Fracture Properties of Fiber Reinforced Concrete

Open Access
Author:
Amirineni, Krishna C
Graduate Program:
Civil Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 20, 2009
Committee Members:
  • Maria De Los Angeles Lopez, Thesis Advisor
Keywords:
  • notch
  • crack width
  • optimization
  • inverse analysis
  • crack opening
  • stress
  • fracture
  • softening
Abstract:
Fracture properties of four different steel fiber reinforced concrete (SFRC) mixtures are determined in the present study. Two types of hooked end steel fibers having aspect ratios of 80 and 65 respectively were used employing volume fractions of 0.5% and 1.0%. Three point bending tests have been performed conforming to RILEM technical committee TC 162-TDF (RILEM, 2002a). The equivalent, feq, and residual, fR, flexural tensile strength parameters, proposed by RILEM TC 162-TDF (RILEM, 2002a), to characterize and simulate the post-cracking behavior of SFRC have been evaluated and compared for the various concrete mixtures. It is observed that the equivalent flexural tensile strengths, feq, have less variance compared to the residual flexural tensile strengths, fR. A step wise optimization algorithm was developed to obtain the stress-crack opening (σ-w) curve of fiber reinforced concrete (FRC) using inverse analysis procedures. The optimization algorithm was developed as a three step process calculating the modulus of elasticity, E, in Step 1 and the tensile strength, ft, and the slope of the first leg of the bilinear σ-w curve, a1, in Step 2. Finally the parameters defining the second leg of the bilinear σ-w curve, a2 and b2 are calculated in the third and the final step. It was observed that ft and a1 can be accurately predicted by restricting the optimization interval in Step 2 to [0, 0.05 mm]. It is concluded that the load- crack mouth opening displacement (P-CMOD) data from three point bending tests should be recorded at least until a CMOD of 5.0 mm is reached. The stress-crack opening curve of FRC can be predicted accurately by following the three step procedure, restricting the end level of CMOD to 0.05 mm in Step 2 and by performing the optimization in Step 3 at least until an end CMOD of 5.0 mm.