Mechanism of fiber grid reinforced with end self-locking anchorage
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摘要: 为解决织物增强混凝土(Textile Reinforced Concrete，TRC)加固混凝土梁结构界面端部剥离问题，拟采用端部自锁技术将TRC板锚固在梁底。得益于该技术提供的端部锚固作用，即使发生界面剥离，TRC板仍能继续承载。但与纤维布相比，纤维网格由于各纤维束之间间隙大得多，协同受力性能较差，在不做处理的情况下能否实现自锁尚存疑问。为了提高纤维网格强度利用率，本文通过端部自锁锚固的纤维网格拉伸试验对其端锚自锁增强效应进行了研究。对纤维网格采取增大物理摩擦或增加化学粘结等措施，进而拉伸至破坏，分析比较了各试件的破坏模式、荷载-应变曲线，提出了纤维网格增强后承载力计算公式。试验结果表明：纤维网格端部自锁锚固时的强度利用率最大提升了60.66%，通过与端部锚板的有效结合，三层网格的抗拉承载力能够达到与单层纤维布相近的水平，应用自锁锚固技术有望在TRC加固混凝土梁中解决端部界面剥离问题，提升材料利用率，改善加固效果。所提出的纤维网格增强后承载力计算公式可为相关工程实践提供有益参考。Abstract: In order to solve the problem of interface end peeling of textile reinforced concrete (TRC) reinforced concrete beam structures, an end self-locking technique was proposed to anchor the TRC slabs at the bottom of the beams. Thanks to the end anchorage provided by this technique, the TRC slab can continue to carry the load even if interfacial spalling occurs. However, compared with the fiber cloth, the fiber mesh has poor synergistic stress performance due to much larger gaps between the fiber bundles, and it is doubtful whether self-locking can be achieved without treatment. In order to improve the utilization of fiber mesh strength, this paper investigates the end-anchor self-locking enhancement effect through the end self-locking anchored fiber mesh tensile test. Measures such as increasing physical friction or adding chemical bonding to the fiber grid are taken to stretch it to failure. The failure modes and load-strain curves of each specimen are analyzed and compared, and a formula for calculating the bearing capacity of the fiber grid after enhancement is proposed. The results show that even if the size of the fiber grid is limited, the strength utilization rate of the fiber grid under end anchoring is increased by 60.66% by reinforcement measures, and the tensile bearing capacity of the three-layer grid can be similar to that of the fiber sheet. The application of the self-locking anchorage technology is expected to solve the problem of end-interface spalling in TRC-reinforced concrete beams, enhance the material utilization, and improve the reinforcement effect. The proposed formula for calculating the bearing capacity after fiber mesh reinforcement can provide a useful reference for related engineering practice.
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Key words:
- fiber grid /
- end anchored /
- self locking /
- tensile test
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图 1 锚固装置和网格自锁缠绕方式(单位：mm)
Figure 1. Anchorage device and self−locking of strips (Unit: mm)
图 3 试件加载装置及增大网格接触、夹具夹紧示意图(单位：mm)
Figure 3. Tensile test setup and indication of increasing contact area, external force clamping (Unit: mm)
图 4 试件准备过程(以G3 FE为例)
Figure 4. Specimen preparation procedures (Take G3 FE for example)
图 6 自锁情况网格缠绕部分力学模型[24]
Figure 6. Mechanical model of mesh winding in self-locking condition[24]
NIJ represents the equivalent normal force of each section of the strip; fIJ represents the tangential friction force of each section of the strip; FI represents the axial force at positions I of the strip. For example, FA and FH respectively represent the axial forces at the ends A and H of the strip
图 7 不同工况试件荷载−网格平均应变沿横向方向变化曲线
Figure 7. Load−strain curves along the horizontal direction of different specimens
表 1 试件概况汇总、试验结果对比
Table 1. Summary of specimens and comparison of test results
Specimen
numberExperimental parameters Performance parameters Layers Whether increased
contact treatmentClamp loosened/
fastenedWhether epoxy
impregnationUltimate loads /kN Ultimate
strength/
MPaMaterial
strength/
MPaIntensity utilization/
%Theoretical/experimental
values of ultimate
loads/(kN·kN-1)G1OL 1 No loosened No 1.9 719 2169 33.18 - G1CL Yes 2 757 2169 34.93 - G1OF No fastened 4.5 1704 2169 78.59 4.4/4.5=0.98 G1FE Yes 5.4 2035 2169 94.3 5.3/5.4=0.98 G3 FE 3 16.2 2043 2169 94.3 15.9/16.2=0.98 SE 1 21.2 3173 3319 95.62 21.6/21.2=1.02 SN 15.2 2275 3319 68.56 —— Notes: G (Grid) represents fiber grid, S (CFRP sheet) represents CFRP sheet; O (Overlapped) represents no treatment, i.e., the grid is overlapped vertically; C (Crossed) represents increased contact of the grid, i.e., the grid is staggered vertically; L (Loosened) represents no external force fastening, i.e., loose; F (Fastened) represents fastening with external force, i.e., tight; E (Epoxy) represents epoxy resin impregnated adhesive, N (Not) represents not impregnated. The number represents the number of layers of fiber grid. Example: G3 FE represents 3 layers of fiber grid impregnated with epoxy resin and fastened with external force. Ultimate strength = ultimate load/cross-sectional area, intensity utilization = ultimate strength/material strength × 100%. 
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表 2 材料性能参数
Table 2. Properties of selected materials
Material Kind Density /(kg·m−2) Theoretical
thickness/mmElastic
modulus/GPaTensile
strength/MPaUltimate
strain/µεFiber sheet T700SC12K/0500 300 0.167 230 3319 14430 Fiber grid CFN200/200 - 0.047 124 2169 17520 Epoxy resin CFSR−A/B - - 4.0 55 -
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表 3 不同工况试件拉伸破坏失效模式
Table 3. Failure modes of different specimens
Material No processing increasing
contact areaClamp
clamping1 layer&
epoxy impregnation3 layers&
epoxy impregnationFiber grid 
Fiber sheet 
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