Study On Construction Layout Form Optimization And Structural Performance Of Bidirectional Curved Prestressed Tendons In Concrete Slab

Unbonded prestressed concrete slabs are widely used in large-span floor and roof structures because of their unique advantages.At present,in the construction of bi-directional Curved Prestressing Tendons of prestressed concrete slabs,the linear shape of bi-directional curved prestressing tendons is quadratic parabola,which presents hyperbolic cable network in space,resulting in the phenomenon of cross-netting.This phenomenon greatly increases the difficulty of laying and positioning of prestressing tendons,greatly increases the workload of field construction,delays the construction progress and increases the prestressing.Errors in construction of stress reinforcement arrangement.In order to eliminate the phenomenon of cross-netting of Two-way Curved Prestressing Tendons in concrete slabs,this paper optimizes the construction layout of two-way prestressing tendons in concrete slabs,puts forward the optimization principle and determines the optimization scheme,that is,the linear shape of two-way prestressing tendons is alternately connected with the curve transition section,the top and bottom of slabs are set as straight sections,the straight section of the top of slabs spans the supports and the bottom of slabs are straight lines.The section is located in the middle of the span;the prestressing tendons in one direction are evenly arranged in the linear section of the prestressing tendons in the other direction.Based on the optimization scheme,ABAQUS is used to simulate the structural performance by finite element method.The simulation results are as follows: the bearing capacity of the specimens before and after the optimization of the construction layout of biaxial Curved Prestressing Tendons in concrete slabs is basically the same;the mid-span deflection of the specimens after the optimization of the construction layout of biaxial prestressing tendons in concrete slabs is lower than that before the optimization.In order to compare the crack width of the test piece before and after optimization,this paper analyzes the calculation formula of the standard crack width in various countries,and selects the crack width calculation formula in China's "Concrete Structure Design Code"(GB50010-2010)to optimize the construction layout of the bidirectional curve prestressing tendon.Analysis of the crack width of the concrete slab before and after.Finally,it was found that the crack width under the normal use load of the specimens with optimized two-way prestressed tendons in the concrete slab was compared with that before optimization,and the deviation was 5.6%,that is,the crack widths of the two were basically the same.Then,using the stiffness calculation formula of China's "Concrete Structure Design Code"(GB50010-2010),the calculation of the layout of the two-way curve prestressing tendons before and after the optimization of the concrete plate in the normal use phase is 74%,and the US ACI specification The calculation formula of the two-way curve prestressed tendons obtained by the stiffness calculation formula is about 21.5% between the calculated values of the deflection of the concrete slabs in the normal use stage and the simulated values.Therefore,the designer should choose the American ACI specification stiffness calculation formula when calculating the deflection of the curve prestressed concrete slab according to the specification.Finally,the preparation and prestressing construction process of prestressed construction after optimization of the construction layout of bidirectional curved prestressing tendons are introduced.