Time-Dependent Composite Effect Of The Curved Steel-Concrete Composite Beams In Construction Stage
In order to accurately analyse the mechanical behaviour of the steel-concrete composite beams in construction stage, firstly the change law of the shear strength of the stud connectors with the concrete age was studied using the push-out test, in which the time-dependent shear strength formula of the stud connectors was obtained. Secondly, model tests of two simply-supported curved composite beams were carried out during the casting process of concrete slab, the ANSYS finite element models were built with the time-dependent shear strength formula applied in it, and then the experimental and numerical results were verified for each other. On the above basis, a three-span curved continuous composite beam bridge was taken as the sample, by which the influence of the stud connector’s time dependent shear connector strength on the stress behaviours of composite beam in construction stage was studied.
The analysis results indicate that the shear strength and stiffness of stud connectors cannot be ignored even when the concrete is in rather early stage, and the early shear strength increases more quickly, whereas the later shear strength slowly. During the segmental casting process of concrete slab, if the casting time interval is between 6 hours and 7 days, the time-dependent characteristics of the early composite action should be considered in the stress behaviors analysis of composite beam in construction stage. Meanwhile, for the hardened concrete segment, the relative slip between the steel girder and concrete slab should also be considered, or else unsafe calculation results will be induced.
During the construction of the steel-concrete composite bridges without supports, usually the concrete slabs are cast in segments. Because the strength of the concrete will increase with the concrete age, as well as the shear strength at the joint surface between the concrete slab and steel girder, as a result, different degree of the time-dependent composite action at the interface will be produced between the adjacent segments which are cast at different time, consequently the structural stiffness of the composite beams will change with different casting sequence and casting time, which will lead to different mechanical characteristics of the composite beams in construction stage.
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