Experimental and Numerical Investigation of Strongback Braced Frame System to Mitigate Weak Story Behavior
Publication: Journal of Structural Engineering
Volume 144, Issue 2
Abstract
Multistory steel braced frames tend to concentrate damage in a few weak stories in response to severe earthquake shaking. This paper presents the numerical and experimental results for a strongback system, a modification of the conventional braced frame that uses an essentially elastic truss that vertically spans the structure’s height to delay or prevent weak-story behavior. A cyclic test is performed on a nearly full-scale two-story specimen in which the strongback is introduced as a seismic retrofit of an existing vintage-era concentrically braced frame. The retrofit design is composed of two halves: an inelastic truss using a buckling-restrained brace (BRB) to dissipate seismic input energy and an elastic vertical truss designed to control weak-story behavior. The strongback specimen prevented formation of a weak-story mechanism and mobilized the reserve strength of other structural components, even after the core of the BRB ruptured. Test results establish that the strongback system can be a successful method of mitigating weak-story behavior. A simple numerical model incorporating a low-cycle fatigue material is able to predict the global response of the frame, including the rupture of the BRB.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
This research was supported in part by the National Science Foundation (NSF) under Grant No. CMMI-1208002. The principal investigator for the NSF project was Charles Roeder of the University of Washington, Seattle. The work reported on herein was carried out as a subaward under the supervision of the second author. This project would not have been possible without the donation of specimen fabrication by Schuff Steel and of the buckling restrained brace by StarSeismic. Special thanks go to Dr. Jiun-Wei Lai and the many practicing engineers whose advice was invaluable to this research. The authors also express their appreciation to the technical staff of the University of California, Berkeley site for the NSF George E. Brown, Jr. Network for Earthquake Engineering Simulation for their invaluable assistance. The findings, opinions, recommendations, and conclusions in this paper are those of the authors alone and do not necessarily reflect the views of others, including the sponsors.
References
Aiken, I. D., and Kelly, J. M. (1990). “Earthquake simulator testing and analytical studies of two energy-absorbing systems for multistory structures.”, Earthquake Engineering Research Center, Univ. of California, Berkeley, CA.
AISC. (2010). “Seismic provisions for structural steel buildings.” ANSI/AISC-341-10, Chicago.
AWS (American Welding Society). (2005). “Specification for carbon steel electrodes for flux cored arc welding.” ANSI/AWS A5.20-05, Miami.
Chen, C. H., and Mahin, S. A. (2012). “Performance-based seismic demand assessment of concentrically braced steel frame buildings.”, Pacific Earthquake Engineering Research Center, Univ. of California, Berkeley, CA.
Christopoulos, C., Tremblay, R., Kim, H.-J., and Lacerte, M. (2008). “Self-centering energy dissipative bracing system for the seismic resistance of structures: Development and validation.” J. Struct. Eng., 96–107.
Djojo, G. S., Clifton, G. C., and Henry, R. S. (2014). “Rocking steel shear walls with energy dissipation devices.” Proc., New Zealand Society for Earthquake. Engineering Conf., NZSEE, Wellington, New Zealand.
Filippou, F. C., Popov, E. P., and Bertero, V. V. (1983). “Effects of bond deterioration on hysteretic behavior of reinforced concrete joints.”, Earthquake Engineering Research Center, Univ. of California, Berkeley, CA.
Foutch, D. A., Goel, S. C., and Roeder, C. W. (1987). “Seismic testing of full-scale steel building—Part I.” J. Struct. Eng., 2111–2129.
Grigorian, M., and Grigorian, C. (2016). “An introduction to the structural design of rocking wall-frames with a view to collapse prevention, self-alignment and reparability.” Struct. Des. Tall Spec. Build., 25(2), 93–111.
Hines, E. M., Appel, M. E., and Cheever, P. J. (2009). “Collapse performance of low-ductility chevron braced steel frames in moderate seismic regions.” AISC Eng. J., 46(3), 149–180.
Hsiao, P.-C., Lehman, D. E., and Roeder, C. W. (2013). “A model to simulate special concentrically braced frames beyond brace fracture.” Earthquake Eng. Struct. Dyn., 42(2), 183–200.
ICBO (International Conference of Building Officials). (1985). Uniform building code, Whittier, CA.
Ji, X., Kato, M., Wang, T., Hitaka, T., and Nakashima, M. (2009). “Effect of gravity columns on mitigation of drift concentration for braced frames.” J. Constr. Steel Res., 65(12), 2148–2156.
Khatib, I. F., Mahin, S. A., and Pister, K. S. (1988). “Seismic behavior of concentrically braced frames.”, Earthquake Engineering Research Center, Univ. of California, Berkeley, CA.
Lai, J., and Mahin, S. A. (2013). “Experimental and analytical studies on the seismic behavior of conventional and hybrid braced frames.”, Pacific Earthquake Engineering Research Center, Univ. of California, Berkeley, CA.
Lai, J., and Mahin, S. A. (2014). “Strongback system: A way to reduce damage concentration in steel-braced frames.” J. Struct. Eng., 04014223.
Lin, P.-C., Tsai, K.-C., Chang, C.-A., Hsiao, Y.-Y., and Wu, A.-C. (2016). “Seismic design and testing of buckling-restrained braces with a thin profile.” Earthq. Eng. Struct. Dyn., 45(3), 339–358.
