1
CHAPTER 1
INTRODUCTION
1.1 Rationale
The Philippines is a country that is very vulnerable to natural disasters, such
as earthquakes and typhoons, due to its location in the Ring of Fire. There have
been numerous fatalities and massive building and infrastructure destruction as a
result of the destructive effects of these catastrophes. A number of large
earthquakes that occurred in recent years, including the 6.3 magnitude earthquake
in Mindanao in 2019 and the 7.2 magnitude earthquakes that struck Bohol in 2013,
Leyte in 2017, and Bohol in 2013, have brought attention to the urgent need for
thorough assessments of structural vulnerability and seismic risk in buildings.
The Philippine Institute of Volcanology and Seismology (Phivolcs) fault
finder has located a faultline close to the three-story Maghaway Elementary
School. The structural integrity of this school building must be evaluated in order
to safeguard the safety and wellbeing of its occupants, especially the pupils and
staff, given its closeness to a seismic danger.
In addition, the built environment suffers greatly as a result of the
approximately 15 typhoons that hit the Philippines each year. One eminent
instance is the typhoon Yolanda in 2013, which claimed over 6,000 lives and
destroyed a great deal of property and infrastructure. To ensure a building's
resilience in the face of natural catastrophes, the structural vulnerability of
structures like Maghaway Elementary School must be thoroughly assessed in light
of the combination of seismic and typhoon risks.
This study aims to perform a comprehensive assessment of the structural
vulnerability and seismic risk of the three-story Maghaway Elementary School
building in order to address this urgent concern. The researchers will conduct a
thorough investigation of the building's response to seismic forces using pushover
analysis, a commonly used tool for assessing structural integrity under seismic
loading. The study's objective is to locate potential weaknesses and offer
2
suggestions for essential structural upgrades by subjecting the building to realistic
seismic stress scenarios.
The results of this study will not only add to the body of knowledge already
available on structural vulnerability and seismic risk assessment, but will also offer
useful information for decision -makers in the fields of policy, engineering, and
architecture who are responsible for designing and retrofitting structures in
earthquake- and typhoon-prone areas. In the end, the objective is to protect lives
and well-being of the Filipino people, especially the vulnerable school -aged
children, and to strengthen the resilience of key infrastructure, including
educational buildings.
1.2 Conceptual Framework
INPUT
-Structural design
documents and
specifications
-Ground motion
data and seismic
hazard information
- Codes and
standards for
seismic design
and retrofitting
PROCESS
-Survey and
assess building's
structural
vulnerability
-Perform pushover
analysis and
simulation
-Evaluate
effectiveness of
wire mesh,
shotcrete, and
steel plating
bracing
OUTPUT
-Detailed
assessment report
on structural
vulnerability
-Retrofitting
recommendations
tailored to the
building
1.3 Problem Statement
This study aims to assess the structural vulnerability and seismic
performance of the 3-story Maghaway Elementary School building located on
Maghaway Road, Talisay City, Cebu. The primary objective is to answer the
following research questions:
3
1. What is the structural vulnerability and seismic risk of the 3-story
Maghaway Elementary School building in relation to potential
earthquakes, and what measures can be implemented to mitigate
further damage and ensure the safety of the occupants?
2. What are the potential risks and damage that the building may encounter
during seismic events, and how does its current structural vulnerability
contribute to these risks?
3. What retrofitting measures can be proposed to enhance the earthquake
resistance of the Three-Storey Maghaway Elementary School building,
taking into account its specific structural composition and the limitations
of wire mesh, shotcrete, and steel plating bracing methods?
1.4 Significance of the Study
The Philippine education system is widely recognized as one of the most
challenging in the world, with a literacy rate of 99.27% in the last decade according
to global data. Schools are essential safe spaces for students of all ages, providing
an environment that fosters academic discipline and learning. However, it is
common for these safe spaces to be vulnerable to structural damage during natural
disasters.
