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中文摘要：
利用焦散线实验系统,进行了冲击加载下含预制裂纹梁柱试件的断裂实验,研究了梁柱试件的梁柱节点、梁上和柱端裂纹的扩展轨迹、扩展速度和应力强度因子的变化规律。实验结果表明：受冲击后,试件首先在梁柱节点处开裂,并在裂纹扩展过程中发生明显的曲裂运动,证明梁柱节点处最容易受到破坏。预制裂纹条数越多,梁柱节点处开裂越晚,说明裂纹条数少,能量可以在裂纹尖端积聚得更集中、更快。含柱端预制裂纹的试件,2条裂纹的开裂相隔时间要长于含梁上预制裂纹的试件;同时,试件的第2条裂纹优先在梁上裂纹处开裂,说明固端支座比简支梁断裂需要更多的能量。随着预制裂纹的增多,梁上裂纹在扩展过程中的曲裂现象减弱,由于部分能量在柱端裂纹处积聚,用于推动梁上裂纹扩展的能量相应地减少。并且由于柱端裂纹的存在,梁上裂纹受到的拉应力分量减小,导致裂纹尖端受到弯矩变小,影响了裂纹的曲裂运动。
英文摘要：
An experimental system of dynamic caustics was applied to carry out fracture experiments for pre-cracked beam-column specimens. The following dynamic fracture behaviors of the specimens under impact loads were discussed： the crack extension tracks, velocities and stress intensity factors at the beam-column joints, the beams and the column ends. The experimental results indicate the fol- lowing findings. Under impact loads, first, the specimens were cracked at the beam-column joints, and in the process of crack extension, the specimens underwent apparent bending fracture, both of which can explain that the beam-column joints are most vulnerable to damage. The more the pre- cracks, the later the beam-column joints crack, which displays that the less the pre-cracks, the more concentrated and faster the energy can accumulate at the crack tips. For a specimen with pre-existing cracks at the ends, the time interval between the initiations of two cracks is longer than that for one with pre-existing cracks at the beam. However, the second crack, in most cases, tends to occur in the beam. This phenomenon indicates that the fracture of a fixed bearing requires more energy than a sim- ply-supported beam. The bending fracture phenomenon of a beam weakens as the pre-existing cracks increases. This is because the partial energy accumulates at the crack tips of the column ends, accord- ingly the energy inducing the cracks at the beam to expand, decreases. Due in large part to the cracks on the columns, the tensile stresses and bending moments at the crack tips on the beams decrease, which affect the bending fracture phenomenon of the specimens.
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