MacRae, G., Kimura, Y., and Roeder, C. (2004). “Effect of column stiffness on braced frame seismic behavior.” J. Struct. Eng., 381–391.
Mar, D. (2010). “Design examples using mode shaping spines for frame and wall buildings.” Proc., 9th U.S. National and 10th Canadian Conf. on Earthquake Engineering, Earthquake Engineering Research Institute, Oakland, CA.
McKenna, F. (1997). “Object-oriented finite element programming: frameworks for analysis, algorithms and parallel computing.” Ph.D. dissertation, Dept. of Civil and Environmental Engineering, Univ. of California, Berkeley, CA.
Merzouq, S., and Tremblay, R. (2006). “Seismic design of dual concentrically braced steel frames for stable seismic performance for multi-story buildings.” Proc., 8th U.S. National Conf. on Earthquake Engineering, EERI, Oakland, CA.
OpenSees version 2.4.6 [Computer software]. Pacific Earthquake Engineering Research Center, Berkeley, CA.
Panian, L., Bucci, N., and Janhunen, B. (2015). “BRBM frames: An improved approach to seismic-resistant design using buckling-restrained braces.” 2nd ATC & SEI Conf. on Improving the Seismic Performance of Existing Buildings and Other Structures, Reston, VA, 632–643.
Pollino, M., Slovenec, D., Qu, B., and Mosqueda, G. (2017). “Seismic rehabilitation of concentrically braced frames using stiff rocking cores.” J. Struct. Eng., 04017080.
Popov, E. P., Ricles, J. M., and Kasai, K. (1992). “Methodology for optimum EBF link design.” Proc., 10th World Conf. on Earthquake Engineering, CRC Press/A.A. Balkema, Rotterdam, Netherlands.
Qu, B., Sanchez-Zamora, F., and Pollino, M. (2014). “Transforming seismic performance of deficient steel concentrically braced frames through implementation of rocking cores.” J. Struct. Eng., 04014139.
Qu, Z., Wada, A., Motoyui, S., Sakata, H., and Kishiki, S. (2012). “Pin-supported walls for enhancing the seismic performance of building structures.” Earthquake Eng. Struct. Dyn., 41(14), 2075–2091.
Rai, D. C., and Goel, S. C. (2003). “Seismic evaluation and upgrading of chevron braced frames.” J. Constr. Steel Res., 59(8), 971–994.
Sabelli, R. (2001). “Research on improving the design and analysis of earthquake-resistant steel braced frames.”, Earthquake Engineering Research Institute, Oakland, CA.
Sen, A. D., et al. (2016). “Experimental investigation of chevron concentrically braced frames with yielding beams.” J. Struct. Eng., 4016123.
Simpson, B. G., and Mahin, S. A. (2017). “Experimental and numerical evaluation of vintage-era concentrically braced frames with hollow and concrete-filled braces.” J. Struct. Eng., in press.
Simpson, B. G., Mahin, S. A., and Lai, J. W. (2017). “Cyclic testing of older steel braced frames.”, Pacific Earthquake Engineering Research Center, Berkeley, CA.
Sloat, D. A. (2014). “Evaluation and retrofit of non-capacity designed braced frames.” M.S. thesis, Univ. of Washington, Seattle.
Slovenec, D., Sarebanha, A., Pollino, M., Mosqueda, G., and Qu, B. (2017). “Hybrid testing of the stiff rocking core seismic rehabilitation technique.” J. Struct. Eng., 04017083.
Takeuchi, T., Chen, X., and Matsui, R. (2015). “Seismic performance of controlled spine frames with energy-dissipating members.” J. Const, Steel Res., 114, 51–65.
Tremblay, R. (2003). “Achieving a stable inelastic seismic response for multi-story concentrically braced steel frames.” AISC Eng. J., 40(2), 111–129.
Tremblay, R., and Poncet, L. (2005). “Seismic performance of concentrically braced steel frames in multistory buildings with mass irregularity.” J. Struct. Eng., 1363–1375.
Uang, C.-M., and Bertero, V. V. (1986). “Earthquake simulation tests and associated studies of a 0.3 scale model of a six-story concentrically braced steel structure.”, Earthquake Engineering Research Center, Univ. of California, Berkeley, CA.
Uriz, P., Filippou, F. C., and Mahin, S. A. (2008). “Model for cyclic inelastic buckling of steel braces.” J. Struct. Eng., 619–628.
Uriz, P., and Mahin, S. A. (2008). “Toward earthquake resistant design of concentrically braced steel-frame structures.”, Pacific Earthquake Engineering Research Center, Univ. of California, Berkeley, CA.
Whittaker, A. S., Uang, C. M., and Bertero, V. V. (1990). “An experimental study of the behavior of dual steel systems.”, Earthquake Engineering Research Center, Univ. of California, Berkeley, CA.
Yang, C. S., Leon, R. T., and DesRoches, R. (2009). “Performance Evaluation of Innovative Steel Braced Frames.”, Pacific Earthquake Engineering Research Center, Univ. of California, Berkeley, CA.
Yang, T. Y. (2006). “Performance evaluation of innovative steel braced frames.” Ph.D. dissertation, Univ. of California, Berkeley, CA.
Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 144 • Issue 2 • February 2018
Copyright
©2017 American Society of Civil Engineers.
History
Received: Mar 19, 2017
Accepted: Aug 9, 2017
Published online: Dec 11, 2017
Published in print: Feb 1, 2018
Discussion open until: May 11, 2018
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.