Experimental Study On Bending Property Of RC T-beams Stengthened By CFRP

For these days, composite materials are greatly used in civil engineering. As a new procedure of concrete strengthening and rehabilitation, externally bonding Carbon Fiber Reinforced Polymer (CFRP) sheets are focused by civil engineers. Many technicians begin to study the structure performance of the concrete members (such as beams and pillars) repaired by CFRP.In this paper, 7 R.C.T-beams under different conditions of CFRP area and anchor condition have been experimentally investigated. The results of experiment show that externally bonded CFRP can be effectively used to increase the load-carry capacity and stiffness of beams while maintaining an adequate level of deformability. CFRP plays a great role after the beam is yielded. Load-carry capacity and stiffness has a less increment before the beam being yielded, but they were greatly increased after the beam being yielded. The width of the concrete cracks is also reduced with many small cracks reproduced in the region of concrete cover thickness. Externally bonding CFRP on the flank of beam is also a good way to increase the flexural strength and restrict the width of cracks.CFRP is bonded on the under surface of T-beams, U-shaped stirrups are used to anchor it. Experimental results show that disposing proportional spacing U-shaped stirrups on the whole span of the beams is a good way for anchoring. Under this anchor condition ,the strain of the CFRP on the under surface of the T-beam is up to 15000με,which indicates that the CFRP is full used .A VB program based on variety of parameters of T-beam is worked out to analyze the effect of concrete compressive strength, steel reinforced ratio and area of CFRP. The whole processes of the bending beams are analyzed, the results obtained as follows:(1) The yielding and ultimate moment are increased with the increment of area of CFRP, but the increasing ratio of ultimate moment run down along with the area increment. (2) The reinforcing effect on higher steel reinforced ratio beam is better than the lower ratio one. (3) The reinforcing effect of higher compressive strength concrete beam is better than the less one.The yielding and ultimate moment of upgraded beams are worked out through the numerical method and analytical method. The results tally well with the experimental data. At last, the paper discusses the ultimate strain of CFRP and puts forward a simple design method for upgrading T-beams.