THE OPTIMIZED DESIGN OF DOG-BONES FOR TENSILE TEST OF ULTRA-HIGH PERFORMANCE CONCRETE

Uniaxial tensile testing is the most effective method for testing ultra-high-performance concrete (UHPC) damage mechanism, tensile strength, and tensile constitutive relationship. The uniaxial tensile test is a very sensitive and difficult test to conduct. In theory, the shape effects are absent. There are currently no testing standards available that define the test conditions and specimen geometry. Then unnotched dog-bones specimens have unique advantages. Due to the typology of a transition region, specimens can be divided into the arc-dog-bone, the trapezoid-dog-bone, and the multiple-dog-bone specimens. Based on the stress analysis of the specimen, two indexes of stress distribution were put forward to evaluate the specimens. The research can improve the success rate of uniaxial tensile test for UHPC by designing special dog-bone specimens. Thusly, the effects of a set of non-dimensional geometric parameters on the stress distribution were numerically investigated. A total of 275 dog-bones specimens were analyzed using non-dimensional parameters, and 15 specimens was proposed to compare the three types of dog-bone specimens. Based on the stress distribution in the effective test area, an optimized design is proposed for the dog-bone shape to improve the success rate of the uniaxial tensile test. Twenty-four dog-bone specimens were tested for the verification of the optimized dog-bone shape, the success rate of which is 95.8%.