Measures for improving the resistance of a flatbed protective doorframe wallunder intensive shock loading
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摘要: 在强冲击波荷载作用下门框墙转角处会产生明显的应力集中，影响门框墙体系甚至整个防护结构的安全。为解决该问题，提出在迎爆面门框墙和衬砌结合部位设置薄弱层的构造方法，从而减小冲击荷载引起的过大的拉应力。运用考虑了剪切变形的悬臂梁理论分析表明，梁端部约束刚度的变化可以影响结构的破坏形态以及结构的内力分布，降低端部的约束刚度可以有效降低端部区域的内力峰值，延缓结构发生破坏的时间。利用有限元模拟的方法，分析了在出入口门框墙位置设置薄弱层对门框墙动力响应和破坏规律的影响。分析结果表明，设置薄弱层可以有效降低门框墙转角处的应力，降低门框墙结构破坏的风险，进而提高门框墙的抗力水平。Abstract: Intensive shock loading can lead to obvious stress concentration at the corner of a doorframe and jeopardize the safety of a doorframe wall and even the whole protective structure where it is installed. To solve this problem, we proposed to install a weak layer between the doorframe and the lining to reduce the excessive tensile stress, based on the cantilever beam theory that takes into account the shear deformation. The results show that, as the constraint stiffness of the beam end can influence the structure's failure mode and distribution of the internal force, lowering the constraint stiffness of the beam end can reduce the peak value of the internal force and delay the failure time of the structure. Using the finite element method, we analyzed the influence of the weak layer on the dynamic response and the failure mode of the doorframe. The results show that the weak layer can effectively reduce the stress of the doorframe's corner and the damaging effect of the doorframe wall structure so that the resistance of the doorframe can be improved.
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Key words:
- doorframe wall /
- high impact load /
- weak layer /
- dynamic response
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图 3 强冲击荷载下不同约束刚度对梁端剪力和弯矩的影响
Figure 3. Influence of different restraint stiffness on the shear force and bending moment of the beam end
图 4 结构和钢筋的有限元模型
Figure 4. Finite element models for doorframe wall and reinforcing bar
图 10 门框墙单元Y方向位移
Figure 10. Y-directional displacement-time curves of doorframe wall elements
图 11 距离门框墙不同距离处衬砌单元的径向位移
Figure 11. Radial displacements of lining elements with different distances away from the doorframe wall
表 1 剪切破坏时的弯矩情况
Table 1. Bending moments at shear failure times
R ts/ms Ms/M ∞ 0.060 5 0.603 2EI 0.067 9 0.632 EI 0.078 1 0.651 0.5EI 0.111 4 0.700 
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表 2 门框墙上单元的最大有效塑性应变
Table 2. Maximum plastic strains of doorframe wall elements
单元编号 εd, before εd, after εd, before/εd, after 1 9.42×10-4 9.27×10-5 0.098 2 9.48×10-4 8.69×10-5 0.092 3 6.32×10-3 6.17×10-3 0.977 4 5.30×10-4 1.63×10-5 0.031 5 1.72×10-3 5.06×10-5 0.029 6 3.16×10-3 1.35×10-3 0.429 7 6.54×10-3 1.24×10-3 0.189 9 4.02×10-3 3.89×10-3 0.967
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表 3 衬砌上单元的最大有效塑性应变
Table 3. Maximum plastic strains of lining elements
单元编号 εl, before εl, after εl, before/εl, after 10 3.20×10-2 7.08×10-2 2.210 11 3.32×10-2 7.43×10-2 2.239 12 2.95×10-2 6.88×10-2 2.333 13 2.58×10-2 5.65×10-2 2.189 14 3.07×10-2 8.93×10-2 2.914 15 5.01×10-3 4.55×10-3 0.907
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表 4 薄弱层深度对门框墙上单元塑性的影响
Table 4. Influence of weak layer depth on plastic strain of doorframe elements
深度/mm εd(单元2) εd(单元6) εd(单元7) εd(单元9) 0 9.58×10-4 3.21×10-3 6.57×10-3 3.98×10-3 300 2.58×10-4 2.04×10-3 2.88×10-3 3.79×10-3 600 1.51×10-4 1.66×10-3 1.88×10-3 3.88×10-3 900 8.69×10-5 1.35×10-3 1.24×10-3 3.89×10-3
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