Experimental Study On Bonding Behavior Between Bar Reinforcement And Grout And Design Of Bar Reinforcement Bulb Anchor Of Composite Anchor

The composite anchor is composed of concrete rod body,steel pipe rod bone in the rod body,grout in the steel pipe and steel strand bar.The pull-out bearing capacity of composite anchor is higher than that of common bolt of equal length,and the cost performance of composite bolt is better than that of common anchor.The composite anchor has the advantages of good anti-corrosion performance,good anti-seepage effect and saving steel and cement.At present,the optimal bonding length of the steel strand with different number of composite anchor in the matched steel pipe is not clear.The relationship between the bearing capacity of bulb anchor and the length and arrangement of bulb anchor is not clear when bulb anchor is used to connect the composite anchor bar and foundation.Therefore,this paper studies the bonding performance between grout and bar and bar bone of composite anchor and the performance of bulb anchor of bar and bar of composite anchor.For the study of the bond property between grout and bar and bar bone of composite anchor,this paper mainly studies by experiment and supplemented by calculation and analysis.Forty specimens were designed and tested,and the weak surface of different steel strands in the matched steel tubes was determined to be the contact surface between the grout and the steel tubes,and the ultimate bond strength of the interface was measured.The main conclusions are as follows:(1)The bond strength between the grout and the steel tube is related to the type of grout.Under the conditions of satisfying the strength and workability requirements of the grout and convenient construction,it is more suitable for the grout to be net cement paste,and the water-cement ratio should be 0.5.(2)The bond strength between the grout and the steel tube is related to the bond length.With the increase of the bond length between the grout and the rod bone,the ultimate load of the grout and the bone will increase,but the ultimate bond strength will decrease.(3)By regression analysis of the test results,the calculation formula of the ultimate bond strength between the grout and the bone was obtained.The design values of the bond length between the grouting body and the bone and bar of various types of composite anchor were analyzed and obtained by the approximate probability method.For the performance study of bulb anchor of composite anchor bar,this paper researches on the performance of bulb anchor mainly by experiment and supplemented by numerical simulation.24 specimens were designed and tested,and the following conclusions were mainly drawn:(1)The bearing capacity of bulb anchor specimen is significantly higher than that of non-embossed anchor strand specimen of the same length.Bulb anchor can effectively reduce the occurrence of untwisting phenomenon of steel strand,prevent the steel strand from rotating out of the concrete,and improve the bearing capacity of bulb anchor specimen.(2)In the actual application process of composite anchor bar bulb anchor,spiral stirrups or local reinforcing bars can be arranged in the straight anchorage section near the concrete surface to improve the crack resistance strength of concrete around the bulb anchor and reduce the cracks in the foundation floor.(3)The finite element model of composite anchor bar bulb anchor is established.Combined with the test results,the ultimate bearing capacity and characteristic value of composite anchor bar bulb anchor are given.The corresponding displacement values of bar bulb anchors under different loads can be reduced by increasing the anchoring length of bar bulb anchors and the distance between the pear-shaped heads of bulb anchors.In engineering application,the bulb anchor can be reasonably arranged according to the actual needs.Through full-scale test and theoretical analysis,the optimal bonding length of steel strand with different numbers in the matched steel tube and the ultimate bearing capacity and characteristic value of the bar bulb anchor are obtained,which provide theoretical basis for the optimal design of composite anchor and promote the standardization and standardization of composite anchor design.