Behavior of High Ductility FRP-confined Large-size Concrete Columns Under Axial Compression
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摘要: 现有纤维增强复合材料(FRP)约束混凝土短柱的研究多基于小尺寸试件,对大尺寸试件的研究较少。聚对苯二甲酸乙二醇酯纤维增强复合材料(PET FRP)和聚萘二甲酸乙二醇酯纤维增强复合材料(PEN FRP)是由回收废弃塑料制成的环保型高延性FRP。高延性FRP具有超过5%的断裂应变,超过传统FRP断裂应变(1.5~3%)。本研究对8个PET FRP约束混凝土圆柱(直径300、400 mm试件各4个)与8个PEN FRP约束混凝土方柱(边长300、400 mm试件各4个)进行轴压力学性能试验,研究构件截面形状、FRP层数等参数对试件轴压力学性能的影响。试验结果表明:高延性FRP约束混凝土柱应力-应变曲线由3个不同的部分组成;部分高延性FRP约束混凝土柱应力-应变曲线第2段出现了下降段,与约束刚度较小有关;相同尺寸的试件,随着高延性FRP层数(厚度)的增加,试件承载力提高,延性更好;对于PEN FRP约束混凝土方柱,在同一轴向变形、高度区域处,环向面应变较环向角应变大,且环向面应变的增加值大于角区域;采用现有高延性FRP约束混凝土柱模型,对约束圆形和方形混凝土柱轴压力学性能提供相对合理的预测。Abstract: Most of the existing researches on fiber reinforced polymer (FRP) composite-confined concrete short columns are based on small size specimens, and large-size columns have not been fully studied. PET (Polyethylene Terephthalate) FRP and PEN (Polyethylene Naphthalene) FRP are environmentally friendly large rupture strain FRPs made from recycled waste plastic. Compared with traditional FRP, high ductility FRP materials have a fracture strain larger than 5%, which is far larger than that of traditional FRP materials with the value of 1.5~3%. In recent years, high ductility FRP has become a research hotspot all over the world. In this paper, the axial compressive behavior of 8 PET FRP-confined concrete columns and 8 PEN FRP-confined concrete columns were experimentally studied. The main research parameters included the shape of specimens and the number of FRP layers. Results show that the stress-strain curve of high ductility FRP-confined concrete columns has three different parts; the second part of stress-strain curve of partially high ductility FRP-confined concrete columns appears a descending section, which is related to the small constraint stiffness; the bearing capacity and ductility of same size specimens increase with the increase of FRP thickness; The middle strain is larger than corner strain of PEN FRP-confined concrete square columns at the same axial deformation. Moreover, the existing stress strain models for high ductility FRP-confined concrete were evaluated with the test results.
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表 1 试件编号及参数
Table 1. Details of specimens
试件编号 直径或边长/mm 高度/mm 角半径/mm 材料类型 FRP层数/层 C-PET-300-2-a,b 300 600 — PET FRP 2 C-PET-300-3-a,b 300 600 — PET FRP 3 C-PET-400-2-a,b 400 800 — PET FRP 2 C-PET-400-4-a,b 400 800 — PET FRP 4
S-PEN-300-2-a,b
300
600
60
PEN FRP
2
S-PEN-300-3-a,b
300
600
60
PEN FRP
3
S-PEN-400-2-a,b
400
800
80
PEN FRP
2
S-PEN-400-4-a,b
400
800
80
PEN FRP
4表 2 圆柱主要试验结果
Table 2. Key results of circular column tests
试件编号 fcu ′ /MPa εcu/% εh,rup/% 最大环向应变对应的应变片编号 C-PET-300-2-a 37.2 1.79 3.38 SG1 C-PET-300-2-b 39.2 2.28 3.86 SG5 C-PET-300-3-a
49.6
3.51
4.16
SG1C-PET-300-3-b 50.4 3.41 4.24 SG4 C-PET-400-2-a 35.9 1.67 3.38 SG1 C-PET-400-2-b 36.2 1.75 3.23 SG2 C-PET-400-4-a 45.2 2.19 3.28 SG5 C-PET-400-4-b 45.0 2.24 3.36 SG1 表 3 方柱主要试验结果
Table 3. Key results of square column tests
试件编号 fcu ′ /MPa εcu/% εh,c/% εh,s/% 最大环向应变对应的应变片编号 S-PEN-300-2-a 37.6 2.34 1.46 2.19 SG9 S-PEN-300-2-b 38.4 2.28 1.75 2.34 SG1 S-PEN-300-3-a 54.8 3.14 1.77 2.84 SG1 S-PEN-300-3-b 53.3 3.42 1.37 2.73 SG1 S-PEN-400-2-a 35.5 1.66 1.60 2.01 SG9 S-PEN-400-2-b 35.5 1.79 2.40 2.38 SG5 S-PEN-400-4-a 47.9 2.64 1.50 2.43 SG9 S-PEN-400-4-b 49.0 2.39 0.90 2.18 SG1 -
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