Study On Shear Capacity Of Steel Fiber Reinforced Concrete Beams Based On The Modified Compression Field Theory

The Modified Compression Field Theory(MCFT) was presented by Vecchio and Collins based on experimental study which was used to analyses the reinforced concrete element under shear stress and principal stress. The characteristics of MCFT were considering the cracked concrete tensile stress,the tension stiffening and compression softening of reinforced concrete.The average sress-strain constitutive relationship was used.The reinforced concrete element was predicted by using equilibrium conditions,compatibility conditons and the local stress check at cracks.Based on the Modified Compression Field Theroy,Four simplified sectional analysis programs for beams under combined action of shear and moment were realized. One group reinforced concrete beams were analyzed with four simplified programes,VT2 and Response2000 based on MCFT. Compared of the analysis results with these programes.Considering the constitutive relationship of the steel fiber concrete and the local stress check at cracks,the simplified sectional analysis method for steel fiber concrete beams was proposed.Moreover,The method considered the steel fiber concrete tensile stress in tension zone.44 experimental steel fiber concrete beams with stirrups and 40 experimental steel fiber concrete beams without stirrups beams which were shear failure were analyzed by proposed method in this paper.Some conclusions can be drawn as followings:1. The predicted ultimate shear strength which were analyzed by simplified sectional analysis methods of concrete reinforced beams agree well with test if only given the reasonable longitudinal strain.2. The predicted ultimate shear strength used bilinear and trilinear model of steel fiber concrete were conservative, but agree well with test used tension stiffening model.and predicted well the effect of steel fiber volume fraction and aspect ratio.3. By simplified sectional analysis method proposed in this paper, it can be showed that the application of stress check method at cracks can avoid the over-big analyzed result which was caused from the ignored crack stress check.4. Ultimate shear strength of the steel fiber concrete beams without stirrups analyzed by thesimplified sectional analysis method agree well with the test ,it shows that the stress check at cracks are reasonable.