UHPC单轴拉伸试验狗骨试件优化设计

单轴拉伸试验是测试超高性能混凝土(Ultra-high Performance Concrete，简称UHPC)破坏机理、抗拉性能与拉伸本构关系最有效的方法。单轴拉伸试验成功率不高。其常用的狗骨试件形状与尺寸对试验成功率有较大的影响，目前还未有统一的标准。调查表明，不带缺口的狗骨试件最适合用于UHPC单轴拉伸试验，主要有梯形、弧形和阶梯形三种类型。通过对试件的受力分析，提出两个应力均匀性指标来评价试件优劣。建立了三种共275根狗骨试件的有限元模型，通过分析，分别给出三种试件均匀性较好的参数。同时，建立了三组15根试件有限元模型，横向对比了三种狗骨试件的应力均匀性。对比结果表明，弧形狗骨试件受力均匀性最好，开展的验证性试验取得了95.8%的成功率，推荐采用。

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%.