Analysis Of Seismic Behavior Of Huge CFST Frame-brace Structures

With the development of economy, the demand for electricity increases evidently.It is necessary to build some large thermal power plants instead of small plants.Therefore, thousands of megawatts generator is imported from foreign countries. Inboiler power plants, the super frame is used to support the self-weight of all equipments,which is very heavy. For Concrete-Filled Steel Tubes (CFST), it has the advantages ofhigh load-carrying capacity, good ductility and excellent earthquake resistance and etc,which is suitable for frame columns in power plants. By using the CFST members, theamount of steel can be reduced significantly comparing with steel frame columns. Thetraditional tower which is commonly over100meters, and braces are added to enhancethe lateral stiffness. The buckling-resistance brace (BRB), as a kind of lateral resistancemember, possesses good ductility and seismic performance. At present, there is littleresearch focusing on seismic performance of huge CFST frame-brace structures. Themain contents are as follows:(1) The strain-stress relationship of steel and concrete are determined, which canbe used to model the nonlinear behavior of composite members. The element types forconcrete-filled steel tubes, steel beams, steel braces and buckling resistance braces areselected. The finite element models are validated by comparing with availableexperimental results.(2) The finite element software Abaqus is used to develop the finite element modelof huge CFST frame-brace structures. Based on the incremental dynamic analysis (IDA)method, the seismic behavior of structure under different earthquake load is investigated.The distribution of inter-storey drift ratio and the development plastic hinges are studied.Based on IDA analysis results, response modification factor of3.70and displacementamplification factor of2.50are proposed.(3) The finite element software Abaqus is used to develop the finite element modelof huge CFST frame-buckling resistance brace structures. Based on the IDA method, theseismic behavior of structure under different earthquake ground motions is investigated.Also, the response of structures with buckling resistance braces is compared with that ofwith common steel braces. The comparison results show that structures with bucklingresistance exhibit stronger earthquake resistance. At last, response modification factor of4.24and displacement amplification factor of2.62for CFST frame-buckling resistancebrace structures are proposed.