A new modified stress-strain model for concrete confined with textile reinforced concrete composites

In order to evaluate numerically the effectiveness of textile reinforced concrete (TRC) in repairing/strengthening for concrete structures, it is necessary to investigate the axial stress-strain relationship of TRC confined concrete. Through the statistical analysis with a series of researches, it has been confirmed that the stress-strain curves of TRC confined concrete have the characteristics of hardening and softening behavior. By modifying the well-known Sargin's stress-strain relationship, a new closed-form algebraic expression for descripting the confinement behavior of TRC has been proposed. The numerical coefficients that characterize the model have been expressed as a function of the stress and the tangent elasticity modulus in three characteristic point of the stress-strain curves (origin, stress of confined concrete corresponding to the peak point of unconfined concrete and ultimate point of confined concrete). It is verified that the model could reproduce the behavior of both very lightly confined members with softening behavior and heavily confined members with hardening behavior for TRC through a series of experimental curves. In addition, the accuracy of the proposed model was quantitatively analyzed with calculating the mean square error (MSE) and mean absolute percentage error (MAPE) on the confined concrete stress-strain curve corresponding the peak strength point of unconfined concrete and the ultimate point of confined concrete, and the confined concrete strain energy integral absolute error (IAE). The results showed that the MSE and MAPE were 0.93, 2.93% and 2.23, 4.02%, respectively, and the IAE was 0.0268. Therefore, the modified stress-strain constitutive model proposed for TRC confined concrete has high accuracy and wide applicability.