Improved simplified constitutive tensile model for fiberreinforced concrete

摘要

Due to the low strain capacity and the weak crack resistance of concrete, fibersare commonly added to concrete to increase its tensile resistance. The most recentstandardized constitutive tensile model is given in the fib Model code 2010, whichis based on a simplified stress profile at serviceability limit state (SLS) and ultimatelimit state (ULS). However, in current research, an improved stress profile at ULSis proposed. Consequently, three new constitutive tensile models, which are valuedfor a specific FRC class, are developed. Those models are constructed with thetest data of fiber-reinforced concrete with natural aggregates (FR-NAC) and threetypes of recycled aggregates (FR-RAC). In addition, macro glass fibers and macropolypropylene fibers are used. The test data indicate that the lower concreteYoung's modulus of FR-RAC, as well as the crack growth resistance due to plasticwork of the recycled concrete mixtures, result in an increased residual tensilestrength at SLS and ULS. The residual tensile strength at 2.5 mm CMOD (f_(Ft,2.5))of the normal recycled aggregate concrete (nRAC) mixture with 0.75 V% glassfibers is 0.95 MPa, while the FR-NAC mixture with the same fiber content onlyindicates a f F_(t,2.5)-value of 0.43 MPa. Consequently, higher linear postcrackingstresses are observed for the FR-RAC mixtures, especially for the FR-RAC mixtureswith 0.75 V% glass fibers and the lower quality of recycled aggregates.