Research On Construction Technology Of Long-span Prestressed String Truss Slip Method

The power plant uses an open-air dry coal shed for coal storage,and coal dust is easy to float into the air,causing air pollution.It is necessary to transform the open-air dry coal shed into a closed coal storage structure.Considering that the construction process cannot affect the coal transportation operation of the bucket turbine,and the construction site is limited,in-situ truss installation and cable tensioning cannot be carried out,so the sliding method is usually used for construction.The prestressed string truss structure has a large span and many construction steps,and the stress state of the structure during the sliding construction process is inconsistent with the stress state after forming.It is necessary to study and analyze the construction process of the structure.This paper introduces the suitable structure types of dry coal sheds with different spans,and expounds several common classification methods of sliding construction,calculation methods of sliding force,and construction technology of tensioning of chord trusses and cables.Taking the construction of a string truss slip method as an example,the construction method and stress state of the string truss slip method are analyzed.By changing the sequence of truss slipping construction and cable tensioning construction,the arrangement of slip rails and the number of arrangements,5 different construction methods are designed to improve structural deformation,assembly accuracy,cable force change,cable force loss,The force of the sliding bearing and the maximum asynchronous displacement limit are analyzed and compared,and the influence degree of the above factors on the structural deformation and force is obtained,and the variation law of the structural deformation and force in each construction method is summarized.The selection of the construction method of the string truss slip method and the on-site monitoring provide the basis.According to the analysis and comparison results of each construction method,the optimal construction method is determined,and the structure is simulated and analyzed by the tension relaxation method,and the over-tension value of the cable force of each axis is calculated in turn.In addition,the force analysis was carried out for the construction method of the truss sliding first and then the cable tensioning and the construction method of the truss sliding and the cable tensioning crossing.Correlation between structural displacement increments and structural forces.Combined with the important and difficult problems in the construction process of this project,some key technologies of the tensioned truss slip method are analyzed.(1)Aiming at the difficult problem of determining the position coordinates of the lifting point in the process of hoisting asymmetric trusses,a new method for determining the horizontal coordinates of the lifting point is proposed,and the feasibility and practicality of this method are verified through finite element simulation analysis.sex.(2)By analyzing the stress state of the sliding support when the sliding rails on both sides are inclined and laid horizontally,the reinforcement schemes of the sliding rails in the two cases are respectively proposed.(3)Aiming at the problem that the maximum asynchronous displacement value is small,a variety of reinforcement schemes for adding reinforcement members between the slip elements are proposed,and the optimal reinforcement method is determined through finite element simulation analysis and comparison.(4)Simulate the construction process of splicing between partitioned trusses,analyze the influence of splicing construction on truss deformation and cable force,and provide a basis for on-site monitoring of the construction process of splicing between partitioned trusses.In order to ensure the accuracy of the structural installation and the safety of the construction process,the cable force,structural displacement and structural stress are monitored during the construction process.Regarding the change law of cable force and structural displacement,the results of field measurement and analysis are the same as the results of finite element simulation analysis,and the data error between the measured value and the simulation value is small,which verifies the reliability of the simulation analysis and the feasibility of this construction method.