Research On Ratio Between Side Span And Main Span Of Continuous Rigid Frame Bridge

The continuous rigid frame bridge is more and more widely used. But there still existsharm such as midspan scratch, beam body crack, and so on, which not only affects drivingcomfort, but also largely obstacles future development of the continuous rigid frame. Thereasonable span arrangement is the key to reduce the harm. So it is necessary to carry outresearch on reasonable ratio between side span and main span of continuous rigid frame.The author starts with ratio between side span and main span of continuous rigid frame.Analytic method and finite element method are used to get reasonable ratio between side spanand main span, which provides guidance for ratio between side span and main span design.Firstly,3spans,4spans and5spans continuous rigid frame bending moment and beam endangle formulas are derived by means of structural mechanics displacement method. Throughanalysis of bending moment and beam end angle changing rule of different control sectionunder different ratio between side span and main span value, it is concluded that impact ofratio between side span and main span on structure bending moment is larger than that onbeam end angle. Then, based on a three spans continuous rigid frame bridge, its finite elementmodel was established using MIDAS/CIVIL software. Benchmark bridge structure internalforce under the influence of gravity load, lane load, overall temperature rise20℃, andsunshine temperature difference load is obtained. It is found that impact of gravity load andoverall temperature rise20℃load on bridge structure internal force is very big. The maingirder mainly suffers from bending moment and shear force, and piers mainly suffer fromaxial force. Then on the basis of benchmark bridge, benchmark bridge span, main girderfulcrum and cross section, piers geometry size and cross section remain the same and threespans continuous rigid frame bridge model under13different ratio between side span andmain span is established using MIDAS/CIVIL software. Through the analysis of13differentkinds of control section’s internal force values, when the ratio between side span and mainspan equals0.7, the structure is reasonable, and two pairs of thin-walled pier stress gets close to each other. Finally three spans continuous rigid-frame structure optimization model isestablished, the minimum required prestress of box girder as the objective function ofoptimization model, and the calculation results are fitted. Through the derivation of fittedquadratic function, the reasonable ratio between side span and main span of0.702899isobtained. The ratio between side span and main span of0.7should be selected in actualapplication, which is consistent with the finite element method result. So it is suggested that0.7is the reasonable ratio between side span and main span of three spans continuous rigidframe bridge when parameters of three span continuous rigid frame bridge get close toparameters of the article.