Research On Mechanical Behavior Of Concrete-filled Steel Tubular And Reinforced Concrete Structures

As a new structural system, concrete-filled steel tubular(CFST) structure is moreand more used in high-rise, super high-rise, large span structures because it has betterseismic performance. But for the new structural system of CFST, researches are quitea few both in the theory and in the experiment. Relatively speaking, the traditionalreinforced concrete (RC)structural system has been studied by many scholars at homeand abroad for many years, its development of the theory is more mature. Startingfrom this idea, this paper takes reinforced concrete as the reference to carry on thecomparative study on the mechanical properties of the concrete filled steel tubularstructure. This research works mainly have the following several parts.Introducing some key questions which are involved in non-linear calculation ofconcrete-filled steel tubular and reinforced concrete when using ANSYS finiteelement software,it include the material constitutive model,element,ANSYS nonlinearbasic principle, modelling and some tips in practical application.The mechanical properties of CFST cloumn and RC column subjected to axialforce is compared under the same conditions. The design formula of CFST cloumnand RC column is compared under axial load from the different country codes andtheir formula characteristic is analyzed. Based on RC columns with spiral stirrupcalculation principle, a new capacity formula of square CFST column is proposedthrough dividing the areas of core concrete of CFST column into weak and strongrestraint area according to its restraint characteristic and compared the calculatedresults with the experimental results to verify the proposed formula.The mechanical properties of CFST cloumn and RC column,including failuremodes, mechanical mechanism, deformation and bearing capacity are compared underthe same eccentric load.The eccentricity and the slenderness ratio of CFST cloumnand RC column are analyzed to obtain their influence on the mechanical properties bythe parameter method.The design formula of CFST cloumn and RC column undereccentric load is compared and their design formula characteristic is analyzed.Base onRC column formula under eccentric load,a new formula of CFST column isproposed adopting the concept of large eccentricity and small eccentricity.The finite element model of CFST column under cyclic loading is establishedand the model reliability is verified through the experiment. On this basis, CFSTcolumn and RC column subjected to cyclic load is simulated to compare their mechanical properties,including the failure modes, hysteresis curve, skeleton curve,bearing capacity, ductility, dissipation energy capacity, strength degradation andstiffness degradation and so on under the same conditions.Selecting Tianjin wave, seismic response analysis is done by using time historyanalysis method in CFST frame and RC frame, compared with their dynamicresponses including the dynamic characteristics, the displacement and the acceleration.The analysis results indicate that CFST frame is not obvious advantage over RC frameunder frequently occurred earthquake,but seismic behavior of CFST frame isobviously superior to the RC frame under rare earthquake.