Higher Mode Effects in the Pushover Analysis of RC Buildings Subjected to the Near-Fault Ground Motions

Document Type : پژوهشی

Authors

• A. Mortezaei
• A. Kheyroddin

10.22067/civil.v25i2.40587

Abstract

Accurate identification of seismic hazard and the estimation of associated seismic demands are the key components in the performance-based seismic design (PBSD). Although nonlinear time history (NTH) analysis is the most precise procedure to evaluate the seismic demands of buildings structures, it is relatively complex and time-consuming for routine applications. Nonlinear static procedures (NSPs) are now prevalently used in engineering practice instead of nonlinear time history analysis for the prediction of seismic demands in building structures. Current Instruction for Seismic Rehabilitation of Existing Buildings (No. 360) uses invariant load distributions. While those invariant load distributions (such as inverted triangle, uniform, or mass proportional) are based on the assumption that the response is primarily in its fundamental mode of vibration, it can lead to incorrect estimates for structures with significant higher mode contributions.The objective of this paper is evaluation of the assumptions, approximations and limitations of pushover analysis and the differences between static and dynamic methods to estimate seismic demands in building structures subjected to both far- and near-fault ground motions. Analytical results show that lateral load pattern used to estimate demands can have a significant influence on the computed demands. When compared to nonlinear time history estimates, pushover methods tend to underestimate demands at the upper levels signifying the relevance of high mode participation in mid to high rise structures.

Keywords

• Pushover Analysis
• near-fault earthquake
• higher modes
• lateral load distribution
• Drift

---

References

1. American Society of Civil Engineers,“Prestandard and commentary for the seismic rehabilitation of buildings”, FEMA-356, Washington D.C., (2000).

2. دستورالعمل به‌سازی لرزه‌ای ساختمان‌های موجود، نشریه‌ی شمار‌ی 360، سازمان مدیریت و برنامه‌ریزی کشور، معاونت امور فنی، دفترامورفنی، تدوین معیارها وکاهش خطرپذیری ناشی از زلزله، (1385).

3. FEMA-350, Recommended Seismic Design Criteria for New Steel Moment-rameBuildings, Developed by the SAC Joint Venture for the Federal EmergencyManagement Agency, Washington D.C., (2000).

4. Applied Technology Council (ATC), Seismic Evaluation and Retrofit of Concrete Buildings, Volumes 1 and 2, Report No. ATC-40, Redwood City, CA., (1996).

5. Maniatakis, C.A., Psycharis, I.N. and Spyrakos, C.C., “Effect of higher modes on the seismic response and design of moment-resisting RC frame structures”, Engineering Structures, 56, pp. 417-430, (2013).

6. Chopra, A.K. and Goel, R., “A modal pushover analysis procedure for estimating seismic demands for buildings”, Earthquake Engineering and Structural Dynamics, 31, pp. 561-582, (2002).

7. Jan, T. S., Liu, M. W., Kao, Y. C., “An upper-bound pushover analysis procedure for estimating seismic demands of high-rise buildings”, Engineering Structures, 26, pp. 117-128, (2004).

8. Chopra, A. K, Goel, R. K, Chintanapakdee, C., “Evaluation of a modified MPA procedure assuming higher modes as elastic to estimate seismic demands”, Earthquake Spectra, 20(3), pp.757-778, (2004).

9. Kalkan, E. and Kunnath, K., “Adaptive modal combination procedure for nonlinear static analysis of building structures”, Journal of Structural Engineering, 132(11), pp. 1721-1731, (2006).

10. Mortezaei, A., Ronagh, H.R., Kheyroddin, A., Ghodrati Amiri, G., “Effectiveness of modified pushover analysis procedure for the estimation of seismic demands of buildings subjected to near-fault earthquakes having forward directivity”, The Structural Design of Tall and Special Buildings, 20(6), pp. 679-699, (2011).

11. مرتضایی، علیرضا، “پاسخ دینامیکی ساختمان‌های بتن‌آرمه به زلزله‌های حوزه‌ی نزدیک”، رساله دکتری، دانشگاه سمنان، سمنان، (1389).

12. Somerville, P. G., “Development of an improved representation of near-faultground motions”, SMIP98 Proceedings of the Seminar on Utilization of Strong-Motion Data, Oakland, CA, Sept. 15, California Division of Mines and Geology,Sacramento, pp. 1-20, (1998).