Analysis Of Bearing Performance And Temperature Effect Of CFRP Strengthened Box Beam

Maintenance and reinforcement of existing structures are one of the main problems the structural engineering facing currently. As a new type of composite material, CFRP has been widely used in reinforcement of civil engineering. Because it has several advantages such as high tensile strength and modulus ofelasticity, light weight, corrosion resistance and facilities of construction. Box girder is widely used in medium-span and long span of the road bridges and railway bridges. Because of box section beam's own characteristics, shear lag effect caused by shear deformation has to consider in internal force calculation. Because of thermal stress is the important factor caused cracks of concrete box girder, temperature effect of CFRP reinforced box girder becomes hot issues at home and abroad. This article analyzes the bearing performance and temperature effect of CFRP reinforced box girder bridges by theoretical analysis and finite element method. The main works are as follow:(1) On the basis of searching relevant literature, application and research status of plastering carbon fiber reinforced method are summarized.(2) For the two bending failure modes of concrete crushing after steel yielded and carbon fiber reinforced plastic reaching the allowed tensile strain after steel yielded, the evaluation formula of ultimate bearing capacity are presented. It offers a theoretical basis for the bending designs of CFRP-strengthened RC beams and engineering applications.(3) On the based of the assumption of plane cross-section and the self-equilibrating force system, the equation of temperature self-restrained deformation and the analytic formula of temperature self-restrained stress due to solar radiation and uniform of CFRP reinforced concrete box girder load are established. Verified with the versatility of the analytic, it is also applicable to concrete box girder not reinforced.(4) Application of finite element software-ANSYS, simply supported box girders subjected to concentrated loads in the span before and after reinforcement of CFRP are simulated. Box models' deformed, crack development and concrete, steel, CFRP stress distribution are received. The results show that the bearing performance of box girder improved by CFRP reinforced.(5) Simply supported box girders under temperature load by CFRP reinforcement are simulated. Compared with its calculated results and theoretical values, they are coincided.