Experimental Study On Flexural Tensile Strength Of Hooked-end Steel Fiber Reinforced Concrete

Compared with ordinary concrete,steel fiber reinforced concrete?SFRC?has higher strength,toughness and crack resistance,and is widely used in water conservancy,civil engineering,construction,transportation and port engineering.Steel fibers improve the performance of concrete rely on its excellent cracking resistance and cracking,especially the improvement of concrete bending and tensile properties.Among various types of steel fibers,the single hooked-end steel fiber is outstanding in crack resistance and cracking,but the bonding and anchoring performance between the steel fiber and concrete is relatively limited,and it is not completely suitable for application in high strength concrete structures.Therefore,the bending and tensile properties of steel fiber reinforced concrete with continuous hooks at both ends are studied through bending and tensile tests in this paper.The main contents are as follows:1.Through the 3-points bending tests on 468 notched steel fiber reinforced concrete?SFRC?prisms?150 mm×150 mm×550 mm in dimensions?to obtain the bending load-crack opening displacement?CMOD?curves.The effects of the steel fiber content,steel fiber type,and matrix strength grade on the bending load-CMOD curves were investigated.The results show that with the increase of the steel fiber content,the bending load-CMOD curve of the specimen became more full.With the increase the number of hooks and the improve of the matrix strength grade,the descending section of the bending load-CMOD curve did not continue to increase with the change of a single factor.2.According to the European standard BS EN 14651:2005+A1:2007,the limit of proportionality?LOP?and residual flexural strength can be calculated.The effects of the fiber content,fiber type,and matrix strength grade on LOP and residual flexural stress were analyzed by contrast.The results show that the increase of matrix strength grade could improve LOP,and the increase of the steel fiber content was effective method to improve residual flexural strength.4D and 5D steel fibers with continuous hooked ends could be better anchored to the matrix than 3D steel fibers with single hooked-end,so that the efficiency of steel fibers was improved.However,for steel fiber reinforced concrete with different matrix strength grade,the residual flexural strength did not increase continuously with the change of steel fiber type.According to the test results,4D and 5D steel fibers were recommended for high strength concrete,and 3D steel fibers were recommended for ordinary strength concrete.3.According to the influence of the steel fiber content,steel fiber type,and matrix strength grade on LOP and residual flexural strength,the prediction models suitable for LOP?f _L?and residual flexural strength f _R,j?j=1,2,3,4?of the hooked-end steel fiber reinforced concrete were established.4.An integrated model of the steel fiber reinforced concrete notched prisms was established by ANSYS.First,the constitutive relationship and material parameters of the steel fiber reinforced concrete were determined by the experimental data.Then,a non-linear finite element analysis was performed on the crack development process at the mid-span.Finally,the bending load-CMOD curve was simulated.