Continuous surface cap model for ultra-high-performance concrete under static and low strain rate loadings: Calibration, experiment, and simulation

Abstract

The ultra-high compressive strength and ductile tensile behavior of ultra-high-performance concrete (UHPC) make it promising in the application of civil and crashworthy facilities. Although numerous experimental studies have been conducted to investigate the performance of UHPC, studies on the methods for simulating the behavior of UHPC are few. In this paper, an overview of widely used constitutive models of concrete-like materials in hydrocode was presented first, and then a comprehensive calibration of the continuous cap surface (CSC) model was performed to simulate the mechanical behavior of UHPC under static and low strain rate loadings. Four groups of parameters: (1) failure surface parameters; (2) cap and hardening parameters; (c) damage parameters; and (4) strain rate parameters were systematically calibrated via extensive available material test data of UHPC with uniaxial compressive strength ranging from 101 MPa to 238 MPa. A calculation method was proposed to address the inconsistency of existing conclusions regarding the fracture energy of UHPC, which significantly affects the modeling of UHPC damage. Moreover, a method was proposed to convert the engineering uniaxial tensile strain of UHPC to the true uniaxial tensile strain, and so does the tensile fracture energy of UHPC. To validate the accuracy of the calibrated CSC model in simulating the behavior of UHPC under static loading, uniaxial tension and compression tests of UHPC samples and three-point bending tests of steel-UHPC-steel composite beams were conducted and simulated. Existing triaxial compression tests of UHPC cylinders were simulated to validate the accuracy of the calibrated CSC under confinement. Moreover, low-velocity impact tests of UHPC columns were simulated to further validate the reliability of the calibrated CSC model to capture the structural behavior of UHPC members under low strain rate loading. It was found that the calibrated CSC model showed excellence in simulating the material properties of UHPC and the structural behavior of UHPC members under static and low strain rate loadings.