考虑尺寸效应的高强轻骨料混凝土深受弯构件受剪性能分析

High-strength lightweight aggregate concrete has a good prospect of engineering application for the advantage of its high strength, light weight, high refractoriness and durability, and good thermal insulation. However, high brittleness and prominent size effect also exist. Shear failure is the mainly failure pattern in deep flexure members because of the high sectional height, the size effect and the brittle shear failure on lightweight aggregate concrete is more significant and obvious, it is necessary to study the size-effect of shear performance on these members. Based on the experimental study together with theoretical analysis,the project pretends to test two group experiments on shear behavior of 30 deep flexure members. Modified compression field theory and softened strut-and-tie model are appliedto micro structural concrete and macro strut-and-tie model to carry out shear behavior research. The failure mechanism and influence factors of this kind of deep flexure members are revealed. Base on modified compression field theory,a shear model of deep flexure member is presented considering the size effect. The strut-and-tie model design method considering size effect and simplified calculation method are proposed. The structure design theory and method of lightweight aggregate concrete are established considering the size effect. The research is of both theoretical significance and practical value for filling the current code and promoting the innovation of shear design of high-strength lightweight aggregate concrete members.

高强轻骨料混凝土具有轻质高强、保温隔热性能好、耐久耐火性高等优点，在工程中有良好的应用前景，但也存在脆性显著、尺寸效应突出等不足。深受弯构件截面高度大，剪切破坏是其主要破坏模式，加之轻骨料混凝土构件尺寸效应较普通混凝土构件更加显著，有必要深入研究尺寸效应对该类新型混凝土构件受剪性能的影响。项目采用试验研究与理论分析相结合的方法，拟完成两批30件深受弯构件的受剪性能试验，揭示该类深受弯构件的破坏机理及影响因素，应用改进斜压场理论、软化拉压杆模型分别从细观结构混凝土、宏观拉压杆模型对深受弯构件受剪性能开展研究，建立基于修正压力场理论考虑尺寸效应的深受弯构件计算模型，提出考虑尺寸效应影响的拉压杆模型设计法及简化计算方法，建立覆盖大尺寸的考虑构件尺寸效应的轻骨料混凝土结构设计理论与方法。研究成果对于填补轻骨料混凝土规程空白、推动高强轻骨料混凝土构件抗剪设计创新具有重要的理论意义和实用价值。

本项目以轻骨料混凝土力学性能分析为基础，采用试验研究与理论分析相结合的方法，系统开展了高强轻骨料混凝土深受弯构件的受剪性能研究。材料层面，研发了不同强度轻骨料混凝土的配制工艺，明确了其微观结构特征和宏观力学性能指标，为该类符合国家可持续发展要求的绿色建筑材料在实际工程中的推广应用提供了基础数据。构件层面，完成了15根大尺寸高强轻骨料混凝土深受弯构件的受剪试验，明确了截面高度、剪跨比、加载板宽度等关键因素对该类构件全寿命工作机制的量化影响，揭示了其剪切破坏机理及尺寸效应作用规律，基于修正斜压场理论、拉压杆理论和断裂能量释放理论，结合轻骨料混凝土自身特性，构建了不同尺度下考虑尺寸效应影响且力学概念清晰的受剪分析模型，并提出了与拉压杆模型相协调的受剪设计方法。研究成果为高强轻骨料混凝土深受弯构件的工程应用提供了理论支撑，丰富了混凝土结构的受剪理论。