independent hazards: mechanical and environmental hazards Time-dependent models have been developed that can simulate all stages of corrosion including corrosion initiation, crack initiation and propagation (Akiyama, Frangopol, & Suzuki, 2012c; Akiyama, Frangopol, & Takenaka, 2017; Akiyama, Frangopol, & Yoshida, 2010; Papakonstantinou & Shinozuka, 2013). Regarding the life-cycle reliability estimation of RC structures in an aggressive environment, the exact influence of environmental factors affecting degradation mechanisms is difficult to predict as they vary in time and space. Probabilistic hazard assessment associated with environmental stressors has to be included in the life-cycle reliability analysis of RC structures. Figure 18 shows the flowchart for evaluating the degradation process of RC slab in a marine environment (Miyamoto, Akiyama, & Frangopol, 2015). Several challenges for enhancing the lifecycle structural reliability estimation of bridge in an aggressive environment are introduced herein. It is well-recognised that the material properties of a RC structure and structural dimensions are random due to the spatial variability associated with workmanship and other factors. This randomness cause spatially corrosion damages such as corrosion cracks and cover spalling. It is of great importance to simulate deterioration processes in a stochastic field context. Modeling the spatial variability of model parameters gives one the ability not only to quantify the probability of degradation but the extent of damage as well. As an example, based on the formulations presented by Papakonstantinou and Shinozuka (2013), spatial variability associated with the random variables used in the degradation process of a RC slab is represented by a 2D Gaussian stochastic field. The power spectral density is: " 2 2 # b b b j b j 1 2 1 1 2 2 Sf0 f0 ðj1 ; j2 Þ ¼ r2 exp (3) 4p 2 2 where b1 and b2 are proportional to the correlation distance of the stochastic fields along the x1 and x2 axes, respectively. Figures 19 and 20 illustrate examples of RC slab plan views in Niigata City and Uwajima City, respectively, and present the elements with corrosion cracks from a random realisation at 30 years and 60 years after the construction (Miyamoto et al. 2015). Due to the difference of airborne chloride hazard, RC slab in Niigata City has more elements with corrosion cracks. For this case study, it was simply assumed that the concrete element cracks when the tensile stresses due to the volume expansion of corrosion products reach the tensile strength of concrete. If a bridge is located in earthquake-prone region or heavy traffic route, or both, it is necessary to consider the effect of material corrosion on life-cycle structural performance considering the spatial distribution associated with the material properties and mechanical stressors. In Figures 19 and 20, the difference of wind speed, distance from coast line and percentage of time during one day when the wind is blowing from sea toward land between two cities are considered when quantifying the airborne chloride hazard. A calculation model for predicting concentration of airborne chloride ion at an arbitrary time and location has to be developed considering the transportation and adhesion processes of airborne seawater particles. STRUCTURE AND INFRASTRUCTURE ENGINEERING 37 Figure 21. Buckling model of a longitudinal rebar in the plastic hinge of corroded RC column subjected to cyclic loading. Figure 22. Estimation of steel weight loss distribution based on limited inspection results. Studies on spatial variability associated with the airborne chloride over the bridge are scarce. In the seismic probabilistic risk assessment, the annual probability of exceedance of seismic capacity is: ð1 dp0 ðcÞ pfa ¼ (4) dc P½De Ca jC ¼ cdc 0 where p0 ðcÞ is the annual probability that the seismic intensity, C, at a specific site would exceed a value c and P½De Ca jC ¼ c is the fragility, which is the conditional probability of the seismic demand De exceeding the seismic capacity Ca conditioned upon the seismic intensity c. In the calculation of the conditional probability P½De Ca jC ¼ c of bridge piers in a marine environment, the effect of corrosion has to be taken into consideration. As the steel weight loss of rebars increases, the seismic capacity decreases. Using the total probability theorem, the annual probability of exceedance of seismic capacity Ca under earthquake excitation at t years after construction can be expressed as: ð 100 ð 1 dp0 ðcÞ pfa ðt Þ ¼ dc 0 0 P De Ca jC ¼ c; Cw ¼ cw ðt Þ f ðcw ðt ÞÞdcdcw (5) where P [De Ca| C¼c, Cw ¼ cw (t)] is the probability of the seismic demand De exceeding the seismic capacity Ca conditioned upon the seismic intensity c and steel weight loss cw (t), and f (cw (t)) is the probability density function (PDF) of cw (t). In the calculation of P [De Ca| C ¼ c, Cw ¼ cw (t)], the effect of steel corrosion, cover cracking and debonding between concrete and rebar on the deterioration of lateral strength and ductility capacity of RC columns needs to be considered in the non-linear analysis as shown in Figure 21. Performing the structural analysis using the reduced steel rebar cross-section is an oversimplification for evaluating the relationship between load and displacement of deteriorating RC components. For existing bridges, what is actually important and difficult in their life-cycle reliability estimation is how to accurately predict the degree and location of the current material deterioration and how to adequately quantify this deterioration in terms of input data in the fragility analysis (Akiyama & Frangopol, 2014; Yanweerasak, Akiyama, & Frangopol, 2016). As shown in Figure 22, identifying the possible spatial distribution of material corrosion over a large-scale structure based on the limited number of inspection results and updating the life-cycle reliability are demanding and challenging problems. Owing to the uncertainties, the predicted life-cycle performance, despite how accurate or advanced the tools used to obtain this performance were, may deviate from the actual performance exhibited by the structure over time. A frequent updating of the life-cycle performance is required as new information (e.g. monitoring results) becomes available (Okasha & Frangopol, 2011). Yanweerasak et al. (2016) presented a procedure for estimating the mean and variance of steel weight loss in the plastic hinge of corroded RC structures based on inspection results. Variance of steel weight loss depends on the number and space interval of inspection locations based on the statistical estimation error process (Honjo & Otake, 2013). The variance is used as the observation noise during the updating process. P [De Ca| C¼c, Cw ¼ cw (t)] in Equation (5) is estimated using the updated random variables. As an illustrative example, the locations of the steel weight loss measurements are assumed as shown in Figure 23. The simple average is almost the same among Cases 2, 3 and 4; however, the number of inspection points are different. Figure 24 displays the updated cumulative-time failure probability based on the inspection data using Sequential Monte Carlo Simulation (SMCS) (Akiyama et al., 2010). The cumulative-time failure probabilities of Cases 2, 3 and 4 at Year 30 are smaller compared with that of Case 1. From Figure 24, although the cumulative-time failure probabilities are nearly identical for Cases 2, 3 and 4 because the magnitudes of steel weight loss from the inspection results are 38 M. AKIYAMA ET AL. Figure 23. Assumed location of the steel weight loss measurements in the plastic hinge. Figure 24. Relationship between the cumulative-time failure probability and the time after construction (years). almost identical, a significant difference in the correlation among random variables can be confirmed. Figure 25 depicts the correlations between x3 and x5 using 100,000 samples of SMCS, where x3 and x5 are random variables associated with airborne chloride and surface chloride concentration relation, and associated with estimation by diffusion equation, respectively. Before updating, the random variables are assumed statistically independent. After updating, all random variables related with the prediction of the steel weight loss were updated simultaneously by SMCS. These results illustrate that, as expected, having more inspection locations can provide a more accurate reliability assessment. To understand the steel corrosion growth process