Cap truss and steel strut to resist progressive collapse in RC frame structures

  • Zahrai, Seyed Mehdi (Center of Excellence for Engineering and Management of Infrastructures, School of Civil Engineering, College of Engineering, The University of Tehran) ;
  • Ezoddin, Alireza (Faculty of Civil Engineering, Semnan University, Department of Civil Engineering, Semnan Branch, Technical and Vocational University (TVU))
  • Received : 2017.05.20
  • Accepted : 2017.12.25
  • Published : 2018.03.10


In order to improve the efficiency of the Reinforced Concrete, RC, structures against progressive collapse, this paper proposes a procedure using alternate path and specific local resistance method to resist progressive collapse in intermediate RC frame structures. Cap truss consists of multiple trusses above a suddenly removed structural element to restrain excessive collapse and provide an alternate path. Steel strut is used as a brace to resist compressive axial forces. It is similar to knee braces in the geometry, responsible for enhancing ductility and preventing shear force localization around the column. In this paper, column removals in the critical position at the first story of two 5 and 10-story regular buildings strengthened using steel strut or cap truss are studied. Based on nonlinear dynamic analysis results, steel strut can only decrease vertical displacement due to sudden removal of the column at the first story about 23%. Cap truss can reduce the average vertical displacement and column axial force transferred to adjacent columns for the studied buildings about 56% and 61%, respectively due to sudden removal of the column. In other words, using cap truss, the axial force in the removed column transfers through an alternate path to adjacent columns to prevent local or general failure or to delay the progressive collapse occurrence.


progressive collapse;reinforced concrete (RC) frame;alternate load path method;steel strut;cap truss;nonlinear dynamic analysis


