Study On The Reliability Of Lattice Girder Metal Structure Of Crane

The crawler crane is enjoying a popularity much wider than other machineries in the construction field due to its great hoisting capacity,large working scope and remarkable operating height.As a key equipment in a large-scale engineering project and a type of the special equipments,its reliability and safety are attracting increasingly attention., Because of its core role in the proper functioning of the crane, the lattice boom is intensively researched and its reliability and safety are facing an ever stricter scrutiny.Thus researches into the reliability of the lattice boom of crawler crane are of extreme importance especially in reducing chances of accidents,and improve the working efficiency and producing economic benefits.This project aims at obtaining the system reliability of the metal structure of lattice boom of crane.First chord members and web members with attached weld are considered a unit,and the failure modes of static strength, of stability and of weld failure of the unit and the interference of these three modes are to be researched. Through calculations of the distribution zones of various failure modes the judgment formula of interferences of failure modes is deduced and the corresponding interference figure is achieved. The single failure mode of lattice boom structure under given operating conditions is also drawn out,which can reduce the calculation load of bars’ failure mode under various operating conditions.Failures of chord member and of cross section stability are taken respectively as the failure criterion. Failure of web members is used to derived a next failure member,and the failure path can be thus obtained. According to the rule above, the reliability of bars bearing a re-distributed load can be acquired considering the effects of safety coefficients. By scanning member bars of the system,the most vulnerable bars are detected to form the failure paths.Then PNET method is adopted to obtain the overall reliability of the lattice boom metal structure. The dominant failure modes of boom can be divided into several groups, and the system reliability is ultimately achieved. Based to the algorithms above, a MATLAB program is coded to calculate the reliability of the boom metal structure.In conclusion, through analysis of interfered failure modes and the adoption of the "safety factor-reliability" scanning method,the project provides a new approach and an improved working efficiency in calculation of the reliability of the boom metal structure.The integration of theories,algorithms and a software lays down a steppingstone for engineering design and theoretical study in the future.