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International Journal of Civil Engineering and Technology (IJCIET) Volume 10, Issue 1, January 2019, pp.285–296, Article ID: IJCIET_10_01_027 Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=1 ISSN Print: 0976-6308 and ISSN Online: 0976-6316 ©IAEME Publication Scopus Indexed SEISMIC PERFORMANCE EVALUATION OF A BASE-ISOLATED BUILDING U. Wijaya Department of Civil Engineering, Universitas Tarumanagara, Jakarta, Indonesia R. Soegiarso Department of Civil Engineering, Universitas Tarumanagara, Jakarta, Indonesia Tavio Department of Civil Engineering, Institut Teknologi Sepuluh Nopember (ITS), Surabaya, Indonesia ABSTRACT The Lombok and Palu Earthquakes that have recently occurred in Indonesia caused significant damage. Earthquakes are closely related to damage, landslide, and the loss of life and economy. However, the causes of these things are not solely due to the earthquake itself. The cause loss of life and economy caused solely due to the collapse of buildings that built by humans during an earthquake. To reduce impact loss of life and economy, Performance Based Seismic Design (PBSD) using based isolator can be one of the solution. By using PBSD economic considerations the cost of repair after an earthquake can be predicted. In this study, modeling 12-storey reinforced concrete buildings located in Yogyakarta Indonesia stands on soft soil using base isolator High Damping Rubber type (HDR HH090X4S, thickness 20 cm product of Bridgestone). The average of non-linear dynamic time history analysis of seven ground motion respectively Denali earthquake 2002, Imperial Valley 1940, Kobe 1995, Loma Prieta 1989, Northridge 1994, San Fernando 1971, Superstition Hills 1987 was conducted. Seismic response modification coefficient R was taken respectively 2.5, 3.5, 5.5, and 8. From these coefficients, the performance of the building is obtained with R 2.5 and R 3.5 performance building in the category of immediate occupancy, R 5.5 and R 8 Category damage control. Thus the building with R 2.5 and R 3.5 according to FEMA 273 will produce a building with a repair cost of 25% and repair time only 1 day, so that after the earthquake the building can resume normal operation. Keywords: earthquake, PBSD, time history analysis, base isolator. http://www.iaeme.com/IJCIET/index.asp 285 [email protected] U. Wijaya, R. Soegiarso, and Tavio Cite this Article: U. Wijaya, R. Soegiarso and Tavio, Seismic Performance Evaluation of A Base-Isolated Building, International Journal of Civil Engineering and Technology (IJCIET), 10 (1), 2019, pp. 285–296. http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=1 1. INTRODUCTION Indonesia is located at the subduction zone of tectonic plates, the Eurasian Plate, the IndoAustralian Plate and the Pacific Plate. In the most recent earthquake in Indonesia, the earthquake in Lombok and Palu caused significant damage. Earthquakes are closely related to damage, landslide, and the of loss of life and economy. However, the causes of these things are not solely due to the earthquake itself. The cause loss of life and economy caused solely due to the collapse of buildings that built by humans during an earthquake. To reduce impact loss of life and economy, Performance Based Seismic Design (PBSD) using based isolator can be one of the solution. By using PBSD economic considerations the cost of repair after an earthquake can be predicted. Rubber Base Isolator is the most effective tools to reduce earthquake force that is transmitted to the building. Separating structures from the effects of earthquakes is the main goal in using this device [1-2]. In principle, rubber base isolator can extend the fundamental period of the structure far beyond the period