Mechanical Behavior Research Of Steel Box Girder Strengthened With CFRP

With the rapid development of economy, there are numerous steel structures around the world infrastructures. Now the safety of numerous steel structures has been unable to meet the operating requirements, it’s necessary to strengthen and repair them. At present, using the Carbon Fiber Reinforced Polymers (CFRP) to strengthen the steel structure has become a hot field of structural strengthening. Compared with the traditional strengthening technology of steel structure, the strengthening technology with CFRP has its unique advantages, such as no serious stress concentrations, no residual stress and easy to construct. However, further studies are needed on the strengthening technology of steel structure with CFRP. This paper focuses on the systematic theoretical analysis of the strengthening technology of steel structure with CFRP and researches the lift-up inverted arch method to strengthen the steel box girder by gluing CFRP. The main research contents are as follows:(1) First, the key problems of steel structure strengthened with CFRP are elaborated comprehensively, including bonding mechanism.. destruction type of structure after strengthened、construction technology and the bond durability.(2) The interfacial stress between CFRP and tension component as well as the effective bond length are analyzed. By analyzing the interfacial stress of flexural steel girder glued with CFRP, the interfacial shear stress and peeling stress are deduced, which can provide theoretical basis for further engineering practical study.(3) The basic principle and construction technology of the lift-up inverted arch method to strengthen the steel box girder with CFRP are disussed based on practical engineering, and the changes of the bottom strain and deflection of steel box girder before and after strengthening are measured. By analyzing the data, it shows that the strengthening technology with CFRP can improve the bearing capacity of steel box girder effectively.(4) Mechanical behavior of flexural steel box girder strengthened with CFRP is analyzed by using the finite element software ANSYS, and the load-stress curve、the load-deflection curve are obtained. By contrasting the numerical analysis results with the actual strengthening results, the accuracy of model is verified, then the parameter analysis of the main influence factors of the strengthening effect is conducted to explore their influence on the strengthening effect.Through the theoretical analysis and practical engineering research of the strengthening technology of steel box girder with CFRP, several conclusions and recommendations are obtained, which can provide the reference for the design and construction of CFRP strengthening and repairment of steel structure in engineering practice in the future.