Seismic performance assessment of special concentrically mega braced frames with different spans ratio

Document Type : Research Article


1 Civil Engineering School, Engineering Department, University of Zanjan

2 Civil Engineering Group, Engineering Department, University of Zanjan, Zanjan, Iran.


Special concentrically braced frames achieve good seismic performance in the earthquake, these frames maintain the stability of the structure with linear behavior in weak to moderate earthquakes and with nonlinear behavior in extreme earthquakes. The design of structures is often based on linear analysis, so it is necessary to study the performance of mega-braced frames with different spans ratio by nonlinear analysis. In this study, the seismic performance of special concentrically mega-braced frames with different spans ratio is investigated. For this purpose, eight configurations of four and eight-story structures with special concentrically braced frame were designed in three dimensions, with conventional X and mega brace configurations with different spans ratio, then a braced frame of them was modeled in OpenSees in two dimensions, taking into account the second-order effects of the removed gravitational section, through a leaning column. Finally, in order to investigate the seismic performance of structures and perform incremental dynamic analysis, 14 far-field earthquakes were selected according to the characteristics of the construction site. Evaluation of analysis results according to NIST GCR 10-917-8 report and Hazus Technical Manual in maximum inter-story drift ratio, comparison of fragility curves and comparison of period and weight of structures indicates that in special concentrically mega braced frames, if the spans are equal, mega braces have a suitable and economic performance, and if the ratio of spans is different, the use of mega braces has a better performance than conventional X braces and is much more economical. For example, in eight-story structures with a span ratio of 1.5, the weight of the structure with the mega-brace is about 20% less than the similar structure with a conventional X brace. Also, the main period of frames with conventional X braces is about 20 to 30% longer than structures with mega braces, which indicates the higher stiffness of mega braces.


Main Subjects

[1] M. Bruneau, C. M. Uang, R. Sabelli, Ductile design of steel structures, Second ed., McGraw-Hill Companies Inc., NY, USA, 2011.
[2] Office of Iranian National Building Regulations, 10th Topic: Design and Execution of Steel Buildings, fourth ed., Iran Development Publishing, Tehran, Iran, 2013. (in Persian).
[3] P. C. Hsiao, D. E. Lehman, C. W. Roeder, Evaluation of the response modification coefficient and collapse potential of special concentrically braced frames, Earthquake engineering & structural dynamics, 42(10) (2013) 1547- 1564.
[4] P. A. Kumar, D. R. Sahoo, A. Kumar, Seismic response of concentrically braced frames with staggered braces in split- x configurations, Journal of Constructional Steel Research, 142 (2018) 17-30.
[5] L. Di Sarno, A. S. Elnashai, Bracing systems for seismic retrofitting of steel frames, Journal of Constructional Steel Research, 65(2) (2009) 452-465.
[6] H. Sheikh, A. Massumi, Effects of bracing configuration on seismic behavior of tall steel structures subjected to earthquake ground motions, In Proceedings of the 10th US National Conference on Earthquake Engineering, Anchorage, Alaska, 2014.
[7] J. Shen, R. Wen, B. Akbas, B. Doran, E. Uckan, Seismic demand on brace-intersected beams in two-story X-braced frames, Engineering Structures, 76 (2014) 295-312.
[8] D. B. Merczel, J. M. Aribert, H. Somja, M. Hjiaj, Plastic analysis-based seismic design method to control the weak storey behaviour of concentrically braced steel frames, Journal of Constructional Steel Research, 125 (2016) 142- 163.
[9] J. G. Sizemore, L. A. Fahnestock, E. M. Hines, C. R. Bradley, Parametric study of low-ductility concentrically braced frames under cyclic static loading, Journal of Structural Engineering, 143(6) (2017) 04017032.
[10] S. Momenzadeh, J. Shen, Seismic demand on columns in special concentrically braced frames, Engineering Structures, 168 (2018) 93-107.
[11] J. G. Sizemore, L. A. Fahnestock, E. M. Hines, Seismic performance assessment of low-ductility concentrically braced frames, Journal of Structural Engineering, 145(4) (2019) 04019016.
[12] S. Mazzoni, F. McKenna, M. H. Scott, G. L. Fenves, The open system for earthquake  engineering simulation (OpenSEES) user command-language manual, Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA,, 2007.
[13] A. Kheyroddin, M. Gholhaki, Gh. Pachideh, Seismic evaluation of reinforced concrete moment frames retrofitted with steel braces using IDA and pushover methods in the near-fault field, Journal of Rehabilitation in Civil Engineering, 7(1) (2019) 159-173.
[14] M. Gholhaki, Gh. Pachideh, O. Rezayfar, S. Ghazvini, Specification of response modification factor for steel plate shear wall by incremental dynamic analysis method, Journal of Structural and Construction Engineering, 6(2) (2019) 211-224. (in Persian).
[15] Permanent Committee for Revising the Iranian Code of Practice for Seismic Resistant Design of Buildings, Iranian Code of Practice for Seismic Resistant Design of Buildings, Standard No. 2800, fourth ed., Road, Housing and Urban Development Research Center, Tehran, Iran, 2014. (in Persian).
[16] CSI, Extended three-dimensional analysis of building systems, ETABS version 16.2.1, Computers and Structures Inc., Berkeley, CA, 2016.
[17] Office of Iranian National Building Regulations, 6th Topic: Loads on Building, third ed., Iran Development Publishing, Tehran, Iran, 2013.) in Persian).
[18] P. C. Hsiao, D. E. Lehman, C. W. Roeder, Improved analytical model for special concentrically braced frames, Journal of Constructional Steel Research, 73 (2012) 80-94.
[19] D. Vamvatsikos, C. A. Cornell, Incremental dynamic analysis, Earthquake engineering & structural dynamics, 31(3)(2002) 491-514.
[20] PEER, Strong Ground Motion Database, Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA,, 2013.
[21] NIST, Evaluation of the FEMA P-695 methodology for quantification of building seismic performance factors, NIST GCR 10-917-8, National Institute of Standards and Technology, Gaithersburg, 2010.
[22] J.D. Newell, C.M. Uang, Cyclic behavior of steel columns with combined high axial load and drift demand, Department of Structural Engineering, University of California, San Diego, 2006.
[23] FEMA, Multi-Hazard Loss Estimation Methodology–Earthquake Model, Hazus®MH 2.1 Technical Manual, Federal Emergency Management Agency, Washington DC, 2013.
[24] J. W. Baker, Efficient analytical fragility function fitting using dynamic structural analysis, Earthquake Spectra, 31(1) (2015) 579-599.
[25] L. F. Ibarra, H. Krawinkler, Global collapse of frame structures under seismic excitations, Report No.152, The John Blume Earthquake Engineering Center, Stanford, CA, 2005.
[26] S. Salehi, M. S. Ghobadi, Seismic resilient bracing structure equipped with hybrid device at base, Soil Dynamics and Earthquake Engineering, 138 (2020) 106256.
[27] ASCE, Minimum Design Loads for Buildings and Other Structures, ASCE 7-05, American Society of Civil Engineers, Reston, VA, 2005.
[28] Gh. Pachideh, M. Gholhaki, A.S. Daryan, Analyzing the damage index of steel plate shear walls using  pushover analysis, Structures, 20 (2019) 437-451.