This study aims to contribute to the assessment of rigid buildings'
susceptibility to damage, especially for those with minimal knowledge and
understanding of structural vulnerability. The study will help advance the
recognition of the role that a building's condition plays in effective disaster risk
reduction management. Specifically, this research will benefit:
The country: The findings of this study will provide additional information
to public elementary schools administered by the government on soil, column, and
beam foundations, thereby locally embodying parallel layouts of plans and
schedules relevant to these structures.
The environment: The study will serve as a double backtracking from the
primary seismic evaluation succeeding the construction process being 4
4
developed. This presents detailed assistance in reducing secondary impacts such
as ground failures and surface faults induced by earthquakes.
The community: The study will function as a criterion directed to the
students, educators, and evacuators in integrating awareness of infrastructures
rational to their welfare and the building's scale of security.
Researchers: The study will yield an advantage in favor of meeting the
needs of further professional understanding of the deeper side of sci ence behind
a four-walled three-story building.
Future researchers: The study will act as a motivator to make extensive
significant operations in developing necessary methods of construction and
materials and promote extra findings as a basis for their references.
1.5 Scope and Limitation
This study is to determine the seismic vulnerability of the three-story
Maghaway Elementary School structure in Talisay, Cebu City, and to recommend
seismic retrofitting solutions to increase that structure's resilience to earthquakes.
The study's primary area of attention will be the school's main building, which is
made of plywood or concrete on the upper levels and concrete on the ground.
Within the school complex, no other buildings will be included in the assessment.
The study also attempts to assess three particular retrofitting techniques:
steel plate bracing, shotcrete, and wire mesh. To improve the seismic performance
of the building, these techniques will be looked at for both their viability and
effectiveness. The research will not, however, take into account other retrofitting
methods or creative strategies.
The limitations of this investigation must be acknowledged. The ThreeStorey Maghaway Elementary School building is the only structure covered by the
research, and other buildings on the school grounds are not included. Therefore,
it's possible that the conclusions and retrofitting advice won't apply to various
buildings or structures in various settings.
5
Second, additional potential solutions are not explored and the study
concentrates solely on the aforementioned retrofitting options. Innovative methods
might not be evaluated, while wire mesh, shotcrete, and steel plate bracing will all
be carefully explored.
Last but not least, due to time restrictions, th is study project will be carried
out within a specific time frame, from February 2023 to December 2023. This
means that some elements that might possibly affect the building's seismic
performance might not be fully taken into account or thoroughly explored.
Despite these drawbacks, the study's main objectives are to offer insightful
information on the three-story Maghaway Elementary School building's seismic
susceptibility and to suggest retrofitting solutions that are within the study's
established parameters. In order to address the seismic problems of the school
building, the research can ensure a realistic and open approach by accepting these
constraints.
1.6 Definition of terms
The researchers defined the following terminologies either operationally or
conceptually:
Ground motion - the movement of the ground during a seismic event, which can
cause damage to structures and buildings.
Seismic hazard - the potential of an area to experience a seismic event,
determined by factors such as the location and type of fault lines, soil type, and
proximity to bodies of water.
Seismic performance – the ability of a building or structure to withstand seismic
forces without considerable damage or collapse.
Seismic risk evaluation – the process of assessing the potential damage and
loss of life that may result from a seismic event.
Structural vulnerability - refers to the susceptibility of a building or structure to
damage or collapse during a seismic event due to poor design or construction.
6
CHAPTER 2
THEORETICAL BACKGROUND
Using earthquake engineering techniques like inter-story drift, seismic
capacity spectrum method, and STERA 3D software, this study aims to assess the
structural vulnerability and seismic resilience of a three-story building located in
Maghaway Elementary School. Nonlinear static analysis, also known as pushover
analysis, is used in this evaluation.
To evaluate the danger vulnerability, damage posed to a building during an
earthquake, structural vulnerability and seismic risk evaluation are used.
