Research On Macroscopic Characterization Of Looseness Of Connecting Bolts In Standard Section Of Tower Body

Tower crane(hereinafter referred to as Taji)is one of the indispensable key equipment in the construction industry,which greatly improves the work efficiency of the construction industry.However,the accidents caused by Taji structural damage such as loosening of high-strength bolts and fracture of main structure limb are more incalculable.In order to ensure the safe operation of Taji,aiming at the structural damage problem of Taji caused by the loosening of connecting bolts of standard section of tower body,thesis thinks that it is one of the key technologies to quickly identify the loose parts of connecting bolts of standard section of tower body in the Taji industry,the main research contents are as follows:(1)The solid model of bolt connection of two standard sections of tower body is established and verified,the parametric finite element model of connect-ing bolt of 6010 Taji standard section is established by solid modeling and command flow method.The model includes main limb,web member,connecting bolt and other parts,and the physical experiment and optimization finite element model are designed and implemented.(2)The macro characterization of the pre-tightening force of standard section connection bolts under static load was studied(Magnified displacement).Based on the finite element solid model,under the static load(the Taji does not rotate or lift),the influence of the pre-tightening of single connecting bolt or connecting bolt group on the macro characterization of the Taji standard section is studied,and the displacement curves of the main limb characteristic points of the tower standard section at different positions of the tower body are obtained.(3)This paper studies the derivation of the force formula of the standard section of tower body in the process of Taji rotation.Considering the time-varying load in the process of Taji rotation,the force formula of the top of four main limbs of the top two standard sections of the tower body in the process of Taji rotation is obtained through theoretical analysis.(4)The macro characterization of the pre-tightening force of the connecting bolts of the standard section under the dynamic load(the rotating process of the Taji)was studied.Taking the looseness of the connecting bolts of the top two standard sections of 6010 Taji as the research object under dynamic load,the influence of the looseness of single connecting bolt or connecting bolt group on the displacement of the top of the main limb of the standard section of the tower body is explored through the finite element solid model.(5)The evolution law of bolt looseness of the main limb under static load is studied.According to the existing loosening theory of connecting bolts,the evolution law of loosening of connecting bolts on the tension side of the main limb is studied under the static load on the top of the main limb and the full constraint on the bottom of the main limb.Therefore,this article obtains the change law curve of the main limb displacement during the loosening of the connecting bolts of the standard section of the tower under static and dynamic loads.The theoretical formula of the force on the main limb of the tower body during the rotation of the tower crane is deduced.The process of loosening the connecting bolts one by one on the side of the main limb under tension.This article lays the foundation for the next step to quickly identify loose bolts.