of the high energy period of an earthquake when it was deformed. For low-rise buildings under fifth floors can use the type hyperelastic low damping rubber where it obtained from recycled rubber material, but for buildings higher than fifth floors can use the type of hyperelastic high damping rubber combined with steel plate material to get certain rigidity [3]. In this study modeling 12-storey reinforced concrete buildings located in Yogyakarta Indonesia stands on soft soil using a High Damping Rubber type isolator (HDR HH090X4S thickness 20 cm product of Bridgestone were used) [4]. Average of non-linear dynamic time history analysis of seven ground motion respectively Denali earthquake 2002, Imperial Valley 1940, Kobe 1995, Loma Prieta 1989, Northridge 1994, San Fernando 1971, Superstition Hills 1987. According to ASCE 7-16, Seismic response modification coefficient for the design of earthquake resistant buildings using a base isolator was taken to respond the elastic conditions (R 2.5). Basically, base isolators can extend the fundamental period of a building structure. Since the fundamental period of the building extended, the acceleration response will be reduced and it will minimize building damage [57]. However, from the regulations of ASCE 7-16 limiting the coefficient of seismic response modification is only R 2.5 so that in the economic value with the base isolator the economic value of building prices will increase, but building performance will also increase [8]. Therefore in this paper It will study buildings using base isolators designed in elastic responses (R 2.5), R3.5, R5.5 and inelastic response (R 8.0) regarding the performance due to damage and building repair costs after the earthquake according to FEMA 273. 2. BASE ISOLATOR DESIGN 2.1. Seismic Elastic Response According to ASCE 7-16 the base isolators design considered is based on seismic elastic response. Maximum consideration earthquake is 2500 years return period. For base isolator design, there is no seismic response coefficient reduction. Regarding PBSD in this paper tried to study the seismic response coefficient until reach inelastic condition (reduce factor up to 8). http://www.iaeme.com/IJCIET/index.asp 286 [email protected] Seismic Performance Evaluation of A Base-Isolated Building 2.2. Bearing Stiffness The horizontal rubber bearing stiffness can be shown in equation (1) and (2) as follows [9]: = (1) Where: G = shear modulus of elastomer (MPa). A = section area (mm). tr = total thickness of rubber (mm). D = maximum horizontal displacement (mm). γ = maximum shear strain. = (2) The vertical rubber bearing stiffness can be described in equation (3) as follows [6]: = (3) Where: Ec = compression modulus of composite rubber-steel plate (MPa) 2.3. Design Displacement Design displacement of base isolator can be illustrated in equation (4) and (5) as follows [10]: = Where: DD g TD CVD BD (4) = design displacement at the center of rigidity at the DBE (mm) = gravity acceleration. = isolated period (sec). = seismic coefficient. = damping coefficient for DBE. = Where: DM g TM CVM BM (5) = design displacement at the center of rigidity at the MCE (mm) = gravity acceleration. = isolated period (sec). = seismic coefficient. = damping coefficient for MCE 2.4. Composite Damping Coefficient Composite damping coefficient of base isolator can be illustrated in equation (6) as follows [11]: = ∑ (6) " Where: β = base isolator damping ratio KD = effective stiffness of isolation system DD = design displacement at the center of rigidity at the DBE (mm) http://www.iaeme.com/IJCIET/index.asp 287 [email protected] U. Wijaya, R. Soegiarso, and Tavio ED = effective linear properties from cyclic load 2.5. Base Shear Isolator Base shear of base isolator