Numerical study on the progressive collapse of cable-stayed columns due to cable loss

Extreme loading events, such as accidents, impacts, or malicious attacks, may generate local failures that can propagate to subsequent elements, leading to the ultimate collapse of a structure. Research into progressive collapse has mainly focused on structures characterised by high levels of redundancy (e.g., moment-resisting frames). Conversely, little attention has been given to low-redundant structures (e.g., cable-stayed), which may be characterised by higher vulnerability to progressive collapse due to limited alternative load paths. This paper focuses on a distinct form of cable-stayed structures, i.e., cable-stayed columns, evaluating their robustness by considering a cable loss scenario and identifying measures able to reduce the risk of progressive collapse. A variety of bay/branch configurations with fixed and pinned cross-arms were investigated through Finite Element (FE) models developed in OpenSees, accounting for material and geometric non-linearities. An extensive parametric study was initially performed to evaluate the influence of variables on the load-carrying capacity. Cable loss scenarios were successively simulated in non-linear quasi-static and dynamic analyses. Incremental Dynamic Analyses (IDAs) were also conducted to estimate Dynamic Increase Factors (DIFs) for mid-node displacement, axial, and reaction forces (proxy for load-carrying capacity) for several non-dimensional slenderness ratios. In all cases, significant reductions in the buckling load were recorded, with dynamic effects amplifying the columns' response. The present paper sheds light on the performance and design of cable-stayed columns under cable loss scenarios. The results show that, whilst additional branches in the geometric configuration were found to be beneficial in maintaining capacities under cable loss, the appropriate selection of cross-arm profile and its bending stiffness were vital in reducing the risk of collapse.