ارزیابی اثر شکست اتصال ها و چیدمان اتصال های شکننده بر عملکرد لرزه ای قابهای خمشی فولادی

نوع مقاله : مقاله پژوهشی

نویسنده

استادیار، دانشکده فنی و مهندسی، دانشگاه بی نالمللی امام خمینی

چکیده

تأمین شکل پذیری در اعضا در طرح لرزه ای سازه ها همواره مورد توجه مهندسین بوده است. با این حال، پراکندگی فراوانی در عملکرد اتصال های خمشی فولادی در زلزله های اخیر رخ داده که اغلب به علت رفتار ترد اتصال بوده است. هدف در این پژوهش، بررسی تأثیر چیدمان اتصال های شکننده قاب های خمشی فولادی بر رفتار کلی این قابها است. برای این کار، توزیع اتصال های شکننده قبل از نورتریج با استفاده از الگوریتم ژنتیک بهینه شده است تا حساسیت پاسخ لرزه ای سازه به چیدمان اتصال های با شکست زودهنگام برای دو سطح خطر مختلف برآورد گردد. از این رو، شکست در تیرها و ستون ها به صورت جداگانه مدل شده اند. همچنین اتصال های غیرکاهنده نیز به موازات اتصال های شکننده مدل شده اند تا امکان مقایسه عملکرد لرزه ای سازه ها فراهم گردد. در ادامه یک ارزیابی احتمالاتی برای تخمین قابلیت اطمینان سازه تحت شرایط فوق با استفاده از تحلیل دینامیکی غیرخطی افزایشی انجام گرفته است. نتایج نشان می دهد که بهینه کردن چیدمان اتصال ها، تأثیر بسزایی را بر پاسخ جابجایی قاب خواهد داشت.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Evaluation of the effect of connection fracture and configuration of fracturing connections on seismic performance of steel moment frames

نویسنده [English]

  • B. Mohebi
Assistant Professor, Faculty of Civil Engineering, Imam Khomeini International University
چکیده [English]

Provision of ductility has always been of concern in seismic design of structures. However, large
variability in connection performance is observed during the recent earthquakes, due to brittle fracture of
steel moment frame connections. In this study, distribution of early fracturing pre-Northridge connections
is optimized by genetic algorithm tool to quantify the sensitivity of seismic response of the structures
to spatial variation of early fracturing connections for two hazard levels. Also, a non-degrading ductile
connection is modeled to compare the seismic performance of the structures. Probability assessment
is carried out by implementation of incremental dynamic analysis to find the reliability of structures
under this condition. Results show that configuration of fracturing connections in beams, in contrast to
columns, can significantly affect the collapse capacity of structures.

کلیدواژه‌ها [English]

