Retrofit of reinforced concrete structures by CFRP/GFRP sheets against blast load

Nowadays, destructive bomb effects and terroristic attacks to buildings have become a challenge for structure engineers. Reinforcement of structures with composite materials has been extensively increased in recent decays, because of their individual and unique characteristics like high impact strength, flexibility, high-weight ratios, etc. The technique of wrapping concrete with CFRP/GFRP sheets can significantly increase its axial load capacity, flexibility and seismic behavior of columns in the plastic hinge areas or overlapping regions of column bars. In this research, blast phenomena and its effects on buildings will be analytically investigated. CFRP/GFRP sheets will be applied to the retrofitted building frames and their performance in strengthening structural members will be studied. The concrete nonlinearity behavior is considered in using concrete damage plasticity model and CFRP/GFRP sheet has been assumed to be elastic and isotropic, while steel retrofitting bars have elasto-plastic behavior. For validation of analytical results, a model has been compared with a series of experimental results, and good agreements have been obtained. Results show that external reinforcement increases energy absorption of the system up to three times, and in this case, reinforcement by CFRP sheets represents better performance. In addition, it is shows that external reinforcement of connections leads to decrease total displacement of the frame up to 40 %. Moreover, effects of the number of reinforcement layers are considered