Assessing a building's structural integrity and identifying its flaws and
potential failure modes under seismic loads is known as structural vulnerability
evaluation. This assessment aids in determining which parts of the structure need
to be retrofitted or reinforced to increase its seismic resistance. On the other hand,
seismic risk evaluation determines the degree of seismic hazard posed to a
building by considering the possibility of earthquake-induced ground motion, as
well as the building's proximity to active faults, the state of the soil, and other
variables. It entails evaluating the likelihood of an earthquake occurring and the
strength of the resulting ground motion before calculating the possible loss and
damage that could happen to the building because of the earthquake. In
conjunction, these assessments offer crucial data that may be used to increase
buildings' seismic resilience and create practical earthquake risk reduction plans.
Capacity, demand, and performance are the three main principles in
pushover analysis. The capacity curve illustrates how a structure's ability to
tolerate
incremental lateral force determines its capacity. The biggest
displacement anticipated during an earthquake serves as a proxy for demand. By
comparing capacity and demand, as well as analyzing global and component
deformations, performance is assessed. The fixed distributions of lateral forces
used in traditional pushover methods are inaccurate for tall or asymmetrical
7
structures with strong vibration mode effects. Accuracy has been proposed to be
increased by using advanced pushover techniques including modal processes (12) and adaptive pushover (3-4). The adaptive pushover approach adjusts the
vertical force distribution at each increment to identify changes in the structure's
stiffness and dynamic characteristics beyond the elastic limit (Tarta and Pintea,
2012).
Method of modal combinations for pushover analysis (vertical variation for applied
forces):
𝐹𝑖,𝑗 = ∑ 𝛼𝑗 Γ𝑗 𝑚𝑖 𝜙𝑗 𝑆𝑎𝑗 (𝜁𝑗 𝑇𝑗 )
(1)
𝑇
Γ𝑗 = (
[𝜙𝑗 ] [𝑚]{𝑖 }
𝑇
[𝜙𝑗 ] [𝑚][𝜙𝑗 ]
)
(2)
The modal procedures technique necessitates numerous analyses using various
modal load patterns to increase pushover analysis accuracy. Following that, a
range of demand values is created by considering the peak demands at each story
level. To put it simply, this method entails studying the structure using various load
patterns, determining the maximum demand at each level, and then creating an
overall demand envelope.
According to the adaptive pushover approach, the lateral load distribution is
updated at each stage of the analysis based on the participation factors and modal
shapes obtained through eigenvalue analysis. This multimodal approach
considers the softening of the structure and the alteration of inertia forces brought
on by spectrum amplification. A force distribution or deformation profile can be
used to load the structure, and spectral amplification can be considered by
employing a design spectrum or a reaction spectrum from a seismic accelerogram.
The vertical force distribution is computed at each stage of the analysis using the
force-based scaling adaptive pushover approach (Tarta & Pintea, 2012).
At each stage of the analysis, the following adaptive pushover vertical force
distribution with forced-based scaling is calculated:
8
𝐹𝑖,𝑗 = Γ𝑗 𝜙𝑗 𝑆𝑎𝑗 𝑚𝑖 ,
𝐹𝑖 = √∑𝑛𝑗=1 𝐹𝑖.𝑗 2 ⇔ 𝐹𝑖 = √∑𝑛𝑗=1(Γ𝑗 𝜙𝑗 𝑆𝑎𝑗 𝑚𝑖)2 ,
𝐹̅𝑖 =
𝐹𝑖
max( 𝐹𝑖 )
(3)
The following formula is used to calculate the inter-storey drift-based scaling
adaptive pushover vertical displacement distribution at each stage of the analysis:
2
𝐷𝑖 = ∑𝑖𝑘=1 Δ𝑘 , Δ𝑖 = √∑𝑛𝑗=1[Γ𝑗 (𝜙𝑖 ,𝑗 − 𝜙𝑖−1,𝑗 ] ,
̅𝑖 =
𝐷
𝐷𝑖
max(𝐷𝑖)
(4)
Where:
Fi,j
Force at the i-th story in the j-th mode
αj
Modification Factor, can be positive or negative
Φj
Mode shape vector corresponding to mode j
Saj
the spectral acceleration coresponding to the j-th mode
Δi,j
the inter-storey drift at i-th story in the j-th mode mi the mass of the
i-th
story
Γj
the modal participation factor for the j-th mode
F-bar
normalized distribution of forces
D-bar
normalized distribution of displacements
Buildings that were displacements withstand earthquakes have in the past
sustained substantial damage because of earthquakes. This has highlighted the
drawbacks of the conventional method for developing earthquake-resistant
buildings. The Performance-Based Seismic Design (PBSD) method analyzes a
building's likelihood of performing well in an earthquake. Building safety and
minimal financial damage are guaranteed by PBSD. Pushover analysis, which
forecasts how a building will behave under lateral loads, is one of the techniques
employed in PBSD. Using SAP2000 software, a four-story reinforced concrete
building was developed and examined for this project. To ascertain the bui lding's
performance level, an analysis was conducted in accordance with the ATC 40
guidelines. The outcomes demonstrated that the building's performance level
complied with the needed norms (Chaudhari & Dhoot, 2016).
