Experimental study on influence of post-pouring joint on long-term performance of steel-concrete composite beam

摘要

The long-term behaviour of steel-concrete composite beam with assembled concrete bridge decks should be different from that of composite beam with monolithic concrete bridge decks when the new-old concrete age difference is considered. Two simply supported T-shaped steel-concrete composite beams with post-pouring joints were designed and tested to evaluate the influence of concrete age difference between the precast slabs and the post-pouring joints on their long-term performance. Long-term performance tests of 223 days were performed on composite beams A and B subjected to uniformly distributed load and axial load, respectively. Shrinkage and creep tests were also conducted on concrete prisms made with the same batch for precast slabs and post-pouring joints of test beams. Moreover, an incremental differential model of creep and shrinkage considering the concrete age difference between the precast slabs and the post-pouring joints was developed by age-adjusted effective modulus method, and a long-term performance model of assembled composite beam based on the deformation coordination conditions was proposed in this paper. The experimental results were compared with the results predicted by the traditional method ignoring the age difference and the results calculated based on the proposed model considering the age difference. The comparison of results indicate that the results from the proposed model agree well with the test results, and the traditional method ignoring the age difference would severely underestimate the effect of creep and shrinkage of assembled concrete decks. The proposed model indicates the normal stress of concrete in post-pouring joints may develop from compressive stress to tensile stress with time. Moreover, the cracking phenomenon of post-pouring joints in assembled composite beam in engineering practice can be understood by the proposed model.