Study Of The Strengthening Mechanism And Fracture Toughness Of Steel Fiber Reinforced Concrete

Rencently, steel fiber reinforced concrete(SFRC) has been widely used, A lot of research have indicated that the steel fiber mixing into concrete can evidently improve the nonlinear characteristic and softening characteristic after peak value of SFRC .Fracture capability of SFRC is one of important capability in its mechanical characteristic,but there are a few people on studying the fracture characteristic of SFRC in our country.Introduced double-K fracture criterion used in concrete and considered softening characteristic of SFRC, this paper primarily study the strengthening mechanism and the method of calculating the fracture toughness of SFRC. Based on the difference between concrete and SFRC, amended the relative parameters,the paper tries to find the proper way to calculate the fracture toughness of SFRC.Through the experiment of a three-point bending beam which is mixed into different lengh and volum rate of steel fiber,it measures the P-△ curve and P-CMODcurve of SFRC. Combined with the result of experiment, the reason that steel fiber enhanced the toughness is analyzed. It is found that the specimen canbe divided into two cases : ρf < ρfcrit and ρf >ρfcrit.Based on the two cases, two methods to calculate thedouble-K fracture parameter of SFRC are given. Then,using the data of experiment,we can received the fracture parameter of every specimen .Through analyzing the fracture parameter, the method can be provedproper to calculate the fracture toughness .The analysis proves that the volum rate value ρf which is chose should meet ρf > ρfcrit in order to make use of steel fiber .The discuss to the application of the double-Kfracture parameter also proved that it is difficult to make KIC as a controled index to the structure.The conception of steel fiber slippage was brought forward, the connection between steel fiber slippage and character parameters of steel fiber was simulated, too. Through dealing with the P- A curve,the softening curve of SFRC which can reveal the strain softening law was attained .Finally, the author sums up all the content and brings forward some advice about the study to the fracture of SFRC.