Progressive Collapse Analysis Of The Steel Moment-Frame With Composite Floor Slabs Based On Membrane Action

In recent years, all kinds of sudden explosion caused by terrorist attacks or accident in production and life, which causes local destruction of structures and even the whole progressive collapse and brings a great threat to people's life and property security, therefore it is urgent to investigate the progressive collapse-resistant capacity of the structure.However, the current research has mainly focused on progressive collapse resistant demand of the pure steel frame and the RC frame structures, and the mechanical characteristics research of the composite structures especially composite floor slabs in the process of progressive collapse is not completed. The composite floor slabs as planar components have a bidirectional beneficial tension effect on the frame structures, which could enhance the ability of progressive collapse-resistant capacity of the structure through the tensile membrane action at the large deformations. It has great theoretical and practical meaning to investigate the progressive collapse-resistant capacity of the steel moment-frame with composite floor slabs.In this paper, the failure mechanism of the membrane action of the composite floor slabs and the impact on the collapse resistance of the structure are studied from aspects of theoretical analysis and numerical simulation. The main contents are as following:(1) The basic structure and working mechanism of composite floor slabs is introduced, and the mechanical characteristics and failure mechanism of the composite floor slabs under the condition of ultimate load condition is analysed. Also, the development mechanism and the engineering application of the membrane action of composite floor slabs under the condition of progressive collapse are analyzed. Based on the orthotropic plate finite element theory, the orthogonal anisotropy analysis method and the practical simplified calculation model of the composite floor slabs are presented by fitting plate method orthogonal anisotropy of composite floor slab calculation analysis method.(2) In order to investigate the progressive collapse-resistant performance of the steel moment-frame with composite floor slabs, four analytical models of removing the corner column, the long side column,the short side column and the internal column were established by using the alternative path method. The influence of the composite floor slabs on the displacement of the failure point and the internal force of the remaining structure is analyzed ,which evaluated the progressive collapse ability of the remaining structure.(3) Through the analysis of the force mechanism and deformation model of the beam-slab collapse-resistant system in direct affecting area,the residual vertical bearing capacity model considering of the membrane action of composite floor slabs is developed to obtain the nonlinear static resistant requirements; An energy-based theoretical framework is proposed for calculating the maximum allowable dynamic demands based on the nonlinear static analysis, which is used to explore the relationship between of dynamic and static response in the progressive collapse process. The finite element software SAP2000 is used to calculate the numerical example to verify the applicability and reliability of this simplified approach and the relationship curve between the residual bearing capacity and the ultimate displacement is obtained to evaluate the mechanical behavior of the composite floor slabs.(4) According to the characteristics of the explosive load, the load time-history function is simplified to study the progressive collapse dynamic effect of steel moment-frame with composite floor slabs, and the relationship between the failure time and structural dynamic response is obtained; An elastic-plastic dynamical analysis model was established by using the finite element software SAP2000, which is used to investigate the effect of composite floor slabs on the structural resistance of the steel moment-frame. The structural resistance effect of composite slabs in the progressive collapse process is quantified by using the resistance coefficient.