轻骨料无腹筋混凝土梁剪切破坏及尺寸效应:细观模拟

轻骨料混凝土具有轻质、高强及保温隔热性能好等优点，被广泛应用于工程结构中。采用细观数值模拟方法，将普通及轻骨料混凝土看作由骨料颗粒、砂浆基质及界面过渡区组成的三相复合材料，建立了无腹筋混凝土梁剪切破坏行为模拟的三维细观力学分析模型，研究了不同尺寸普通及轻骨料无腹筋混凝土悬臂梁在单调加载下的剪切破坏模式与失效机制，揭示了名义剪切强度的尺寸效应规律。此外，结合模拟结果对相关设计规范抗剪承载力计算公式的准确性和安全性进行了初步探讨。研究结果表明:区别于普通混凝土梁，轻骨料混凝土梁由于骨料强度较低而首先发生破坏；不同尺寸混凝土梁的剪切破坏模式基本一致，梁的名义剪切强度展现出明显的尺寸效应；相比于普通混凝土梁，轻骨料混凝土梁剪切破坏表现出具有更强的尺寸效应。

SHEAR FAILURE AND SIZE EFFECT OF LIGHTWEIGHT AGGREGATE CONCRETE BEAMS WITHOUT WEB REINFORCEMENT: A MESO-SCALE STUDY

Lightweight aggregate concrete (LWAC) is more and more utilized in engineering structures because of the advantages of light weight and good thermal insulation performance. Both lightweight aggregate concrete and ordinary concrete were regarded as three-phase composites consisting of the aggregate particles, mortar matrix and interface transition zones (ITZs) between them. A 3D meso-scale mechanical model was established to simulate the shear failure behavior of concrete beams without web reinforcement. The shear failure modes and failure mechanism of ordinary and light aggregate concrete cantilever beams with different structural sizes under monotonic loading were modelled and studied. The size effect on the nominal shear strength was examined. In addition, the accuracy and safety of the formula for calculating the shear capacity of the relevant design codes are preliminarily discussed based on the simulation results. The results show that different from the ordinary concrete beam, the LWAC specimens sustained serious damage due to the lower strength of the aggregates. The shear failure modes of concrete beams with different sizes were basically the same. An obvious size effect on the nominal shear strength of both LWAC and ordinary concrete specimens was observed. Compared with the ordinary concrete beams, lightweight aggregate concrete beams showed a stronger size effect in shear failure behavior.