and the change in the spatial variability of steel corrosion with time, continuous monitoring is necessary. X-ray photography has been applied to observe steel corrosion in RC beams (Akiyama & Frangopol, 2014; Lim, Akiyama, & Frangopol, 2016; Lim, Akiyama, Frangopol, & Jiang, 2017; Zhang, Song, Lim, Akiyama, & Frangopol, 2019). They estimated the steel weight loss by the digital image processing of the X-ray photograms. The non-uniform distribution of steel weight loss along rebars inside RC beams determined using X-ray radiography and its correlation with longitudinal crack widths and loading capacity were experimentally investigated (Figure 26). Although Gumbel distribution parameters were derived from the experimental data of steel weight loss to model spatial steel corrosion (Lim et al. 2016), further experimental research is needed to determine whether these parameters are stationary over the steel corrosion process, and to investigate the effect of concrete quality, rebar amount and arrangement, and climatic condition on them. A finite element (FE) analysis method has been used to simulate the structural responses of the corroded beams when considering two different inputs (i.e. uniform and non-uniform cross-sectional area of rebars over the beam). Comparing the numerical results of the flexural responses of the simulated beams to those of the test beams in the experimental study, the effect of mesh size on the accuracy of the FE model was investigated. Figure 27 presents the comparison of computational and experimental results of the relationship between load and deflection, and the comparison of contour of the principal tensile strain obtained from the FE analysis, flexural cracking caused during the bending test, and steel weight loss. Average steel weight losses over RC beam shown in Figure 27(a, b) are 12.1 and 25.5%, respectively. As presented in Figure 27, when the spatial distribution of steel weight loss seems to be more uniform, the effect of mesh size on the computational results can be ignored. However, when the spatial variability becomes larger, the computational results depend on the mesh size. Spatial distributions associated with the bond properties and internal and external cracks due to the volume expansion of corrosion products are not taken into consideration in the computational results shown in Figure 27. More studies on this topic are needed for further improvement in FE modeling (Zhang et al. 2019). In addition, because of the budget shortage, the number of inspection and/or monitoring results to understand the corrosion condition inside existing RC component has to be limited. Further research is needed to develop a procedure of providing the possible input data for FE analysis (e.g. material properties and constitutive models of corroding RC component) based on the limited number of inspection results. 5. Life-cycle reliability of bridges under interacting hazards: seismic and tsunami hazards Frameworks for multi-hazard risk assessment have been reported in the literature as described previously. Tsunami intensity is correlated with the magnitude of the oceanic earthquake, and a bridge may have severe damage due to the strong ground motion before the tsunami arrives. STRUCTURE AND INFRASTRUCTURE ENGINEERING 39 Figure 25. Effect of the number of inspection locations on the variability associated with random variables used in the prediction of steel weight loss (adapted from Yanweerasak et al., 2016). Figure 26. X-ray machine at Waseda University to visualise the corroded rebars embedded in the concrete beam. Difficulties in estimating the reliability of bridges under tsunami hazards are similar to those associated with bridges under aftershocks. Strong aftershocks have the potential to cause extensive structural damage. Damaged structures due to mainshock are even more susceptible to incremental damage due to aftershocks because their reduced structural capacity decreases the threshold of the ground motion intensity needed to cause further damage. Yeo and Cornell (2005) divided the seismic performance assessment and design process into simpler components in terms of the description, definition and quantification of earthquake intensity measures (IMs), engineering demand parameters (EDPs), damage measures (DMs) and decision variables (DVs). Commonly used examples of the above parameters are peak ground acceleration (PGA) and firstmode spectral acceleration (IMs), interstory drift ratios, inelastic component deformations and floor acceleration spectra (EDPs), damage states of structural and non-structural elements (DMs) and fatalities, financial losses and downtimes (DVs). Based on the total probability theorem, the mean annual rate t(DV) of exceeding a given level of DV ¼ x, is Yeo and Cornell (2005): ððð tðDV Þ ¼ GðDVjDMÞdGðDMjEDPÞdGðEDPjIMÞdkðIM Þ (6) where k (IM) is the mean annual rate of exceeding a given IM and is obtained from a conventional probabilistic hazard analysis. G(EDP | IM) is the complement of the cumulative distribution function of EDP conditioned by a given level of IM (i.e. G(EDP | IM) ¼ P[EDP y | IM ¼ x] while in the continuous case G(EDP | IM) ¼ fEDP|IM (y | x) dy is the conditional probability density function times dy). Based on Equation (6), Yeo and Cornell (2005) discussed the reliability of structures under aftershock hazard. If a structure had the mainshock with the intensity MI and damage state SI due to the mainshock, the mean rate exceeding a given DV in post-mainshock time interval [0, tmax] is Yeo & Cornell (2005): ð ð ð ð ttamax ðDVjMI; SI Þ ¼ Ga ðDVjDM; iÞ DM EDP IM i dGa ðDMjEDP; iÞdGa ðEDPjIM; iÞdktamax ðIM; ijMI ÞdGa ðijMI; SI Þ (7) where the subscript a refers to the aftershock environment, ktamax is the mean number of aftershocks exceeding a given IM in post-mainshock time interval and Ga (i | MI, SI) is the probability that the structure is in damage state i after the mainshock given MI and SI. The inclusion of Ga (i | MI, SI) means an additional integral over all possible post-mainshock damage states i. Equation (7) can be used for estimating the reliability of bridges under tsunami hazards. IM could be the hydrodynamic features such as tsunami wave velocity and height, and EDP and DM could be the tsunami demands and structural damage states due to the tsunami in the estimation of dGa in Equation (7). In addition, if reliability will be estimated given the occurrence of the earthquake, Equations (6) 40 M. AKIYAMA ET AL. Figure 27. Effect of element size in FE model on the computational results of corroded RC beam: (a) average steel weight loss over RC beam ¼ 12.1% and (b) average steel weight loss over RC beam ¼ 25.5%. and (7) can be simplified because it is not necessary to consider the earthquake occurrence rate. It is expected that the damage and the economic loss resulting from the anticipated Nankai Trough earthquake and its associated tsunami would be larger than those resulting from the 2011 Great East Japan earthquake. As an illustrative example, reliabilities, economic loss and recovery time of road networks including bridges and embankments in Town A in Kochi-Prefecture and Town B in MiePrefecture under both seismic and tsunami hazards due to the anticipated Nankai trough earthquake are computed. Figure 28 displays the schematic layouts of the investigated networks in Towns A and B. Akiyama and Frangopol (2016) estimated the reliabilities of individual bridge and embankment under seismic and tsunami hazards based on the parameters associated with the fault movement caused by the anticipated Nankai trough earthquake provided by Central Disaster Management Council (2003). Taking into consideration the lessons from the 2011 Great East Japan earthquake, these parameters were updated by Cabinet Office, Government of Japan (2012a, 2012b). In this case study, these updated parameters are used to estimate the seismic and tsunami intensities. It is difficult to evaluate the exact fault movement during the seismic event since uncertainties associated with fault movement vary in time and space. The average stress drop at the seismic fault is assumed to be random. Seismic intensity at the bridge site given seismic event is estimated by the attenuation relation. In this case study, the relationship between the seismic intensity and the distance from seismic fault taking into consideration the effect of seismic fault type and soil condition on the attenuation rule provide by Si and Midorikawa (1999) was used to estimate