对剪跨比为3.36的1根无腹筋钢筋混凝土梁和2根FRP加固无腹筋钢筋混凝土梁进行了落锤冲击试验，研究无腹筋混凝土梁在冲击荷载作用下的动力响应和FRP加固形式对其抗冲击性能的影响；为了对比动态冲击承载力，还进行了1根FRP加固无腹筋钢筋混凝土梁的静载试验。试验结果表明，粘贴FRP条带尤其是端部锚固FRP条带加固可显著提高无腹筋混凝土梁的抗冲击承载力。通过对实测的冲击力、跨中位移及纵向钢筋应变时程曲线等试验数据进行分析，并结合试件的破坏模式，获得了FRP加固无腹筋混凝土梁的动态抗剪失效机理，即冲击荷载下无腹筋混凝土梁的失效过程分为两个阶段：跨中局部受冲击瞬间的剪切破坏和随后的冲击作用点指向支座处的剪切破坏阶段。分两个阶段讨论了冲击荷载下FRP对抗剪承载力的贡献值，并与各规范理论承载力进行比较，数据比较表明两个阶段FRP动态抗剪承载力均高于静态抗剪承载力和理论值，并与以往CFRP－混凝土界面动态抗剪承载力评估方法比较，为获得合理的FRP抗剪承载力评估方法提供有价值的参考。
Abstract
In order to further understand the impact behavior of reinforced concrete beams strengthend with externally bonded FRP sheet, one RC beam without stirrups and two FRP strengthened RC beams without stirrups were tested against impact loads and one FRP strengthened beam was tested under static load. Test results showed that the impact resistance of FRP strengthened RC beams significantly increased, especially when the beams was strengthened with end anchorage. The failure modes and time-histories of impact force, mid-span displacement, strain of longitudinal reinforcement were analyzed and discussed, the shear mechanism of CFRP strengthened RC beams without stirrups under impact loading was obtained. The failure process can be divided into two stages, the shear failure of local part of the beams adjacent to the mid-span section under impact loading and the subsequent shear failure of near-support section under reaction force. The FRP contribution to shear strength at the two stages was discussed respectively and compared with the predicted shear strength according to different design codes. The comparisons showed that, FRP contribution to shear strength under impact loading at both stages was higher than predicted shear strength. Compared with the previous method to predict the bond strength of CFRP-to-concrete interface under impact loading, it could offer reliable reference to reasonably evaluate the contribution of FRP to shear strength.
关键词
无腹筋梁 /
CFRP加固 /
抗冲击性能 /
抗剪机理
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Key words
RC beams without stirrups /
CFRP strengthened /
impact behavior /
shear mechanism
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