Transverse shear behaviour of novel FRP-UHPC hybrid bars
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摘要: 纤维增强树脂复合材料(FRP)-超高性能混凝土(UHPC)组合筋是一种新型无钢组合筋(简称“组合筋”),由外FRP管、中心FRP筋及两者之间填充的UHPC组成。该组合筋解决了 FRP筋受压易屈曲问题,同时因其不含钢材等易腐蚀成分而具有良好的耐久性。因其亦具有较好剪切性能,本文对组合筋的横向剪切性能进行了试验研究,关键变量为外FRP管纤维缠绕角,对照试件为FRP管约束UHPC试件和FRP裸筋。研究结果表明,在横向剪切荷载作用下,组合筋的两个峰值荷载均比对照试件的峰值荷载大58%以上,变形能力比FRP管约束UHPC对照试件的变形能力大220%以上,因此组合筋各组分之间良好的协同工作使其具有良好的抗剪性能。最后,提出了一种组合筋剪切强度的计算方法,并用试验结果验证了该方法的准确性。
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关键词:
- FRP筋 /
- UHPC /
- FRP管约束UHPC试件 /
- 组合筋 /
- 横向剪切性能
Abstract: Fibre-reinforced polymers (FRP)-ultra-high performance concrete (UHPC) hybrid bars are a new type of steel-free hybrid bars, which comprise an outer FRP tube, a central FRP bar and an annular layer of UHPC. Hybrid bars are proposed to fix the issue that the fibers in FRP bar are easily buckled under compression and are expected to have an excellent durability because all the components in hybrid bars are anti-corrosion materials. As it is expected that the hybrid bars have satisfactory shear behavior, this paper presents an experimental study on the transverse shear behaviour of hybrid bars. The key variable was the fibre winding angle of the outer FRP tube and the counterparts included the UHPC-filled FRP tubes and the bare FRP bars. It is demonstrated that the two peak loads of hybrid bars are at least 58% larger than the peak load of their counterparts under the transverse shear loading. The deformation capacities of hybrid bars are also found to be at least 220% larger than that of the UHPC-filled FRP tubes, and the UHPC-filled FRP tube and the central FRP bar in hybrid bars are in an optimal combination, leading to excellent shear behaviour of hybrid bars. An equation for calculating the shear strength of hybrid bars is proposed and verified by the test results.-
Key words:
- FRP bars /
- UHPC /
- UHPC-filled FRP tube /
- hybrid bars /
- transverse shear behaviour
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表 1 试件的详细参数
Table 1. Details of specimens
Type Specimen FRP thickness/mm Fibre winding angle/(°) Diameter of the central FRP bar/mm Hybrid bar HB-45-1/2/3/4 2.90 45 25 HB-60-1/2/3/4 2.25 60 25 HB-80-1/2/3/4 1.81 80 25 UHPC-filled FRP tube FU-45-1/2/3/4 2.90 45 — FU-60-1/2/3/4 2.25 60 — FU-80-1/2/3/4 1.81 80 — FRP bar FB-1/2/3/4/5 — — 25 表 2 UHPC的配合比
Table 2. UHPC mix proportions
wt% Cement Quartz
powderSilica
fumeSand Water Super-
plasticizer1.00 0.37 0.25 1.10 0.19 0.04 表 3 FRP小管轴压试验结果
Table 3. Compressive properties of small FRP tubes
Fiber winding
angle/(°)Compressive
strength/MPaPeak
strainSecant elastic
modulus/GPaPoison’s
ratio±45 93.69 0.0189 4.98 0.85 ±60 98.86 0.0199 4.98 0.34 ±80 86.35 0.0130 6.74 0.14 表 4 FRP筋的拉伸和受压性能
Table 4. Tensile and compressive properties of FRP bars
Nominal diameter/mm Tensile elastic modulus/GPa Tensile strength/MPa Ultimate tensile
strainCompressive elastic modulus/GPa Compressive strength/MPa Ultimate compressive
strain25 41.0 711.6 0.0172 40.6 274.5 0.0077 表 5 各试件横向剪切试验的主要结果
Table 5. Key results of specimens under transverse shear tests
Type Specimen First transverse shear strength $ {\tau }_{\mathrm{u}1} $/MPa Mean/MPa Standard deviation/MPa Second transverse
shear strength
$ {\tau }_{\mathrm{u}2} $/MPaMean/MPa Standard deviation/MPa Hybrid bar HB-45-1 70.1 66.7 HB-45-2 69.0 68.3 2.32 60.1 64.5 3.09 HB-45-3 64.9 66.6 HB-45-4 69.2 HB-60-1 58.3 60.1 3.91 67.5 65.6 1.29 HB-60-2 56.1 65.0 HB-60-3 60.9 64.6 HB-60-4 65.2 HB-80-1 51.2 50.1 1.58 67.6 66.3 1.38 HB-80-2 51.3 66.1 HB-80-3 47.9 64.4 HB-80-4 50.0 UHPC-filled
FRP tubeFU-45-1 42.6 44.1 2.60 — — — FU-45-2 41.6 FU-45-3 47.5 FU-45-4 44.6 FU-60-1 27.9 30.1 1.52 — — — FU-60-2 30.9 FU-60-3 30.8 FU-60-4 31.0 FU-80-1 17.3 19.1 2.69 — — — FU-80-2 22.7 FU-80-3 19.7 FU-80-4 16.8 FRP bar FB-1 165.7 160.7 6.97 — — — FB-2 155.8 FB-3 161.9 FB-4 168.5 FB-5 151.6 表 6 FRP管的剪切模量和抗剪强度
Table 6. Shear modulus and shear strength of FRP tubes
Fiber winding angle/(°) Transverse shear strength $ {\tau }_{\mathrm{u}} $/MPa Shear modulus $ {G}_{xy} $/GPa ±45 148.40 11.26 ±60 55.74 4.23 ±80 18.55 1.41 -
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