the PDF of the PGA given the occurrence of the anticipated Nankai Trough earthquake. Figure 29 displays an example of tsunami propagation computation to obtain the PDF of the tsunami wave height and velocity at the locations of bridges and embankments analysed. Horizontal 2D tsunami analysis based on non-linear long-wave theory (Goto, Ogawa, Shuto, & Imamura, 1997) is performed in this simulation. The PDF is calculated by Monte Carlo Simulation (MCS) using the random variables associated with the seismic fault and considering the difference of roughness coefficient among the locations of interest. Figures 30 and 31 present an example of PDF of PGA and tsunami height at the Towns A and B, respectively. As the difference of distances between each structure and seismic fault is negligible, PDFs of PGA shown in Figures 30 and 31 are applied to all structures in Towns A and B STRUCTURE AND INFRASTRUCTURE ENGINEERING 41 Figure 28. Example of road network affected by the anticipated Nankai Trough earthquake. Figure 29. Propagation analysis of tsunami caused by the anticipated Nankai Trough earthquake. (Figure 28), respectively. Since tsunami intensities depend on the location of structures (e.g. distance from the coastline), tsunami fragility is estimated by using the PDF considering the location of each structure. In this case study, it was assumed that the sea level around Japan is not changing over time (i.e. time-independent). However, since sea level rise appears to be a real and longterm effect observed around the world (FEMA, 2016), further research is needed to consider non-stationarity in tsunami intensities in the structural reliability and risk analysis. Li, Wang and Ellingwood (2015) proposed a life-cycle reliability estimation method in the presence of non-stationary loads. Seismic fragility curves are developed by comparing the seismic demand and capacity. The demands of bridge and embankment are estimated using non-linear time history analysis and Newmark’s method, respectively. In this case study, three damage states (i.e. no, moderate and complete) are considered and related to an anticipated level of post event functionality (Padgett, Dennemann, & Ghosh 2010). Details of the methodology used for obtaining the seismic fragility are found in Akiyama et al. (2014). Figure 32 presents an example of seismic fragility curves of hypothetical bridge and embankment. The PDF of the hydrodynamic forces given the tsunami height can be identified based on MCS. Then, the hydrodynamic horizontal and uplift forces are applied to bridges. When estimating the tsunami fragility of bridges, a push-over analysis using hydrodynamic forces given tsunami height is performed to compare the tsunami capacity with the tsunami demand in MCS. A detailed procedure for developing the tsunami fragility is described in Akiyama & Frangopol (2013). Figure 33(a) depicts an example of tsunami fragility curve of bridges assuming that the bridge has no damage before the tsunami arrive. It is necessary to develop the tsunami fragility curve of bridges and embankments given seismic damage state Dss ¼ ds1, Dss ¼ ds2 and Dss ¼ ds3 where ds1, ds2 and ds3 are no damage state, moderate damage state and complete damage state due to the ground motion, respectively. Recent studies have attempted to model the degradation of physical 42 M. AKIYAMA ET AL. Figure 30. Example of probability densities of peak ground acceleration and tsunami height at the Town A in Figure 28. Figure 32. Example of seismic fragility curves: (a) bridge and (b) embankment. damage caused by a ground motion (Jalayer, Asprone, Prota, & Manfredi, 2011; Nogami, Murono, & Sato, 2008). Figure 33(b) displays an example of tsunami fragility curve associated with the complete damage state given Dss¼ds1 and Dss¼ds2. It is confirmed in Figure 33(b) that the damaged bridge due to the ground motion is more vulnerable to the tsunami attack. For the embankment, tsunami fragility can be developed by comparing the heights of embankment and tsunami considering the residual displacement due to the ground motion based on the Newmark’s method. Equation (4) for estimating the failure probability can be rewritten to include the damage state of structure k due to a ground motion: ð1 PðDSs ¼ dsi jC ¼ cÞ fC ðcÞdc (8) pfs;k ðiÞ ¼ 0 Figure 31. Example of probability densities of peak ground acceleration and tsunami height at the Town B in Figure 28. vulnerability over a seismic sequence (Amadio, Fragiacomo, & Rajgelj, 2003; Li & Ellingwood, 2007; Polese, Ludovico, Prota, & Manfredi, 2013). Cyclic stiffness degradation model needs to be used for the bridge to evaluate the residual where DSs is the seismic damage state, and fC(c) is the PDF of seismic intensity c (i.e. PGA) due to the anticipated Nankai Trough earthquake. The probability that the structure k is in damage state DSt¼dsj after the tsunami taking into consideration the seismic damage DSs¼dsi is: Ð Ð Ð1 P DSt ¼ dsj jFW ¼ f w ; DSs ¼ dsi pft;k ði;jÞ ¼ 0 (9) fFW jH fw jh fHjC ðhjcÞ fC ðcÞ dfw dh dc ðj iÞ where DSt is the tsunami damage state, fH|C (h|c) is the PDF of the tsunami wave height H given c and fFW|H (fw|h) is the conditional density function of the wave load Fw given H. Since the wave load depends not only on the tsunami wave height but also on the tsunami velocity and tsunami features (e.g. hydraulic bore), fFW|H (fw|h) was evaluated using several types of tsunami waves using MCS. STRUCTURE AND INFRASTRUCTURE ENGINEERING Finally, the probability that the structure k is in damage state DS¼dsj after the occurrence of both the seismic and tsunami events is provided by: j X pfs;k ðiÞ pft;k ði;jÞ pfk DS ¼ dsj ¼ (10) i¼1 Table 1 lists an example of failure probabilities of bridges and embankments at the Towns A and B in Figure 28. Because of the difference of seismic and tsunami intensities between Towns A and B, the probabilities associated with the complete damage state at Town A are higher than those at Town B. As listed in Table 1, the seismic and tsunami reliabilities depend on the locations of bridge and embankment in the road network. When the structure is located near the coast line, the failure probabilities need to be estimated considering the effect of both seismic and tsunami hazards on the structural performance. The ground motion induced- and/or tsunami induceddamage to bridges and embankments cause the deterioration Limit state probability (a) 1.0 Moderate damage state 0.8 0.6 0.4 0.2 Complete damage state 0.0 0 10 20 Tsunami height (m) 30 Limit state probability (b) 1.0 0.8 0.6 0.4 0.2 0 k¼1 k¼1 where nb and ne are the number of bridges and embankment located in the investigated link, and BDI and EDI are the damage index of bridge and embankment and classified as shown in Table 2. Chang et al. (2000) define the damage states of the link according to LDI. The increase in the damage state of the link will reduce the link traffic capacity and speed limit. In this case study, the relationship between damage state and residual percentage of traffic-carrying capacity and free-flow speed listed in Table 3 (Guo, Liu, Li, & Li, 2017) was used. The consequences associated with each damage state corresponding to a bridge and embankment are evaluated and quantified by the expected economic loss and full recovery time (Dec o, Bocchini, & Frangopol, 2013; Dong & Frangopol, 2016; Dong, Frangopol, & Saydam 2014). The expected economic loss of the investigated link can be provided by: 10 20 Tsunami height (m) Rdir ¼ nb X mb X ne X me X pfk;b DS ¼ dsj Cdsj;b þ pfk;e DS ¼ dsj Cdsj;e k¼1 j¼1 k¼1 j¼1 30 Figure 33. Example of bridge tsunami fragility curves: (a) fragility curves assuming that bridge has no damage before the arrival of the tsunami and (b) fragility curves associated with complete damage state due to tsunami assuming that the bridge has moderate or no damage due to ground motion before tsunami will arrive. Rindir ¼ Rrun þ Rtl Town A Town B Damage state A C F G Moderate 2.21 101 2.95 101 2.29 101 1.16 101 1.54 101 7.33 102 3.29 102 2.11 102 Complete 7.99 101 5.01 101 5.44 101 3.11 101 4.96 101 4.39 101 8.72 101 2.17 101 (13) (14) Cdsj;b and Cdsj;e are the direct repair costs associated with a given damage state of bridge and embankment, respectively, mb and me are the number of damage statues of bridge and Table 1. Example of failure probability of bridges and embankments under seismic and tsunami hazards. Bridge 1 Bridge 5 Bridge 8 Bridge 12 Embankement Embankement Embankement Embankement (12) where With no damage