  • Pre-Northridge
  • Connection Fracture
  • Steel Moment Frame
  • IDA
  • Performance Based Evaluation
[1]Bonowitz, D. and Youssef, N.; “SAC Survey of Steel Moment-resisting Frame Buildings Affected by the 1994 Northridge Earthquake,” Technical Report 95–06: Surveys and Assessment of Damage to Buildings Affected by the Northridge Earthquake, SAC Joint Venture, pp. 2–1 to 2–169, 1995.
[2]Kaufmann, E. J.; Fisher, J. W.; Di-Julio-Jr, R. M. and Gross, J. L.; “Failure Analysis of Welded Steel Moment Resisting Frames Damaged in the Northridge Earthquake,” Tech. Rept. 5625, NIST, 1995.
[3]Roeder, C. W.; “Connection Performance for Seismic Design of Steel Moment Frames,” Journal of Structural Engineering, Vol. 128, No. 4, pp. 517–525, 2002.
[4]Mele, E.; “Moment Resisting Welded Connections: An Extensive Review of Design Practice and Experimental Research in USA, Japan and Europe,” Journal of Earthquake Engineering, Vol. 6, No. 1, pp. 111–145, 2002.
[5]Bernuzzi, C.; Calado, L. and Castiglioni, C.; “Ductility and Load Carrying Capacity Prediction of Steel Beam-to-Column Connections under Cyclic Reversal Loading,” Journal of Earthquake Engineering, Vol. 1, No. 2, pp. 401–432, 1997.
[6]Foutch, D. A. and Yun, S.; “Modeling of Steel Moment Frames for Seismic Loads,” Journal of Constructional Steel Research, Vol. 58, No. 5, pp. 529–564, 2002.
[7]Rodgers, J. E. and Mahin, S. A.; “Effects of Connection Fractures on Global Behavior of Steel Moment Frames Subjected to Earthquakes,” Journal of Structural Engineering, Vol. 132, No. 1, pp. 78–88, 2006.
[8]Goldberg, D. E.; “Genetic Algorithms in Search, Optimization and Machine Learning,” Addison Wesley, Vol. 1, No. 98, 1989.
[9]Vamvatsikos, D.; Jalayer, F. and Cornell, C. A.; “Application of Incremental Dynamic Analysis to an RC-Structures,” Proceedings of the FIB Symposium on Concrete Structures in Seismic Regions, Athens, 2003.
[10]FEMA-350; “Recommended Seismic Design Criteria for New Steel Moment-frame Buildings,” Prepared by the SAC Joint Venture for the Federal Emergency Management Agency, Washington, DC., 2000.
[11]Maison, B. and Bonowitz, D.; “Opinion Paper: How Safe are Pre-Northridge WSMFs? A Case Study of the SAC Los Angeles 9-Storey Building,” Earthquake Spectra, EERI, Vol. 15, No. 4, pp. 765-789, 1999.
[12]Luco, N. and Cornell, C. A.; “Effects of Random Connection Fractures on the Demands and Reliability for a 3-Storey Pre‑Northridge SMRF Structure,” Proceedings of the 6th U.S. National Conference on Earthquake Engineering, Seattle, WA, Earthquake Engineering Research Institute, Oakland, CA, 1998.
[13]Pinto, P. E.; “Probabilistic Methods for Seismic Assessment of Existing Structures,” LESSLOSS Report No. 2007/06, 1996.
[14]Challa, V. R. M. and Hall, J. F.; “Earthquake Collapse Analysis of Steel Frames,” Earthquake Engineering and Structural Dynamics, Vol. 23, No. 11, pp. 1199–1218, 1994.
[15]Maison, B. and Kasai, K.; “Analysis of Northridge Damaged 13-Storey WSMF Building,” Earthquake Spectra, Vol. 13, No. 3, pp. 451–473, 1997.
[16]Wang, C. H. and Wen, Y. K.; “Evaluation of Pre-Northridge Low-rise Steel Buildings-I: Modeling,” Journal of Structural Engineering, Vol. 126, No. 10, pp. 1160–1168, 2000.
[17]Holland, J. H.; “Adaptation in Natural and Artificial Systems,” Ann Arbor: The University of Michigan Press, 1975.
[18]Chou, C. C., Tsai, K. C., Wang, Y. Y. and Jao, C. K.; “Seismic Performance of Steel Side Plate Moment Connections,” The 14th World Conference on Earthquake Engineering, Beijing, China, 2008.
[19]Spears, W. M.; “Adaptive Crossover in Genetic Algorithms,” Artificial Intelligence Center Internal Report, Naval Research Laboratory, Washington, DC, 1994.
[20]Overview Standing Committee of Regulations for Design of Buildings against Earthquake; “Regulations for Design of Buildings against Earthquake,” Building and Housing Research Center, 3rd Edition, 2005 (in Persian).
[21]Shome, N. and Cornell, C. A.; “Probabilistic Seismic Demand Analysis of Non-linear Structures,” Report No. RMS-35, RMS Program, Stanford University, Stanford, 1999.
[22]Amiri, G. G.; Motamed, R. and Es-Haghi, H. R.; “Seismic Hazard Assessment of Metropolitan Tehran, Iran,” Journal of Earthquake Engineering, Vol. 7, No. 3, pp. 347–372, 2003.
[23]Kunnath, S. K.; “IDASS–A Program for Inelastic Damage Analysis of Structural Systems,” Technical Report, Department of Civil Engineering, University of Central Florida, Orlando, 2000.
[24]Kunnath, S. K.; Reinhorn, A. M. and Lobo, R. F.; “IDARC: A Program for the Inelastic Damage Analysis of Reinforced Concrete Structures,” Report No. NCEER-92-0022, National Center for Earthquake Engineering Research, State University of New York at Buffalo, 1992.
[25]Cornell, C. A. and Luco, N.; “The Effects of Connection Fractures on Steel Moment Resisting Frame Seismic Demands and Safety: A Report on SAC Phase II Task 5,4.6,” Rep. No. SAC-BD/99-03, SAC Joint Venture, Sacramento, Calif., 1999.
[26]Vamvatsikos, D. and Cornell, C. A.; “Incremental Dynamic Analysis,” Earthquake Engineering and Structural Dynamics, Vol. 31, No. 3, pp. 491–514, 2002.
[27]Jalayer, F. and Cornell, C. A.; “A Technical Framework for Probability-based Demand and Capacity Factor (DCFD) Seismic Formats,” Report No. RMS-43, RMS Program, Stanford University, Stanford, CA., 2002.
[28]Luco, N.; “Probabilistic Seismic Demand Analysis, SMRF Connection Fractures and Near-source Effects,” Ph.D. Dissertation, Department of Civil and Environmental Engineering, Stanford University: Stanford, California, 2002.
[29]Cornel, C. A.; Jalayer, F.; Hamburger, R. O. and Foutch, D. A.; “Probabilistic Basis for 2000 SAC Federal Emergency Management Agency Steel Moment Frame Guidelines,” Journal of Structural Engineering, Vol. 128, No. 4, pp. 526–533, 2002.
[30]AISC; “Manual of Steel Construction Load and Resistance Factor Design,” American Institute of Steel Construction Inc., Chicago, IL, Second Edition, 1994.