Research On Bond-anchorage Behavior Of Recycled Concrete Beam-column Joints

The environmental pollution of construction waste were getting more and more serious,this was one problem that must be faced.The recycled concrete as an environmentally and friendly building material provided a new way to solve the environmental pollution.The frame beam-column joint is an important force transmission member for the frame structure,so the research on the beam-column joints of recycled concrete frame have far-reaching significance.In the low-cycle cyclic loading test,three full-scale frames middle joints and three full-scale frame side joints were completed.The focused parameters of experiment were the relative anchoring length of the core of the joint,the anchorage form of the joints and the strength of the longitudinal reinforcements.In order to study the bond-anchorage performance of the joints,the components were replaced with 50% recycled coarse aggregate and 30%recycled fine aggregate.Through the analysis of test phenomena,hysteresis curves,skeleton curves,stiffness curves,displacement ductility and energy dissipation performance,and based on the experimental results of the previous 12 middle frame joints,in according to “the common concrete design code GB 50010”,the formulas of shear capacity correction and bonding and anchoring of recycled concrete frame joints were proposed.Test results and conclusions as below:1.At the low cyclic loading,this six beam-column joints of recycled concrete frame were damaged by plastic hinges.Good seismic performance and anchoring performance were demonstrated.2.Combined with the results of previous test,it was shown that when the relative anchorage length was 25,the joint had sufficient anchoring strength to meet the seismic requirements.3.When the regenerated concrete frame joints could not meet the requirement of "strong anchorage",the measures of anchorage performance could be effectively improved by adopting the method of welding transverse short tendons and adding horizontal axils horizontally.4.Under the low cyclic loading,the plastic hinges at the beam ends of the recycled concrete frame was occurred,it shown that the design principles of "strong joint and strong anchorage" could be satisfied by the normal concrete design of the side joints of recycled concrete frame.It was found that the mechanical anchors with 90 o bend anchors and welded anchor plates had strong anchorage strength.The combination of recycled concrete with high strength steel(HRB500)could exert good seismic performance.5.The test results of 18 recycled concrete frame joints were analyzed.And the calculation method that was corrected about the shear strength of recycled concrete frame joints,it was obtained under this test condition.