| Green building and energy saving is the main developing direction of the building industry.On the one hand,the prefabricated concrete structure has outstanding advantages in construction quality and environmental protection.On the other hand,the development and application of recycled concrete technology not only saves natural aggregate resources,but also reduces the environmental pollution of the wasting concrete,which brings vitality to the recycling of the construction waste.Based on the existing research,a type of the precast recycled concrete beam-column connections with pressed couplers is put forward and the seismic experimental studies were carried out.The main research works and results are as follows:(1)Based on the relevant literature and the purpose of the research,the design of the specimens and the test plan were carried out,including the size and research parameters of the specimens,determination of strain gauges layout and loading system.Before the experiment,the material properties of the recycled concrete,steel bars and sleeves were tested.(2)The cyclic loading experimental studies were carried out on 9 fabricated specimens and 1 cast-in-place specimen to analyze the effects of longitudinal reinforcement ratio,axial compression ratio,recycled fine aggregate replacement ratio and precast or cast-in-place on the seismic performance of the connections.The seismic performances content that were analyzed in this paper include the hysteresis curve,skeleton curve,stiffness and strength degradation curve,energy dissipation capacity,ductility coefficient,strain of steel bar and sleeve used in the specimens.The results show that the prefabricated specimens connected by the sleeve can achieve the similar seismic performance of the cast-in-place specimens,and can be used in practical engineering;the minimum displacement angle of all specimens is 1/20,which is larger than the limit of the displacement angle of 1/50 in the specification;the ductility coefficient of the specimen is basically greater than 3,which means that the ductility is great;the strength and stiffness degradations of all specimens are small;the reinforcement ratio on the beam has the greatest impact on the bearing capacity and ductility of the specimens,the axial compression ratio has the greatest impact on the cumulative energy consumption of the specimens,and both parameters have the greatest impact on the shear deformation of the core area.(3)The results of the finite element models analyzed by ABAQUS fit well with the test results.On this basis,an extended parametric analysis is carried out.The analysis results show that the eccentric compression boundary of the specimens is between 0.6 and 0.8;the ratio of beam longitudinal reinforcement has the greatest influence on the bearing capacity of the specimens;the column axial compression ratio can limit the development of shear cracks in the core area of the connections;the sleeve stress of each specimen has reached the yield strength but not the ultimate strength,indicating the reliability of the sleeve connection.(4)Based on the existing calculation formula in the specification and the test bending bearing capacity of the specimen,the influence coefficient of the beam longitudinal reinforcement ratio and the replacement ratio of recycled fine aggregate is introduced,and the calculation formula is fitted by regression calculation.Based on the test and finite element results,corresponding suggestions are put forward for the design and construction of the sleeve-connected fabricated recycled concrete beam-column joint specimen. |
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