Progressive collapse resistance prediction of truss string structures under key chord failure

Cables and lower chords at the support play a crucial role in the resistance of truss string structures (TSSs) against progressive collapse. However, the available studies have predominantly focused on cable failure, with seldom research on the progressive collapse mechanism analysis and resistance prediction under the failure of the lower chord at the support. In this study, the accuracy of the finite element (FE) model is verified based on the test results of the TSS exposed to cable failure. Secondly, the criterion for progressive collapse failure of TSSs is given, namely, the structure is considered to have suffered progressive collapse failure when the vertical displacement in the mid-span exceeds 1/60 of the structural span or local collapse occurs. Then, the mechanisms of progressive collapse failure of TSSs exposed to the failure of the lower chord at the support are outlined, and the results show that after the failure of the lower chord at the support, the load paths transmitting the support and the cable are blocked, and the support and the mid-span become the weakest locations of the damaged structure. Moreover, a simplified prediction equation for the progressive collapse resistance of TSSs exposed to the failure of the lower chord at the support is proposed in accordance with some assumptions and simplifications. The comparison reveals that there exists no >20% error between the predicted and FE values, which indicates that the equation has good accuracy and reliability. Therefore, the equation provides a certain reference value for engineering applications.