Research On The Section Parameters Optimum Of I-Steel And Concrete Composite Bridge

As a new structure style, steel and concrete composite structure has wide application foreground in bridge engineering with many advantages of making full use of material, material saving, convenient construction, high rigidity, good aseismicity and so on. Focused on I-steel and concrete simple-supported composite beams, this thesis studies I-steel and concrete composite bridges section parameter optimum which is seldom involved. The achievements will provide reference for highway bridge design.On the basis of composite beams structure theory and structure optimum design idea, section parameter optimum theoretical model is founded, and a series of restraint equations which met character restraint condition of resisting moment, resisting shear, resisting torsion and local stability are deduced. Then, section design variable optimum value confines corresponding variable parameter are obtained through analysis by Matlab. Change pattern and sensitivity of I-steel section parameters, which named design variables, are analyzed with changes of moment, concrete slab thickness, longeron interval and so on. Based on bending stress and shear stress restraint equations, moment and shear force interactive restraint control conversion order are analyzed with various shear force. It is found that object design variables increasing sequence are I-steel web slab height, I-steel flange slab thickness, I-steel flange slab width, I-steel web slab thickness with progressive increase of moment , concrete slab thickness, longeron interval and span length. I-steel web slab height is the most sensitive parameter to satisfy restraint equations. With different parameter, the shear force threshold value is various corresponding to various valid shear stress restraint equations. When some group of parameters is given, the shear force, which corresponding to valid shear stress restraint equations, is decided. When shear force is less than this decided value, bending stress restraint equation becomes main control condition. When shear force is more than this decided value, both bending stress restraint equation and shear stress restraint equations are main control conditions. I-steel web slab thickness is the most sensitive parameter to satisfy the requirements of shear stress restraint equations.