Study On Optimization Of Prestressed Pier For Pull-Type Anchor Shaft

With the development of water conservancy cause,the high dam hydropower station has developed rapidly in hydraulic engineering,and its working head and the size of discharge building are also increasing,which leads to the large thrust of the radial gate.In order to meet the ultimate limit state requirements of concrete structure,the extension of the prestress technology has become inevitable.In this paper,the prestressed pier of the pull-type anchor shaft of a hydropower project is used as the research carrier,and the parameterized integral model of the prestressed pier is established by the APDL parametrized language of the finite element analysis software ANSYS to study the stress distribution of the key parts of the anchor shaft in the under normal operation conditions(normal water retaining on both sides of the radial gate)and the maintenance conditions(maintenance door retaining water on left side,radial gate normal retaining water on right side),by using sub-model analysis technology,the parameterized submodel of anchor shaft is established,the size of anchor shaft is optimized,and the change of the stress in key parts of anchor shaft is studied.In this paper,the sub-model method is combined with the parametric modeling technology to optimize the size,which provides a reference for the size optimization of local structure of the large-volume complex models.The main contents of this paper are as follows:(1)Three-dimensional finite element analysis of the prestressed pier.The geometrical dimensions of the anchor shaft are used to parameterize and the parametric finite element model of the prestressed pier of the pull-type anchor shaft is established by APDL.The distribution law of the X,Y,and Z stresses on the top surface,the bottom surface,the downsteam surface and the upstream surface under normal operation and maintenance conditions is analyzed.Under the action of prestressing,the stresses in Y and Z direction of the anchor shaft are larger under the two working conditions,the maximum stresses in the Y and Z directions are respectively generated at the intersection of the downstream surface and the downstream folded surface,and the intersection of the downstream folded surface and the bottom surface.The reason for this is that there is a certain concentration of stress on the one hand,on the other hand,the geometry of the anchor shaft.Therefore,the size of the anchor shaft is optimized to reduce the maximum tensile stress.(2)Feasibility analysis of the sub-model technical is study.The optimization module of ANSYS software is used to optimize the size of the anchor shaft,but it is difficult to achieve the local optimization by using the integral model.In this paper,the sub-model technology is used to establish the parameterized sub-model of the anchor shaft.A reasonable cutting boundary is selected for the sub-model,and the stress values of the X,Y and Z directions of each node on the cutting boundary of the anchor shaft parameterized sub-model are compared with the corresponding stress values of the integral model to verify the rationality of the cutting boundary.The results show that the stress of the anchor shaft sub-model is basically fitted with the prestressed pier integral model on the cutting boundary,and the stresses of the key parts of the anchor shaft sub-model are compared with the corresponding parts of the integral model.It is found that the basic anastomosis is obtained,and it is concluded that the cutting boundary of the parameterized sub-model of the anchor shaft is reasonable.(3)The optimization of the anchor shaft of the prestressed pier is studied.The size optimization of the anchor shaft is based on the parameterized sub-model.Taking the normal operation condition as an example,the Z-direction maximum stress of the anchor shaft is taken as the objective function under normal operation condition.The volume of the anchor shaft is used as the constraint variable.The zero-order optimization is used to optimize the parameter size of the anchor shaft,and the optimal design sequence is obtained.The group of the data is sorted and substituted into the integral model of the prestressed pier for the anchor shaft parameterized size.Under normal operation and maintenance conditions,the stress distribution in each direction is calculated.The calculation results show that the optimized size mainly reduce the stresses in Y and Z directions,under normal operation condition,the stresses in Y and Z direction decreases by 0.6 MPa and 1.1 MPa respectively.The stress in Y-direction is not changed greatly,the stress in Z-direction decreases by 1.1 MPa under maintenance condition.Combined with engineering examples,this paper comprehensively uses APDL of ANSYS software,sub-model technology and the structural optimization analysis module of the software to optimize the size of the anchor shaft structure of the prestressed pier,and obtains the relatively optimal size of the anchor shaft,which provides a basis for the design of the anchor shaft size of the project.At the same time,this paper combines the sub-model technology with the structural optimization design to realize the paramemetric modeling,loading,calculation and optimization of the local structure of the anchor shaft.This technology greatly reduces the workload of the designer,enhances the accuracy of the optimization results,and has a high guiding significance and reference value for the local structure optimization design of complex engineering.