钢筋-GFRP筋增强混凝土梁的疲劳力学性能

许家婧; 朱鹏; 屈文俊

doi:10.13801/j.cnki.fhclxb.20210809.001

钢筋-GFRP筋增强混凝土梁的疲劳力学性能

doi: 10.13801/j.cnki.fhclxb.20210809.001

1.
南通大学交通与土木工程学院，南通 226019
2.
同济大学土木工程学院，上海 200092

基金项目: 国家重点研发计划专项项目 (2017YFC0703000)；国家自然科学基金 (51678430)；上海市浦江人才计划 (12PJ1409000)

详细信息

通讯作者:
朱鹏，博士，副教授，研究方向为绿色超高性能混凝土材料、耐久性混合配筋混凝土结构等　E-mail: pzhu@tongji.edu.cn

中图分类号: TU375.1
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出版历程
- 收稿日期: 2021-05-11
- 修回日期: 2021-07-10
- 录用日期: 2021-07-15
- 网络出版日期: 2021-08-09
- 刊出日期: 2022-03-23

Fatigue behaviors of steel bars-GFRP bars reinforced concrete beams

XU Jiajing¹,
ZHU Peng^{2
, ,},
QU Wenjun²

1.
School of Transportation and Civil Engineering, Nantong University, Nantong 226019, China
2.
College of Civil Engineering, Tongji University, Shanghai 200092, China

摘要

摘要: 钢筋-玻璃纤维增强树脂复合材料 (GFRP)筋增强混凝土 (RC) 梁设计结合了钢筋和GFRP筋的优点，可以提高构件承载力，同时改善纯纤维增强复合材料 (FRP) 筋构件使用性能存在的问题，但是关于其疲劳性能的研究十分有限。因此，本论文进行了7根钢筋-GFRP筋增强RC梁的疲劳试验，研究参数包括疲劳荷载幅、有效配筋率、配筋面积比。结果表明，钢筋-GFRP筋增强RC梁疲劳破坏始于钢筋的疲劳断裂，钢筋疲劳断口光滑平整，显著区别于静力拉伸破坏断口。疲劳加载过程中，截面平截面假定仍然满足。疲劳荷载幅对疲劳寿命有显著影响，随着疲劳荷载幅的增大，梁中钢筋、GFRP筋和混凝土应力和应力幅均随之增大，疲劳寿命减小。增大有效配筋率，跨中挠度和最大裂缝宽度均减小，正常使用性能改善。配筋面积比(A_f/A_s)的增加不利于构件抵抗疲劳荷载，A_f/A_s由0.25增大到2.0，疲劳寿命从36.6万次降低到8.3万次。对比了各种疲劳挠度计算公式，CEB-FIP 2010规范的预测结果较好，误差范围在7%以内，推荐作为钢筋-GFRP筋增强RC梁疲劳挠度的计算公式。
- FRP筋 /
- 混合配筋 /
- 混凝土梁 /
- 疲劳性能 /
- 疲劳挠度
Abstract: Steel bars-glass fiber-reinforced polymer (GFRP) bars reinforced concrete (RC) beams combined the advantages of steel bars and GFRP bars. Flexural capacity was increased compared with RC beams and serviceability performance was improved compared with the pure fiber-reinforced polymer (FRP) reinforced concrete beams, however, the investigation of fatigue behaviors was limited. In this study, seven beams were fabricated for fatigue tests, and the test parameters were load amplitude, effective reinforcement ratio and area ratio of FRP to steel bars (A_f/A_s). The test results show that fatigue failure of the steel bars-GFRP bars RC beams start with fatigue fracture of steel bars and the fracture surface is significantly different from that of static tensile failure modes. Plane section assumption is verified under fatigue. The fatigue load amplitude has significant effects on the fatigue life. With the increase of fatigue load amplitude, strains in steel bars, GFRP bars and concrete increases, and the fatigue life decrease. The increase of effective reinforcement ratio contribute to decreasing mid-span deflection and crack width, and improve the serviceability. The increase of area ratio of FRP to steel bars (A_f/A_s) has negative effects on the fatigue behaviors of steel bars-GFRP bars RC beams. The fatigue life decrease from 366 thousand cycles to 83 thousand cycles with A_f/A_s increasing from 0.25 to 2.0. Different theoretical models for the mid-span deflection of beams under fatigue load are compared and the CEB-FIP 2010 presented satisfactory prediction, and thus is recommended.
- FRP bars /
- hybrid reinforcement /
- concrete beam /
- fatigue performance /
- fatigue deflection

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图 1 钢筋-玻璃纤维增强树脂复合材料 (GFRP) 筋增强混凝土梁试件尺寸及配筋 (单位：mm)

Figure 1. Specimen dimensions and reinforcement details for steel bars-glass fiber-reinforced polymer (GFRP) bars reinforced concrete beams (Unit: mm)

A, w, B—Parameters of sine wave; SG—Beam ID; —Steel bars of grade HRB400; Φ—Diameter of GFRP bars

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图 2 疲劳加载情况

Figure 2. Fatigue loading conditions

P_max, P_min—Upper and lower limit of fatigue load

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图 3 钢筋-GFRP筋增强混凝土梁构件疲劳破坏模式

Figure 3. Failure modes for steel bars-GFRP bars reinforced concrete beams

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图 4 钢筋-GFRP筋增强混凝土梁筋材疲劳破坏模式

Figure 4. Failure modes for steel bars-GFRP bars reinforced concrete beams

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图 5 疲劳上限荷载作用下钢筋-GFRP筋增强混凝土梁跨中截面应变分布曲线

Figure 5. Strain distribution of mid-span section for steel bars-GFRP bars reinforced concrete beams under the upper limit of fatigue load

