Experimental Study On Progressive Collapse Of Precast Concrete Frame Structures Under Fire

Building fire has become one of the biggest threats to the life of buildings.The precact concrete structure has been widely used in engineering because of its good quality,energy saving and environmental protection,and manpower saving.Accidental loads such as explosions,impacts,gas leaks,and car accidents cause fire disasters.After the structure is damaged by accident,the high temperature stress performance is worth studying.Structural collapse may be initiated by a stabilitymechanism as a result of geometry changes caused by thermal expansion effects,particularly when temperatures are not high enough to generate significant reduction in material properties In-depth study of the mechanical properties of the precast beam-column joints under high temperature is of great significance for future structural design,fire protection design and post-fire evaluation.In this paper,the precast concrete beam column substructure is taken as the research object.The main work is as follows:(1)In this paper,a space frame structure is designed by PKPM.Eight half-scale beams-column substructure specimens were designed.Each specimen contains one column and two half beams.The precast specimen beam and column were respectively connected by mechanical sleeves joint?90 bend anchored joint ?lap-spliced joint and scope system joint.The test of the beam-column structure specimen under high temperature was completed.(2)Recording the temperature field of the precast beam-column joints under different fire scenario,and obtaining the temperature variation law of each measuring point of the section,which provides a basis for the high-temperature stress analysis of the precast beam-column structure.The load-displacement curve,column deformation curve and axial force variation of the beam were analyzed.The high-temperature stress mechanism of the precast reinforced concrete beam-column joints was analyzed,and the high-temperature collapse mechanical properties of the beam-column joints were further analyzed.(3)Comparing the mechanical properties and failure modes of the specimens under different fire scenario and exploring the similarities and differences of the bearing capacity and failure modes of the fabricated concrete beam columns under different heating loading paths.The failure mode of the fabricated beam-column substructure is analyzed.The position and order of the plastic hinges of the joints are compared at high temperature and high temperature.At the same time,the rotational performance of the components in the test is analyzed to explore the high temperature and high temperature of the fabricated beam and column structure.Post-deformation performance.(4)To research the progressive collapse resistance performance of fully assembled precast concrete frame structure,two half-scale precast concrete(PC)specimens were designed.The PC specimens were built by high-strength bolt and anchor plate with ductile rod connections in the beam-column joint region,where PC1 was designed without corbel component while the hided corbel was employed in PC2.The static load test was conducted for the specimens under mid-column loss scenario,and the structure response of ultimate loading capacity,strain response,deformation performance and failure mode were discussed,respectively.