| With the accelerated pace of urban construction and development of construction science & technology, as the products of residential buildings, special-shaped (T-shaped, L-shaped,+-shaped) reinforced concrete columns, which can avoid the appearance of edge angles in the room, are benefit for the layout of building and increasing the utilization area of building, because the thickness of reinforced concrete column limbs are the same as that of the wall. But because of its poor ductility, strict limitation of the ratio of axial compression stress to strength, more complicated construction and so on, the further development of special-shaped reinforced concrete columns are restricted. Compared with special-shaped reinforced concrete columns, special-shaped concrete-filled steel tubular columns have higher bearing capacity and better plasticity. Because of the merits, special-shaped concrete-filled steel tubular columns have better application prospects, then more and more scholars are attracted all around the world. However, the current studies on special-shaped concrete-filled steel tubular columns are limited in the field of mechanical behavior. Supported by the Project of Construction Scientific Research of Wuhan City in 2008 (project number:40) and the Project of Construction Science and Technology Research (Development) of Hubei Province in 2008 (project number:44), the experimental study and non-linear finite element analysis on the earthquake resistant capability of special-shaped (T-shaped, L-shaped) concrete-filled rectangular composite steel tubular columns have been finished. The results of the research will provide reference for Technical Specification for Structures with Special-shaped Concrete-filled Steel Tubular Members. At the same time, it has important practical significance and engineering application value to the further application of concrete-filled steel tubular structure.The main content of the paper includes the following aspects:(1) Based on the generalization of the related research and engineering application of all kinds of special-shaped concrete-filled steel tubular columns all around the world, and the analysis of the existential problems, two kinds of improved special-shaped (T-shaped, L-shaped) concrete-filled rectangular composite steel tubular columns are presented. One is made of a rectangle steel tube and a U-shaped steel plate, which are directly welded together. The other is also made of a rectangle steel tube and a U-shaped steel plate with restraint sticks. According to a certain distance, the restraint sticks are set along the steel tube. The comparison and analysis show that improved special-shaped concrete-filled rectangular composite steel tubular columns and improved special-shaped concrete-filled rectangular composite steel tubular columns with restraint sticks are more economical, and the constructions are more convenient.(2) According to Specification of Testing Methods for Earthquake Resistant Building (JGJ101-96) and other related specifications, considering the influencing factors of ratio of axial compression stress to strength, concrete strength, thickness of steel tube, cross-section type and so on,6 special-shaped concrete-filled rectangular composite steel tubular column specimens (3 T-shaped columns,3 L-shaped columns),6 improved special-shaped concrete-filled rectangular composite steel tubular column specimens (3 T-shaped columns,3 L-shaped columns), as well as 6 improved special-shaped concrete-filled rectangular composite steel tubular column specimens with restraint sticks (3 T-shaped columns,3 L-shaped columns) are designed according to the proportion of 1 to 2. Through pseudo static test, the earthquake resistant capability is studied under low cycle repeated load. The experimental results show that the shapes of hysteresis curves of all specimens are full and fusiform, the displacement ductility factors are greater than 2, the equivalent viscous damping factors are greater than 0.17. every specimen has good earthquake resistant capability (including improved special-shaped concrete-filled rectangular composite steel tubular columns and improved special-shaped concrete-filled rectangular composite steel tubular columns with restraint sticks).(3) Using orthogonal test analysis methods, the pseudo static experimental results of 9 T-shaped and 9 L-shaped concrete-filled rectangular composite steel tubular column specimens under low cycle repeated load are orthogonal analyzed. The impacts of 4 factors (ratio of axial compression stress to strength, concrete strength, thickness of steel tube and cross-section type) to the ultimate bearing capacity, ductility and energy dissipation performance of special-shaped concrete-filled rectangular composite steel tubular columns are analyzed separately. The influence degree of different factors to the ultimate bearing capacity, ductility and energy dissipation performance are compared. The results show that for T-shaped columns, improved special-shaped concrete-filled rectangular composite steel tubular columns with restraint sticks are benefit for improving the ultimate bearing capacity and earthquake resistant capability; for L-shaped columns, improved special-shaped concrete-filled rectangular composite steel tubular columns with restraint sticks are benefit for improving the ultimate bearing capacity, and improved special-shaped concrete-filled rectangular composite steel tubular columns are benefit for improving the earthquake resistant capability.(4) Using large-scale finite element software ABAQUS, the 3D nonlinear finite element analysis of 9 T-shaped and 9 L-shaped special-shaped concrete-filled rectangular composite steel tubular column specimens have been finished. The calculated results and experimental results are compared. At the same time the results show that the calculated results of finite element are consistent with the experimental results basically. This also shows that the constitutive models of steel and concrete, the finite element model, the solving method and so on are reasonable and reliable. This provides reliable basis for the following multi-parameter analysis.Based on the generalization of the paper, the research prospects about the project are brought up. |
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