9
Table 1: Pushover analysis details
Table 2: Capacity Spectrum method outputs
Fig 1: Pushover Curve
Fig 2: Inter-storey Drifts
H. Krawinkler (1996), stated that static pushover analysis is a valuable
technique for assessing the performance of buildings and anticipating seismic
forces and deformations in buildings. It has some restrictions though, and if used
incorrectly, it could lead to misunderstandings. In addition to highlighting certain
potential difficulties, this paper offers a general review of the benefits, history,
implementation, and applications of pushover analysis. It demonstrates the
significance of employing pushover analysis carefully and wisely, as well as how it
might yield important data that cannot be gained by other analytic techniques.
10
According to Freeman (1998), a graphical method called the Capacity
Spectrum Method (CSM) is used to assess how effectively a structure can
withstand lateral stresses during an earthquake. The approach contrasts the
requirements of the seismic response spectrum with a structure's ability to
withstand lateral stresses. A lateral load force-displacement diagram (figure I) that
accounts for the structural parts' sequential yielding when the structure is laterally
pushed past its linear-elastic limits illustrates this. To immediately compare the
force-displacement diagram to earthquake response spectra, it is then transformed
into spectral coordinates (figure II). The CSM is a straightforward and simple-tocomprehend strategy that incorporates higher mode effects and considers the
nonlinear behavior of structures during powerful earthquake ground motion.
It is possible to evaluate the inelastic deformation of structures using interstory drift, a significant indicator of structural performance. The most popular
technique for determining in ter-story drift, double integration of observed
acceleration, has several drawbacks, including sparse instrumentation and signal
processing stages. The different contact and noncontact techniques for precisely
measuring inter-story drift are presented in this work. The limits of the double
integration approach are demonstrated using shake table tests and data from two
heavily instrumented buildings. The work highlights the requirement for precise
inter-story drift measurements to guide structural engineering procedures (Skolnik
& Wallace, 2010).
11
A three-dimensional line model of the structure must be made using the
STERA 3D program before performing an earthquake study on a reinforced
concrete building. Each structural member's material qualities, such as the
concrete's compressive strength, reinforced concrete's tensile strength, the
primary reinforcement bars, and the tensile strength of the ties and stirrups, must
be specified. In addition, specifics regarding the dimensions, size, number of
reinforcing bars, and slab reinforcement are required. These specifications, which
can be found in as-built plans or existing structures, are based on the 2015
Philippine National Structural Code (NSCP 2015). The right interpretations and
levels of a building structure's performance, including safety and serviceability, can
be established using structural technologies like STERA 3D. It's crucial to explain
the structure's performance response to users in straightforward language that
non-technical people can comprehend. The significance of the structure's
performance in society should be explained by design engineers. The study by
Aoki et al. (2000) highlights the value of technical expertise in comprehending the
functionality and significance of a building. The pushover analysis of reinforced
concrete and steel structures is carried out using the Structural Earthquake
Response Analysis (STERA-3D) program, which is described in this study.
