| Recycled aggregate concrete (RAC) filled square steel tube structure has the advantages of easy construction, attractive appearance, good seismic behavior, effectively solving the construction waste problem and so on. At the same time, with the increase of building functional requirements or irregular plane shape, some parts often form short span frame beams which ratio of calculated span and section height is between 3-6, and it belongs to the category of deep flexural such as the transfer beams in high-rise buildings, the short span beams which formed in the two sides of longitudinal inside corridor when laying columns, some important construction parts such as the position of fire evacuation routes; these position directly concern the structure safety, and it is likely to happen irreparable personal and wealth losing when these parts damaged. Based on the background, this article make the further research towards to the RAC filled square steel tube structure on the structure level, mainly study the seismic behavior of hybrid frame with RAC filled square steel tube column versus reinforced RAC deep flexural beam, thus providing reference for the further theoretical research and application of RAC filled square steel tube structure.This article designs 8 frames of RAC filled square steel tube column versus deep flexural reinforced RAC beam under the cyclic reversed loading with the changing parameters of replacement rates, different stiffness of beam and column, RAC strength and filled wall. During the process, we observe the failure process and mode of frames and filled walls (2 specimens with filled wall), also obtain the hysteresis curve, skeleton curve and key position strain changes; and in order to study the influence of each parameter to the structure, we analyze the bearing capacity, deformability; energy dissipation ability; strength decaying; stiffness degradation and some other seismic behavior indexes in detail.The test study shows that the recycled coarse aggregate can be made to RAC to fill in the square steel tube to form the square steel tube structure; recycled fine aggregate can be made to recycled concrete hollow block to construct in the square steel tube structure as its fill wall, and the wall can be the first seismic line of the frame. The failure characteristics of the frame structure mainly present deep flexural beam priority with shear failure, the bottom of the column forming obvious bending plastic hinge, filler wall with local failure and block dropping and some other failure phenomenon. According to the related design in this article, the structure can satisfy the seismic design requirements of "strong column and weak beam, strong shear and weak bending, strong node and weak component". At the same time, this article also verifies that the RAC filled square steel tube column has good seismic behavior and the external square steel tube can effectively confine the lateral deformation of RAC.On the foundation of experimental study, based on some theoretical models and related codes, this article proposes the calculation method of related lateral stiffness and interlaminar shear bearing capacity of RAC filled square steel tube frame which divided into with fill wall or not two conditions respectively. And based on the statistical analysis, the paper respectively proposes some related correction factors. The calculation results have good agreement to the test results, proving the calculation methods this paper proposes can provide reference for some theoretical calculation of this structure.The article respectively analyses the hysteresis rule, skeleton curve and unloading stiffness of RAC filled square steel tube frame which divided into with wall or not two conditions. On the foundation, the article respectively proposes three linear restoring force model which can apply to RAC filled square steel tube frame without fill wall and four linear restoring force model which can apply to RAC filled square steel tube frame with fill wall. The calculation restoring force curves have good agreement to the test hysteresis curves. The results can provide reference for the elastic plastic dynamics analysis of the structure.Based on related single parameter and double parameters damage assessment models, the article obtains the damage index D of RAC filled square steel tube frame which divided into with fill wall or not two conditions respectively. On the foundation, the article assesses and analyses the damage performance of RAC filled square steel tube frame which divided into with fill wall or not two conditions respectively. Also proposes the calculation formula of hysteresis dissipated energy Ec. At last, based on the performance design, the article divide the performance level of RAC filled square steel tube frame into 5 levels. At the same time, the research also gives the damage quantitative index which based on performance.The paper uses ABAQUS to verify the seismic behavior of the frame, and the results calculated by using ABAQUS have good agreement to the test results, proving the established model of RAC filled square steel tube frame is accurate. On the basis, this article extendedly analyze the seismic behavior of RAC filled square steel tube frame, on this account, to study the influence of recycled coarse aggregate replacement rates, axial load ratio, steel tube strength, column steel ratio, RAC strength, longitudinal reinforcement yield strength, longitudinal reinforcement ratio to the RAC filled square steel tube structure. On the basis, this article also gives the limit value of design axial load ratio of the structure which can provide some reference to related engineering design. |
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