Efficiency of Beam-Column Joint Strengthened by FRP Laminates

The recent earthquakes have shown that the vulnerability and the defects of the concrete joints in beam column framed structures were the main causes for many building collapses. Such vulnerability and defects are in general the consequences of many factors. External strengthening with composite materials represents an alternative and a sound and efficient technique to improve the performances and aptitude to withstand seismic action. However, while the use of such strengthening technique offers many advantages, it has some disadvantages, particularly a remarkable loss of ductility. The present study examines the effects of an external strengthening of reinforced concrete beam-column joints against cyclic loading using CFRP laminates and GFRP sheet. The experimental program is constituted of three beam-column reinforced concrete joints at a scale of one to three (1/3) tested under the effect of a prestressing axial load acting over the column. The beams were subjected at their ends to a reverse cyclic loading under displacement control to simulate a seismic action. Strain and cracking fields were monitored with the help a digital recording camera. Following the analysis of the results, a comparison was made concerning the performances in terms of ductility, strength and mode of failure of the different strengthening solutions. (C) Koninklijke Brill NV, Leiden, 2010