冻融劣化后预加载历史对混凝土损伤特性影响

为了研究冻融劣化和荷载预损伤对混凝土动态损伤特性的影响,利用10 MN大型多功能液压伺服静动力三轴仪及TR-TSDRSL冻融仪,对历经不同冻融循环后混凝土进行一定幅值的加载历史后,按照不同应变率单调加载直至破坏,并通过Najar能量法对损伤变量D进行了定义,从弹性模量、应变速率和预加载历史三个因素对试件进行损伤分析。试验结果表明,随应变速率的增加,混凝土强度总体呈线性增长,强度增加比例为40%左右,两者拟合后发现预加载历史对混凝土强度的增幅更敏感;随着预加载历史的增大,混凝土强度呈现出先增大后减小的趋势;弹性模量、应变速率和预加载历史三者之间预加载历史的损伤率敏感性更高。随着预加载历史的增大,正式加载时混凝土的压密阶段提前,损伤快速发展阶段提前。

Influence of Pre-loading History on Damage Characteristics of Concrete after Freezing and Thawing Deterioration

In order to study the influence of freeze-thaw deterioration and load pre-damage on the dynamic damage characteristics of concrete, a 10 MN multifunctional hydraulic servo static-dynamic triaxial tester and TR-TSDRSL freeze-thaw tester were used to load the concrete after different freeze-thaw cycles at a certain amplitude, and then monotonously loaded to failure according to different strain rates. Damage variable D was defined by Najar energy method. Damage analysis of specimens was carried out from three factors: elastic modulus, strain rate and preloading history. The results show that with the increase of strain rate, the strength of concrete increases linearly, and the proportion of strength increases is about 40%. After fitting the results of two methods, it is found that the pre-loading history is more sensitive to the increase of concrete strength. With the increase of pre-loading history, the strength of concrete increases first and then decreases. The damage rate sensitivity of pre-loading history is higher between strain rate and pre-loading history. With the increase of pre-loading history, the compaction stage of concrete under formal loading is ahead of schedule, and the rapid damage development stage is ahead of schedule.