Experimental Test On Progressive Collapse Resistance Of Monolithic Precast Concrete Spatial Frame Substructures

Since the Ronan Point apartment event in London,England(the partial vertical collapse of the fabricated wall panel structure),the concept of progressive collapse had begun to become known to engineers and scholars.Every major progressive collapse accident will basically attract more attention and update from the norms of many countries.In foreign and Chinese norms,it was mentioned that the alternate path method(AP method)was used to review the structure’s ability to resist progressive collapse.Many scholars had carried out experimental research on cast-in-place concrete(RC)and fully-assembled concrete planer frame substructures,but there were not many experiments to study the monolithic precast concrete(PC)spatial frame substructures.Nodes of PC and fully assembled structures the form was not the same,and the node area was the weak part of the fabricated structure.And in recent years,China was vigorously promoting prefabricated buildings.To this end,this paper mainly studied the performance of the progressive collapse test of the PC spatial frame substructure through test methods.In this paper,a 5-layer reinforced concrete frame structure was designed by PKPM software.According to China’s standard AP method,the bottom pillars of the bottom layer were removed,and the two spans in the longitudinal outer frame of the bottom layer and the transverse cross-section connected to the pillars were selected as the experimental research area.Six concrete frame substructure test pieces were designed and fabricated according to the 2/3 scale.The middle column was statically loaded,and the middle column of the space frame substructure did not exert lateral restraint.The parameters studied are: comparison of RC and PC spatial frame substructure,difference of three structural forms of PC structure beam-column joints,comparison of PC spatial and planar frame substructures.Three kinds of beam-column joints structure form were 90° hooked bar,lap splice in U-shaped PC beam and headed bar using welded anchor plate.Through the load-displacement relationship of the specimens,the lateral displacement of the side columns,the deflection of the beam and the development of the plastic hinge of the beam end,the strain of the steel and concrete,the crack development of the specimens and the failure mode,the progressive collapse mechanism of the specimen was explored.On the basis of the results of the six specimen tests,combined with the existing norms and the theoretical results of the existing research,theoretical analysis was carried out to investigate the difference between the peak loads of the arches of the RC and PC structures,spatial and planer frame substructures.The resistance mechanism of spa tial and planer frame substructures was discussed.Finally,the deformation constraints in the progressive collapse specification were discussed based on the experimental data.