Collapse Mechanisms of Controlled Rocking Steel Braced Frames: Base Rocking Joint vs. Capacity-Protected Frame Members

Abstract:

Controlled rocking steel braced frames (CRSBFs) have been proposed as a low-damage seismic force resisting system with reliable self-centering capabilities. The frame members in CRSBFs are selected to remain elastic during design-level earthquakes, so they must be designed to resist the peak forces from at least the first-mode pushover response. However, several researchers have shown that higher mode effects can contribute significantly to the peak member forces. Some collapse assessment studies on CRSBFs have included member yielding and buckling in the numerical models, but the studies have not examined a range of possible design intensities for the higher modes, and have not separated the influence on the collapse risk of the capacity design from that of the design of the base rocking joint. This paper presents the collapse assessment results for 12-story CRSBFs that were designed either excluding the higher-mode forces, or including the higher-mode forces at the DBE level, MCE level 1.5 times the MCE level, and 2.0 times the MCE level. The ground motions were selected conditionally based on the first-mode period of each example frame. The probability of collapse during an MCE-level event was computed for the frames when buckling and yielding of the frame members was modeled, and compared to the probabilities of collapse when the members were modeled as elastic. The results indicate that the base rocking joint design was more conservative than required to provide adequate collapse prevention compared to the design of the frame members. Including the higher-mode forces at the MCE level for capacity design seems appropriate from a collapse prevention perspective.

• Periodical: Key Engineering Materials (Volume 763)
• Pages: 669-677
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.763.669
• Online since: February 2018
• Authors: Taylor C. Steele*, Lydell D.A. Wiebe
• Keywords: Capacity Design, Collapse Assessment, Controlled Rocking Steel Braced Frames, Higher Mode Effects, Multiple Stripe Analysis, Self-Centering Systems

References

[1] D. Roke, R. Sause, J.M. Ricles, N.B. Chancellor, Damage-free seismic resistant self-centering concentrically-braced frames, ATLSS Report 10-09, Advanced Technology for Large Structural Systems Engineering Research Center, Bethlehem, PA, United States, (2010).

DOI: 10.1061/41031(341)155

[2] M.R. Eatherton, J.F. Hajjar, Large-scale cyclic and hybrid simulation testing and development of a controlled rocking steel building system with replaceable fuses, Report NSEL-025, Newmark Structural Engineering Laboratory, Urbana IL, United States, (2010).

[3] X. Ma, H. Krawinkler, G. Deierlein, Seismic design and behaviour of self-centering braced frames with controlled rocking and energy dissipating fuses, Report 174, John A. Blume Earthquake Engineering Center, Stanford, CA, United States, (2011).

DOI: 10.1002/stco.201110023

[4] L. Wiebe, C. Christopoulos, R. Tremblay, M. Leclerc, Mechanisms to limit higher mode effects in a controlled rocking steel frame. 2: Large-amplitude shake table testing, Earthquake Eng. Struct. Dyn., 42 (2013) 1069-1086.

DOI: 10.1002/eqe.2258

[5] L. Wiebe, C. Christopoulos, Performance-based seismic design of controlled rocking steel braced frames. II: Design of capacity-protected elements, J. Struct. Eng., 141 (2014) 04014227.

DOI: 10.1061/(asce)st.1943-541x.0001201

[6] T.C. Steele, L.D.A. Wiebe, Dynamic and equivalent static procedures for capacity design of controlled rocking steel braced frames, Earthquake Eng. Struct. Dyn., 45 (2016) 2349-2369.

DOI: 10.1002/eqe.2765

[7] T.C. Steele, L.D.A. Wiebe, Collapse risk of controlled rocking steel braced frames with different post-tensioning and energy dissipation designs, Earthquake Eng. Struct. Dyn., (2017), doi: 10. 1002/eqe. 2892.

DOI: 10.1002/eqe.2892

[8] D. Roke, S. R., J. Ricles, N. Gonner, Design concepts for damage-free seismic-resistant selfcentering steel concentrically braced frames, in: Structures Congress 2009, Austin, TX, American Society of Civil Engineers, Reston, VA, 2009, pp.1421-1430.

DOI: 10.1061/41031(341)155

[9] D.A. Latham, A.M. Reay, S. Pampanin, Kilmore Street Medical Centre: Application of a posttensioned steel rocking system, Proc., 2013 Steel Innovations Conf., (2013).

[10] L. Wiebe, C. Christopoulos, Performance-based seismic design of controlled rocking steel braced frames. I: Methodological framework and design of base rocking joint, J. Struct. Eng., 141 (2014) 04014226.

DOI: 10.1061/(asce)st.1943-541x.0001202

[11] DYWIDAG Systems International, DYWIDAG post-tensioning systems, Product Brochure, DYWIDAG Systems International, (2006).

[12] Pacific Earthquake Engineering Research Centre (PEER), Open System for Earthquake Engineering Simulation v2. 5. 0 [Computer Software], (2016).

[13] T.C. Steele, L.D.A. Wiebe, Influence of member inelasticity on the performance of controlled rocking steel braced frames, in: F. Mazzolani, G.Q. Li, S. Chen, X. Qiang (Eds. ), Proc., 8th STESSA Conf., Shanghai, China, China Architecture & Building Press, Beijing, 2015, pp.128-135.

[14] P. Jehel, P. Léger, A. Ibrahimbegovic, Initial versus tangent stiffness-based rayleigh damping in inlastic time history seismic analyses, Earthquake Eng. Struct. Dyn., 43 (2014) 467-484.

DOI: 10.1002/eqe.2357

[15] J.W. Baker, T. Lin, S.K. Shahi, New ground motion selection procedures and selected motions for the PEER transportation research program, PEER Report 2011/03, University of Califonia, Berkeley, (2011).

[16] J. Baker, Efficient analytical fragility function fitting using dynamic structural analysis, Earthquake Spectra, 31 (2015) 579-599.

DOI: 10.1193/021113eqs025m

[17] Federal Emergency Management Agency, Quantification of building seismic performance factors, FEMA Report P695, Federal Emergency Management Agency, Washington, DC, United States, (2009).

DOI: 10.4135/9781412952446.n202