due to ground motion d 0.0 of the post-disaster road network functionality. The damaged structures can be open, closed or partially open within a road network. Consequently, traffic flow in the links can be different and speed limits might be reduced for various damage conditions of the link (Frangopol, Dong, & Sabatino, 2017). The damage state and the number of each bridge and embankment can affect the functionality of the investigated link. Chang, Shinozuka, and Moore (2000) proposed the performance indicator of a link including bridges after an earthquake which is expressed in terms of link damage index (LDI). In this case study, to evaluate a link performance including bridges and embankments after the seismic and tsunami events, LDI is modified by: vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi u nb ne X uX ðBDIk ðtÞÞ2 þ ðEDIk ðtÞÞ2 LDI ðtÞ ¼ t (11) Re ¼ Rdir þ Rindir With moderate damage due to ground motion d 43 Damage state Bridge 4 Bridge 5 Bridge 6 Bridge 7 Embankement Embankement Embankement Embankement A B D E Moderate 1.34 101 8.98 102 9.90 102 4.51 102 1.11 101 1.33 101 7.43 102 6.33 102 Complete 3.46 101 2.01 101 2.13 101 9.29 102 3.98 101 3.11 101 1.12 101 1.10 101 44 M. AKIYAMA ET AL. Table 2. Damage index of bridge and embankment. Damage state BDI EDI No Moderate Complete 0 0.3 1.0 0 0.3 1.0 Table 3. Damage state and residual percentage relation (after Guo et al., 2017). Residual percentage (%) Link status (LS) LI LI LI LI LI ¼ ¼ ¼ ¼ ¼ 1 2 3 4 5 LDI Traffic-carrying capacity Free-flow speed 0 LDI < 0.5 0.5 LDI < 1.0 1.0 LDI < 1.5 1.5 LDI < e 1 100 100 75 50 0 100 75 50 50 0 Figure 34. Expected economic loss and full recovery time of links at the Towns A and B. Table 4. Assumed recovery time from a damage state. Damage state Network component Bridge Embankment Moderate Complete 30 days 5 days 180 days 60 days Table 5. Information on links and traffic at Town A. Average daily traffic Average daily traffic ratio Length of link (km) Link speed (km/h) Link 1 Link 2 Link 3 Detour 10,000 30% 7.3 40 6000 20% 7.1 40 5000 10% 9.1 40 19.0 40 Estimated in Equations (15) and (16). Table 6. Information on links and traffic at Town B. Average daily traffic Average daily traffic ratio Length of link (km) Link speed (km/h) Link 1 Link 2 Link 3 Link 4 Detour 6000 10% 5.5 40 4000 10% 4.1 40 6000 10% 5.0 40 6000 10% 3.5 40 7.8 40 Estimated in Equations (15) and (16). embankment, respectively (mb ¼ me ¼ 3 in this case study), and Rrun and Rtl are the economic loss associated with running vehicles on detour and monetary value of the time loss for users traveling though the detour and damaged link at a given damage state, respectively. In addition, Rrun and Rtl depend on the link status LS listed in Table 3 (Dong et al., 2014): Rrun ¼ ( tIL X i¼1 CRun;car 5 X PðLS ¼ lÞ ) l¼1 T T þ CRun;truck Dld ADTDði; lÞ 1 100 100 ( tIL X (15) T T cAW Ocar 1 þ cATC OTruck 100 100 i¼1 i¼1 ) Dld ll ll þ ADTEði; lÞ ADTDði; lÞ S SD S0 5 X Rtl ¼ PðLS ¼ lÞ Figure 35. An example of a temporary bridge using precast girder, column and foundation. (16) where P(LS ¼ l) is the probability that the link is in status of l (l¼ 1, 2, … , 5) listed in Table 3, tIL is the time interval until all structures in the investigated link reaches full functionality, CRun,car and CRun,truck are the costs for running cars and trucks per unit length, respectively, Dld is the length of the detour, ADTD (i, l) is the average daily traffic to detour at time i given LS¼l; T is the average daily truck traffic ratio, cAW and cATC are the wage per hour and compensation per hour, respectively, ADTE (i, l) is the average daily traffic remaining on the damaged link at time i given LS ¼ l; Ocar and OTruck are the average vehicle occupancies for cars and trucks, respectively, ll is the link length, S0 and STRUCTURE AND INFRASTRUCTURE ENGINEERING 45 Figure 36. An example of flowchart managing the debris generated by the anticipated Nankai Trough earthquake. SD are the average speed on the intact link and damaged link, respectively and S is the average detour speed. The expected full recovery time FRT is estimated as: FRT ¼ maxfT1b ; T2b ; . . . ; Tnb ; T1e ; T2e ; . . . ; Tne g (17) where Tib ¼ mb X pfi;b DS ¼ dsj CFRT;dsj;b ði ¼ 1; 2; . . . ; nb Þ (18) pfi;e DS ¼ dsj CFRT;dsj;e ði ¼ 1; 2; . . . ; ne Þ (19) j¼1 Tie ¼ me X j¼1 CFRT;dsj;b and CFRT;dsj;e are the recovery times associated with a given damage state of bridge and embankment, respectively. In this case study, the expected economic loss and full recovery time are estimated by Equations (8)–(19), and parameters associated with the consequence evaluations including damage index BDI and EDI of bridge and embankment listed in Table 2, relationship between link damage state and traffic-carrying capacity and free-flow speed given in Table 3, recovery time of each network component from a damage state listed in Table 4, information on link and traffic at Towns A and B provided in Tables 5 and 6, respectively, and direct and indirect cost information provided by Shinoda, Miyata, Yonezawa and Hironaka (2010); Shoji, Fujino and Abe (1997) and Ministry of Land, Infrastructure, Transport and Tourism in Japan (2008). Figure 34 illustrates the expected economic loss and days necessary to be fully recovered from the event of all links at the Towns A and B. The bridges and embankments belonging to Link 1 at both Towns A and B have higher failure probabilities, resulting in higher economic loss and larger days necessary to be fully recovered. In addition, because of higher seismic and tsunami hazards, and larger daily traffic at the Town A, the expected economic loss and FRT at the Town A are larger than those at the Town B. Reliability and risk approaches are useful to identify the dominant hazard and most vulnerable structure, and to make the decision on the priority for upgrade and/or repair actions. Hypothetical bridges and embankments were used in this case study. As shown in Figure 32, it was assumed that their fragility curves shift right compared with the structures designed according to the old design specification (Akiyama et al., 2014). However, the probabilities associated with the complete damage state are extremely large given the occurrence of the Nankai Trough earthquake. Constructing or retrofitting all structures with high-performance requirements 46 M. AKIYAMA ET AL. that prevent any damage or failure due to strong ground motion and giant tsunami caused by the anticipated Nankai Trough earthquake would be too expensive and impractical. Before the occurrence of Nankai Trough earthquake, structural engineers in Japan have to contribute to resilience and sustainability considering the very high failure probability of individual structures in the region where the effects of both seismic shaking and the tsunami waves would be very intense. Recently, in very populated urban centres and a critical network location an ABC methodology which combines durable materials and low-damage technology has been developed for minimising the traffic disruption. Although there have been several reports on seismic damage resistant technology for ABC (El-Bahey & Bruneau, 2012; Mehrsoroush & Saiidi, 2016; Palermo & Mashal, 2012; Varela & Saiidi, 2017), ABC technology taking into consideration the situation after the catastrophic event has to be developed for enhancing the resilience. Using precast members as structural elements is the integral part of ABC. Making precast element lighter, providing constructible beam-column and column-foundation connections and assembling the elements without heavyconstruction-equipment are the primary challenge for ABC in the affected regions. Figure 35 presents an example of a temporary bridge using precast girder, column and foundations. As already mentioned, it is very important before the occurrence of the anticipated Nankai Trough earthquake to establish the procedure of how the estimated debris generated by the disaster will be managed. In the case study, the consequences in Equation (12) were associated with the monetary loss and recovery time. Based on the estimated amount of debris in the affected regions under seismic and tsunami hazards, a procedure for optimising the localisation of processing sites, selection of processing capacities, and debris flow decisions encompassing collection, transportation and disposal with balancing the cost and duration of the operations is needed (Lorca et al., 2017). Figure 36 depicts an example of flowchart managing the debris