Inelastic Analysis Of Prestress Steel-concrete Composite Beams

Steel-concrete composite beams with externally prestressed tendons integrate the modern prestressing technology into the traditional steel-concrete composite beam, which show evident economic and social advantages and possess great extensive prospect in bridge and structural engineering. This paper focuses on the flexural behaviors of prestressed steel-concrete composite beams with partial shear connection. The main work included as follows: 1. Twelve specimens shifted on concrete strength and degree of shear connection were tested under monotonous loads, which were simulated under positive and hogging moment, to study the ultimate flexural capacity,deflection,slip property and increment of extrenal tendons of the prestressed steel-concrete composite beams. 2. The nonlinear FE models of the prestressed steel-concrete composite beams were established and analysis were conducted to investigate the flexural capacity and slip property under different parameter, such as concrete strength,partial shear connection,prestressing of the external tendons,corss-section dimentions,etc. 3. Based on the static testing and nonlinear FE analysis, the simplified calculation model of the prestressed steel-concrete composite beam with externally prestressed tendons is established with consideration of the partial shear connection and comparison was conducted between the proposed model and the ultimate plastic theory. Some important conclusions were extracted from the research and listed in the followings: 1.(a)The lower concrete strength as well as degree of shear connection will result in the reduction of the flexural capacity and the deflection increment of composite beam under positive moment. (b)Concrete strength and degree of shear connection will make rare influence on the mechanical performance of the prestressed composite beam under hogging moment. (c)The greatest slip appeared near the quarter of the span in the positive moment area and the pure bending region in the hogging moment area. 2. The nonlinear FE models can predict the elastic and elasto-plastic flexural load-carrying capacity,deflection,slip development and distribution, and increment of extrenal tendons of the pretressed steel-concrete composite beams. The results extracted from the models agree well with those from static testing. 3. (a)For the composite beam with externally prestressed tendons under positive moment, concrete strength has greater influence on mechanical performance of the beam than the prestressing of the external tendons, lower degree of shear connection will result in the reduction of the flexural capacity and the deflection increment of prestressed composite beam, But the influence turned to inapparent while the connection degree is larger than 1.0. 4. The simplified calculation models of the ultimate flexural capacity of the prestressed composite beams can predict the elasto-plastic ultimate flexural capacity. The ultimate flexural capacity under positive moment according to the simplified formula is less about 10% than the result of ultimate plastic theory, but the ultimate flexural capacity under hogging moment is greater about 10% than that from the ultimate plastic theory.