冻融循环作用下混凝土受压本构特征研究

采用混凝土棱柱体试件,通过快速冻融试验方法,对经受冻融损伤的混凝土受压性能进行了试验研究,分析了冻融循环次数、混凝土等级、相对动弹性模量对混凝土受压性能的影响,通过碟簧耗能装置,得到了完整的应力-应变关系试验结果.将冻融次数和混凝土等级作为参数,回归试验结果,提出了冻融循环后受压性能的计算公式以及适用于立方体抗压强度为20～50 MPa的冻融循环作用下混凝土的应力-应变全曲线方程,并将曲线控制参数与相对动弹性模量和混凝土等级建立关系.结果表明:碟簧耗能装置起到了吸收机械能量的作用,是应力-应变关系试验成功的重要保证.随着冻融循环次数的增加,受压应力-应变曲线趋于扁平；受压峰值应力降低,受压峰值应变、受压极限应变增大,三者随冻融循环的变化关系均近似线性；随着混凝土等级的提高,冻融对于混凝土材料的影响下降.此外,结合所建立的破坏准则所得到的数值分析结果与试验曲线有较好的一致性.

Study on Constitutive Relations of Compressed Concrete Subjected to Action of Freezing Thawing Cycles

Using prismatic specimens of concrete, the compressive properties of concrete exposed to freezing thawing cycles were examined. Impact of the cycle times, concrete grade and relative dynamic elastic modulus on compressive properties of concrete, including peak compressive stress, peak compressive strain, ultimate compressive strain were studied. Complete compressive stress stain curves were studied with the help of energy dissipating equipment, disk spring. The specimens were experienced 0, 25, 50, 75, 100 and 125 freezing thawing cycles. The strength grade of concrete is C20, C30, C40 and C50. Using cycle times and concrete grade as the criteria, the equations of compressive properties and the complete compressive stress strain curves for frozen thawed concrete are obtained, which are suitable for concrete with cubic strength of 2050MPa. The test results show that the energy dissipating equipment and disk spring perform quite well. With the increase of freezing thawing cycles, the stress strain curve becomes more flat, the peak stress decreases, the peak strain and ultimate compressive strain increase. With the increase of concrete grade, the effect of freezing thawing cycles reduces. Numerical results from the proposed constitutive model are in good agreement with the test results.