Experiment And Analysis Of Seismic Performance Of Steel Reactive Powder Concrete Beams

With the development of society and the advancement of urbanization.more and more super highrise buildings and long-span Bridges are emerging.Therefore,higher requirements are put forward for structural mechanical properties such as load-bearing capacity,stiffness and durability.In order to improve the mechanical properties of components such as load bearing capacity,stiffness and durability,this paper proposes Reactive Powder Concrte(RPC)composite structure by replacing common concrete in RC structure with reactive powder concrte.Due to the particularity of concrete materials,this composite structure has higher bearing capacity,greater stiffness and good seismic performance.At the same time,the reduction of concrete porosity makes the built-in steel and steel bars not easy to rust,which improves the durability and fire resistance of members.Therefore,this new combination structure has a good application prospect.In order to study the seismic performance of section steel reactive powder concrete beams,this paper designed and manufactured 4 section steel reactive powder concrete beams and 1 section steel ordinary concrete beam,and carried out low cycle reciprocating load tests to study the influence of reinforcement ratio,stirrup ratio,steel content and concrete strength on the seismic performance of steel RPC beams.The skeleton curves,ductility,stiffness degradation and energy dissipation capacity of steel reactive powder concrete beams are analyzed based on the hysteresis curves and failure modes of beams obtained by experiments.By using ABAQUS software and OpenSEES software,a finite element model of RPC beam is established,and its unidirectional horizontal displacement loading and horizontal low cycle reciprocating loading are investigated,and the seismic performance such as bearing capacity and energy dissipation capacity of RPC beam is compared with the test results.The calculation formula of normal section bearing capacity of shaped RPC beam is presented.The results show that:(1)Bending failure occurred in 4 steel reactive powder concrete beams and 1 steel ordinary concrete beam.At the initial stage of loading,the specimen is elastic,and there is no obvious crack on the surface.With the increase of horizontal displacement,cracks gradually increase upward from the end of the specimen,while the cracks extend to the middle of the specimen,and the width gradually increases.The shaped RPC beam is accompanied by the crisp sound of steel fiber fracture.At the later stage of loading,concrete cracks broke through on the surface of the specimen,the concrete in the corner of the ordinary concrete specimen was crushed,and the concrete in the plastic hinge area was spalled in a large area.Due to the bridge action of steel fiber,the concrete at the end of the beam of the RPC specimen did not spallate in a large area,so the anti-spallation effect of RPC was good.(2)The ratio of reinforcement,steel content and concrete strength are all important factors affecting the seismic performance of steel ractivate powder concrete beams.The increase of reinforcement ratio,steel content ratio and concrete strength can effectively improve the bearing capacity and stiffness of the specimen.The increase of the stirrup ratio can only slightly increase the initial stiffness and peak load of the steel reactive powder concrete beams.There is no significant improvement in the ductility of the members.The bridge action of steel fiber in reactive powder concrete inhibits the development of cracks and replaces part of the role of stirrup in bending specimens.(3)Through a large number of finite element parameter analysis,it is found that the increase of section size,reinforcement ratio and steel content can effectively improve the bearing capacity of the specimen.However,for specimens with RPC strength above 120MPa,continuing to greatly increase RPC strength is not significant enough to improve the bearing capacity of flexural members.Therefore,in the actual engineering application,considering the economic applicability of the structure,the RPC strength can be appropriately reduced,and the section size,reinforcement ratio and steel content of the component can be improved to improve the bearing capacity of the structure.(4)The formula for calculating the flexural bearing capacity of the normal section of RPC beam is proposed,in which the influence of the tensile property of reactive powder concrete on the member is fully taken into account.The calculation results are in good agreement with the experimental results,which provides a theoretical basis for calculating the flexural bearing capacity of the normal section of RPC beam.