|Title:||Cyclic Tests on Seismically Damaged Reinforced Concrete Walls Strengthened Using Fiber-Reinforced Polymer Reinforcement|
|Author(s):||Konstantinos K. Antoniades, Thomas N. Salonikios, and Andreas J. Kappos|
|Keywords:||fiber-reinforced concrete; polymer; reinforced concrete; seismic; wall.|
|Date:||July 1, 2003|
The paper presents results from tests on low-slenderness reinforced concrete (RC) walls designed to modern code provisions, initially subjected to cyclic loading to failure, and subsequently conventionally repaired and then strengthened using fiber-reinforced polymer (FRP) jackets. Repair involved replacement of damaged concrete by a high-strength mortar and lap-welding of fractured reinforcement in the plastic hinge region, while strengthening involved wrapping of the walls with FRP jackets, as well as the addition of FRP strips at the wall edges, to enhance both flexural and shear capacity. In addition to different arrangements of steel and FRP reinforcement in the walls, a key parameter was the manner in which carbon FRP (CFRP) strips added for flexural strengthening were anchored; combinations of glass FRP (GFRP) anchors and anchoring strips, as well as anchoring steel plates, were used. Test results have shown that the addition of steel plates to the GFRP anchors and strips leads to a more effective anchorage; strength increases of up to approximately 30% with respect to a conventionally repaired specimen were measured when properly anchored FRP strips were used, but energy dissipation capacity of the original walls (designed to modern code provisions) could not be fully restored.
|Title:||Flexural Ductility of CFRP Strengthened Concrete Beams - Experimental Investigation|
|Author(s):||R. S. Aboutaha, P. Wattanadechachan, and S. H. Kim|
|Keywords:||bond; bridges; carbon fiber reinforced polymer (CFRP); CFRP anchorage; composite; concrete beams; ductility; fiber reinforced polymer (FRP); flexural strength; strengthening|
|Date:||May 22, 2003|
The amount of tension reinforcing steel bars plays a major role in determining the flexural ductility of reinforced concrete beams. The addition of Carbon Fiber Reinforced Polymer (CFRP) composites, which is another form of tension reinforcement, affects the ductility of concrete beams strengthened with CFRP sheets. Several researches have'investigated the use of CFRP for increasing the flexural strength of concrete beams. However, the flexural ductility of beams with respect to the amount and yield strength of existing ordinary steel bars has not been investigated in depth. In addition, delamination of CFRP sheets dominates the ultimate mode of failure of flexural members strengthened with CFRP sheets, which limits the ductility of strengthened members. There is a need to investigate the effect of CFRP anchorage system on the overall ductility of strengthened girders. This paper presents the results of an experimental investigation of nine large-scale reinforced concrete beams strengthened with CFRP composite sheets. The main variables are the amount of the existing reinforcing steel bars, yield strength of steel bars, and the type of CFRP anchorage. The amount (size and type) of the longitudinal CFRP sheets was maintained constant. Test results showed that the lower the amount of existing ordinary steel bars the lower the flexural ductility of the CFRP strengthened beams. Test results have also shown that CFRP anchorage could significantly increase the flexural ductility of CFRP strengthened beams. Such important findings should be reflected on the design equations of CFRP sheets required for strengthening existing reinforced concrete beams to ensure an acceptable level of flexural ductility.