Acoustic-Emission-Based Multiscale Tensile Constitutive Model for Ultra-High-Performance Concrete Considering...

Ultra-high-performance concrete (UHPC) has attracted extensive attention because of its superior mechanical performance and durability. However, many existing tensile constitutive models are still obtained mainly by fitting macroscopic stress-strain curves, and the coupling among tensile damage development, steel-fiber parameters, and structural-scale response has not been sufficiently clarified. In this work, an acoustic-emission-informed tensile damage model was established for UHPC. Direct tensile tests were carried out on UHPC specimens containing steel fibers with aspect ratios of 43, 65, and 100 and volume fractions ranging from 0.5% to 3.0%, while acoustic emission signals were collected during loading. The normalized cumulative AE count was adopted as a damage indicator, and its evolution with tensile strain was described using a Weibull-type function. A fiber factor combining fiber volume fraction and aspect ratio was further incorporated into the damage constitutive equation. The proposed relationship was checked against 14 independent tensile datasets reported in the literature. After correction, the mean relative error of the predicted model parameter was reduced to 2.6%, with a standard deviation of 4.1%, and the fitted stress-strain curves all achieved R² values above 0.85. The constitutive model was then implemented in ABAQUS for the simulation of reinforced UHPC beams. By introducing a member-level reduction coefficient of μ = 0.84, the numerical load-deflection curve showed improved agreement with the experimental beam response. The coefficient is empirical and is applicable only to the beam configuration investigated here unless further validation is performed. Overall, the proposed model provides a damage-based link among AE monitoring, steel-fiber reinforcement parameters, and member-scale numerical analysis.