BRITTLE FRACTURE BEHAVIORS OF BUILDING STRUCTURES

研究了构件中含有初始裂纹的建筑结构的断裂行为。基于断裂力学理论，将边界元法应用于裂纹扩展行为的数值分析。应用边界元裂纹扩展分析，确定了矩形脆性梁和宽翼缘脆性梁的端弯矩-端转角关系，它们代表了裂纹扩展的不稳定平衡路径。在此基础上，提出了用旋转弹簧模型代替裂纹单元的简单而有效的方法。该模型对含裂纹单元的建筑结构脆性断裂行为的数值分析是有效的。对于构件中含有初始裂纹的脆性结构，裂纹扩展的稳定性将受到无裂纹部分结构刚度的影响。如果没有裂纹部分的结构的刚度大，则裂纹扩展将快速增长。提出了结构刚度矩阵的特征值和特征向量可用于裂纹扩展稳定性的判定，并可采用其凝聚刚度矩阵代替刚度矩阵。该方法适用于具有多个初始裂纹的结构。许多，裂纹扩展试验进行了检查，并提出了一些增长的特点。深切口试件试验包括钢板的拉伸、宽翼缘钢梁的弯曲、钢梁与钢柱节点的弯曲和T形聚苯乙烯模板梁的弯曲。

We have researched on fracture behaviors of building structures with initial cracks in the elements. Based on the fracture mechanics, Boundary Element Method is applied to numerical analysis of crack growth behavior. Applying the BEM crack growth analysis, we determined the end moment-end rotation relations for, the, rectangular brittle beam and wide flange brittle beam, which represent unstable equilibrium paths for the crack growth. On the basis of them, we propose the rotation spring models as simple and effective substitute for the crack elements. These rotation spring models are effective for numerical analysis of brittle fracture behaviors of building structures with crack elements. On the brittle structures with initial cracks in the elements, the stability on crack propagation will be influenced by the stiffness of the structure without the crack part. If the stiffness of the structure without the crack part is large, crack propagation will grow rapidly. We presented that eigen-value and eigen-vectors of the stiffness matrix of the structure are useful for determination of the stability on crack propagation, and that its condensed stiffness matrix can be used instead of the stiffness matrix. This method can be applied to the structures with plural number of initial cracks. Many, crack growth tests are examined and some characteristics of the growth are presented. Deeply-notched specimen tests consist of the extension of steel plate, bend of wide-flange steel beams, bend of steel beam and steel column joints, and bend of T-shaped styrene form beams.