generated by the anticipated Nankai Trough earthquake. shock and subsequent cascading hazard events. A risk-based decision-making approach at the network-level is necessary for identifying the dominant hazard and vulnerable structures requiring strengthening and retrofit. After a catastrophic event, the functionality of transportation networks can be significantly affected, leading to disastrous effects on the economy. To quantify the promptness of the restoration, it has become customary to use the concept of resilience. In addition, the economic, environmental and social impacts of disaster debris need to be investigated in terms of sustainability. Consequences associated with the resilience and sustainability must be studied and implemented into the risk estimation of bridge network under multiple hazards. Life-cycle design and assessment methodology can encompass all the key concepts such as risk, resilience, sustainability and multiple hazards learning from the past disaster lessons. Finally, the concepts and methods presented are illustrated on both single bridges and bridge networks with an emphasis on earthquake, tsunami and continuous deterioration. Further research is needed to enhance the framework for estimating the reliability and risk of bridges under multiple hazards. Specifically, the integration of bridge performance under multiple independent or interacting hazards in a comprehensive life-cycle infrastructure network in terms of performance, management and optimisation under uncertainty (Frangopol, 2011; Frangopol & Soliman, 2016) must be investigated. Acknowledgments The authors express sincere appreciation to Dr. Masayuki Yoshimi, National Institute of Advanced Industrial Science and Technology of Japan, for his suggestions related to seismic fault parameters. The authors also thank Prof. Shunichi Koshimura at Tohoku University for many suggestions on the topic of tsunami propagation analysis. Special appreciation is extended to Dr. Sopokhem Lim and Mr. Kengo Nanami at Waseda University. Disclosure statement 6. Conclusions This article presents an overview of the progress of structural design methodology from the deterministic ASD method toward the life-cycle-based design and assessment of bridges and bridge networks under multiple hazards. Field investigations after recent large earthquakes in Japan confirmed that several bridges were severely damaged and collapsed not only due to the earthquake, as an independent hazard, but also due to the subsequent tsunami, landslide or fault displacement. Material corrosion caused further damage to structures under earthquake excitations. In addition, the collapse of as-built bridges over highways prevented the traffic passage. Even if the bridge has no damage during the seismic event, damage to embankment can substantially decrease the functionality of the post-disaster road network. A probabilistic life-cycle framework for quantifying the functionality loss of road networks involving bridges and other road structures is needed for the occurrence of a main No potential conflict of interest was reported by the authors. Funding This work was financially supported by JSPS KAKENHI [Grant Number JP 16H02357, 16KK0152 and 16H04403], the Institute for Research on Safety and Security of Greater Tokyo, US National Science Foundation Award [CMMI-1537926] and the US Federal Highway Administration Cooperative Agreement Award [DTFH61-07H-00040]. The opinions and conclusions presented in this paper are only those of the authors. References Akg€ ul F., & Frangopol, D. M. (2003). Rating and reliability of existing bridges in a network. Journal of Bridge Engineering, 8(6), 383–392. doi:10.1061/(ASCE)1084-0702(2003)8:6(383) Akiyama, M., Abe, S., Aoki, N., & Suzuki, M. (2012). Flexural test of precast high-strength reinforced concrete pile prestressed with unbonded bars arranged at the center of the cross-section. STRUCTURE AND INFRASTRUCTURE ENGINEERING Engineering Structures, 34(1), 259–270. doi:10.1016/ j.engstruct.2011.09.007 Akiyama, M., & Frangopol, D. M. (2012b). Lessons from the 2011 Great East Japan earthquake: Emphasis on life-cycle structural performance. Paper presented at the Proceedings of the Third International Symposium on Life-Cycle Civil Engineering (A. Strauss. D. M. Frangopol, K. Bergmeister eds.), Vienna, Austria, October 3–6, 2012, CRC Press, 13–20. Akiyama, M., & Frangopol, D. M. (2013). Life-cycle design of bridges under multiple hazards: Earthquake, tsunami, and continuous deterioration. Paper presented at the Proceedings of the Eleventh International Conference on Structural Safety and Reliability, ICOSSAR2013, New York, NY, USA, June 16–20, 2013; In Safety, Reliability, Risk, and Life-Cycle Performance of Structures and Infrastructures, G. Deodatis, B.R. Ellingwood, and D. M. Frangopol, eds., CRC Press, Taylor & Francis Group, Boca Raton, London, New York, Leiden, 2013, 3–4, and full paper on USB stick, Taylor and Francis Group, London, 2014, 3–16. Akiyama, M., & Frangopol, D. M. (2014). Long-term seismic performance of RC structures in an aggressive environment: Emphasis on bridge piers. Structure and Infrastructure Engineering, 10, 865–879. doi:10.1080/15732479.2012.761246 Akiyama, M., & Frangopol, D. M. (2016). Probabilistic approach for road network retrofitting prioritization under seismic and tsunami hazards. Paper presented at the 5th International Symposium on Reliability Engineering and Risk Management, Seoul, South Korea. Akiyama, M., Frangopol, D. M., Arai, M., & Koshimura, S. (2013). Reliability of bridges under tsunami hazards: Emphasis on the 2011 Tohoku-oki earthquake. Earthquake Spectra, 29, S295–S314. doi: 10.1193/1.4000112 Akiyama, M., Frangopol, D. M., & Matsuzaki, H. (2011). Life-cycle reliability of RC bridge piers under seismic and airborne chloride hazards. Earthquake Engineering & Structural Dynamics, 40, 1671–1687. doi:10.1002/eqe.1108 Akiyama, M., Frangopol, D. M., & Mizuno, K. (2014). Performance analysis of Tohoku-Shinkansen viaducts affected by the 2011 Great East Japan earthquake. Structure and Infrastructure Engineering, 10, 1228–1247. doi:10.1080/15732479.2013.806559 Akiyama, M., Frangopol, D. M., & Suzuki, M. (2012). Integration of the effects of airborne chlorides into reliability-based durability design of reinforced concrete structures in a marine environment. Structure and Infrastructure Engineering, 8, 125–134. doi:10.1080/ 15732470903363313 Akiyama, M., Frangopol, D. M., & Takenaka, K. (2017). Reliabilitybased durability design and service life assessment of reinforced concrete deck slab of jetty structures. Structure and Infrastructure Engineering, 13, 468–477. doi:10.1080/15732479.2016.1164725 Akiyama, M., Frangopol, D. M., & Yoshida, I. (2010). Time-dependent reliability analysis of existing RC structures in marine environment using hazard associated with airborne chlorides. Engineering Structures, 32, 3768–3779. doi:10.1016/j.engstruct.2010.08.021 Akiyama, M., Matsuzaki, H., Dang, H. T., & Suzuki, M. (2012). Reliability-based capacity design for reinforced concrete bridge structures. Structure and Infrastructure Engineering, 8, 1096–1107. doi:10.1080/15732479.2010.507707 Alipour, A., & Shafei, B. (2016). Seismic resilience of transportation networks with deteriorating components. Journal of Structural Engineering, 142, C4015015. doi:10.1061/(ASCE)ST.1943541X.0001399 Alipour, A., Shafei, B., & Shinozuka, M. (2011). Performance evaluation of deteriorating highway bridges located in high seismic areas. Journal of Bridge Engineering, 16, 597–611. doi:10.1061/ (ASCE)BE.1943-5592.0000197 Alipour, A., Shafei, B., & Shinozuka, M. (2013). Reliability-based calibration of load and resistance factors for design of RC bridges under multiple extreme events: Scour and earthquake. Journal of Bridge Engineering, 18, 362–371. doi:10.1061/(ASCE)BE.19435592.0000369 Amadio, C., Fragiacomo, M., & Rajgelj, S. (2003). The effects of repeated earthquake ground motions on the non-linear response of 47 SDOF systems. Earthquake Engineering and Structural Dynamics, 32, 291–308. doi: 10.1002/eqe.225 Andrade, C., Alonso, C., & Sarrıa, J. (2002). Corrosion rate evolution in concrete structures exposed to the atmosphere. Cement & Concrete Composites, 24, 55–64. doi:10.1016/S0958-9465(01)00026-9 Asprone, D., Jalayer, F., Prota, A., & Manfredi, G. (2010). Proposal of a probabilistic model for multi-hazard risk assessment of structures in seismic zones subjected to blast for the limit state of collapse. Structural