ABSTRACT
A strengthening method for old steel I-girder bridges by concrete encasement under hogging moment was adopted in this context. The mechanic performance of steel I-girder before and after strengthened by concrete encasement was investigated experimentally and analytically. Model test of steel-I girders with or without concrete encasement under shear force and bending moment were carry out to investigate the strengthen effect of concrete encasement. The test results showed the strength and stiffness of concreteencased composite girders were improved in comparison to those of steel girders, as shear bucking of steel web and local buckling of steel flange were restricted by concrete encasement. Based on experiment results, analytical methods to predict the shear and flexural strength of concrete-encased composite girders were proposed and verified. All the findings of present study may provide reference for the application of such strengthening method for old steel girder bridges.
