Use Of Carbon Fiber Reinforced Polymer Cfrp Including Sheets Rods And Ropes In Strengthening And Repairing Long Reinforced Concrete Columns

Download or read book Use of Carbon Fiber Reinforced Polymer (CFRP) Including Sheets, Rods, and Ropes in Strengthening and Repairing Long Reinforced Concrete Columns written by and published by . This book was released on 2020 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of FRP materials in strengthening and repairing of reinforced concrete (RC) structures has increased in the past two decades. Recently, FRP materials have become one of the most used materials in rehabilitation engineering. For seismic retrofitting of RC structures, usually the process involves strengthening or repairing the vertical support elements of the buildings or bridges. Although glass FRP (GFRP) and basalt FRP (BFRP) rods have been used in flexural strengthening of RC columns, NSM-CFRP rods have not been used yet. In addition, studies in the use of CFRP ropes in flexural strengthening or repairing of RC columns are not available. To address these gaps, an experimental investigation was conducted on the use of CFRP materials in strengthening and repairing RC columns. The investigation consisted of three main parts. The three parts focused on strengthening and repairing slender RC columns using CFRP materials. The first part of the investigation focused on the use of CFRP sheets, rods, and ropes in flexural strengthening of RC columns. The results showed that both EB and NSM techniques can effectively be used in strengthening slender RC columns. In addition, CFRP ropes are very effective in strengthening RC columns. Finally, a theoretical model was created to predict the load-displacement response of RC columns strengthened with EB-CFRP sheets and NSM-CFRP rods and ropes. The theoretical results showed good agreement with the experimental results. The second part of the investigation focused on the use of CFRP sheets and ropes in repairing damaged RC columns. Recently, RC columns have been upgraded and strengthened with FRP confinement all around the globe. Future cases of repair will likely encounter RC columns that were strengthened previously with FRP confinement. However, studies on repairing damaged columns that were enhanced by confinement before damage are not currently available. Moreover, there is a vital need for an emergency repair technique that can be used to rapidly repair damaged columns of essential structures after a seismic event. In this study, the time required to complete the repair was a key factor to propose a rapid CFRP-based repair technique. Test results showed that the proposed repair technique was effective not only by restoring the original strength, but also by improving the strength significantly. Moreover, the measured and idealized load-displacement response showed that the ductility of the repaired column was reasonably sufficient. The proposed technique appears promising and may be considered as a permanent repair technique. The third part of the investigation focused on the tensile strength of CFRP ropes anchored to concrete using chemical epoxy. One of the major problems with using fiber reinforced polymer (FRP) in strengthening reinforced concrete (RC) structures is premature debonding of FRP. Anchoring FRP materials to concrete has become associated with most of the strengthening techniques. In the present study, FRP anchors were made from carbon fiber reinforced polymer (CFRP) ropes and had long embedment to be used for flexural strengthening of RC columns. Test results showed that the pullout strength of CFRP anchors increased with the increase in embedment length, and no significant effect of the hole diameter on the pullout strength was observed. However, the bond strength increased with decreasing embedment length and hole diameter. For shorter embedment lengths, the distribution of the bond stress along the length of the anchor is expected to be more uniform than that of anchors with longer embedment lengths. The average bond stress (strength) is calculated by dividing the maximum pullout force by the embedment length. Therefore, increasing the embedment length without significant improvement in the pullout load results in lower bond strength. The observed pullout results and failure modes were compared to the predictions using available models. Finally, a modified model was proposed to predict the pullout strength of CFRP rope anchors.