Techno Press

Steel and Composite Structures   Volume 26, Number 5, March10 2018, pages 635-647
Cap truss and steel strut to resist progressive collapse in RC frame structures
Seyed Mehdi Zahrai and Alireza Ezoddin

Abstract     [Full Text]
    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.
Key Words
    progressive collapse; reinforced concrete (RC) frame; alternate load path method; steel strut; cap truss; nonlinear dynamic analysis
(1) Seyed Mehdi Zahrai:
Center of Excellence for Engineering and Management of Infrastructures, School of Civil Engineering, College of Engineering, The University of Tehran, Tehran, Iran;
(2) Alireza Ezoddin:
Faculty of Civil Engineering, Semnan University, Semnan, Iran and lecturer, Department of Civil Engineering, Semnan Branch, Technical and Vocational University (TVU), Semnan, Iran.

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