| With the vigorous development of domestic shipbuilding enterprises in recent years,the number of large-scale shipbuilding gantry cranes in shipyards has also increased.The larger lifting capacity and flexible nature of work are playing more and more important roles in the closure of ship sections.In recent years,the design trend of shipbuilding gantry cranes has developed toward larger spans and larger lifting capacities.Meanwhile,as the country’s requirements for environmental protection are getting higher and higher,some shipping companies have to relocate their sites to meet these new requirements.In the process of relocation,the shipbuilding gantry crane cannot match the actual situation of the site,and it is necessary to carry out the transformation.How to confirm the safety of the shipbuilding gantry crane after the transformation is particularly important.To make sure the safety of the renovated shipbuilding gantry crane,the lower deflection value should meet the requirements of the national standard and inspection regulations during the static rigidity test on site.In addition,we should adopt many other ways to see whether the value of the lower stress is below the allowable stress under its daily operating conditions.In this paper,the finite element analysis method is adopted to mathematically analyze the reconstructed crane.The mathematical analysis compares the finite element calculation results with the down-deflection value in the actual static load test on site to determine the correctness of the model.At the same time,where the stress is greater in the structure should be found out.Finally,we should perform stress test on the reconstructed crane,compare the results of software calculation with field test,and find out the problems of the established model.At last,according to the actual working conditions,by using finite element software to calculate the service life of crane,we can see whether it meets the design requirements.First,this article briefly introduces the application scenarios and development background of shipbuilding gantry cranes,describes the current domestic and foreign developments for safety assessment of in-use and modified cranes,and explains the current technical methods for crane safety assessment.Then,it introduces the crane under study and its parameters,and establishes a finite element model.The finite element analysis software ANSYS was used to carry out the finite element simulation analysis of the daily working condition of the overall structure of the MEC150-53A5 shipbuilding gantry crane that was moved and modified in the local shipyard.Finally,the crane was subjected to on-site stress testing.The rigidity and strength of the MEC150-53A5 shipbuilding gantry crane are comprehensively analyzed from the two dimensions of field actual measurement and theoretical analysis.By comparing the theoretical analysis data with the actual measurement data on site,the accuracy of the crane finite element model is verified.This article describes the establishment and simplification requirements and simplification methods of the MEC150-53A5 shipbuilding gantry crane finite element model.The statics analysis of the whole machine structure is carried out on its operating conditions.In addition,to test the stress of the crane under static 1.25 times the rated load,the strain gauge measurement technology is used.The results of finite element calculations and on-site static rigid main girder deflection experiments and actual stress test all show that the rigidity and strength of the steel structure of the MEC150-53A5 shipbuilding gantry crane after span lengthening still meets the needs of actual use on site.The results also show that the finite element results and the on-site test results are within the error range.By comparing between the measured value and the finite element analysis value of the rated load test and the 1.25 times the rated load test site and between the calculated value of the stress test and the actual measured value,they all fully illustrate that the finite element analysis result has great guiding significance for the design and verification of cranes.Finally,the service life of the crane is calculated by the fatigue testing of the crane by understanding the operating conditions. |
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