can be illustrated in equation (7) as follows [7]: Vb = KDmax DD (7) Table 1 Isolator Properties HH070X4S Outer Diameter (mm) Weight (kN) Mass (tonf) Compressive Stiffness (103 kN/m) Kv Initial Stiffness (103 kN/m) Ki Post yield Stiffness (103 kN/m) Characteristic Strength (kN) Equivalent shear Stiffness (103 kN/m) Equivalent Damping Ratio 700 7.90 0.80 2290 4.42 0.44 61.50 0.75 0.24 Figure 1 High Damping Rubber Bearing (Product catalogue Bridgestone) 2.6. Response Spectrum In this research study the seismic area was located at Yogyakarta Indonesia and the response spectrum can be illustrated in Figure 3. Site class categorized as soft soil based on soil investigation data as illustrated in Table 2. http://www.iaeme.com/IJCIET/index.asp 288 [email protected] Seismic Performance Evaluation of A Base-Isolated Building Acceleraion (g) Response Spectrum D.I. Yogyakarta 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 1 2 3 4 Period (s) Figure 2 D.I.Yogyakarta Response Spectrum – Soft Soil [12] Table 2 Site Class [12] Sites Class A-Hard Rock B-Rock C-Very dense soil and soft rock D-Stiff soil E- Soft soil Vs (m/sec) >1500 750 to 1500 350 to 750 175 to 350 < 175 N N/A N/A >50 15 to 50 < 15 Su (kPa) N/A N/A > 100 15 to 100 < 50 2.7. Ground Motion Selected Seven ground motion records list in Table 3 and illustrated in Figures 4(a) to (n) [13]. Table 3 Selected Earthquake the Ground Motions Earthquake Year Magnitude Distance (Km) Vs 30 (m/s) Imperial Valley 1940 6.95 2.66 223.03 Denali San Fernando 2002 1971 7.9 6.61 270.25 11.34 212.48 256 Superstition Hills Kobe 1987 1995 6.84 6.9 5.02 38 1070.34 349.6 Loma Prieta Northridge 1989 1994 6.93 6.69 1.81 5.61 2016.13 362.38 (a) http://www.iaeme.com/IJCIET/index.asp (b) 289 [email protected] U. Wijaya, R. Soegiarso, and Tavio (c) (d) (e) (f) (g) (h) (i) (j) http://www.iaeme.com/IJCIET/index.asp 290 [email protected] Seismic Performance Evaluation of A Base-Isolated Building (k) (l) (m) (n) Figure 3 Selected Ground Motion 2.8. Scaling Procedure According to ASCE 7-16, the target ordinate response spectrum for structures using a base isolator is in the range of 0.5 TD to 1.25 TM. Each of graph should be composite with Indonesia earthquake code (SNI 1726:2012) as shown in Table 4 and Figures 5(a) to (d). The pseudoacceleration target for site class was taken as the median of the damping 5% pseudoacceleration spectrum response that corresponds to the average horizontal component of the record that is not scaled can be illustrated in equation (8) as follows [14]: # = ∑.&/ $%& ' ()*. %& ,- (8) Where A i and Ai are the target spectral acceleration and record's (unscaled) spectral acceleration, respectively. The legend ith is spectral period, and n is the number of periods from 0.5TD up to 1.25TM. The purpose is to determine Scale Factor (SF) that decrease the erratum using equation (9) as follows [14]: )* 0∑.&/ %& %& 1/(∑.&/ %& %& , (9) From Equation (9), it produces an optimal scale factor to ensure a scale spectrum that matches the target spectrum from 0.2TI up to 1.5TI. The ground motion record scale factor according to Equation (9) is shown in Table 4 [14]. http://www.iaeme.com/IJCIET/index.asp 291 [email protected] U. Wijaya, R. Soegiarso, and Tavio Table 4 Scaling Factor of Ground Motion Earthquake Year Denali 2002 Imperial Valley Kobe 1940 1995 Loma Prieta 1989 Northridge 1994 San Fernando 1971 Superstition Hills 1987 Station Direction Magnitude TAPS Pump Station #10 El Centro Array #9 Amagasaki Los Gatos Lexington Dam Anaverde Valley City R Pacoima Superstition Mtn Camera X Y 7.9 12.974 12.424 6.95 6.9 1.339 0.977 1.683 0.832 6.93 0.708 0.743 6.69 8.955 8.955 6.61 0.474 0.509 6.84 0.998 0.634 (a) (b) (c) (d) Figure 4 Selected Ground Motion 3. ANALYSIS PROCEDURE A mathematical model of the structure is determined to get seismic response using base isolator. Computer program that will be used is ETABS non-linear v16.2.1. Analytical procedure is determined as follows [9]: 1. Determined Risk Category. 