Experimental Study On Shear Performance Of Post-anchor Anchor Bolts

In recent years,anchor steel plate reinforcement technology has become very popular,and it has become one of the commonly used reinforcement methods.The technical principle of anchor steel plate reinforcement is to rely on the shear performance of the anchor bolt,so that the steel plate fixed on the surface of the member is subjected to the force of the original member under the load,thereby improving its bearing capacity.The core component of the anchor steel plate reinforcement method is the anchor bolt,and its reinforcement effect is inseparable from the constitutive relationship of the anchor bolt.Therefore,it is very important to test the shear-slip relationship of the anchor bolt more realistically and effectively.There have been many studies on this technology at home and abroad,but there are still many problems with its test method and engineering application: First,the traditional single-anchor shear test cannot avoid the shear warping effect of the loaded plate,which is almost the same as the actual anchor bolt.There are differences in the stress-bearing forms;the second is that China’s specifications require that this technology anchor bolt should adopt the form of full thread.Although the full thread and the anchor glue have better bonding effect,it is bound to reduce the effective force of the bolt.The area reduces the shear bearing capacity,so the rationality of this regulation needs to be re-discussed.The third is that the direct shear group anchor reinforcement developed by our group has many engineering application cases,but it has not yet involved the shear performance of a single direct shear anchor.Research;Fourth,in the direct shear anchor bolt reinforcement project,due to the size limitation of the component,the anchorage depth requirement of 8d is often not met.It is still necessary to analyze and compare the shear performance difference of the anchor bolt when the buried depth is 6d.Fifth,the thickness of steel plates varies in engineering reinforcement.However,many studies rarely involve the influence of steel plate thickness changes on the shear performance of anchor bolts.In order to solve the above five problems,this paper uses 6mm,10 mm and 15 mm steel plates with three thicknesses corresponding to the loading plates of 40 Cr material anchors of 16 mm,18mm and 20 mm diameters,and designs direct shear for each diameter anchor Group(buried depth of 6d,8d),ordinary full thread group,ordinary half thread group,48 single anchor shear tests were carried out on C30 concrete substrate plate to explore the effect of different parameter combinations on the shear performance of anchor bolts And the law of change.On the basis of previous experiments,a brand-new test device was optimized and designed,and a double-anchor shear loading scheme with auxiliary anchors was used to suppress the end of the steel plate from lifting.Through the analysis and comparison of the failure phenomena of each group of test anchors and the measured shear-displacement relationship curve,the following conclusions are drawn: the double-anchor shear test method with auxiliary anchors has good linearity and early stiffness in the measured load-displacement curve.Consistency;semi-threaded anchors have greater early stiffness,higher ultimate bearing capacity and better displacement ductility,and are more suitable for engineering applications than full-threaded anchors;ordinary half-threaded and direct-shearing single anchors have almost the same shear performance;The direct shear single anchor has basically no effect on the performance of the anchor’s own shear resistance when the burial depth is 6D and 8D.In addition,the ABAQUS finite element analysis simulation and thickness change parameter analysis of the test group were also carried out in this paper,and it was concluded that the thickness of the loading plate mainly affects the second-stage stiffness of the shear-slip curve.The smaller the displacement.The innovation of this article:(1)Optimized design of a new single-anchor test loading device,compared with the complicated and bulky traditional loading device,it has the advantages of simple loading and unloading,high reutilization rate,small space occupation and so on.(2)The double-anchor shear test scheme with auxiliary anchor bolts is adopted to solve the shear warping effect of the traditional single-anchor test loading plate,and the actual measurement results are closer to the stress of the single anchor bolt in the reinforcement project.(3)For the first time,a comprehensive analysis of the shear performance of anchor bolts with different steel plate thicknesses was carried out.At the same time,the shear test of a single direct shear anchor bolt was carried out for the first time.