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图 6 荷载幅对钢筋 (a)、GFRP (b)、混凝土应变 (c) 及跨中挠度 (d) 的影响

Figure 6. Effects of load amplitude on steel strain (a), GFRP strain (b), concrete strain (c) and mid-span deflection (d)

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图 7 有效配筋率对钢筋应变 (a)、GFRP应变 (b) 、混凝土应变 (c) 及跨中挠度 (d) 和裂缝宽度 (e) 的影响

Figure 7. Effects of effective reinforcement ratio on steel strain (a), GFRP strain (b), concrete strain (c), mid-span deflection (d) and maximum crack width (e)

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图 8 配筋面积比A_f/A_s 对钢筋应变 (a)、GFRP应变 (b)、混凝土应变(c)、跨中挠度(d)及最大裂缝宽度(e)的影响

Figure 8. Effects of A_f/A_s on steel strain (a), GFRP strain (b), concrete strain (c), mid-span deflection (d) and maximum crack width (e)

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图 9 钢筋-GFRP筋增强混凝土梁跨中挠度试验值和计算值对比

Figure 9. Comparisons between test results and calculated results for steel bars-GFRP bars reinforced concrete beams

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表 1 钢筋和GFRP筋力学性能

Table 1. Properties of steel bars and GFRP bars

First batch				Second batch
Type	Yield strength/MPa	Tensile strength/MPa	Elastic modulus/GPa	Type	Yield strength/MPa	Tensile strength/MPa	Elastic modulus/GPa
S8	464	580	192	S8	456	592	190
S10	541	643	191	S10	450	588	194
S16	450	611	188	S12	511	675	197
S20	510	627	194	S14	476	634	194
G8	—	1210	46	S16	435	606	200
G10	—	1163	44	S20	473	626	202
				G6	—	1235	48
				G8	—	1205	48
				G10	—	1184	44
				G20	—	695	42
Note: Glass fiber volume fractions are 75% and 78% for the first batch and the second batch, respectively.

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表 2 疲劳加载信息及试验结果

Table 2. Fatigue loading information and fatigue life

Specimen	${\rho _{{\rm{eff}}}}$	A_f/A_s	Minimum load/Maximum load/kN	Frequency/Hz	Fatigue life/10⁶ Cycles
S16 G8-1	1.13%	0.25	13.3/66.3 (0.1P_u/0.5P_u)	4^(a), 6^(b)	135.4
S16 G8-2	1.13%	0.25	13.3/79.6 (0.1P_u/0.6P_u)	6	46.1
S20 G10-1	1.76%	0.25	19.6/108.0 (0.1P_u/0.55P_u)	6	167.8
S20 G10-2	1.76%	0.25	20.2/131.3 (0.1P_u/0.65P_u)	6	31.9
S16 G8-3	1.13%	0.25	13.8/89.7 (0.1P_u/0.65P_u)	6	36.6
S12 G6	0.63%	0.25	10.2/66.3 (0.1P_u/0.65P_u)	6	16.6
S14 G20	1.13%	2.00	19.4/126.1 (0.1P_u/0.65P_u)	6	8.3
Notes: (a)—Before 1 million cycles；(b)—After 1 million cycles；P_u—Ultimate flexural capacity; ρ_eff—Effective reinforcement ratio; A_f/A_s—Area ratio of GFRP bars to steel bars.

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表 3 疲劳上下限荷载作用下钢筋-GFRP筋增强混凝土梁钢筋、GFRP筋应力(第一次疲劳后)

Table 3. Stress in steel bars and GFRP bars for steel bars-GFRP bars reinforced concrete beams under the upper and lower limit of fatigue load after the first cycle

Specimen	${\sigma _{\max ,{\rm{s}}}}$/MPa	${\sigma _{\min ,{\rm{s}}}}$/MPa	$\Delta {\sigma _{\rm{s}}}$/MPa	${\sigma _{\max ,{\rm{f}}}}$/MPa	${\sigma _{\min ,{\rm{f}}}}$/MPa	$\Delta {\sigma _{\rm{f}}}$/MPa
S20G10-2	342	85	257	70	15	55
S16G8-3	354	99	255	81	21	60
S12G6	428	133	295	95	26	69
S14G20	512	154	358	139	39	100
Notes: ${\sigma _{\max ,{\rm{s}}}}$, ${\sigma _{\min ,{\rm{s}}}}$—Steel stress under upper and lower limit of fatigue load, respectively; ${\sigma _{\max ,{\rm{f}}}}$, ${\sigma _{\min ,{\rm{f}}}}$—GFRP stress under upper and lower limit of fatigue load, respectively; $\Delta {\sigma _{\rm{s}}}$, $\Delta {\sigma _{\rm{f}}}$—Steel stress range and GFRP stress range, respectively.

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表 4 钢筋-GFRP筋增强混凝土梁跨中挠度计算值和试验值统计结果

Table 4. Comparisons between predicted mid-span deflection and tested results for steel bars-GFRP bars reinforced concrete beams

Specimen	Balaguru^[21]		Lovegrove and EI Din^[23]		CEB-FIP 2010^[24]
Specimen	Ave.	COV/%	Ave.	COV/%	Ave.	COV/%
S16G8-1	1.04	15.95	0.95	7.30	0.97	5.85
S16G8-2	1.02	23.45	0.92	7.85	0.99	1.45
S20G10-1	1.03	16.05	0.95	6.38	0.96	2.07
S20G10-2	1.17	23.28	0.92	7.90	1.00	1.24
S16G8-3	1.09	22.55	0.91	8.97	0.97	2.35
S12G6	1.13	19.13	0.87	12.89	0.99	2.41
S14G20	1.04	16.88	0.73	9.63	0.90	6.64
Notes: Ave.—Abbreviation of average; COV—Abbreviation of coefficient of variation.

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