A sawtooth constitutive model describing strain hardening and multiple cracking of ECC under uniaxial tension

By collecting engineered cementitious composite (ECC) uniaxial tensile experimental research data, aiming at the multiple cracking characteristics of the strain hardening stage of the ECC stress-strain curve, a theoretical model describing the constitutive relationship of the ECC uniaxial tensile stress-strain - the multiple cracking sawtooth model - is proposed. Several model parameters were obtained with the fitting analysis of many ECC uniaxial tensile stress-strain curves. The application conditions and influencing factors of the three-order multi-crack "sawtooth" model of polyvinyl alcohol (PVA)-ECC and polyethylene (PE)-ECC and the four-order multi-crack "sawtooth" model of PVA-ECC are studied. The result shows that the higher the fiber reinforcement index, the better the tensile properties of ECC. The fiber reinforcement index is linearly correlated with the initial crack stress and ultimate tensile stress of PVA-ECC and with the ultimate tensile stress and ultimate tensile strain of PE-ECC. The characteristic points of PVA-ECC in the multi-crack cracking stage are as follows: the greater the initial cracking strain, the smaller the ultimate tensile strain, showing an exponential correlation; The greater the initial cracking stress is, the greater the ultimate tensile stress is, and the two are linearly correlated.