Safety, 32, 25–34. doi:10.1016/j.strusafe.2009.04.002 Attary, N., Unnikrishnan, V. U., van de Lindt, J. W., Cox, D. T., & Barbosa, A. R. (2017). Performance-based tsunami engineering methodology for risk assessment of structures. Engineering Structures, 141, 676–686. doi:10.1016/j.engstruct.2017.03.071 Banerjee, S., & Prasad, G. G. (2013). Seismic risk assessment of reinforced concrete bridges in flood-prone regions. Structure and Infrastructure Engineering, 9, 952–968. doi:10.1080/ 15732479.2011.649292 Barone, G., & Frangopol, D. M. (2014). Reliability, risk and lifetime distributions as performance indicators for life-cycle maintenance of deteriorating structures. Reliability Engineering & System Safety, 123, 21–37. doi:10.1016/j.ress.2013.09.013 Bastidas-Arteaga, E., & Stewart, M. G. (2015). Damage risks and economic assessment of climate adaption strategies for design of new concrete structures subjected to chloride-induced corrosion. Structural Safety, 52, 40–53. doi:10.1016/j.strusafe.2014.10.005 Biondini, F., Frangopol, D. M., & Restelli, S. (2008). On structural robustness, redundancy and static indeterminacy. Proceedings of the ASCE Structures Congress, Vancouver, Canada, April 24-26, 2008; in Structures 2008: Crossing Borders, ASCE, 2008, 10 pages on CDROM. Biondini, F., Camnasio, E., & Palermo, A. (2014). Lifetime seismic performance of concrete bridges exposed to corrosion. Structure and Infrastructure Engineering, 10, 880–900. doi:10.1080/ 15732479.2012.761248 Biondini, F., Camnasio, E., & Titi, A. (2015). Seismic resilience of concrete structure under corrosion. Earthquake Engineering & Structural Dynamics, 44, 2445–2466. doi:10.1002/eqe.2591 Biondini, F., & Frangopol, D. M. (2016). Life-cycle performance of deteriorating structural systems under uncertainty: Review. Journal of Structural Engineering, 142, F4016001. doi:10.1061/ (ASCE)ST.1943-541X.0001544 Biondini, F., & Frangopol, D. M. (2018). Life-cycle performance of civil structure and infrastructure systems: Survey. Journal of Structural Engineering, 144, 06017008. doi:10.1061/(ASCE)ST.1943541X.0001923 Bocchini, P., & Frangopol, D. M. (2011). A stochastic computational framework for the joint transportation network fragility analysis and traffic flow distribution under extreme events. Probabilistic Engineering Mechanics, 26 (2), 182–193. doi:10.1016/ j.probengmech.2010.11.007 Bocchini, P., & Frangopol, D. M. (2012a). Optimal resilience- and cost-based postdisaster intervention prioritization for bridges along a highway segment. Journal of Bridge Engineering, 17, 117–129. doi: 10.1061/(ASCE)BE.1943-5592.0000201 Bocchini, P., & Frangopol, D. M. (2012b). Restoration of bridge networks after an earthquake: Multi-criteria intervention optimization. Earthquake Spectra, 28, 426–455. doi:10.1193/1.4000019 Bocchini, P., Frangopol, D. M., & Deodatis, G. (2011). A random field based technique for the efficiency enhancement of bridge network life-cycle analysis under uncertainty. Engineering Structures, 33, 3208–3217. doi:10.1016/j.engstruct.2011.08.024 Bocchini, P., Frangopol, D. M., Ummenhofer, T., & Zinke, T. (2014). Resilience and sustainability of civil infrastructure: Toward a unified approach. Journal of Infrastructure Systems, 20, 04014004. doi: 10.1061/(ASCE)IS.1943-555X.0000177 Brito, M. B., Ishibashi, H., & Akiyama, M. (2018). Shaking table tests of a reinforced concrete bridge pier with a low-cost sliding pendulum system. Earthquake Engineering and Structural Dynamics, 48, 366–386. doi:10.1002/eqe.3140 48 M. AKIYAMA ET AL. Brown, C., Milke, M., & Seville, E. (2011). Disaster waste management: A review article. Waste Management, 31(6), 1085–1098. 10.1016/ j.wasman.2011.01.027 Bruneau, M., Chang, S. E., Eguchi, R. T., Lee, G. C., O’Rourke, T. D., , … Reinhorn Winterfeldt, D. (2003). A framework to quantitatively assess and enhance the seismic resilience of communities. Earthquake Spectra, 19, 733–752. doi:10.1193/1.1623497 Cabinet Office, Government of Japan. (2012a). Investigative commission on the modelling of giant earthquake caused by Nankai Trough: Modelling of seismic fault. (in Japanese) Retrieved from http://www.bousai.go.jp/jishin/nankai/model/pdf/20120829_2nd_ report05.pdf Cabinet Office, Government of Japan. (2012b). Investigative commission on the modelling of giant earthquake caused by Nankai Trough: Modelling of tsunami fault. (in Japanese) Retrieved from http://www.bousai.go.jp/jishin/nankai/model/pdf/20120829_2nd_ report01.pdf Central Disaster Management Council. (2003). Conference Document 16th expert examination committee on Tonankai, and Nankai Earthquake. (in Japanese) Chandrasekaran, S., & Banerjee, S. (2016). Retrofit optimization for resilience enhancement of bridges under multiple scenario. Journal of Structural Engineering, 142, C4015012. doi:10.1061/ (ASCE)ST.1943-541X.0001396 Chang, S. E., Shinozuka, M., & Moore, J. E. (2000). Probabilistic earthquake scenarios: Extending risk analysis methodologies to spatially distributed systems. Earthquake Spectra, 16, 557–572. doi:10.1193/ 1.1586127 Chulahwat, A., & Mahmoud, H. (2017). A combinational optimization approach for multi-hazard design of building systems with suspended floor slabs under wind and seismic hazards. Engineering Structures, 137, 268–284. doi:10.1016/j.engstruct.2017.01.074 Dec o, A., Bocchini, P., & Frangopol, D. M. (2013). A probabilistic approach for the prediction of seismic resilience of bridges. Earthquake Engineering & Structural Dynamics, 42, 1469–1487. doi: 10.1002/eqe.2282 Domaneschi, M., & Martinelli, L. (2016). Earthquake-resilience-based control solutions for the extended benchmark cable-stayed bridge. Journal of Structural Engineering, 142, C4015009. doi:10.1061/ (ASCE)ST.1943-541X.0001392 Dong, Y., & Frangopol, D. M. (2015). Risk and resilience assessment of bridges under mainshock and aftershocks incorporating uncertainties. Engineering Structures, 83, 198–208. doi:10.1016/j.engstruct.2014.10.050 Dong, Y., & Frangopol, D. M. (2016). Probabilistic time-dependent multihazard life-cycle assessment and resilience of bridges considering climate change. Journal of Performance of Constructed Facilities, 30, 04016034. doi:10.1061/(ASCE)CF.1943-5509.0000883 Dong, Y., & Frangopol, D. M. (2017). Probabilistic assessment of an interdependent healthcare-bridge network system under seismic hazard. Structure and Infrastructure Engineering, 13, 160–170. doi: 10.1080/15732479.2016.1198399 Dong, Y., Frangopol, D. M., & Saydam, D. (2013). Time-variant sustainability assessment of seismically vulnerable bridges subjected to multiple hazards. Earthquake Engineering & Structural Dynamics, 42, 1451–1467. doi:10.1002/eqe.2281 Dong, Y., Frangopol, D. M., & Saydam, D. (2014). Pre-earthquake multi-objective probabilistic retrofit optimization of bridge networks based on sustainability. Journal of Bridge Engineering, 19, 04014018. doi:10.1061/(ASCE)BE.1943-5592.0000586 Eatherton, M. R., & Hajjar, J. F. (2011). Residual drifts of self-centering systems including effects of ambient building resistance. Earthquake Spectra, 27, 719–744. doi:10.1193/1.3605318 Echevarria, A., Zaghi, A. E., Christenson, R., & Accorsi, M. (2016). CFFT bridge columns for multihazard resilience. Journal of Structural Engineering, 142, C4015002. doi:10.1061/(ASCE)ST.1943541X.0001292 El-Bahey, S., & Bruneau, M. (2012). Bridge piers with structural fuses and bi-steel columns. I: Experimental testing. Journal of Bridge Engineering, 17, 25–35. doi:10.1061/(ASCE)BE.1943-5592.0000234 Ellingwood, B. R. (2006). Mitigating risk from abnormal loads and progressive collapse. Journal of Performance of Constructed Facilities, 20, 315–323. doi:10.1061/(ASCE)0887-3828(2006)20:4(315) Ellingwood, B. R. (2007). Strategies for mitigating risk to buildings from abnormal load events. International Journal of Risk Assessment and Management, 7, 828–845. doi:10.1504/IJRAM.2007.014662 Estes, A. C., & Frangopol, D. M. (2001). Bridge lifetime system reliability under multiple limit states. Journal of Bridge Engineering, 6, 523–528. doi:10.1061/(ASCE)1084-0702(2001)6:6(523) Esteva, L., Campos, D., & Dıaz-L opez, O. (2011). Life-cycle optimization in earthquake engineering. Structure and Infrastructure Engineering, 7, 33–49. doi:10.1080/15732471003588270 Esteva, L., Dıaz-L opez, O. J., Vasquez, A., & Le on, J. A. (2016). Structural damage accumulation and control for life cycle optimum seismic performance of buildings. Structure and Infrastructure Engineering, 12, 848–860. doi:10.1080/15732479.2015.1064967 FEMA. (2016). Guidance for flood risk analysis and mapping: Coastal water levels. Guidance Document 67, Federal Emergency Management Agency. https://www.fema.gov/media-library-data/ 1472001436394-84b6440ba15f6af5723869b3443f89c4/Coastal_Water_ Levels_G FEMA. (2007). Public assistance: Debris management system. FEMA325, Federal Emergency Management Agency. https://www.fema. gov/pdf/government/grant/pa/demagde.pdf Frangopol, D.M., & Estes, A.C. (1997). Lifetime bridge maintenance strategies based on system reliability. Structural Engineering International, IABSE, 7(3), 193–198. doi:10.2749/101686697780494662 Frangopol, D. M. (2011). Life-cycle performance, management, and optimization of structural systems under uncertainty: Accomplishments and challenges. Structure and Infrastructure Engineering, 7, 389–413. doi:10.1080/15732471003594427 Frangopol, D. M., Dong, Y., & Sabatino, S. (2017). Bridge life-cycle performance and cost: Analysis, prediction, optimization and decision-making. Structure and Infrastructure Engineering, 13, 1239–1257. doi:10.1080/15732479.2016.1267772 Frangopol, D. M., & Kim, S. (2014). Life-cycle analysis and optimization. In W.