| With the development of large-span and high-rise in modern buildings,the load carrying capacity and seismic performance of column are required to be increasingly improved.The application of lattice steel reinforced concrete(LSRC)column is limited due to the disadvantage of load carrying capacity and seismic capacity.Therefore,considering the superior features of spiral reinforced concrete,this study proposed a new column that can meet the requirement of heavy-load carrying capacity and named spiral-confined lattice steel reinforced concrete(SLSRC)column.It can improve the load carrying capacity and seismic performance by placing a spiral hoop inside the LSRC column to strengthen the confinement on concrete.The spiral hoop will not obstruct the longitudinal bar of beam across the column in the beam-column joints of SLSRC column.By studying the mechanism and seismic behavior of SLSRC column,the main works and outcomes are as follows:(1)19 spiral confined concrete specimens were tested under axial load.The strength,deformation,crack-development and failure mode of specimens were analyzed by means of parametric analysis.The factorial analysis method was used to investigate the size effect of axial compressive mechanical properties of confined concrete.The results indicated that,there is size effect in confined concrete.Base on the test results and existing constitutive model at home and abroad,the strength and deformation mode of spiral confined concrete were studied.(2)47 specimens of SLSRC column and 13 reference specimens of LSRC column and spiral stirrup concrete column were tested under static axial load.The failure mode of specimens was observed.The mechanism of combined confinement was investigated by the analysis of damage evaluation,load-deformation curve and section stress distribution of specimens.The improvement of load carrying capacity,stiffness and ductility,compare to LSRC column and the spiral stirrup concrete column,were analyzed by means of parameter analysis.Results showed that the load carrying capacity,stiffness and ductility of SLSRC columns were improved significantly.SLSRC columns could meet the requirement of heavy-load carrying capacity.(3)28 specimens of SLSRC column and nine reference specimens of LSRC column and spiral stirrup concrete column were tested under static eccentric load.The failure mode of specimens was observed.The load-deflection curves,load-strain curves,stiffness degeneration curves and strain characteristic of cross-section were obtained.The mechanism of combined confinement of SLSRC column,which under eccentric load was investigated by the analysis of sectional confined characteristic under non-uniform compression.The effects of different parameters on load carrying capacity,flexural stiffness were analyzed.Finally,by a comparison study,the improvement of load carrying capacity and flexural stiffness for SLSRC columns were analyzed.Results showed that the load carrying capacity and flexural stiffness of SLSRC columns were improved significantly compare to LSRC column and the spiral stirrup concrete columns.The improvement of flexural rigidity was more significantly.(4)Base on the study of mechanism and failure mode of SLSRC columns,two calculation methods of axial load carrying capacity of SLSRC column were proposed.One is a correction method base on different standards.The other is a partition calculation method base on a confined concrete model which was proposed by Mander.The confinement effect of confined concrete under non-uniformly compression was analyzed.Considering the effect of strain gradient,the confined concrete model by Mander was adjusted.Base on this adjusted model,the limit equilibrium theory and the superposition principle,a calculation method of load carrying capacity for SLSRC column under eccentric load were proposed.The calculation results of the proposed load carrying capacity methods were agreed well with the test results.In the case of axial load carrying capacity,the results of second method had higher precision.(5)8 SLSRC columns,one LSRC column and one spiral stirrup concrete column were tested under low cycle load.The damage evolution processes of specimens were observed.The failure mechanism under cycle loads was obtained.The seismic performance such as hysteresis characteristics,strength,stiffness,inter-story displacement angle,ductility,and energy dissipation capacity were analyzed.The influence of the parameters including axial load ratio,stirrup ratio,form of steel and kinds of section were studied.Results showed that comparing with LSRC column and the spiral stirrup concrete column,the hysteresis curves of SLSRC columns are plumper,and the load carrying capacity,stiffness and energy dissipation capacity were improved significantly.The mean values of elastic inter-story displacement angle and elastoplastic inter-story displacement angle were 1/245 and 1/40 respectively.The ductility coefficient was between 4.17 and 6.06.(6)The nonlinear finite element analysis model of SLSRC columns was built to study its mechanical behavior under monotonic horizontal load by using the Abaqus software.The expanding analysis of key design parameters for the mechanical behavior of SLSRC columns was performed after the validity of the finite element model was verified by experiments.(7)Base on the characteristic of hysteresis curves and skeleton curves of SLSRC columns,the restoring model was built,in which the effect of combined confinement was considered.In the calculation of the peak load,the elastoplastic stiffness,the softening stiffness,and the unloading stiffness,the magnitude of confining force was quantitatively calculated.The restoring model and skeleton curve model were agreed well with the test results,and reflected the effect of the axial load ratio and combined confinement. |
PDF Full Text Request