Study On Seismic Behavior Of Recycled Aggregate Concrete Filled Steel Tube Component And Frame

Recycled aggregate concrete filled steel tube(RACFST) structure is a new system for the combination of concrete filled steel tube structure and recycled aggregate concrete(RAC) structure. It not only inherits the advantages of concrete filled steel tube structure, such as high bearing capacity, good seismic performance and so on, but also solves the resource recycling problem of construction waste effectively. Research group has carried out research about the basic compression behavior of RACFST component. Based on such research, in-depth and systematic study about seismic behavior of RACFST component and frame structure was carried out in this paper.Under the cyclic reversed loading, ten circular specimens and six square specimens were tested. Replacement rate, recycled coarse aggregate, slenderness rate, axial compression rate and steel rate were taken as design parameters. The entire loading process and failure mode were observed, the seismic behavior indexes including hysteretic curve, skeleton curve, ductility, dissipation capacity, strength attenuation and stiffness degeneration were obtained. It is shown that the hysteretic curves are plump; The displacement ductility factors of circular specimens are more than three, and ones of square specimens are closed to three; The displacement angle of circular specimens at failure point are between1/28 and1/17, ones of square circular specimens are between1/21and1/17; The equivalent viscous damping coefficients of circular specimens at failure point are between0.305and0.460, ones of square circular specimens are between0.323and0.360; Based on the seismic behavior indexes, RAC could be used to engineering capacity-bearing structure of concrete filled steel tube.With replacement rate of100%, RAC filled circular steel tube column versus reinforced RAC beam frame and RAC filled square steel tube column versus reinforced RAC beam frame were tested under the cyclic reversed loading. It is shown that the design methods of strong column and weak beam, strong shear capacity and weak bending capacity, strong node and the weak components are met; The hysteretic curve like a full fusiform is symmetrical; The displacement ductility factors are all more than three; The displacement angle of circular specimen at failure point is1/33, and one of square specimen is1/24; The equivalent viscous damping coefficient of circular specimen at failure point is0.243, and one of square specimen is0.216. The frame of RACFST column versus reinforced RAC beam shows excellent seismic behavior.Based on the theory of equivalent plastic hinge, the calculated plastic hinge length of circular specimens are between0.45h and0.95h, and ones of square specimens are between0.65h and0.75h; According to special method including fixed point, dropped bearing capacity of displacement amplitude and model softening point, restoring force model of a trilinear model was established for RACFST component under cyclic reversed loading, such model expressed well the hysteretic relation between load and displacement; Damage development process and seismic capacity of RACFST component was evaluated comprehensively by various earthquake damage models.The present relation between compressive stress and strain was revised by factor of replacement rate, the seismic behavior of RACFST component was analyzed by Abaqus, and the calculated hysteretic curve agreed well with the measured hysteretic curve. Based on existing finite element model, expanded analysis of seismic behavior was carried out, the seismic behavior indexes of one-parameter specimens were obtained, the influence rule replacement rate of recycled aggregate coarse, steel rate, steel type, axial compression rate and slenderness rate made on the seismic behavior indexes was discussed.According to measured hysteretic curve, skeleton curve and stiffness degradation rule, restoring force model of a trilinear model was established for RACFST frame structure under cyclic reversed loading; such model expressed well the hysteretic relation between load and displacement; Based on test result, the one-story, one-bay RACFST frame calculation method about the shear bearing capacity between the layers was discussed; Damage development process and seismic capacity of RACFST frame structure was evaluated effectively by double parameters including deformation and accumulated energy dissipation earthquake damage models. Based on performance design, performance level of RACFST structure was divided into normal use, temporary use, use after repair, life safety and collapse prevention, displacement angle and damage index were taken as quantitative index for performance level, and based on the considerable probability, the limit of the displacement angle and damage index were determined, performance goals were established under different performance levels and different seismic fortification levels.