Professor Saito from the Toyohashi University of Technology in Japan created
STERA-3D, a nonlinear finite element program. Elastic modal analysis, nonlinear
lateral static pushover analysis, nonlinear lateral static cyclic analysis, and
nonlinear earthquake response analysis are all included in the software. A userfriendly interface is offered by the program, and analysis resu lts are shown quickly
and effectively. For columns and beams, nonlinear axial and bending moment
springs and nonlinear bending and shear springs are used as line elements in the
STERA-3D modelling of structural members. To mimic their interaction, nonlinear
axial and multiple reinforcement springs are also used. The software uses
nonlinear multi springs for wall reinforcements and nonlinear springs for concrete
to accurately model concrete and wall parts (Saito, 2017).
Earthquakes and typhoons can have significant and damaging effects on
various types of structures. Earthquakes can inflict horizontal, vertical, and
12
rotational ground motion, causing the earth to shake violently, and resulting ground
motion can cause severe structural damage to building stru ctures. Earthquakes
can also trigger landslides or ground liquefaction, which can cause large-scale
damage or collapse of structures. Moreover, earthquakes can affect the soil
underneath buildings, leading to differential settlement, which can cause cracks,
wall displacement, and other structural issues. On the other hand, typhoons or
hurricanes are known for their strong winds, heavy rain, and storm surges that can
cause severe damage to buildings, roofs, and other structures. Additionally, storm
surges can lead to coastal erosion, flooding, and damage to shoreline structures.
In conclusion, both earthquakes and typhoons can cause significant structural
damage and loss of life. Therefore, it is important to implement adequate structural
design and construction standards to mitigate the impact of natural disasters.
As Garcia & Tingatinga (2018) stated, the severity of the earthquake, as
well as the combined effect of bending, axial, and shear force interaction, have a
significant impact on reinforced concrete (RC) structures. During powerful
earthquakes, reinforced concrete structures are subjected to cyclic lateral
stresses, which cause load-carrying capacity deterioration and column collapse in
shear and flexure. Recognizing the cost of conducting trials, n umerical models are
becoming more common and have evolved over the years. Analyzing and
investigating nonlinear behavior during cyclic stress is required to design
earthquake-resistant reinforced concrete members or to improve the performance
of columns. The nonlinear analysis must be performed for seismic evaluation of
reinforced concrete structures to determine their behavior during earthquakes and
offer a better knowledge of how effectively the components are built. The research
suggesting that pushover/nonlinear analysis is necessary for seismic evaluation of
reinforced concrete structures aims to investigate the effectiveness of this analysis
technique in determining the behavior of such structures during earthquakes and
to identify potential weaknesses in their design or construction. The research
concludes that pushover/nonlinear analysis is a necessary tool for the seismic
evaluation of reinforced concrete structures, as it offers a better understanding of
the behavior of the components during earthqu akes and can help identify potential
13
weaknesses in the structure's design or construction. The findings of the analysis
can be used to improve the seismic performance of the structure and enhance its
safety during earthquakes, by identifying retrofitting or strengthening strategies
that can be implemented to mitigate the effects of seismic loads.
14
CHAPTER 3
RESEARCH METHODOLOGY
3.1 Research Design
The research will make use of performance-based engineering and applied
research, which focuses on developing systems and structures that achieve
certain
performance
objectives.
It
entails
evaluating the
performance
specifications, identifying potential dangers, and applying engineering techniques
to increase safety and resilience. This approach is reinforced by applied research,
which investigates intriguing techniques, instruments, and materials that may be
used to boost output and tackle new problems in engineering and related
disciplines. Performance-based engineering and applied research work together
to generate novel solutions and breakthroughs across numerous sectors. This
study will use pushover analysis to assess a structure's overall performance and
durability, pinpoint any potential weak spots, and come to wise conclusions about
any necessary retrofitting or strengthening. It helps assess the strength of
structural elements, determine how well lateral force-resisting systems work, and
enhance the design for better seismic performance. The data acquired from this
study will serve as a comprehensive manual and a foundation for the
implementation of potential retrofitting methods intended to lessen earthquakeinduced damage. This study will address the increasing concerns of local
populations in seismically active areas, considering the possible threats to both
human life and the economy. Engineers along with other stakeholders will be able
to reduce the possibility of fatalities and reduce financial losses due to earthquakes
by using the findings to make sensible choices and take preventative action to
improve the structural resilience of the building.
