冲击荷载下节段拼装梁的响应与破坏特征研究

Response and Failure Characteristics of Segmental Assembled Beams Under Impact Loading

由于节段拼装梁在接缝处混凝土和钢筋均不连续,导致其剪切破坏机制更加突出,冲击荷载作用会进一步加剧其破坏向更具局部特征的剪切破坏演变。为了解冲击荷载下节段拼装梁的响应与破坏特征,开展了试验梁落锤冲击试验,并结合LS-DYNA数值模拟分析,得到冲击荷载作用下梁的裂缝发展、破坏过程、形态等破坏特征,获得梁体变形、支座反力、内力分布等动力响应,揭示了节段长度、冲击能量、冲击作用位置等因素对节段拼装梁的动力响应与破坏特征的影响规律。结果表明:冲击荷载作用下节段拼装梁的局部剪切破坏特征突出,损伤和破坏位置集中于冲击作用点所在节段及接缝,典型破坏形式有斜截面破坏和接缝截面直剪破坏2种,冲击作用点与接缝的相对位置对破坏形式影响显著;混凝土和预应力筋的变形是冲击能量耗散的主要原因,普通钢筋耗能贡献可以忽略;梁体变形在接缝位置呈折线状,位移响应时间比整体梁更长,残余变形小;冲击作用点附近截面剪力峰值达到冲击力峰值的40%左右,较大剪力是导致节段拼装梁在局部形成斜截面破坏和直剪破坏的主要原因。

Because of the discontinuity of concrete and ordinary reinforcements at the joints,the shear failure mechanism of segmental assembled beams becomes more prominent,and the impact load further exacerbates their failure and evolves toward more localized shear failure.To understand the responses and failure characteristics of segmental assembled beams under impact load,drop hammer impact tests were conducted on the experimental beams and combined with LS-DYNA numerical simulation analysis to obtain the crack development,failure process,failure modes,etc.The dynamic responses of the deformation,support force,internal force distribution,and other factors were also obtained.The influences of such factors as segment length,impact energy,and impact position on the dynamic responses and failure characteristics were revealed.The results show that the local shear failure characteristics of segmental assembled beams under an impact load are prominent,and the damage and failure positions are concentrated in the segment and joint where the impact point is located.Typical failure modes include oblique section failure and joint section direct shear failure.The relative position between the impact point and joint significantly affects the failure mode of the segmental beam.Segmental beams mainly rely on concrete and prestressed tendons to absorb impact energy,whereas the contribution of ordinary reinforcements can be ignored.Compared with monolithic beams,the displacement response time is longer,the residual displacement is smaller,and the displaced profile shows a broken line at the joint.The peak shear force of the section near the impact point reaches approximately 40%of the peak impact force,and the large shear force is the main reason for the oblique section failure and joint section direct shear failure of segmental assembled beams in localized areas.