Experimental Research On Oblique Section Shear Capacity Of Prestressed Composite Concrete Beam With Encased H-steel

It has a gradual transition to a new phase of equal importance with new-built and reconstruction compared with new-built mainly before of construction engineering in our country.The reconstruction technique using outer-jacketing structure for adding storie around the existing building has become one of the hot issues of civil engineering. The existing building need works as usual which requried to avoid the added load transferred to the roof of the existing building during reconstructure.Prestressed concrete technology is a technological revolution to concrete structure.High efficient prestressed concrete which designed by modern concepts and methods, can effectively improve the structure performance of using stage (such as controlling development of crack and eliminating deflection of structure, etc.), raise the shear and fatigue strength, improve resilience after load, make full use of high strength steel and adjust internal force of structure effectively. Prestressed composite concrete beam with encased H-steel is one of the structural design forms for the outer-jacketing structure for adding story.Prestressed composite concrete beam with encased H-steel is constituted with the skeleton combination of concrete,steel,prestressed tendons and non-prestressed reinforcement. A number of prestressed tendons are arranged rationally between the upper and lower flange of the steel. And lash non-prestressed reinforcement frame in the steel periphery and poured concrete.Such beams has both advantages of the steel beam and concrete beam,and there is a broad application space. After read a large number of references, we understand the research of concrete structures encased steel at home and abroad, compared the structural characteristics of prestressed concrete encased steel, clear of the value of the research and application. This structure is better for the conditions of the performance which is large-span, and heavy force.It often appear small shear span ratio of shear in the engineering of prestressed concrete composite beams encased steel. Research of these components has not been reported. In this paper,base on the shear theory,we analysis the shear mechanism of reinforced concrete,prestressed reinforced concrete, concrete encased steel and prestressed concrete composite member encased steel. Discussed the main damage form of oblique section and the influence on section bearing capacity which originated from key parameters such as shear span ratio and concrete strength grade.In order to solve these problems the we completed shear tests of five simple beams with small shear span ratio, and accumulated test data.Based on shear tests of these beams and mechanism analysis, we studied the development of deformation under load and made the shear strength formula of these beams.