15
3.2 Research Environment
The location of this study happened upon Maghaway Elementary
School, which is addressed along Maghaway Road, Talisay City, Cebu,
Philippines. The 3-storey and 9-room institutional structure had an integrated sum
relevant to its floor area totaling 705 square meters. The original school building
was built last January 1, 1949. Within its 6 decades, DepEd decided to renovate
last 2013 and add new educational premises albeit it was still established 3.2
kilometers away on account of its closest degree towards active fault trace in the
country named Cebu Fault System according to the 1:50,000 mapping scale data
from the Philippine Institute of Volcanology and Seismology or PHIVOLCS.
Nevertheless, one of the central setbacks of the research was its point of
geographical placement per se.
By the 2020 census source from PhilAtlas, Barangay Maghaway is
populated by about 7,119 individuals and hence, a significant percentage of the
community were schoolers despite having mountainous topography. This also
means that the area is more vulnerable to the effects of tremor wave occurrences.
These tremor wave incidents can be recorded and detected but are difficult to
forecast. Geologists commonly consider hazard zones when regions are located
near active faults.
With the aid of the PHIVOLCS Earthquake Intensity Scale or PEIS, forces
along the fault that causes shearing and stresses can measure quakes
qualitatively, as well as quantitatively; via magnitude means. By sole source, the
Intensity Scale VI generates wall cracks on residential houses that were venerable
or badly built, in the same manner as man-made structures that can also have
significant damage. Whereas well-built structures were unaffected or even
undisturbed. According to DepEd, their school buildings' performance standards
and specifications are approximately 25 years old with or without natural
occurrences.
16
Together with the daily volcanic discovery along the Cebu fault system, the
average of moving earth's zone fractures ranges from 20 seismic within a period
of 365 days and at least 2 shocks for a month. This indicates that the locale has
an influential probability of earthquake generation. An intensity Scale of VII and
above is classified as destructive shaking as its moment’s liquefaction of soil. And
as Barangay Maghaway sustains harsh and rough slopes, PHIVOLCS considers
the area as one of the most exposed to the susceptibility of seismic motions. In
any case, this unanticipated wild phenomenon causes great loss of life, assets,
and habitat.
Figure 1: Location of the Study: 7RCC+VXG, Maghaway Rd, Talisay, Cebu
(Sources: Google Earth)
17
Figure
2:
Location Topography:
Elev: 2,259
ft/689
meters
TopoViewMaps)
Figure 3: Location of the Study: Maghaway Elementary School Building
(Sources:
18
3.3 Research Procedure
The study aims to assess the 3-storey Maghaway Elementary School
Building's structural Vulnerability and seismic risk to approaching earthquakes,
stop further damage from occurring, and stop collateral damage to the building.
The researchers will go immediately to the DepEd office to seek a paper
copy and a soft copy of the structural design for the Maghaway Elementary School
to gather data. After that, the researchers will carry out comprehensive research
to obtain the data needed to create nonlinear static analyses, which are useful for
determining the seismic vulnerability of a current building.
The basic design of the school building's yield strength will be calculated by
the researchers using STERA 3D to simulate the structure. They will also
consider the calculated dead and live loads based on NSCP code 2015, as well as
the concrete's compressive strength (fc') and steel's yield strength (fy) determined
by the rebound hammer. With a maximum X-directional drift ratio of 1/100 at 500step increments, the building will be subjected to a static load distribution using
artificial intelligence.
The researchers are going to apply pushover analysis to quicken up the
reaction to find the maximum inter-story drift angle. The structural joints and other
components of the building that are prone to malfunction will be identified with the
aid of this assessment. To estimate how long a building will last before failing, the
main goal is to acquire enough accurate data. Additionally, the researchers aim to
foresee any impending building collapse and offer the school plans or
recommendations to make sure the people are safe.
To determine the risk and potential harm the building may experience during
an earthquake, structural vulnerability and seismic risk evaluation will be used.
