Experimental And Theoretical Research On Partially Encased Composite Castellated Beams With Different Details

Partially encased concrete composite beam(referred to as PEC beam)is a new type of composite structure formed by pouring concrete on both sides of the web of H type steel beam.The existence of concrete in the PEC beam can effectively prevent the local instability of the member and enhance the bearing capacity of the member.This research introduced the recent development of partially encased concrete composite beams in modular construction and then summarized the advantages and disadvantages of the PEC castellated beam.The experimental study and theoretical analysis of the new partially encased concrete composite castellated beam are carried out.The PEC castellated beam is cut at the web of the original PEC beam,so that the hole through the web can be formed in a single time,without secondary casting,which can improve the processing efficiency of the component and reduce the construction cycle.Meanwhile,the stirrup through the hole arrangement can restrain more concrete and save welding stirrup and web studs,which can improve the integrity of the component.In this paper,four PEC castellated beams,a traditional PEC beam and a steel castellated beam were designed to conduct four-point bending tests to study the bending performance of the new composite structure.It mainly includes the web opening,the longitudinal steel bar diameter,the flange and the welded stud of the web.A four-point bending static test has been conducted on each specimen.The ultimate bearing capacity of PEC castellated beam In a pure bend,the crack in concrete,the stress and flexibility distribution patterns,were studied.The test results can be referenced by design of the PEC castellated beam.Based on equivalent stiffness replacement method,the deflection calculation formula of deflection for PEC castellated beams are proposed.Also,based on vierendeel truss and thickness of web converted theory,reduced calculation formulas of stress and the calculation formulas of ultimate bearing capacity for PEC castellated beams are deduced.Test results shows the formulas can predict accurately the value and position of critical stress on the edge of hole,the formulas is applicable to analyze the strength of composite castellated beam in elastic stage.According to the characteristics of PEC castellated beam,the spatial finite element model is built with suitable elements and material constitutive laws,nonlinear finite element analysis on ultimate bearing capacity of PEC castellated beam is done.Besides,test results of ultimate bearing capacity test of PEC castellated beam is analyzed,the test results are consistent with the theoretical and Finite Element Modeling results.