超长循环荷载下轻质混凝土疲劳特性

Fatigue Characteristic of Expanded Polystyrene Concrete under Ultra-long Cyclic Loading

采用MTS万能试验机对外掺30%体积分数聚苯乙烯颗粒的轻质混凝土试件施加不同频率(5,10Hz)及荷载幅值(30,35,40kN)的超长循环荷载,进行累计2 000×104振次的疲劳试验,研究其动应力-应变滞回曲线形态随振次的变化规律,并计算了对应的阻尼比、动弹性模量等动力学性能.结果发现:与同强度等级的混凝土相比,轻质混凝土阻尼比较大,动弹性模量稍低,表明其吸能效果更好,韧性与抗裂性能也更为优异;轻质混凝土试件在1 570×104振次左右出现了细微裂缝,根据其附近的应力应变关系发现,该试件的阻尼比与动弹性模量在疲劳损伤前后基本保持稳定;提出和验证了轻质混凝土疲劳寿命预测公式,并对其应用于道床的可行性进行了研究.

The cyclic loading with different frequencies(5,10 Hz)and different amplitudes of the bias force(30,35,40 kN)was applied to the fatigue test on expanded polystyrene concrete with volume mixing ratio of 30%by MTS 810 for accumulative vibration cyclic number of 20 million times.Based on the analysis of variation of the dynamic stress-strain hysteresis curves at different cyclic number,corresponding damping ratio and dynamic elastic modulus were calculated.Calculation results of damping ratio and dynamic elastic modulus indicate that expanded polystyrene concrete has superior performance of vibration attenuation,toughness and crack resistance.A slight crack occurs on the expanded polystyrene concrete specimen at about cyclic number of 1 570×10 4,and damping ratio as well as dynamic elastic modulus is relatively stable before and after the small crack occurs.The fatigue life prediction formula of expanded polystyrene concrete is proposed and verified.In addition,the feasibility of applying expanded polystyrene concrete to ballast bed is explored with this prediction formula.