Study On The Fast Solution Of Finite Element Analysis Of The Tower Crane Under Multiple Working Conditions

Tower crane is widely used in the construction of high-rise buildings.It can lift and carry items in a large space according to the requirements of the project.It has a long working time and high working intensity.The working conditions of tower crane are complicated and changeable.The working process of tower crane needs to start and brake frequently.With the change of the position of Luffing trolley and rotation mechanism,the internal force and the stress of tower crane metal structure change very frequently.Because of its special working conditions,the load of tower crane structure is a continuous stochastic process.The failure of the structure under the action of the load is mostly fatigue failure.In recent years,it happened frequently that the tower crane collapse and the tower crane arm break.A part of the reason lies in the fatigue failure of tower crane structure under normal working conditions.Therefore,it is very important to structural analysis of the tower crane structure under different working conditions.We should determine the stress of each bar element of tower crane and the maximum stress value position of tower crane under different working conditions,and obtain the change trend of displacement of each node and stress value of each member.We also should make an accurate analysis and evaluation of the safety of tower crane according to the results of structural analysis.The structural analysis is very important for the safety of tower crane,determines the reliability and safety of the tower crane.Finite element method is an important method of structural analysis.However,we can only load few working conditions at a time when we do finite element analysis by using conventional commercial finite element softwares.Solving under multiple working conditions by using conventional softwares needs to be carried out in batches according to the load step.It is time-consuming and difficult to solve multiple working conditions by finite element softwares when the number of working conditions is large(for example,there are thousands of working conditions).In this paper,based on the principle of finite element of beam-bar structure and the principle of solving large sparse linear equations,combining the calculation principle of working conditions data translating into loading data,we developed a finite element static analysis solver of tower crane that using Fortran programming language and APDL parametric language.The multi working conditions parameters can be collected by tower crane recorder.According to using full sparse storage technology and the method of multi-threaded parallel computing,the solver can solve any number of working conditions for the same model of tower crane at the same time.The solver can obtain the internal force and stress of any bar member of tower crane under different working conditions and establish the database.Finally,we verify the accuracy and rapidity of the calculation results of the multi working solver through the analysis of the tower crane engineering examples.The characteristics of the solver developed in this paper are as follows:1.The solver solve finite element equations of the overall stiffness by using the Bi conjugate gradient method.This method can not only reduce the storage capacity,but also can improve the efficiency and speed of the solver.2.Using OpenMP(shared memory parallel programming)multi-threaded parallel computing method in Fortran and fully sparse storage technology,the software can not only save lots of storage space,but also can greatly accelerate the speed of solving linear equations.It ensures the rapidity and efficiency of the finite element parallel solution of tower crane under multi working conditions.3.The input and output process of the solver is done by reading the data file directly.According to Formatted read APDL format data file,the solver eliminated the cumbersome interactive parameter input interface.The input format of the solver uses the ANSYS parametric design language APDL format,which can be used to realize the visualization of the solution model by using the pre-processing and post-processing platform of ANSYS software.4.According to the results of the database file obtained under the multi working conditions,we can draw the stress curve of different bar members under any single working condition and draw the internal force and stress time history curves of any member under different working conditions.It is helpful for tower crane to do dynamic safety evaluation and life assessment that we obtain the stress variation law of the member with the change of working condition and time.