Towards Modeling Progressive Collapse in Reinforced Concrete Buildings

Abstract

This paper presents the results of a study to simulate progressive collapse in a structural system with seismically-deficient components. The range of investigated seismic deficiencies includes inadequate transverse reinforcement, inadequately-developed lap splices, and insufficient lateral confinement leading to buckling in longitudinal bars and/or rupture in transverse ties. The progression of damage into a deficient component is tracked using component models calibrated to trigger an element removal algorithm upon the loss of load-carrying capacity. The component models include a strain-compatible confined fiber section model, confinement-sensitive uniaxial material models for concrete, lap-splices, buckling-enabled longitudinal reinforcement, and axially-coupled shear springs. These component models are applied to the finite element model of a structural system to investigate the effect of older construction details on its progressive collapse potential. The structural system consists of three one-story reinforced concrete (RC) frames linked by a RC slab and transverse spandrel beams. The middle frame is infilled by an unreinforced masonry wall. Intentional deficiencies are introduced to the system to render it seismically vulnerable. The analysis procedure is carried out successfully and the element failure sequence and mode are identified until complete collapse. The simulated response to several ground motion levels highlights the path-dependency of the progressive collapse problem and the necessity of applying a probabilistic approach to the assessment of collapse potential.