The Mechanical Performance Of The Pattern Steel-encased Concrete Composite Beam Study Under Negative Moment

As a new type of composite beam, the pattern steel-encased concrete composite beamevolved from steel-concrete composite beam. It has the advantages of steel-saving, goodstability and high bearing capacity. As a result, the study on this type of composite beamis important both in theory and application. The experiment of full scale beam andtheoretical analysis have been carried out to study the capacity of composite beam andlocal buckling of steel beam under compression,considering the bond propertiesbetween concrete and pattern on the inner si-de of the steel.The main work andachievements accomplished in this experiment are presented as follow:(1) The experiment are conducted for pattern steel-encased concrete composite beamunder the negative moment. Through negative moment,which could simulate negativebending moments, the mechanical performance of composite beam at negative momenthas been researched.Experimental results indicate that effective cooperation ofreinforcement in the negative moment area and outer-plated steel beam can be achievedby the shear-resistant connection and bond properties between checkered steel beam andconcrete.(2) Theoretical analyses are made for the ultimate bending capacity and ultimateshear capacity of checkered steel-encased concrete composite beam under the effect ofnegative moment.The corresponding computational formula are proposed for theultimate bending capacity with full shear connection and partial shear connection atnegative moment.The experimental results show an agreement with the computationalresults.(3) Research are made for local buckling property of steel beam at negative momentarea.Based on the mechanical performance research and theoretical analyses,asimplified computation model for bottom plate of steel beam at negative moment area isinvestigated and the computational formula for local buckling capacity of steel plate atcompressive zone is putted forward.