Study On Seismic Performance And Design Method Of Partially Precast Steel Reinforced Concrete Columns

To combine the advantages of steel reinforced concrete structures,high-performance concrete and precast structures,an innovative partially precast steel reinforced concrete column,which can be abbreviated as PPSRC column,is proposed in this thesis.The proposed column is composed of a precast outer part and a cast in situ inner part.The precast part can be prefabricated using high-performance concrete,steel shape and reinforcement skeleton,and the inner part can be cast using conventional concrete.When the proposed column is designed as a structural component of upper floors with low axial load,the inner part can be filled with heat insulating material to enhance the thermotechnical performance and to reduce the deadweight,which can be regarded as a new composite column named as hollow precast steel reinforced concrete column or HPSRC column.If designed rationally,the aforementioned PPSRC column and HPSRC column can achieve high seismic performance,durability ability,low construction cost and good workability.In this thesis,the seismic performances of the PSPRC column and HPSRC column were thoroughly explored through pseudostatic test,numerical analysis and theoretical analysis,and the following achievements were attained:(1)Seven PPSRC column specimens and four HPSRC column specimens with high aspect ratios together with six PPSRC column specimens and four HPSRC column specimens with low aspect ratios were designed and subjected to constant axial compression and cyclic loading,with the main test parameters being the shear span-to-depth aspect ratio,section shape,axial compression,ratios of longitudinal and transverse reinforcement and concrete strength of the inner part.The failure mode,hysteresis loop,skeleton curve,lateral stiffness degradation,energy dissipation and displacement ductility ratio were analyzed to investigate cyclic behavior of these two composite columns.(2)Based on the software OpenSees,a numerical model consisted of fiber sections was established to investigate the cyclic behavior of PPSRC columns and HPSRC columns with high aspect ratios,and the corresponding parametric studies were also conducted with the main parameters being the steel ratio,steel strength,axial load and compressive strength of the outer concrete.Meanwhile,an innovative numerical model consisted of fiber sections and nonlinear shear spring was also proposed to explore the cyclic behavior of PPSRC columns and HPSRC columns with low aspect ratios,and this model was validated using the test results of traditional steel reinforced concrete columns and steel reinforced recycled aggregate concrete columns.(3)Based on the plane section assumption,a calculation method for determining the compressive-flexural capacities of PPSRC columns and HPSRC columns was put forward and validated,which can also obtain the axial capacity-flexural capacity interaction curves of these two composite columns.Then,based on the balanced failure criterion and the test results of the specimens with different stirrup ratios and inner concrete strengths,the limit values of axial compression ratio of the PPSRC columns and HPSRC columns were proposed.(4)A theoretical model for predicting the shear strengths of shear-critical SRC beams and shear-critical SRC columns was presented in this thesis.In this model,the concept of strength superposition was applied,and the shear strength of the steel shape and that of the RC part were calculated using comprehensive models and related according to the compatibility of shear deformation.Then,the proposed model was validated using the available test database consisting of 66 shear-critical SRC columns and 57 shear-critical SRC beams,and some recommendations for practical design were also proposed.(5)Based on the test results and analyses above,some recommendations for practical design and for construction of the PPSRC columns and HPSRC columns were put forward,including the limit values of steel ratio,steel strength,compressive strengths of precast concrete and cast in situ concrete together with the anti-crack method of the precast part of the PPSRC columns.