Optimization Design Method Of Steel-UHPC Composite Girder Bridge With Waffle Slab Based On Spatial Analysis

In recent years,with the rapid development of composite girder bridge,composite girder has been widely used in medium and small span and long span bridges.In order to solve the defects of the traditional composite structure bridge,such as self weight,poor crack resistance and bearing capacity of the bridge deck,UHPC waffle plate is proposed to replace the ordinary concrete bridge deck to form the steel UHPC waffle plate composite girder bridge.However,at present,there are few steel-UHPC light composite girder bridges in China,and the design experience is scarce.Using the equivalent section width recommended by AASHTO to design the waffle plate,the design results are too conservative to make full use of the advantages of ultra-high performance materials,resulting in a certain amount of material waste.In view of this,based on the adaptive genetic algorithm,this paper optimizes the overall design of the steel-UHPC waffle composite girder bridge,and obtains the most economical design scheme.The main research contents are as follows:1.The optimization method and process based on genetic algorithm and spatial finite element analysis are proposed.The main program of the adaptive genetic algorithm is programmed by MATLAB,and the ABAQUS is redeveloped based on the programming software Python to realize the automation of the parametric modeling analysis and post-processing of the finite element model.Through the interface program of MATLAB and ABAQUS,the genetic algorithm is connected with parametric modeling and post-processing script program to realize the connection between optimization process and finite element analysis process,forming a complete optimization design method.2.Taking a steel-uhpc waffle composite girder with a span of 30 m as an example.Aiming at the cost of materials,taking the construction requirements,strength requirements and stiffness requirements specified in the code as constraints,a single objective and multi constraint optimization mathematical model is constructed.The composite beam is optimized under five different working conditions,and the optimization results are analyzed by finite element method,which verifies the correctness of the optimization method.The results show that the height of longitudinal and transverse ribs of UHPC waffle slab has a great influence on its mechanical properties,and the maximum transverse tensile stress,tensile strain and maximum vertical displacement of composite girder in the top span of waffle slab are close to the specified limits,which should be considered in the design of composite girder.3.The optimal design of three span continuous steel UHPC waffle composite girder bridge is carried out.Based on the three span continuous approach bridge of Guanting Reservoir super large bridge,the small box girder is replaced by the steel UHPC waffle composite girder system,which is optimized by the optimization design method in this paper,and finally an economic and applicable approach bridge design scheme is obtained.Compared with the original small box girder,the section height is reduced from 1600 mm to 1500 mm,and the reduced thickness of the bridge deck is significantly reduced compared with the original.In the design of continuous composite girder bridge,the influence of negative moment area should be considered.