Experimental Study On Shear Performance Of Reinforced Concrete Beams After Fire Damage And Strengthened With CFRP

The Carbon Fiber Reinforced Polymer (CFRP) is used to strengthen thereinforced concrete structures after fire in recent years. However, the researches onshear behavior of RC beams after fire strengthened with externally bonded CFRPsheets have rarely been reported. Therefore, this paper investigates the shearbehaviors and design method of the fire-damaged beams with externally bondedCFRP by test and practical calculation method. Moreover, this paper compares theformulations in different codes to calculate the contributions of CFRP to shearcapacity of RC beams without fire. The main work and conclusions are as follows:1. The paper has collected the experimental results of22beams withside-bonded CFRP,26beams with U-shaped CFRP jackets and28beams with fullywrapped CFRP. Comparing with calculated results, based on American, Europeanand Chinese codes, and experimental results, besides, putting forward corrections andsuggestions taking the existence problems of Chinese codes into consideration, theresults show that: the prediction of European design standard is more accurate as forside-bonded and the prediction of Chinese regulations design model is less reliablefor U-jackets. However, to the fully wrapped, the predictions of these three models,especially Chinese model, are in good agreement with the experimental values.2. The four points loading tests of two concrete beams without fire, two concretebeams after fire, four concrete beams after fire and strengthened with CFRP werecarried out to investigate the influence of shear span ratio, CFRP usage and flange onshear strengthened performance of concrete beams after fire. Test results show that:(1)The shear capacity of RC beams after fire decreases obviously. The shear capacity ofbeam (200×300) is decreased about9.5%after exposure to fire for1h.(2) The shearstrength of beam firstly exposed to fire and latterly wrapped with CFRP is about105.3%~134.3%of that without fire and without wrapping. Considering the influenceof the flange, the retrofitting effect is more obvious of the beam with U-wrap andlayering.(3) The limit deformation capacity of the fire-damaged beams with externally bonded CFRP impoves obviously and which goes up as the CFRP usageincreases.(4) The reinforcement effect of CFRP is great influenced by the shear spanratio, which is significant as the shear span ratio increases.3. Using the program RCSSCF, the average reduction coefficient of concretetensile strength that was calculated considering to repairring the beam cross sectionhaving been damaged seriously due to fire. A practical calculation method for shearstrength of concrete beam after fire and strengthened with CFRP was proposed.