冻融循环下混凝土疲劳损伤试验研究

Experimental Study on Fatigue Damage of Concrete under Freeze-Thaw Cycles

为研究混凝土在实际使用中受到冻融循环和疲劳加载作用时的损伤特性,对经历不同冻融循环次数、不同疲劳荷载上限应力比以及不同疲劳加载次数的混凝土,进行施加轴向荷载的受压破坏试验,探究混凝土在冻融循环、疲劳荷载影响条件下的残余强度变化规律、相对动弹性模量及峰值应变的演化规律.结果表明:随着冻融循环次数的增加,混凝土的残余强度呈现较明显的3个衰减阶段;相对于冻融循环次数作用,疲劳荷载上限应力比对混凝土峰值应变的影响起着更显著的作用;随着冻融循环次数的增加和疲劳荷载上限应力比的增大,两种因素同时作用下的相对动弹性模量下降量,相对其中任意单因素作用下混凝土试件相对动弹性模量下降量更大,同时,相对动弹性模量变化可以分为2个阶段.

To investigate the damage characteristics of concrete under the combined effects of freeze-thaw cycles and fatigue loading in practical applications,the compressive damage test with axial load was carried out on concrete specimens subjected to different numbers of freeze-thaw cycles,different fatigue load upper limit stress ratios and different numbers of fatigue loading cycles to study the residual strength of concrete specimens under the coupling of freeze-thaw cycle-fatigue load.The development law of residual strength,relative dynamic elastic modulus,and peak strain of concrete structures under the coupled influence of freeze-thaw cycle and fatigue loading are investigated.The results show that:The residual strength of concrete structures exhibits three distinct stages with increasing freeze-thaw cycles.Compared to the effect of freeze-thaw cycles,the fatigue load upper limit stress ratio has a more significant impact on the peak strain of concrete.Moreover,as the number of freeze-thaw cycles and fatigue load upper limit stress ratio increase,the relative dynamic modulus of concrete specimens under the combined effect of these two factors decreases more compared to under any single factor alone,and the variation of the relative dynamic modulus occurs in two stages.