| The PBL shear connector which is increasingly widely used in steel-concrete composite structure is studied in this dissertation. Systematical research on its static performance is conducted, and the fatigue property is preliminarily explored.Some of the typical push-out tests at home and abroad are summarized, and the differences between the results are comparatively analyzed. Based on the construction feature of the test specimen, the push-out configurations are grouped into two categories, and a variety of push-out tests is designed to verify the differences between them. The results show that the load-slippage curve, ultimate load, ultimate slippage, failure process and failure mode are significantly different from each other, reasons for which are the embedment depth of the PBL shear connector and the stress environment of the surrounding concrete. Moreover, the PBL shear connector in steel-concrete composite beam and steel-concrete composite joint should not be generally treated.On the basis of the push-out test results, the reasonable definition for the mechanical property of the PBL shear connector is researched, and the design bearing capacity, shear stiffness, ultimate bearing capacity and ductility factor in various specifications are obtained. The factors influencing the mechanical property of the PBL shear connector is analyzed, and the research achievement of the design bearing capacity formula is overall compared. In accordance with the push-out test results, a regressive design bearing capacity formula considering all kinds of influencing factors is presented.A bilinear spring simplified model for PBL shear connector is proposed, and the load-slippage coordination model for PBL shear connector group is established. Applying the bilinear spring simplified model into the load-slippage coordination model, a simplified calculation method for PBL shear connector group is presented and proved to be reliable. The law of the load distribution of PBL shear connector group and its influencing factors are analyzed.The nonlinear numerical simulation for push-out tests of PBL shear connector is performed, and the numerical results are proved reliable by comparing with test results. The PBL shear connector’s failure process is represented through the numerical simulation method. Combining the results from push-out test and the numerical simulation method, the load transfer mechanism of PBL shear connector at each stage for two configurations is analyzed. On the basis of the research on the failure mechanism of the PBL shear connector, causes of different failure modes are studied, and diversities of the failure mode and mechanical property resulted from different structural parameters are summarized.Based on the orthogonal experimental method, numerical simulation tests are designed to investigate the structural parameters’effect on the mechanical property of PBL shear connector. Statistical analysis of simulation results show that the significant influencing factors of design bearing capacity are successively the diameter of opening hole, diameter of perforate rebar, strength of concrete and thickness of perforate plate, while the factors of the shear stiffness are successively strength of concrete, diameter of opening hole, diameter of perforate rebar and thickness of perforate plate. According to the order and interaction of influencing factors and the relationship between index and factors, the reasonable structural parameters are determined. Considering the actual situation of steel-concrete composite structure, the rational parameter range for the steel-concrete composite beam and composite joint is presented.Fatigue tests of18specimens are carried out to inverstigate the fatigue property of PBL shear connector. The fatigue life and residual slippage corresponding to fatigue load are obtained by fatigue tests. Comparing fatigue failure process with static failure process, the fatigue failure mechanism is studied. Through range analysis and variance analysis, the structural parameters’impact on fatigue performance is studied. The results show that in the case of same concrete strength, the open hole diameter and the thickness of perforate plate are main influencing factors of PBL shear connector’s fatigue performance, and the open hole diameter has greater impact.The relationship between fatigue load and fatigue life is established which provide a convenient to evaluate the fatigue life of PBL shear connectors.The residual slippage between steel and concrete is selected as the damage variable. According to the relationship between residual slippage and load cycles, the two-stage linear fatigue damage accumulation model is proposed. Model tests are performed to investigate the static performance of fatigue damaged PBL shear connectors. The test results show that fatigue damage make PBL shear connectors’bearing capacity reduced, and make the shear stiffness increase for PBL shear connectors with perforate rebar while decrease without perforate rebar. |
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