Overall Structural Safety Assessment And Life Prediction Of Hydraulic Gantry Cranes

Hydraulic gantry crane(referred to as portal machine)is a large-scale lifting equipment commonly used in various water conservancy projects.It has been used for a long time under the conditions of fatigue,wear and corrosion.Its main purpose is to increase the production capacity of loading and unloading heavy objects,while at the same time reducing labor intensity.This gantry crane was designed and manufactured by Taiyuan Heavy Machinery Factory in 1985 to serve the Gezhouba water conservancy project.It is used for daily lifting operations of water gates,trash racks and other equipment.The design standards at that time only considered whether the strength,stiffness and stability of the metal structure met the design requirements,while ignoring the impact of fatigue stress cycles on the service life of the crane.The door machine has been in service for 35 years so far.Will it continue to be safe and reliable in the future? The operation is unknown.As we all know,the design and manufacturing costs of large gantry cranes are expensive.If they are scrapped prematurely,it is undoubtedly a waste and will cause significant economic losses.If they are overdue,there will be significant production risks,and even a collapse accident will cause casualties.In addition,there are no domestic or foreign promulgated standards or guidelines related to health assessment and life expectancy.Therefore,it is of great theoretical significance and engineering application value to carry out evaluation studies on the remaining life of metal structures and the safety performance of the whole machine for hydraulic gantry cranes that have been in harsh working environments such as fatigue,corrosion,and wear for a long time.Out of the requirements of China Yangtze Electric Power Co.,Ltd.and Hubei Provincial Special Procuratorate for safe production,this article takes hydraulic gantry cranes as the research object to study the remaining life of metal structure and the safety performance evaluation of the whole machine.Firstly,the three-dimensional solid model of the door machine was established based on the door machine design drawings and site survey data,and then the model was imported into the finite element analysis software to analyze the stress and deformation of the whole machine,and the structural dangerous points and stress concentration parts were determined.According to the simulation results,a stress test program was developed for the corresponding parts and the data was collected on the spot with the help of the DH3816 N static strain gauge.The stress and strain data collected on the spot were statistically analyzed,and the load spectrum was combined withthe rain flow counting method.Combine the linear cumulative damage criterion,comprehensive damage factor,and edited load spectrum to predict the life of the door operator.Finally,the risk matrix method is combined with the probability of injury occurrence to determine the safety level of the door machine,and provide reasonable maintenance and repair suggestions.The paper introduces the important parameter of comprehensive damage factor for the first time,comprehensively considers many external influence factors such as corrosion,welds,cracks,safety factors,etc.,and makes twice the stress amplitude of the standard sample curve in the nominal stress method Amendments to make it more relevant to the actual working environment;a safety assessment level has been formulated based on the possible failures and probabilities of the portal crane,which provides a more scientific and operable code of practice for the health assessment of hydraulic portal cranes.