Analysis On Progressive Collapse Performance And Mechanism Of Steel-Concrete Composite Beams

Accidents like gas explosion, terror attack and earthquake might cause failure of some critical components in construction, which would trigger progressive collapse of the structure. Steel-concrete composite beam is a type of important bearing component in composite structures, consisting of various structural elements and connection details and resulting in complicated influence on progressive collapse performance and mechanism. Currently, related studies on composite beam are relatively limited, and it has important scientific value and engineering significance to carry out system ones.A series of nonlinear static analyses on multi-span steel-concrete composite beams under the condition of interior column failure were carried out, figuring out progressive collapse performance and collapse resistance mechanism of the structure. The key points are showed as follows:1) Based on the software of ANSYS, twelve finite element models of steel-concrete composite beam-column substructures were developed, parameters like studs spacing, reinforcement ratio et al were discussed on the progressive collapse performance. It shows that collapse resistance capacity has been enhanced by 25% to 75% considering catenary mechanism, and reinforcement ratio, span-depth ratio, height of steel beam as well as longitudinally conditional boundary at both beam ends have a great effect on the capacity. By using energy conservation method, stactic ultimate bearing capacity is converted to equivalent dynamic one, and dynamic increase factor of composite beams falls between 1.13 to 1.32.2) Night finite element models of externally presteressed steel-concrete composite beam-column substructures were developed, effect of layout of deviation blocks, slab reinforcement ratio were discussed. It shows that collapse resistance capacity has been enhanced by 47% to 88% considering catenary mechanism, span-depth ratio, layout of deviation block have a great effect on the capacity. Dynamic increase factor of externally prestressed composite beams is between 1.24 to 1.32.3) Ultimate bearing capacity of catenary mechanism of simplified calculation formula is identical with the value of finite element calculation, which indicates that ultimate collapse resistance bearing capacity of steel-concrete composite beam can be approximately estimated by simplified calculation method. Besides, bearing capacity of plastic hinge mechanism is about 45%～70% to that of catenary mechanism, which indicates that the former one can be considered as ultimate collapse resistance bearing capacity of composite beam, with adaptive safety reserve.The results of this paper can be referenced for the design of steel-concrete composite beams to resist progressive collapse.