Long-term Behavior Analysis Of Pretressed Composite Beam Bridge And The Repair And Reinforcement Research

Steel-concrete composite beams are increasingly being used in bridge construction field due to its excellent structural performance and economical efficiency. Prestressing on steel-concrete composite beam bridge can expand flexible working range of composite structure, reduce the deformation caused by service load, and improve fatigue and fracture properties. Taking externally prestressed steel-concrete composite bridge as the research object, this paper in-depth studies the interface slip and long-term deformation, etc. And repair and reinforcement strategies for composite bridge in service are given. The main conclusions are as follows:1) In the current criterion, the problem of insufficient consideration of interface slip exists when designing steel-concrete composite beam bridge. Based on the assumption of linear slip and none uplift between concrete and steel beam, this paper used age-adjusted effective elastic modulus method to consider concrete creep, and derived formula of steel-concrete composite beams slippage considering long-term performance of concrete bridge decks. By examples analysis and comparative validation, the correctness of the derived formulas was proved,which was also more general and applicability.2) Based on the overall and isolates balance equations, strain coordination and constitutive relationship of steel and concrete materials, this paper used age-adjusted effective elastic modulus method to consider concrete creep, and externally prestressed composite beam deflection formula considering Long-term slip effect was derived. Examples analysis showed that consideration of interface slip effect could cause the results of composite beam deformation calculation increasing. And the calculation results of long-term deflection formula given in design specifications were small.3) Based on force method and energy method, considering the influence of steering block friction, stress increment formulas of externally prestressed tendons in three forms of fabric were derived respectively. With selecting examples to analyze and calculate, the results and specification formula results were compared to confirm the correctness of the formula and the applicability for Standardized test fitting formula.4) By summarizing and investigating the common diseases for current steel-concrete composite bridge in service, the causes of the diseases were discussed and analyzed. And key points were proposed so as to reduce the occurrence of disease in the composite beams from a design perspective. Finally the reinforcement strategy of common diseases was summarized, and the transverse shear checking method was discussed on transverse prestressing reinforced composite beam bridges.