  1. Abbasnia, R., Mohajeri Nav, F., Usefi, N. and Rashidian, O. (2016), "A new method for progressive collapse analysis of RC frames", Struct. Eng. Mech., Int. J., 60(1), 31-50.
  2. ACI Committee 318 (2014), Building Code Requirements for Structural Concrete and Commentary (ACI 318 R-14); American Concrete Institute: Farmington Hills, MI, USA.
  3. American Institute of Steel Construction (AISC) (2016), Load and resistance factor design specification for structural steel buildings; Chicago, IL, USA.
  4. American Society of Civil Engineers (ASCE) (2016), "Minimum Design Loads for Buildings and Other Structures", ASCEISEI 7-16.
  5. ASCE 41-13, American Society of Civil Engineers (2013), "Seismic evaluation and retrofit of existing buildings", Public comment draft, Reston, VA, USA.
  6. Cai, J.G., Xu, Y.X., Zhuang, L.P., Feng, J. and Zhang, J. (2012), "Comparison of various procedures for progressive collapse analysis of cable-stayed bridges", J. Zhejiang Univ.-SCIENCE A (Appl. Phys. Eng.), 13(5), 323-334. DOI: 10.1631/Jesus. A1100296
  7. Chen, Y. (2012), "Progressive collapse analysis and safety assessment method for steel truss roof", J. Perform. Constr. Facil., 26(3), 230-240. DOI: 10.1061/(ASCE)CF.1943-5509.0000236
  8. Corley, W.G., Mlakar, P.F., Sozen, M.A. and Thorton, C.H. (1998), "The Oklahoma City Bombing: Summary and Recommendations for Multi-hazard Mitigation", J. Perform. Construct. Facial ASCE, 12(3), 100-112.
  9. Crawford, J.E. (2002), "Retrofit methods to mitigate progressive collapse", Multihazard Mitigation Council National Workshop on Prevention of Progressive Collapse, Chicago, IL, USA, July.
  10. CSI, SAP2000 (2009), "Three dimensional static and dynamic finite element analysis and design of structures", Analysis, Reference, Version 14.1, Computer and Structures, Inc., Berkeley, CA, USA.
  11. DoD (Department of Defense) (2016), "Unified facilities criteria (UFC: Design of structures to resist progressive collapse", UFC 4-023-03 change 3, 1 November 2016, Washington, DC, USA.
  12. Gerasimidis S. (2014), "Analytical assessment of steel frames progressive collapse vulnerability to corner column loss", J. Constr. Steel Res., 95, 1-9.
  13. GSA (2013), "Alternate Path Analysis & Design Guidelines for Progressive Collapse Resistance", General Service Administration, Washington, DC, USA.
  14. Hadi, M. and Alrudaini, T.S. (2012), "New building scheme to resist progressive collapse", J. Architect. Eng., 18(4), 324-331.
  15. Izadi, I.T. and Ranjbaran, A. (2012), "Investigation on a mitigation scheme to resist the progressive collapse of reinforced concrete buildings", Front. Struct. Civil Eng., 6(4), 421-430.
  16. Izzuddin, B.A., Vlassis, A.G., Elghazouli, A.Y. and Nethercot, D.A. (2008), "Progressive collapse of multi-storey buildings due to sudden column loss-Part I: Simplified assessment framework", Eng. Struct., 30(5), 1308-1318.
  17. Jalali Larijani, R., Dashti Nasserabadi, H. and Aghayan, I. (2017), "Progressive collapse analysis of buildings with concentric and eccentric braced frames", Struct. Eng. Mech., Int. J., 61(6), 755-763.
  18. Kim, T. and Kim, J. (2009), "Progressive collapse-resisting capacity of steel moment frames considering panel zone deformation", Adv. Struct. Eng., 12(2), 231-240.
  19. Kim, J. and Park, J. (2010), "Progressive collapse resisting capacity of building structures with outrigger trusses", Struct. Des. Tall Special Build., 25(1), 19-26. DOI: 10.1002/tal. 628
  20. Kim, J., Lee, S. and Min, K.W. (2014), "Design of MR dampers to prevent Progressive collapse of moment frames", Struct. Eng. Mech., Int. J., 52(2), 291-306.
  21. Li, Y., Lu, X., Guan, H. and Ye, L. (2011), "An improved tie force method for progressive collapse resistance design of reinforced concrete frame structures", Eng. Struct., 33(10), 2931-2942.
  22. Longinow, A. and Mniszewski, K.R. (1996), "Protecting buildings against vehicle bomb attacks", Practice Periodical Structure Design Construct, 1(1), 51-54.
  23. Malla, R.B., Agarwal, P. and Ahmad, R. (2011), "Dynamic analysis methodology for progressive failure of truss structures considering inelastic post buckling cyclic member behavior", Eng. Struct., 33(5), 1503-1513.
  24. Marjanishvili, Sh. and Agnew, E. (2006), "Comparison of various procedures for progressive collapse analysis", J. Perform. Constr. Facil., 20(4), 365-374.
  25. National Institute of Standards and Technology (NIST) (2007), Best Practices for Reducing the Potential for Progressive Collapse in Buildings; Technology Administration, U.S. Department of Commerce, Washington, D.C., USA.
  26. Sasani, M., Kazemi, A., Sagiroglu, S. and Forest, S. (2011), "Progressive collapse resistance of an actual 11-story structure subjected to severe initial damage", J. Struct. Eng., 137(9), 893-902.
  27. Sasani, M. and Kropelnicki, J. (2008), "Progressive collapse analysis of an RC structure", Struct. Des. Tall Special Build., 17(4), 757-771.
  28. Shi, Y., Li, Z.X. and Hao, H. (2010), "A new method for progressive collapse analysis of RC frames under blast loading", Eng. Struct., 32(6), 1691-1703.
  29. Stylianidis, P.M. and Nethercot, D.A. (2015), "Modelling of connection behaviour for progressive collapse analysis", J. Constr. Steel Res., 113, 169-184.
  30. United States Army Corps of Engineers (1999), "Technical instructions: structural design criteria for buildings", TI 809-02, US Army Corps of Engineers, Washington DC, USA.
  31. Vlassis, A.G., Izzuddin, B.A., Elghazouli, A.Y. and Nethercot, D.A. (2008), "Progressive collapse of multi-storey buildings due to sudden column loss-Part II: Application", Eng. Struct., 30(5), 1424-1438.
  32. Vlassis, A.G., Izzuddin, B.A., Elghazouli, A.Y. and Nethercot, D.A. (2009), "Progressive collapse of multi-storey buildings due to failed floor impact", Eng. Struct., 31(7), 1522-1534.
  33. Wang, H., Su, Y. and Zeng, Q. (2011), "Design Methods of Reinforce-concrete Frame Structure to Resist Progressive Collapse in Civil Engineering", Syst. Eng. Procedia, 1, 48-54.
  34. Xiao, Y., Kunnath, S., Li, F., Zhao, Y., Lew, H. and Bao, Y. (2015), "Collapse test of three-story halfscale reinforced concrete frame building", ACI Structure Journal, 112(4), 429.
  35. Zahrai, S.M. and Ezoddin, A. (2014), "Numerical study of progressive collapse in intermediate moment resisting reinforced concrete frame due to column removal", Civil Eng. Infrastruct. J., 47(1), 71-88.