Experimental and numerical research of ultrahigh performance concrete layered shell element based on a two-dimensional fixed crack model

Abstract

Ultrahigh performance concrete (UHPC) is a cement-based material with superior characteristics including tension strain-hardening and multi-cracking, which is attractive for application in the field of assembled structures. However, a reliable method for simulating the mechanical behaviour of UHPC structures is lacking. Thus, this study proposes a two-dimensional fixed crack constitutive model for UHPC using the MSC.MARC software based on the experimental results, which is expected to offer high reliability. The stirrup restraint effect, tensile strength hardening, stiffness degradation, and the tension–compression softening of UHPC were considered in the constitutive model. To calibrate the relevant parameters of the constitutive model, UHPC prism and dog-bone specimens with different steel fibre contents were fabricated. Through uniaxial compressive and tensile tests with different loading regimes, the effects of steel fibre content, maintenance mode, and the loading regime on the uniaxial mechanical properties of UHPC were analysed. The test results showed that the peak compressive strain of the specimen with 2% steel fibre content was significantly higher than those of the specimens with 1% and 3% steel fibre content. Furthermore, UHPC exhibits strain hardening and ductility in the tensile experiments. The steel fibre content and steam curing significantly improved the tensile strength of the UHPC specimens. Based on the test data, the skeleton curves and hysteresis criteria of UHPC under compression and tension were proposed, and the formulae describing the process of unloading and reloading, which can be used for the basic constitutive model of UHPC, were fitted. Finally, five UHPC shear wall specimens were designed and simulated through the proposed model. The numerical results obtained using the proposed constitutive model and modelling methodology, including the skeleton curves, failure modes, ductility, and the deformation capacity of the UHPC shear walls, agreed significantly with the experimental results, confirming the reliability and high accuracy of the proposed UHPC constitutive model, thereby increasing the applicability of UHPC.