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为研究应变速率和分级加载持荷对混凝土动态抗弯拉力学性能和变形性能(抗弯拉强度、弹性模量、泊松比、峰值应变)的影响,分析混凝土动态抗弯拉试验破坏形态特点,在应变率分别为10-6/s、10-5/s、10-4/s下,对强度为C50的混凝土试件进行动态直接破坏和分级加载持荷弯拉破坏试验。试验结果表明:当应变速率为定值时,与直接破坏相比,经历荷载历史的混凝土的动态抗弯拉强度和弹性模量都有一定幅度的降低,而峰值应变有一定幅度的增高;当加载方式确定时,随着应变速率的提高,混凝土的抗弯拉强度有所提高,但应变率和加载历史对混凝土弯拉条件下弹性阶段泊松比变化范围内的最大值基本没有影响,可以采用0.2;初始裂纹的形成和发展是分级持荷影响混凝土抗弯拉强度降低的主要原因,而粗骨料破坏数量的增加是应变速率影响混凝土抗弯拉强度增加的直接结果,随应变速率的增加,混凝土试块的破坏面趋于平整,破坏时间变短。
In order to study the influence of strain rate and graded loading on dynamic mechanical properties and deformation properties (flexural strength, elastic modulus, Poisson’s ratio, peak strain) of concrete, the dynamic characteristics of concrete under dynamic buckling test , The specimens of concrete with strength of C50 were dynamically destructed and graded and loaded with load-pull bending failure test under the strain rates of 10-6 / s, 10-5 / s and 10-4 / s, respectively. The experimental results show that the dynamic bending strength and elastic modulus of concrete subjected to load history decrease to a certain degree and the peak strain increases to a certain extent when the strain rate is constant, When the loading method is determined, the flexural strength of concrete increases with the increase of strain rate, but the strain rate and loading history have almost no effect on the maximum value of the Poisson’s ratio within the elastic phase of the concrete under bending conditions, Using 0.2; the formation and development of initial cracks is the main reason that the grading load affects the decrease of the flexural strength of concrete. The increase of the amount of coarse aggregate is the direct result of the strain rate affecting the flexural strength of concrete. With the increase of strain rate Increase, the destruction of concrete test block tends to be flat, the destruction time becomes shorter.