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Sensitivity analysis of influencing factors on concrete shear strength
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摘要: 针对高寒地区混凝土结构发生的冻融破坏现象，以及混凝土结构会发生剪切破坏的特点，利用大型多功能动静力电液伺服三轴试验机和剪切盒装置进行了混凝土剪切试验，研究分析了法向应力、应变速率和冻融循环次数对混凝土剪切强度发展规律的影响。通过定义无量纲形式的敏感性函数，比较了法向应力、应变速率和冻融循环次数3种因素变化对混凝土剪切强度的敏感性，并对各影响因素的敏感性进行排序。分析结果表明：①混凝土剪切强度随法向应力的增大而提高，其试验曲线分为线性上升段、非线性上升段和稳定段3个阶段；混凝土内部微裂缝和孔隙中的自由水是引起混凝土剪切强度随应变速率增大而增大的重要因素；混凝土孔隙率增大是混凝土剪切强度随冻融循环次数的增加而降低的原因。②当混凝土冻融循环次数不高于50次、法向应力不大于35 MPa且加载的应变速率为10-5/s~10-3/s时，冻融循环次数对混凝土剪切强度的敏感性影响较大，法向应力对混凝土剪切强度的敏感性影响较小，应变速率对混凝土剪切强度的敏感性影响最弱。Abstract: In view of the freeze-thaw damage phenomenon of concrete structures in the alpine region and the characteristics of shear failure of concrete structures, the shear tests on concrete are carried out by using a large multifunctional dynamic and static electro-hydraulic servo triaxial testing system and a shear box device. The effects of normal stress, strain rates and freeze-thaw cycle times on the shear strength of concrete are studied and analyzed in this paper. By defining dimensionless sensitivity function, the sensitivities of the normal stress, strain rate and freeze-thaw cycle times to the shear strength of concrete are compared, and the sensitivity of each influencing factor is ranked. The analysis results show that: ① The shear strength of concrete increases with the increase of the normal stress. Its testing curves can be divided into three stages, i.e. linear rising stage, nonlinear rising stage and stable stage. The free water in the micro-cracks and pores of concrete is one of the important factors leading to the increase of the concrete shear strength with the increase of strain rate. The increase of concrete porosity is the reason that the shear strength of concrete decreases with the increase of the freeze-thaw cycles. ② When the freeze-thaw cycle times of concrete are not higher than 50 times. The normal stress is not more than 35 MPa and the loading strain rate is 10-5/s~10-3/s, the freeze-thaw cycle times have great influences on the sensitivity of the shear strength of concrete. The normal stress of concrete has little effect on the sensitivity of the concrete shear strength, while the strain rate has the least effect on the sensitivity of the concrete shear strength.
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Key words:
- concrete /
- shear strength /
- normal stress /
- freeze-thaw cycle /
- strain rate /
- sensitivity analysis
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图 2 剪切强度与法向应力的变化规律及回归曲线
Figure 2. Relationships between shear strength and normal stress and its regression curve
图 3 剪切强度与应变速率的变化规律及回归曲线
Figure 3. Relationships between shear strength and strain rate and its regression curve
图 4 剪切强度与冻融循环次数的变化规律及回归曲线
Figure 4. Relationships between shear strength and freeze-thaw cycle times and its regression curve
图 5 不同冻融循环次数后混凝土试件外观形态
Figure 5. Appearance of concrete specimen after different freeze-thaw cycles
图 7 S$\dot \varepsilon $($\dot \varepsilon $)-$\dot \varepsilon $关系曲线
Figure 7. Relationship between sensitivity function and strain rate
图 8 SN(N)-N关系曲线
Figure 8. Relationship between sensitivity function and freeze-thaw cycles
表 1 混凝土剪切强度影响因素的取值范围与敏感性系数范围
Table 1. Range of factors affecting concrete shear strength and range of sensitivity coefficients
参数 取值范围 敏感性系数波动范围 法向应力 0~35 MPa 0~0.292 应变速率 10-5/s~10-3/s 3.259×10-7~3.259×10-5 冻融循环次数 0~50次 0~2.706 
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