Application of Virtual Work Method for Progressive Collapse Analysis of Steel Buildings

This study utilizes virtual work method to calculate individual member contributions to the vertical displacement at the point on which collapse is initiated. An arbitrary column at the base of the structure is removed to initiate the collapse. The study follows a two-step procedure. The first step addresses internal strain energy stored in the system under gravity loads only. The second step continues from the previous step and it involves an application of a virtual load at the location of the column removed. The analysis at this step is an incremental-iterative procedure so that strain energy increments stored in the system are calculated at each iteration while the load is continuously increased. Each member's contribution to the deflection at the point of load application is continuously monitored. A detailed breakdown of member's different response components (i.e., displacement participation factors such as axial, shear, flexural, torsional, connection and panel zone responses) are reported.