Dynamic compression behaviors of concrete under true triaxial confinement: An experimental technique

Abstract

A dynamic testing system for concrete-like material under static triaxial confinements is developed in the present article. The cubic specimen with length 50 mm is constrained by six steel square bars. The static triaxial confinements are applied on the specimen through six steel bars that independently servo-controlled by three hydraulic cylinders. A striker is then launched to impact the incident bar along the x-axis. The dynamic responses of the cubic specimen are measured by strain gauges stuck on the middle surfaces of the six bars. The dynamic compressive behaviors of concrete specimens under various static triaxial confinements are investigated accordingly. The 3-D dynamic engineering stress- engineering strain relationship, the dynamic volumetric strain- hydrostatic pressure relationship, and the equivalent stress- equivalent strain relationship are obtained and analyzed in details. The results show evidently the load path dependence and the strain rate dependence. Based on the Drucker-Prager (D-P) strength criterion, the effect of the intermediate stress on dynamic strength is discussed, and the material parameters (e.g. α0 and k0) and the strength parameters (e.g. the cohesion c and the inner friction angle ϕ) at various strain rates are demonstrated. The results show that with increasing strain rate, the friction angle ϕ increases, and the cohesion c decreases. The technique provides profound and comprehensive understanding of the dynamic failure properties for concrete-like material under complex stress states.