Collapse mechanism and failure criteria based on layered shell element model for super-large cooling tower under wind action

Many damage events of the super-large cooling towers under wind action have taken place in history, but the current code lacks the collapse mechanism and failure criteria of super large cooling towers under wind action. The layered shell element model was established for a 228 m high cooling tower under construction in Northwest China, considering the multi-scale wall thickness and reinforcement ratio variations of the tower. The surface wind load of the cooling tower was obtained by a rigid body pressure measurement wind tunnel test. The displacement and internal force responses of the tower under typical wind speeds were analyzed by combining the incremental dynamic analysis method. The critical collapse wind speed of was determined as 83 m/s. Based on the von Mises stress variation before and after the node failure, three redistributions of internal forces mechanisms during the collapse of the tower were extracted. Thus, the wind-induced failure criteria were developed based on throat deformation. Research results demonstrate that the layered shell element model can simulate the progressive collapse process of a super-large cooling tower effectively. The central damage area by local element failure diffuses and forms a fracture network until complete collapse. The first unit failure triggers the sliding surface mechanism firstly. Subsequently, internal forces are redistributed mainly according to the rotating hinge mechanism and slipping surface mechanism. The super-large cooling tower developes failure and collapses when the deformation failure index δ is not less than 1.5%, where δ is the ratio between the relative horizontal displacement at the throat upwind surface and backwind surface and the throat diameter.