Finite Element Simulation And Parameter Analysis Of Bolt Anchor Head Connection With Reserved Grouting Hole

The prefabrication technology of bridge piers and abutments has developed rapidly in recent years due to its short construction period and environmental friendliness.The connection performance between precast piers and abutments has always been a hot issue in the field of bridges.At present,the prefabricated bridge pier and the cap connection methods mainly include grouting metal sleeves,socket type and metal bellows,etc.,but it has a series of problems such as complex butt jointing processes,high construction accuracy requirements,large construction costs,and easy corrosion of bellows.In view of the above problems,our research group proposes a new connection method which is suitable for the connection between the precast bridge pier and the cap member,its named"reserved grouting hole bolt anchor head connection method",which is composed of a bolted anchor head connecting steel bars,high-performance self-compacting grout and reserved grout holes.This connection method has the advantages of simple butt joints and high construction efficiency.Through experimental research,the minimum anchor length of this connection method has been obtained by our research group.Research on the influence law of connection performance and parameters are needed to make this new type of connection better applied in actual engineering.This paper funded by the funding of a major technical innovation project in Hubei Province(2018AAA-001),the finite element software ABAQUS is used to carry out the pull-out test to obtain the bond-slip constitutive relationship between the bolt anchor head reinforcement and the grout,and a finite element model of the bolt-anchor head connection method with reserved grouting holes was establish.The influence of parameters such as strength,diameter of grouting hole reserved and concrete strength of the cap on its connection performance,the research work provides a certain theoretical basis and technical support for the engineering application of bolt-anchor head connection method of reserved grouting hole.The main research work is as follows:(1)In order to obtain the bond-slip relationship between the bolt anchor head reinforcement and grouting,eight sets of bolt-anchor head connection test specimens with grouting holes are designed and manufactured.The size of the bearing platform is 900×1000×400mm~3,the rebar diameter d is 32mm(the anchoring length is 6d,8d)and 28mm(the anchoring length is 6d,8d,10d and 12d),the grouting hole diameter is reserved for 2d.Based on the pull-out test,considering the influence of steel bar diameter and anchorage length,a bond-slip constitutive model was established between the steel bar and the grout:(?)(2)Based on the finite element software ABAQUS,the above-mentioned bond-slip constitutive relationship was input,and a finite element model of 550×500×700mm~3 reserved grouting bolt anchor head connection platform was established.The model has 19402 solid elements and 378 truss elements.Analysis of the drawing failure process of 19 sets of different grouting holes with bolts and anchor heads connected to the cap model(diameter of reinforcement(22～32mm),grouting strength(60～120MPa),diameter of grouting hole reserved(1.5～3d),and designation of cap concrete(C30～C80)).The results show that the strength of grouting should be no less than 80MPa,the grouting diameter reserved for the members is not less than 2d,and the concrete number of the cap is not less than C40.(3)Based on the Changsha Xiangfu Road Reconstruction Project,a finite element model of precast piers and integral cast-in-situ connection piers with grouting holes and anchor heads was established respectively.The damage modes and piers of the piers at the bottom of the piers were compared and analyzed.Characteristics of displacement and stress-strain changes at the bottom of the pier.The results show that the connection performance of the bolt-anchored head connection method with the grouting hole is close to the overall cast-in-place method.The load-displacement curves of the two pier tops agree well,and the maximum stress at the bottom of the pier column is less than the concrete design strength.The connection method of bolts and anchor heads with retained grouting holes can meet the connection requirements of precast piers.