الفهرس | Only 14 pages are availabe for public view |
Abstract Recently, Near Surface Mounted (NSM) system presented a better flexural behavior compared to the Externally Bonded (EB) system due to the higher bond strength between concrete and FRP. The aim of this work is to evaluate the ductility and moment redistribution for statically indeterminate beam strengthened with NSM CFRP rods. This scope is selected as the linear-elastic brittle failure behavior of these composite materials can be a serious restriction of assuring the required level of ductility and moment redistribution. A three-dimensional (3D) FE model was developed, using the computer software ABAQUS (2020), in order to validate the flexural performance of experimentally tested beams available in the literature. Two specimens were modelled for this purpose, one control continuous beam without strengthening and the other initially strengthened in bending with two 6 mm diameter CFRP bars in both sagging and hogging regions simultaneously.The obtained results showed very good agreement with the experimental results. A parametric study was conducted to study the ductility and moment redistribution behavior using different CFRP bonded lengths, FRP reinforcement ratios, retrofit patterns and steel reinforcement ratios. The obtained results indicate that partially bonding the CFRP bars can improve the beam’s deformability, ductility, and moment redistribution with a slight decrease in capacity but taking into consideration the resulting possible premature debonding of the bars. The unbonded regions of the CFRP bars can play the role of increasing the section ductility due to the relatively delayed increase of strain of CFRP bars. Hence, the section will have a higher capability of plastic rotation that allows for higher moment redistribution capacity. The arrangement of the CFRP bars can change the direction of moment redistribution and significantly affects the capacity of the beam. Also, increasing the FRP ratio negatively affects the ductility of the section and thus the moment redistribution ratio due to the brittle behavior of these materials. Increasing the ratio between hogging and sagging steel reinforcement ratios increases the hogging stiffness relative to the sagging stiffness, which can reduce the transfer of moment from the intermediate support region to the mid-span region. Thus, the moment redistribution can be enhanced making use of the combined positive effect of decreasing bonded length and decreasing steel reinforcement ratio or CFRP reinforcement ratio between hogging and sagging region. |