-F. Chen and L. Duan (Eds.), Chapter 18 in Bridge Engineering Handbook: Construction and Maintenance (2nd ed., Vol. 5, pp. 537–566). Boca Raton: CRC Press. Frangopol, D. M., & Saydam, D. (2014). Structural performance indicators for bridges. In W.-F. Chen & L. Duan (Eds.). Chapter 9 in Bridge Engineering Handbook: Fundamentals (2nd ed., Vol. 1, pp. 185–205). Boca Raton: CRC Press/Taylor & Francis Group. Frangopol, D. M., & Soliman, M. (2016). Life-cycle of structural systems: Recent achievements and future directions. Structure and Infrastructure Engineering, 12, 1–20. doi:10.1080/ 15732479.2014.999794 Ghosn, M., Moses, F., & Frangopol, D.M. (2010). Redundancy and robustness of highway bridge superstructures and substructures. Structure and Infrastructure Engineering, 6(1-2), 257–278. doi: 10.1080/15732470802664498 Ghosn, G., Duenas-Osorio, L., Frangopol, D. M., McAllister, T. P., Bocchini, P., Manuel, L., … Tsiatas, G. (2016). Performance indicators for structural systems and infrastructure networks. Journal of Structural Engineering, 142, F4016003. doi:10.1061/(ASCE)ST.1943541X.0001542 Gidaris, I., Padgett, J. E., Barbosa, A. R., Chen, S., Cox, D., Webb, B., & Cerato, A. (2017). Multiple-hazard fragility and restoration models of highway bridges for regional risk and resilience assessment in the United States: State-of-the-art review. Journal of Structural Engineering, 143, 04016188. doi:10.1061/(ASCE)ST.1943-541X.0001672 Goto, C., Ogawa, Y., Shuto, N., & Imamura, F. (1997). Numerical method of tsunami simulation with the leap-frog scheme. IUGG/IOC Time Project. UNESCO. Guo, A., Liu, Z., Li, S., & Li, H. (2017). Seismic performance assessment of highway bridge networks considering post-disaster traffic demand of a transportation system in emergency conditions. Structure and Infrastructure Engineering, 13, 1523–1537. doi: 10.1080/15732479.2017.1299770 STRUCTURE AND INFRASTRUCTURE ENGINEERING Honda, R., Akiyama, M., Nozu, A., Takahashi, Y., Kataoka, S., & Murono, Y. (2017). Seismic design for “anti-catastrophe”: A study on the implementation as design codes. Journal of JSCE, 5, 346–356. Honjo, Y., & Otake, Y. (2013). Statistical estimation error evaluation theory of local averages of a geotechnical parameter. In G. Deodatis, B. R. Ellingwood, and D. M. Frangopol (Eds.) Safety reliability risk and life-cycle performance of structure and infrastructure (1987–1994). London: CRC Press. Inui, T., Yasutaka, T., Endo, K., & Katsumi, T. (2012). Geo-environmental issues induced by the 2011 off the Pacific Coast of Tohoku Earthquake and tsunami. Soils and Foundations, 52, 856–871. doi: 10.1016/j.sandf.2012.11.008 Iqbal, A., Fragiacomo, M., Pampanin, S., & Buchanan, A. (2018). Seismic resilience of plywood-coupled LVL wall panels. Engineering Structures, 167, 750–759. doi:10.1016/j.engstruct.2017.09.053 ISO13824. (2009). Based for design of structures – General principles on risk assessment of systems involving structures. Jalayer, F., Asprone, D., Prota, A., & Manfredi, G. (2011). A decision support system for post-earthquake reliability assessment of structures subjected to aftershocks: An application to L’Aquila earthquake. Bulletin of Earthquake Engineering, 9, 997–1014. doi:10.1007/ s10518-010-9230-6 Japan Road Association. (1990). Design specification for highway bridges. Part V: Seismic design. Tokyo, Japan: Maruzen. Kameshwar, S., & Padgett, J. E. (2014). Multi-hazard risk assessment of highway bridges subjected to earthquake and hurricane hazards. Engineering Structures, 78, 154–166. doi:10.1016/j.engstruct.2014.05.016 Kawashima, K. (2000). Seismic design and retrofit of bridges. Paper presented at the Proceedings of 12th World Conference on Earthquake Engineering (WCEE), Keynote paper. Auckland, New Zealand. Kim, J., Deshmukh, A., & Hastak, M. (2018). A framework for assessing the resilience of a disaster debris management system. International Journal of Disaster Risk Reduction, 28, 674–687. doi: 10.1016/j.ijdrr.2018.01.028 Kurtz, N., Song, J., & Gardoni, P. (2016). Seismic reliability analysis of deteriorating representative U.S. west coast bridge transportation networks. Journal of Structural Engineering, 142, C4015010. doi: 10.1061/(ASCE)ST.1943-541X.0001368 Lehman, D. E., Kuder, K. G., Gunnarrson, A. K., Roeder, C. W., & Berman, J. W. (2015). Circular concrete-filled tubes for improved sustainability and seismic resilience. Journal of Structural Engineering, 141, B4014008. doi:10.1061/(ASCE)ST.1943541X.0001103 Li, Q., & Ellingwood, B. R. (2007). Performance evaluation and damage assessment of steel frame buildings under main shock-aftershock earthquake sequences. Earthquake Engineering & Structural Dynamics, 36, 405–427. doi:10.1002/eqe.667 Li, Q., Wang, C., & Ellingwood, B. R. (2015). Time-dependent reliability of aging structures in the presence of non-stationary loads and degradation. Structural Safety, 52, 132–141. doi:10.1016/ j.strusafe.2014.10.003 Liu, M., & Frangopol, D. M. (2005). Bridge annual maintenance prioritization under uncertainty by multiobjective combinatorial optimization. Computer Aided Civil and Infrastructure Engineering, 20(5), 343–353. doi:10.1111/j.1467-8667.2005.00401.x Lim, S., Akiyama, M., & Frangopol, D. M. (2016). Assessment of the structural performance of corrosion-affected RC members based on experimental study and probabilistic modeling. Engineering Structures, 127, 189–205. doi:10.1016/j.engstruct.2016.08.040 Lim, S., Akiyama, M., Frangopol, D. M., & Jiang, H. (2017). Experimental investigation of the spatial variability of the steel weight loss and corrosion cracking of RC members: Novel X-ray and digital image processing techniques. Structure and Infrastructure Engineering, 13, 118–134. doi:10.1080/ 15732479.2016.1198397 Liu, M., Frangopol, D. M., & Kim, S. (2009). Bridge safety evaluation based on monitored live load effects. Journal of Bridge Engineering, 14, 257–269. doi:10.1061/(ASCE)1084-0702(2009)14:4(257) 49 Loli, M., Knappett, J. A., Brown, M. J., Anastasopoulos, I., & Gazetas, G. (2014). Centrifuge modeling of rocking-isolated inelastic RC bridge piers. Earthquake Engineering & Structural Dynamics, 43, 2341–2359. doi:10.1002/eqe.2451 Çelik, M., Ergun, O., € & Keskinocak, P. (2017). An optimizaLorca, A., tion-based decision-support tool for post-disaster debris operations. Production and Operations Management, 26, 1076–1091. doi: 10.1111/poms.12643 Lounis, Z., & McAllister, T. P. (2016). Risk-based decision making for sustainable and resilient infrastructure systems. Journal of Structural Engineering, 142, F4016005. doi:10.1061/(ASCE)ST.1943541X.0001545 Nogami, Y., Murono, Y., & Sato, T. (2008). Nonlinear hysteresis model of RC members considering strength degradation by cyclic loading. RTRI Report, 22, 17–22. (in Japanese) Mackie, K. R., Kucukvar, M., Tatari, O., & Elgamal, A. (2016). Sustainability metrics for performance-based seismic bridge response. Journal of Structural Engineering, 142, C4015001. doi: 10.1061/(ASCE)ST.1943-541X.0001287 Mehrsoroush, A., & Saiidi, M. S. (2016). Cyclic response of precast bridge piers with novel column-base pipe pins and pocket cap beam connections. Journal of Bridge Engineering, 21, 04015080. doi: 10.1061/(ASCE)BE.1943-5592.0000833 Ministry of Land, Infrastructure, Transport and Tourism in Japan. (2008). Guideline on cost and benefit analysis, Road Bureau. (in