Furthermore, pushover analysis utilizing STERA 3D will be carried out, combining
pertinent ground motion data and dynamics ideas. Based on information about
ground motion, accelerations will be compared to anticipated levels. After the
19
investigation is complete, the researchers will compile the inter-story drift and the
highest acceleration values in the X and Y axes.
The pushover analysis approach is being used by the researchers in an
attempt to calculate the maximum load that the structure can support before
collapsing and assess how well the seismic system performs when four distinct
modification parameters are taken into account. By using this method rather of
nonlinear dynamic analysis, it will be possible to evaluate the building's structural
stability and seismic resilience.
3.4 Data Analysis
The researcher will conduct the structure performance of Maghaway
Elementary School Building employing the pushover analysis, and the data will be
processed into STERA 3D. The obtained data will be utilized to determine the
building's ability to withstand seismic forces and identify potential areas of failure.
A building that can withstand elastic deformation without breakage was evaluated
based on its toughness index under the parameters identified by STERA 3D.
Pushover analysis, also known as nonlinear static analysis, is a useful technique
for academics to understand structural behavior, evaluate seismic performance,
and make defensible choices about the design and retrofitting of structures, and
provides a useful and effective way to assess structure behavior and spot potential
weaknesses. It contributes significantly to assuring the safety and resilience of our
built environment and provides a thorough understan ding of the structure's
response to lateral stresses.
The data was collected through field surveys, interviews, and document
analysis. According to Nakano et al. (2004), cracks less than 0.4 mm may be
disregarded, and those larger than 2 mm were considered to have substantial
structural damage. For buildings to be reliable and safe, the structural reaction to
static loads, especially seismic stresses, must be evaluated. To assess the extent
of damage, identify vulnerable regions, and propose appropriate reh abilitation
solutions based on the analysis results produced from STERA 3D, researchers
utilizing STERA 3D in the context of post-earthquake study should take into
20
account the guidelines provided in the publication. By doing this, it is made sure
that the analysis process adheres to accepted procedures for the post-earthquake
damage assessment and rehabilitation of RC structures in Japan, producing
accurate and significant results that can guide decisions on structural safety and
rehabilitation measures.
The process of nonlinear static analysis entails incrementally loading the
structure while monitoring how it responds. Nonlinear static analysis takes into
account nonlinear behavior of materials and elements, such as plasticity and
stiffness degradation, in contrast to linear analysis methods, which assume the
structure remains within the elastic range. When doing a nonlinear static analysis,
lateral loads are sequentially applied to the structure while material nonlinearity,
plasticity, and stiffness degradation are taken into account. Researchers can
create a capacity curve that illustrates the link between applied loads and structural
deformation by monitoring the deformation response at each load stage.
The nonlinear static analysis helps researchers assess the structure's
performance against specific safety criteria and design standards. They can
compare the obtained response with predefined performance objectives, such as
life safety, immediate occupancy, or collapse prevention, and make design
recommendations accordingly. Using the insights gained from the analysis,
researchers can propose design modifications or structural enhancements to
improve the overall safety of the structure. This may involve reinforcing critical
elements, adding additional support, or implementing retrofitting measures to
increase the capacity of the structure to resist seismic forces. Important details
regarding the structural response to static loads are revealed by the results of the
nonlinear static analysis. Identification of deformation patterns, vulnerable areas,
and potential failure modes enables targeted design adjustments and retrofitting
actions. The resulting capacity curve is useful in estimating the structure's safety
margin and establishing its maximum carrying capacity. Using this knowledge,
design changes that improve the structure's safety and resilience are suggested.
21
It is important to note that the proposed design modifications should align
with relevant building codes, regulations, and engineering best practices. The
researchers should carefully consider the feasibility, practicality, and economic
implications of the proposed design changes. Additionally, consulting with
experienced structural engineers and conducting further verification through
additional analysis or experimental testing is advisable to ensure the proposed
design enhances the safety of the structure effectively. This analysis method is
essential for improving the seismic resistance of buildings and guaranteeing
human safety.