Research On Mechanical Behaviors Of Unbonded Prestressed Concrete-Filled Square Steel Tubular Structures

Concrete-filled steel tubular structures have better ability of suffering the press and convenient craft which are widely used in civil engineering. However, they have lower ability in face of tension and bonding moment. If given prestress to the members, it will enhance the stiffness and crack resistance. Also, it will enhance the intereacation between steel pipe and concrete, too. Therefore, it is necessary to lodge and research on prestressed concrete-filled steel pipe regularly. With the calculation theory, it will exploit the field of application of concrete-filled steel tube in modern structural engineering region.The mainly parts of the paper as follows:Aiming at mechanical behaviors of unbonded tedon, three ways of calculation formulas of internal force increament are established in the paper. Aiming at mechanical behaviors of concrete-filled square steel tube, construction methods and line patterns are presented in this paper regularly. Aiming at mechanical behaviors of concrete-filled square steel tube, the influencing facor and calculation procedure of prestress losses are elicited. Also, the calculation formulas of prestress losses are established in this paper. Aiming at mechanical behaviors of concrete-filled square steel tube under axial tension load, bending moment, eccentrcic load, the stress calculation formulas are founded in construction stage, regular service stage, failure stage. Accordingly, the bearing capacity designing formulas are established in the text. Still, the computer program is used to simulate the mechanics behaviors of the member under bending moment. Considering influention factors of steel ratio, concrete strength level, initial tension force, the table of bending moment-curvature and load-deflection are drawn in the paper seperately.In the light of theory of computation, some conclusions are drawn in this paper. Using prestressed concrete-filled steel pipe, it could not only broad the filed of application of concrete-filled steel tube, but also improve the performance of members. Accoradingly, it could give full play to predominance of composite structure.