Non linear progressive collapse analysis of RC frame structure.

A. U.  Qazi; A.  Majid; A.  Hameed; M.  Ilyas

The casualties due to collapse of buildings are enormous either through blast or vehicle strike which could have been reduced if the buildings have resisted progressive collapse after the accidental removal of vital load bearing elements. In this research, progressive collapse (PC) potential of an existing reinforced concrete (RC) building has been evaluated analytically using Nonlinear FEM software following General Services Administration guidelines. Linear static, non-linear static, linear dynamic and non-linear dynamic analyses have been carried out to explore PC potential. Building under consideration was designed for Earthquake Zone-2B and has potential for PC in linear static analysis while non-linear static and non-linear dynamic analysis results have shown that there is no potential for PC. Results of analysis have been compared by taking deflection under joint where the column is removed and is used as base for comparison. Results show that linear static procedure is conservative as compared to non-linear analysis. Non-linear static and non-linear dynamic analysis provides almost similar results. There is negligible effect of material strength and damping variations on PC. In linear static analysis decrease in deflection of joint at column removal location is approximately 7% for every 7MPa (@1000psi) increase in fc’ while 9% reduction is observed in non-linear dynamic analysis. Damping that can be achieved through installation of dampers has been found beneficial up to 10% value. Increase in damping ratio beyond 10% of critical damping has negligible effect on deflection and PC.