Mechanical Behaviors And Seismic Design Of Steel Reinforced High Strength High Performance Concrete Composite Structures

As a new steel-concrete structural system of steel and concrete construction materials, steel reinforced high strength high performance concrete (SRHPC) composite structure are increasingly used in structural engineering because of the satisfaction to high need of the modern complex and special architecture. Since the international and domestic research of SRHPC structural system is still in the primary stage, the systematic researches on materials and structures of SRHPC are conducted in the paper. The test study and theoretical analysis are described as follows.1. Based on the local materials and normal production techniques, the high strength high performance concrete (HSHPC) applied to the SRHPC composite structures is invented through the optimization of mixture ration. The producing process and mechanical properties of HSHPC are provided. According to the microcosmic analysis of the forming process of HSHPC, A new mechanism about the effect of water reducing agent is provided. In response to the results of present tests and compound stirrups in SRHPC structural elements, the stress-strain constitutive relationship of HSHPC is modified to meet the calculating needs of SRHPC composite structures.2. According to the comparative experimental study of 32 specimens with five loanding schemes, the bond-slip characteristics between shaped steel and concrete (HSHPC and common concrete) are systematically explored. The bond-slip mechanism is analyzed and the reasonable equation of bond-slip constitutive relationship is also established. Failure modalities of specimens are analyzed, and 3 failure patterns and corresponding failure criteria are proposed. The formula of bond strength is deductively provided. In view of the tests, the relative magnitude and distribution of local bond stresses on the surfaces of flanges and webs are given. And the shifts and values of 3 parts (chemical adhesive, friction resistance and mechanical interlock) composing bond strength are measured. The results of the pull-push cyclic loading tests show that cyclic load causes serious deterioration of bond behaviour, and the deterioration law is ascertained. The bond-slip constitutive relationship under the pull-push cyclic load is also proposed. In reference to the present study data, the bond behaviours between HSHPC and reinforcing bars are investigated and the load-bearing performances of shear connectors in HSHPC encasement are researched. The calculating formula of the critical development length of reinforcing bar in HSHPC is given. The analytical models and formulas are proposed to predict the minimum concrete covering thickness, tie reinforcement Ration and the critical anchorage length of SRHPC structural elements.3. The fundamental theories of the inelastic behaviours in nonlinear finite element analysis of SRHPC composite structures are explained, the key technical problems are knocked over in the computer simulation of SRHPC structures. The bond patterns of shaped steel and concrete are investigated in microcosmic mechanics, and the bond-link elements and slip-stiffness coefficients are suggested.4. A specimen of SRHPC frame of two-bay and three-story is tested under the cyclic load. The specimen and the experimental scheme are attentively designed. Under the cyclic load, the general behaviours of frame and the failure patterns of structural members are observed. The characteristic parameters (strength, stiffness, ductility and energy consumption), which reflect the mechanical behaviours of frame structure, are measured quantitatively. The degradation rules of the seismic parameters of SRHPC frame are proposed. The results show the excellent seismic behaviours of SRHPC frame. The finite element model is built up to simulate the loading procedure of test specimen, the calculations show that the analysis model is reasonable and the results are reliable. A great lot of simulating specimens are calculated with nonlinear finite element method, in which the 4 main influential factors (axial compression ration, concrete strength, shaped steel strength and steel ration) are taken into consideration. The influences of four factors on SRHPC frame are analyzed.5. After synthesizing the results of experiments and theoretical analysis, the seimatic design recommendations to composite materials and structures of SRHPC are put forward.