Experimental Study On Static Behavior Of Assembled Composite Beams With Grouped Studs

As a new type of composite structure,the mechanical behavior,calculation method and design standard of the assembled composite beams with grouped studs need to be further studied.Supported by the "study on the mechanical behavior and calculation theory of double uncoupled structure of assembled composite beams" of Chongqing Natural Science Foundation(cstc 2018jcyjAX0509),this paper carried out static load test of five assembled composite beams and a cast-in-situ composite,and the refinement numerical simulations method is used to simulate the stress distribution,damage accumulation and the force transfer of the beam.The main achievements of this paper are as follows:1.Taking the cluster degree(an index reflecting the dispersion degree of the stud groups)as the main parameter,the bending loading tests of fiveassembled composite beam with grouped studs and anof uniformly distributed cast-in-situ composite beam are carried out;A new slip measuring device is put forward in the test,and the measuring precision was up to 0.001mm.The theory verifies that the device has good working performance.2.According to the test data and test phenomena,the failure mode of typical assembled composite beams with grouped studs is bending failure.The load-deflection curve of assembled composite beams can be divided into two stages:elastic loading and elastic-plastic loading.The distribution of load-slip curve along the length of half-span beams presents the distribution law of "small at both ends and large in the middle".3.Comparing the test results of assembled composite beam and cast-in-situ composite beam,the load-deflection curves of the two beams are basically consistent,and the influence of lower cluster degree on the ultimate bearing capacity and bending stiffness of the assembled composite beam is relatively small;the distribution law of slip along the half-span beam length is basically the same,but the maximum slip value of the assembled composite beam is obviously larger than that of the cast-in-situ composite beam(about 27.303%),and the failure modes of the two beams are both bending failure.4.The static loading finite element model of assembled composite beams with grouped studs considering the weakening of the interface between new-old concrete and the difference of connection between new-old concrete and steel beams is established.The load-deflection curve,slip distribution along the half-span beam length and failure mode of the finite element model are in good agreement with the measured results.Based on the model,the local mechanical behaviors such as the force of each stud groups in the beam,the shear force transfer between the groups and the damage development process of the concrete interface were analyzed.