Cracking is an important aspect of concrete behavior that considerably affects the overall response of concrete structures. The initiation of cracks is governed by concrete tensile properties. The propagation of cracks is a complicated phenomenon that plays a significant role in the nonlinear analysis of concrete structures. The cracking process in tension starts at a relatively low tensile strain, causing plain concrete to exhibit a gradual softening behavior. This softening is augmented by the tension stiffening of reinforcing bars. The smeared crack approach is typically combined with nonlinear finite-element analysis to generate an accurate global response. The key to such representative accurate predictions relates to material parameters, especially those of tension stiffening effects. For a complete understanding of the crack development process, tests should be performed on concrete specimens at various load histories. However, due to the difficulty of testing concrete in uniaxial tension, only lim...

The aim of this experimental investigation is to study the effect of the ratio of carbon fiber-reinforced polymer (CFRP) precured laminate length to shear span and different end plate anchorage systems on the flexural behavior of reinforced concrete (RC) beams cast with self-consolidating concrete (SCC). SCC with a grade of 54 MPa has been used throughout this research to ensure consistent high quality and high concrete compressive strength in all beams and to eliminate the need of any compaction. Ten RC beams strengthened with CFRP plate lengths to shear span ratio of 0, 25, 70, and 85% with and without end anchorages, were tested under monotonic loading. In particular, a single layer of U-wrap sheet and two layers of U-wrap sheets with one layer in the longitudinal direction and the other in the transverse direction were used as end anchorages (double wrap). The results were compared with each other and with those of the same test conducted on an unstrengthened control beam specimen. The load-deflection response of the tested specimens was recorded along with the associated failure modes. In addition, predicted results for the ultimate load capacity computed according to the ACI 440.2R-08 and FIB-TG9.3-01 documents were compared with those of the measured experimental results and other models from the literature. It is concluded from this study that, depending on the ratio of CFRP plate length/shear span and also on end anchorage arrangement, the increase in load capacity of the strengthened beams range from 5% to 80% of the unstrengthened beam. Therefore, the selection of the optimum combination of plate length and end anchorage arrangement can lead to an overall saving in the cost of the strengthening of beams. Other conclusions and observations as related to the effect of CFRP plate length/shear span ratio and end anchorage on ductility and mode of failure were also drawn.

Citation: Hayder A. Rasheed, Jamal Abdalla, Rami Hawileh, Adil K. Al-Tamimi, Flexural behavior of reinforced concrete beams strengthened with externally bonded Aluminum Alloy plates, Engineering Structures, Volume 147, 15 September 2017, Pages 473-485, ISSN 0141-0296, https://doi.org/10.1016/j.engstruct.2017.05.067.The objective of this experimental investigation is to study the viability and effectiveness of using Aluminum Alloy (AA) plates as externally bonded flexural reinforcement for reinforced concrete (RC) beams. Ten RC beams were prepared and nine of them were strengthened with externally bonded 2 mm and 3 mm thick AA plates with different mechanical properties. Four strengthened beams had no end wraps or anchorages. Single-layer and double-layer U-wrap CFRP sheets were used in the transverse direction as end anchorages for four strengthened beams and one beam had three double anchorages (two at the ends and one at mid-span). The beams were tested under monotonic load until failure. The goal is to study the effect of using AA plates as externally bonded flexural strengthening material and to explore the effect of end anchorages on the flexural strength and ductility of these beams. The increase in strength over the control unstrengthened specimen ranged from 13% to 40% while the ductility significantly surpassed that of beams strengthened with CFRP sheets. It is observed that the use of end anchorages enhanced the ductility but not the strength of the tested beams. It is also observed that beams without end anchorage failed predominantly in flexure with full de-bonding while beams with end anchorage failed by localized de-bonding and flexure. Furthermore, the performance of the tested beams was compared with numerical predictions by a computer program developed in this study. The results of the numerical models were in close agreement with the measured experimental data. It was concluded that AA plates could be used as an external strengthening material to enhance both the strength and ductility of RC beams in flexure