Japanese). http://www.mlit.go.jp/road/ir/hyouka/plcy/kijun/ben-eki_ h30_2.pdf Mitoulis, S. A., & Rodriguez, J. R. (2017). Seismic performance of novel resilient hinges for columns and application on irregular bridges. Journal of Bridge Engineering, 22, 04016114. doi:10.1061/ (ASCE)BE.1943-5592.0000980 Miyamoto, S., Akiyama, M., & Frangopol, D. M. (2015). Life-cycle reliability estimation of large-scale reinforced concrete slabs in a marine environment considering spatial variability. Paper presented at the Proceedings of Symposium on Reliability of Engineering System, SRES’2015, Hangzhou, China. Nazari, N., van de Lindt, J. W., & Li, Y. (2015). Quantifying changes in structural design needed to account for aftershock hazard. Journal of Structural Engineering, 141, 04015035. doi:10.1061/ (ASCE)ST.1943-541X.0001280 Okasha, N. M., & Frangopol, D. M. (2011). Computational platform for the integrated life-cycle management of highway bridges. Engineering Structures, 33, 2145–2153. doi:10.1016/ j.engstruct.2011.03.005 Padgett, J. E., Dennemann, K., & Ghosh, J. (2010). Risk-based seismic life-cycle cost-benefit (LCC-B) analysis for bridge retrofit assessment. Structural Safety, 32, 165–173. doi:10.1016/ j.strusafe.2009.10.003 Palermo, A., & Mashal, M. (2012). Accelerated bridge construction (ABC) and seismic damage resistant technology: A New Zealand challenge. Bulletin of the New Zealand Society for Earthquake Engineering, 45, 123–133. Papakonstantinou, K. G., & Shinozuka, M. (2013). Probabilistic model for steel corrosion in reinforced concrete structures of large dimensions considering crack effects. Engineering Structures, 57, 306–326. doi:10.1016/j.engstruct.2013.06.038 Polese, M., Ludovico, M. D., Prota, A., & Manfredi, G. (2013). Damage-dependent vulnerability curves for existing buildings. Earthquake Engineering & Structural Dynamics, 42, 853–870. doi: 10.1002/eqe.2249 Portugal-Pereira, J., & Lee, L. (2016). Economic and environmental benefits of waste-to-energy technologies for debris recovery in disaster-hit Northeast Japan. Journal of Cleaner Production, 112, 4419–4429. doi:10.1016/j.jclepro.2015.05.083 Rao, A. S., Lepech, M. D., & Kiremidjian, A. S. (2017a). Development of time-dependent fragility functions for deteriorating reinforced concrete bridge piers. Structure and Infrastructure Engineering, 13, 67–83. doi:10.1080/15732479.2016.1198401 Rao, A. S., Lepech, M. D., Kiremidjian, A. S., & Sun, X.-Y. (2017b). Simplified structural deterioration model for reinforced concrete 50 M. AKIYAMA ET AL. bridge piers under cyclic loading. Structure and Infrastructure Engineering, 13, 55–66. doi:10.1080/15732479.2016.1198402 Rodgers, G. W., Mander, J. B., Chase, J. G., & Dhakal, R. P. (2016). Beyond ductility: Parametric testing of a jointed rocking beam-column connection designed for damage avidance. Journal of Structural Engineering, 142, C4015006. doi:10.1061/(ASCE)ST.1943541X.0001318 Rokneddin, K., Ghosh, J., Duenas-Osorio, L., & Padgett, J. E. (2013). Bridge retrofit prioritization for ageing transportation networks subject to seismic hazards. Structure and Infrastructure Engineering, 9, 1050–1066. doi:10.1080/15732479.2011.654230 Sabatino, S., Frangopol, D.M., & Dong, Y. (2016). Life-cycle utilityinformed maintenance planning based on lifetime functions: Optimum balancing of cost, failure consequences, and performance benefit. Structure and Infrastructure Engineering, 12(7), 830–847. doi:10.1080/15732479.2015.1064968 Sanchez-Silva, M., Frangopol, D.M., Padgett, J., & Soliman, M. (2016). “Maintenance and operation of infrastructure systems: A review,” Journal of Structural Engineering, 142(9), F4016004. doi:10.1061/ (ASCE)ST.1943-541X.0001543 Saydam, D., Bocchini, P., & Frangopol, D. M. (2013). Time-dependent risk associated with deterioration of highway bridge networks. Engineering Structures, 54, 221–233. doi:10.1016/ j.engstruct.2013.04.009 Saydam, D., & Frangopol, D. M. (2011). Time-dependent performance indicators of damaged bridge superstructures. Engineering Structures, 33, 2458–2471. doi:10.1016/j.engstruct.2011.04.019 Shinoda, M., Miyata, Y., Yonezawa, T., & Hironaka, J. (2010). Seismic life cycle cost analysis of geosynthetics reinforced and unreinforced earth slope. Journal of International Geosynthetics Society, 25, 189–196. (in Japanese). doi:10.5030/jcigsjournal.25.189 Shoji, G., Fujino, Y., & Abe, M. (1997). Optimal allocation of earthquake-induced damage for elevated highway bridges. Proceedings of Japan Society of Civil Engineers, 563, 79–94. (in Japanese). doi: 10.2208/jscej.1997.563_79 Si, H., & Midorikawa, S. (1999). New attenuation relationships for peak ground acceleration and velocity considering effects of fault type and site condition. Journal of Structural and Construction Engineering, 523, 63–70. (in Japanese). doi:10.3130/aijs.64.63_2 Stergiou, E. C., & Kiremidjian, A. S. (2010). Risk assessment of transportation systems with network functionality losses. Structure and Infrastructure Engineering, 6, 111–125. doi:10.1080/ 15732470802663839 Stewart, M. G., Wang, X., & Nguyen, M. N. (2011). Climate change impact and risks of concrete infrastructure deterioration. Engineering Structures, 33, 1326–1337. doi:10.1016/ j.engstruct.2011.01.010 Stewart, M. G., Wang, X., & Nguyen, M. N. (2012). Climate change adaption of corrosion control of concrete infrastructure. Structural Safety, 35, 29–39. doi:10.1016/j.strusafe.2011.10.002 Torbol, M., & Shinozuka, M. (2014). The directionality effect in the seismic risk assessment of highway networks. Structure and Infrastructure Engineering, 10, 175–188. doi:10.1080/ 15732479.2012.716069 Unjoh, S. (2012). Tsunami damage to bridge structures in RikuzenTakada City and the emergency road network recovery actions. Paper presented at the Proceedings of the International Symposium on Engineering Lessons Learned from the 2011 Great East Japan Earthquake, Tokyo, Japan. Varela, S., & Saiidi, M. S. (2017). Resilience deconstructible columns for accelerated bridge construction in seismically active areas. Journal of Intelligent Material Systems and Structures, 28, 1751–1774. doi:10.1177/1045389X16679285 Yanweerasak, T., Akiyama, M., & Frangopol, D. M. (2016). Updating the seismic reliability of existing RC structures in a marine environment by incorporating the spatial steel corrosion distribution: Application to bridge piers. Journal of Bridge Engineering, 21, 04016031. doi:10.1061/(ASCE)BE.1943-5592.0000889 Yang, D. Y., & Frangopol, D.M. (2019a). Life-cycle management of deteriorating civil infrastructure considering resilience to lifetime hazards: A general approach based on renewal-reward processes. Reliability Engineering and System Safety, 183, 197–212. doi:10.1016/ j.ress.2018.11.016 Yang, D. Y., and Frangopol, D.M. (2019b). Societal risk assessment of transportation networks under uncertainties due to climate change and population growth. Structural Safety, 78, 33–47. doi:10.1016/ j.strusafe.2018.12.005 Yeo, G. L., & Cornell, C. A. (2005). Stochastic characterization and decision bases under time-dependent aftershock risk in performancebased earthquake engineering. California, USA: The John A. Blume Earthquake Engineering Center, Stanford University. Yilmaz, T., Banerjee, S., & Johnson, P. (2016). Performance of two real-life California bridges under regional natural hazards. Journal of Bridge Engineering, 21, 04015063. doi:10.1061/(ASCE)BE.19435592.0000827 Yooh, I.-S., Çopuroglu, O., & Park, K. B. (2007). Effect of global climatic change on carbonation progress of concrete. Atmospheric Environment, 41, 7274–7285. doi:10.1016/j.atmosenv.2007.05.028 Zanini, M. A., Faleschini, F., & Pellegrino, C. (2017). Probabilistic seismic risk forecasting of aging bridge networks. Engineering Structures, 136, 219–232. doi:10.1016/j.engstruct.2017.01.029 Zhang, W., Cai, C. S., & Pan, F. (2013). Fatigue reliability assessment for long-span bridges under combined dynamic loads from winds and vehicles. Journal of Bridge Engineering, 18, 735–747. doi: 10.1061/(ASCE)BE.1943-5592.0000411 Zhu, B., & Frangopol, D. M. (2012). Reliability, redundancy and risk as performance indicators of structural systems during their lifecycle. Engineering Structures, 41, 34–49. doi:10.1016/ j.engstruct.2012.03.029 Zhang, M., Song, H., Lim, S., Akiyama, M., & Frangopol, M. (2019). Reliability estimation of corroded RC structures based on spatial variability using experimental evidence, probabilistic analysis and finite element method. doi: 10.1016/j.engstruct.2019.04.085