2. Determined Importance factor (Ie). http://www.iaeme.com/IJCIET/index.asp 292 [email protected] Seismic Performance Evaluation of A Base-Isolated Building 3. Site specific ground motion procedure. 4. Determined Site soil class (SA-SF). 5. Determined Site coefficient short and long period (Fa, Fv). 6. Design spectral acceleration parameter (SDS, SD1). 7. Determined Seismic Design Category (A-F). 8. Determined Seismic response modification coefficient. 9. Determined base isolator properties. 10. 3D dynamic non-linear time history analysis. 11. Base isolator PBSD method. 3.1. Building Data In this study, the building data as follows: 1. Building function : Apartment. 2. Building height : 43 m. 3. First floor level : 4.5 m. nd th 4. Floor level 2 – 12 : 3.5 m. 5. Floor numbers : 12 storey (43 m). 6. Location : Yogyakarta. 7. Material : Reinforced concrete. 8. Concrete grade (f’c) : 35 MPa. 9. Reinforcement grade (fy) : 420 MPa. 10. Thickness of floor : 12 cm. 11. Thickness of roof : 12 cm. 12. Column (K1) : 60 x 60 cm. 13. Primary beam (B1) x-x : 40 × 60 cm. 14. Primary beam (B2) y-y : 50 × 70 cm. 15. Secondary beam (B3) : 25 × 35 cm. 16. Thickness of Shear wall : 35 cm. 17. Base isolator (BI) : HDR HH090X4S (Bridgestone product). 18. Thickness of BI : 20 cm. 19. Ground Motion : Denali Earthquake 2002, Imperial Valley 1940, Kobe 1995, Loma Prieta 1989, San Fernando 1971, Superstition Hills 1987. 20. Soil type : Soft Soil. http://www.iaeme.com/IJCIET/index.asp 293 [email protected] U. Wijaya, R. Soegiarso, and Tavio Figure 5 Plan view twelve storey building 4. RESULTS AND DISCUSSION From non-linear time history analysis, it obtained that twelve stories building with height 43 m, sitting at soft soil, isolated with HDR HH070X4S product of Bridgestone Japan at each column support. Analysis of seismic modification coefficient of R 2.5; R3.5; R 5,5 and R 8.0 were calculated and illustrated in Figures 6(a), (b), 7(a), and (b). http://www.iaeme.com/IJCIET/index.asp 294 [email protected] Seismic Performance Evaluation of A Base-Isolated Building 0.025 Drift 0.015 0.01 0 Displacement (m) 0.02 R = 2.5 R = 3.5 R = 5.5 R=8 12 11 10 9 8 7 6 5 4 3 2 1 0 180 160 140 120 100 80 60 40 Storey R= 2.5 R= 3.5 20 (b) Story Drift (x-x) 0.005 12 11 10 9 8 7 6 5 4 3 2 1 0 0 Storey Displacement (x-x) (a) Figure 6 Displacement and drift elastic - inelastic X direction (a) 10 9 8 7 7 5 6 5 0 160 140 0 120 1 0 100 2 1 80 3 2 60 3 40 4 20 4 Displacement (m) Drift 0.02 6 0.015 Storey 8 0 Storey 9 11 0.01 10 R = 2.5 R = 3.5 R = 5.5 R=8 12 R = 2.5 R = 3.5 R = 5.5 R=8 11 0.005 12 (b) Story Drift (y-y) 0.025 Displacement (y-y) Figure 7 Displacement and drift elastic - inelastic Y direction Figures 6(a), (b), 7(a), and (b) explain the building deformation occurred when using seismic response modification coefficient, R, i.e. 2.5 and 3.5 It obtained performance level Immediate Occupancy (IO) with repair costing 25% and repair time only one day, otherwise for seismic response modification coefficient R 5.5 and R 8, it can be obtained the performance level damage control with repair costing 50% and repair time is between 7 days to 30 days as shown in Figure 8. All of the coefficient fulfills the minimum requirement for PBSD for base isolator. http://www.iaeme.com/IJCIET/index.asp 295 [email protected] U. Wijaya, R. Soegiarso, and Tavio Figure 8 Illustration of PBSD [15] 5. CONCLUSION This paper obtained the result of performance based seismic design for building that is use base isolator. According to that illustrated, the following below is the conclusion of this study: 1. PBSD using base isolator for seismic response modification coefficient R 2.5 (elastic condition) got the best performance IO and only need one day repair and 25% of repair costing during the earthquake, after that the building can be use and operate. 