Bulletin of Earthquake Engineering

, Volume 17, Issue 4, pp 2059–2091 | Cite as

Seismic collapse performance of Los Angeles soft, weak, and open-front wall line woodframe structures retrofitted using different procedures

  • Henry BurtonEmail author
  • Aryan Rezaei Rad
  • Zhengxiang Yi
  • Damian Gutierrez
  • Koyejo Ojuri
Original Research


The Los Angeles Soft-Story Ordinance was enacted with the goal of reducing the collapse risk of woodframe buildings with soft, weak and open-front (SWOF) wall lines. Four alternative retrofit methods are permitted under the Ordinance including a “SWOF-wall-line-only” retrofit in accordance with the Department of Building and Safety requirements or a “full-story” retrofit based on Appendix A4 of the 2012 IEBC, ASCE 41-13 or FEMA P807. A comparative assessment of the increase in collapse safety provided by the four alternative retrofit methods is presented. Nonlinear static and dynamic collapse analyses are conducted on a set of archetypical structural models, which have been developed based on an extensive survey of Los Angeles SWOF buildings. The effect of several building characteristics (e.g. number of stories, wall layout in 1st story) on the relative enhancement in collapse safety of the retrofitted buildings is also investigated. The number of stories is shown to have the greatest effect on the relative collapse safety benefits derived from the alternative methods. The number of SWOF wall lines and the ductility of the upper stories also impacted the extent to which the retrofits enhanced collapse safety.


Light-frame wood buildings Soft-story ordinance Collapse performance assessment Seismic retrofit Earthquake policy evaluation 



The research presented in this paper is supported by the National Science Foundation CMMI Research Grant No. 1538747.


  1. ASCE (2010) ASCE/SEI 7-10 minimum design loads for buildings and other structures. Reston, VirginiaGoogle Scholar
  2. ASCE (2013) ASCE/SEI 41-13 seismic evaluation and retrofit of existing buildings. Reston, VirginiaGoogle Scholar
  3. Bahmani P, Van De Lindt JW (2012) Numerical modeling of soft-story woodframe retrofit techniques for design. In: Structures congress 2012—Proceedings of the 2012 Structures Congress, pp 1755–1766Google Scholar
  4. Bahmani P, van de Lindt JW, Gershfeld M et al (2016) Experimental seismic behavior of a full-scale four-story soft-story wood-frame building with retrofits. I: building design, retrofit methodology, and numerical validation. J Struct Eng 142:E4014003. CrossRefGoogle Scholar
  5. Christovasilis IP, Filiatrault A, Constantinou MC, Wanitkorkul A (2009) Incremental dynamic analysis of woodframe buildings. Earthq Eng Struct Dyn 38(4):477–496CrossRefGoogle Scholar
  6. Comerio M (2006) Estimating downtime in loss modeling. Earthq Spectra 22:349–365CrossRefGoogle Scholar
  7. FEMA (2012) Seismic evaluation and retrofit of multi-unit wood-frame buildings with weak first stories. FEMA P807, WashingtonGoogle Scholar
  8. Folz B, Filiatrault A (2001) Cyclic analysis of wood shear walls. J Struct Eng. Google Scholar
  9. Harris SK, Egan JA (1992) Effects of ground conditions on the damage to four-story corner apartment buildings, The Loma Prieta, California, Earthquake of October 17, 1989—Marina District. In: O’Rourke TD (ed) United States Government Printing Office, Washington, DC, pp F181–F194Google Scholar
  10. Holmes W, Somers P (1996) Northridge earthquake of January 17, 1994 Reconnaissance Report, Oakland, CAGoogle Scholar
  11. Ibarra LF, Medina RA, Krawinkler H (2005) Hysteretic models that incorporate strength and stiffness deterioration. Earthq Eng Struct Dyn 34(1):1489–1511CrossRefGoogle Scholar
  12. IEBC (2012) 2012 International Existing Building Code. International Code Council, Country Club HillsGoogle Scholar
  13. Jennings E, van de Lindt JW, Ziaei E et al (2015) Full-scale experimental verification of soft-story-only retrofits of wood-frame buildings using hybrid testing. J Earthq Eng 19:410–430. CrossRefGoogle Scholar
  14. Krawinkler H, Parisi F, Ibarra L, Ayoub A. and Medina R (2001) Development of a testing protocol for wood frame structures, Technical Report, Stanford University, Stanford, Calif, CA, CUREE-Caltech Woodframe Project Report No. W-02Google Scholar
  15. LADBS (2015) Mandatory wood frame soft-story retrofit program: structural design guidelines. Los Angeles Department of Building and Safety, Los AngelesGoogle Scholar
  16. Li Y, Yin Y, Ellingwood BR, Bulleit WM (2010) Uniform hazard versus uniform risk bases for performance-based earthquake engineering of light-frame wood construction. Earthq Eng Struct Dyn 39(11):1199–1217CrossRefGoogle Scholar
  17. Lignos DG, Krawinkler H (2013) Development and utilization of structural component databases for performance-based earthquake engineering. J Struct Eng 139:1382–1394. CrossRefGoogle Scholar
  18. Lowes LN, Mitra N, Altoontash A (2004) A beam-column joint model for simulating the earthquake response of reinforced concrete frames. Pacific Earthquake Engineering Research Center, PEER Report 2003/10Google Scholar
  19. Maison B, McDonald B, McCormick D, Schotanus M, Buckalew J (2014) Commentary on FEMA P807 for retrofit of wood-frame soft-story buildings. Earthq Spectra 30(4):1359–1380CrossRefGoogle Scholar
  20. Mazzoni S, McKenna F, Scott MH, Fenves Gregory L et al (2013) OpenSees [Computer Software]: the open system for earthquake engineering simulation. Regents of the University of California, BerkeleyGoogle Scholar
  21. Park S, van de Lindt JW (2015) Genetic optimization for seismic retrofit of soft-story woodframe buildings using FEMA P807 methodology. J Perform Constr Facil 29:04014153. CrossRefGoogle Scholar
  22. Schleuss J, Xia R (2016) Do you know if your L.A. home is at risk in an earthquake? Los Angeles Times.
  23. SEAOSC (2017) SEAOSC design guide: City of Los Angeles soft, weak and open-front wall line building ordiance. Structural Engineers Association of Southern California, Los AngelesGoogle Scholar
  24. Sutley EJ, Van De Lindt JW (2016) Evolution of predicted seismic performance for wood-frame buildings. J Archit Eng. Google Scholar
  25. Van De Lindt JW, Symans MD, Pang W et al (2012) Seismic risk reduction for soft-story woodframe buildings: the nees-soft project. In: World conference on timber engineering 2012, WCTE 2012, pp 237–243Google Scholar
  26. Yin Y-J, Li Y (2010) Seismic collapse risk of light-frame wood construction considering aleatoric and epistemic uncertainties. Struct Saf 32:250–261. CrossRefGoogle Scholar

Copyright information

© Springer Nature B.V. 2018

Authors and Affiliations

  1. 1.Department of Civil and Environmental EngineeringUniversity of CaliforniaLos AngelesUSA
  2. 2.School of Architecture, Civil and Environmental EngineeringÉcole Polytechnique Fédérale de Lausanne (EPFL)LausanneSwitzerland

Personalised recommendations