Performance Research On RC Flat Plates With Opening Strengthened By External CFRP

The technology of strengthening and mending using Carbon Fiber Reinforced Plastic (CFRP) is a kind of new developing reinforcement method. It has the function of strengthening and mending, adopting the special structure glue to paste the carbon fiber material on the surface of the structure component to improve the limit loading capacity and rigidity of the structure. At present, the results of research on CFRP strengthening concentrate on the reinforcement of the reinforced concrete beam. The error of theoretical analysis and experiment result is accepted in application of practical projects. But the research on the CFRP strengthening of slabs is relatively less. On the other way, with the appearance of intelligent architecture, it is often necessary to punch hole through the beams and slabs for all kinds of auxiliary facilities. In the paper, the experimental study and theoretical study are done.Firstly, the experiment was made to investigate the strengthening of concrete flat plates with opening using externally bonded CFRP. four concrete flat plates strengthened by CFRP and one contrast flat plate not strengthened are designed in the article. The experiment appearance is observed with the load adding. It can be turned out from the strengthening experiment results that the limit loading capacity and stiffness of the plates can be increased effectively, and CFRP can increase the flexibility of plates to some extent.Secondly, the mean is studied how to analysis the limit load of strengthened plates, according to the failure modes of the specimens, two kinds of yield line pattern were proposed. And yield line theory was employed to predict the ultimate load of the specimens. And the approximate formula has good agreement with the experimental results and will be a practical design method. Meanwhile, a plastic strip method is attempted to calculate the ultimate load of the specimens, and the results is compared and analyzed with the experimental results.The experiment was simulated with ADINA (Automatic Dynamic Nonlinear Analysis), considering stiffness degradation after the concrete fractures. Deflection, strain of reinforcing bar and CFRP were contrasted with the results of experiments. The regularity has been investigated that reinforcing bar varies in the specimens. And the effect of CFRP onreinforcing bar was found. The regularity of stress of CFRP was investigated to orientate the location where CFRP breaks most possibly. It has been compared between the stress of reinforcing bar and CFRP to testify the phases of plates during loading.Because the bonding damage was common to be observed in test, the interface stress was analyzed using ADINA. The reason of bonding damage was included, and the influent factors of the interface stress were discussed.