2. PBSD using base isolator for seismic response modification coefficient R 8 (inelastic condition) got the performance damage control and need 7-30 days repair and 50% of repair costing during the earthquake, after that the building can be use and operate. 3. Seismic response modification coefficient R 8 is the maximum level that is allowed for PBSD using base isolator, but using this method, investment for base isolator will be useless because level of damage is 50% and need to repair more than 30 days. ACKNOWLEDGEMENTS The authors would like to gratefully acknowledge for all the facilities and the supports received to make this research possible. REFERENCES [1] Habieb, A. B.; Milani, G.; and Tavio, “Two-Step Advanced Numerical Approach for the Design of Low-Cost Unbonded Fiber Reinforced Elastomeric Seismic Isolation Systems in New Masonry Buildings,” Engineering Failure Analysis, Elsevier, V. 90, Aug. 2018, pp. 380–396. [2] Habieb, A. B.; Milani, G.; Tavio; and Milani, F., “Low Cost Frictional Seismic BaseIsolation of Residential New Masonry Buildings in Developing Countries: A Small Masonry House Case Study, Open Civil Engineering Journal, V. 11, No. M2, Jan. 2017, pp. 1026–1035. http://www.iaeme.com/IJCIET/index.asp 296 [email protected] Seismic Performance Evaluation of A Base-Isolated Building [3] Habieb, A. B.; Milani, G.; Tavio; and Milani, F., “Seismic Performance of a Masonry Building Isolated with Low-Cost Rubber Isolators,” WIT Transactions on the Built Environment, V. 172, 2017, pp. 71–82. [4] Bridgestone Product Catalogue, Seismic Isolation Product Line-up., Catalogue 1st edition, Tokyo, 2015. [5] Habieb, A. B.; Milani, G.; Tavio; and Milani, F., “FE Modelling of Fiber Reinforced Elastomeric Isolators (FREI): Mesh Verification and Validation,” AIP Conference Proceedings, American Institute of Physics, USA, V. 1978, 2018, pp. 1–4. [6] Habieb, A. B.; Milani, G.; Tavio; and Milani, F., “Low Cost Rubber Seismic Isolators for Masonry Housing in Developing Countries,” AIP Conference Proceedings, American Institute of Physics, USA, V. 1906, 2017, pp. 1–4. [7] Sugihardjo, H.; Tavio; and Lesmana, Y., “Behavior of A Base-Isolated Residential House in A Highly Seismic Region,” International Journal of Applied Engineering Research, V. 11, No. 14, 2016, pp. 8253–8258. [8] ASCE (2017). Minimum Design Loads and Associated Criteria for Buildings and Other Structures, ASCE/SEI 7-16, Reston, Virginia. [9] Tavio; and Wijaya, U., Desain Rekayasa Gempa Berbasis Kinerja, Penerbit Andi Yogyakarta, Indonesia, 2018. [10] Naeim, F.; and Kelly, J. M., Design of Seismic Isolated Structures: From Theory to Practice, John Wiley & Sons, New York, 1999. [11] FEMA 451B NEHRP Recommended Provisions for Seismic Regulation for new Buildings and Other Structures and Accompanying Commentary and Maps, 2006. [12] BSN, Tata cara Perencanaan Ketahanan Gempa untuk Gedung dan non Gedung, BSN, SNI 1726, 2012. [13] PEER, “Ground Motion Data Base,” Pacific Earthquake Engineering Research Center, 2018. [14] Tavio; Sugihardjo, H.; and Purniawan, A. “Behavior of Rubber Base Isolator with Various Shape Factors,” AIP Conference Proceedings, American Institute of Physics, USA, V. 1903, 2017, pp. 1–10. [15] Hakim, R. A.; Alama, M.S.; and Ashour, S. A., “Seismic Assessment of RC Building According to ATC 40, FEMA 356 and FEMA 440,” Arabian Journal for Science and Engineering, 2014. http://www.iaeme.com/IJCIET/index.asp 297 [email protected]