Mechanical Analysis Of Large-scale Steel Structure During Hoisting Under Eccentric Loads

With the continuous progress of steel structure design and construction technology,a large number of new large-scale steel structure buildings have been built in China.Their structural forms are becoming more and more novel,their structures are becoming more and more complex,and their structural spans are becoming larger and larger.In the process of steel structure construction,it is usually necessary to carry out hoisting operation,and the eccentric load is an important factor affecting the safety of hoisting process,which needs to be paid attention to.Therefore,the mechanical analysis of the hoisting process of large-scale steel structure under the eccentric load has certain theoretical significance and important engineering application value.In this paper,a large-scale steel structure in the nuclear island construction of a nuclear power station in China is taken as the specific object to carry out mechanical analysis on the hoisting and installation process of the structure,focusing on the influence of wind load and its own eccentric load on the structural deformation,and to solve the safety problems of the structure in the hoisting process under the eccentric load.The main work is as follows:1.Review of the theory of computational wind engineering and shape-finding analysis for eccentric load hoistingThrough expounding the background and research status of steel structure hoisting,this paper reveals some potential safety hazards existing in the current hoisting process,and explains the necessity of checking the safety of hoisting process under the influence of eccentric load.Based on the two main eccentric load factors of wind load and structure eccentricity,this paper introduces the calculation wind engineering theory and the shape-finding analysis theory of eccentric load structure,which provides a theoretical basis for the analysis of hoisting process under eccentric load.2.Simulation of the response of the structure under mean wind loadBy using the fluid calculation software Fluent,the steady-state wind pressure distribution on the structure surface under the action of mean wind is analyzed,and the wind-induced structure response is further analyzed by converting the wind pressure result to the pressure load on the structure.By comparing with the stress situation when no wind load is applied,the influence of wind load on the safety of structure hoisting process is evaluated.3.Simulation of the influence of its own eccentric load on the safety of structure hoistingThrough the comparison of structural type selection and the comprehensive consideration of the economy and safety of the structure,a more reasonable structural type is determined.Using the finite element analysis software Midas Gen,this paper analyzes the influence of different degree of eccentric load on the internal force distribution of the hoisting structure,and then gives the scheme to improve the safety of the hoisting structure.4.Analysis of the whole process of structure hoisting under uniform load and eccentric loadMidas Gen software is used to analyze the internal forces of slings in each stage of the structural load test,that is,to analyze the cable forces of slings under different hoisting weights under uniform load,so as to provide comparison and reference for the hoisting process under eccentric load.Abaqus software is used to simulate the state and cable force of the hoisting structure when it is hoisted from the ground to the air under the action of eccentric load.The results show that the eccentric load has a great influence on the stress distribution of the sling and the safety of the structure.Combined with the actual situation of the structure hoisting and the loading scheme,the influence of the counterweight scheme on the hoisting process is simulated and analyzed,which provides the analysis basis for the cable force monitoring.5.Cable force monitoring and safety analysis of typical structure in hoisting processThe real-time cable force monitoring is carried out for the hoisting process of typical structure.According to the monitoring results,the cable force adjustment is guided on site to realize the balanced stress of each hoisting point and the stable hoisting of the structure.The cable force monitoring is carried out for the load test of hoisting fixture structure,SC singlelayer structure and SC two-layer structure in the whole hoisting process.The monitoring results are compared with the simulation results.The results show that the cable force distribution of the simulation analysis is in good agreement with the measured value,which shows that the hoisting scheme is effective and reliable.Based on the above results,it can be found that: the influence of wind load on the safety of structure is limited and can be considered as a secondary factor;its own eccentric load has a great influence on the distribution of cable force when the structure is hoisted,so it is necessary to take reasonable measures to increase the counterweight to reduce the influence of eccentric load;some mechanical measures should be taken to control the influence of eccentric load on the structure when the large-scale steel structure is hoisted,cable force monitoring can effectively improve the safety of large steel structure hoisting process.