冻融劣化后预加载历史对混凝土损伤特性影响

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

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。

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 freezethaw 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.