American Society of Civil Engineers

Inelastic Dynamic Progressive Collapse Analysis of Truss Structures

by Ramesh B. Malla, (Associate Professor, Department of Civil and Environmental Engineering, University of Connecticut, Storrs, CT — 6269-2037 E-mail: and Puneet Agarwal, (Graduate Research Assistant, Department of Civil, Architectural and Environmental Engineering, The University of Texas, Austin, TX — 78712)
Section: Progressive Collapse and Fire, pp. 1-10, (doi:

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Document type: Conference Proceeding Paper
Part of: Structures Congress 2006: Structural Engineering and Public Safety
Abstract: In a truss, dynamic effects may arise not only due to external dynamic loads but also due to sudden reduction in the stiffness and load carrying capacity of a member. The sudden reduction in the load carrying capacity of a member may not only occur due to complete member failure, but also due to postbuckling and subsequent inelastic cyclic member behavior. The resulting dynamic redistribution of internal forces may lead to progressive collapse of the entire truss structure. In the present study, an analytical method to model the dynamic nature of progerssive collapse is presented. A numerical scheme has been developed to track and generate the a complete inelastic cyclic force-diformation characteristics of every member of the truss at each iteration step of the solution scheme of the dynamic equations of motion. The solution methodology is based on the finite element technique and considers elasto-plastic material and large deformation geometric nonlinearities using Pseudo force technique. As an illustration, this methodology is applied to the failure analysis of a two-dimensional redundant truss structure consisting of forty members. The truss is subjected to a slight quasistatic overload such that the failure is initiated by buckling of a member. The results show that postbuckling and subsequent cycles of inelastic force-deformation behavior of truss members give rise to adverse member force redistribution that leads to complete collapse of the structure even if it is built with redundant members.

ASCE Subject Headings:
Progressive collapse