Study On Progressive Collapse Performance Of Strengthening RC Frame Structure With High Performance Ferrocement Laminate And Steel

Collapse capacity of structure becomes an important problem because of that progressive collapse of buildings caused by exploding,terrorist attack,earthquake,fire and other accidents happened frequently.Many academic researchers and engineers have been engaged in the prevention of progressive collapse,but the existing research focuses on the plane frame and the frame without the slabs,ignoring that the slabs enhance structure as a whole.Meanwhile,it is urgent to study the strengthening mechanism of progressive collapse,due to a large number of active structures lack of collapse capacity.In respect of the problems above,study on progressive collapse and strengthening of 1:3 scale spatial frame structure have been done,the main achievements are as follows:1.Study on the mechanism of cast-in-place slab in the process of RC frame structural progressive collapse.A quasi-static test was carried out to experimentally study the progressive collapse of a two-storey by 2 × 1 bay spatial frame structure with slab.The progressive collapse mechanism and deformation failure model of the residual structure due to a side column loss were analyzed.The results indicate that: the resistance provided by slab tensional membrane mechanism occupies more proportion in the whole collapse resistance with the increase of uninstall displacement.Based on the material characteristics and structure size,theoretic calculation methods of the maximum horizontal deformation,the critical displacement of pushing outward section to stringing inward section,the critical displacement of beam failure are proposed.At the same time,simplified calculating model and computational formula of vertical resistance for RC frame structure are raised,and the results of theoretic calculation are well coincident with those of tests.A spatial frame structure is analyzed by the method,and the result indicates that the vertical resistance of structure improves 128% with considering slab.Combined experimental results and theoretical analysis,the checking method of structural vertical resistance and the limit of beam's angle are also proposed.2.Study on failure mechanism and bearing capacity calculation of the frame structure with strengthening beam in the process of progressive collapse.A quasi-static test was carried out to experimentally study the progressive collapse of a spatial frame structure,whose beam was strengthened by high performance ferrocement laminate and steel.The progressive collapse mechanism,deformation characteristic and effective resistance were comparatively analyzed.The results indicate that beam arch mechanism and beam catenary mechanism was enhanced by strengthening,and the ultimate resistance of structure increased 11.9%.Steel strand destroyed before beam steel,which delayed the destruction of beam,increasing of structure ductility effectively.Based on the simplified calculating model of beam catenary mechanism,computational formula of vertical resistance for beam strengthened structure are raised.Combined material characteristics and reinforcement layer parameter,the critical displacement of beam failure are proposed.At the same time,combined action of reinforcement layer and beam is analyzed to propose the structural measures for strengthening beam.3.Study on failure mechanism and bearing capacity calculation of the frame structure with strengthening slab in the process of progressive collapse.A quasi-static test was carried out to experimentally study the progressive collapse of a spatial frame structure with slab strengthened by HPFL and steel.The potentiation of reinforcement layer for slab tensional membrane mechanism,and the influence on structural progressive collapse were comparatively analyzed.The results indicate that: the ultimate resistance of structure increased 24.6%,and the destruction of structure was delayed evidently.After beam damaged,the resistance provided by slab tensional membrane mechanism still exceeded the ultimate resistance of primal structure,so the method could improve structure ductility was proved.Material characteristics and structure of reinforcement layer are analyzed,and the critical displacement of beam failure are proposed for the slab strengthened structure.Based on the simplified calculating model of slab tensional membrane mechanism,computational formula of vertical resistance for slab strengthened structure are raised.Then,the force condition of reinforcement layer is analyzed to verify the structural measures of strengthening slab are effective.4.Analysis on progressive collapse performance of RC frame structure with local strengthening.Connecting to the quasi-static progressive collapse test result of RC frame structure,the accuracy and reliability of SAP2000 is verified,then the eight-story structure is simulated to zone the primary structure and reinforced structure,the method of dividing structure into collapsed area,interrelated area,intact area with the DCR of beam bending moment is proposed.The study indicates that interrelated area increases significantly after collapsed area is strengthened.The local strengthening can effectively enhance the load transfer path and improve the progressive collapse performance of the structure is verified.The analysis and design process of strengthening structure for vertical progressive collapse is proposed at last.