纤维织物增强高延性混凝土加固受损RC梁受剪性能试验

张敏; 邓明科; 智奥龙; 马向琨

纤维织物增强高延性混凝土加固受损RC梁受剪性能试验

张敏¹,
邓明科^1, ,,
智奥龙¹,
马向琨^{1, 2}

1.
西安建筑科技大学土木工程学院, 西安 710055
2.
华夏幸福基金股份有限公司, 西安 710055

基金项目: 国家自然科学基金 (51878545)；西安市科技创新计划项目(20191522415 KYPT015 JC017)

详细信息

通讯作者:
邓明科，博士，教授，博士生导师，研究方向为高性能土木工程材料与新型结构　E-mail:dengmingke@126.com

中图分类号: TU375
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- HTML全文浏览量: 47
- 被引次数: 0
出版历程
- 收稿日期: 2022-03-08
- 录用日期: 2022-04-19
- 修回日期: 2022-04-04
- 网络出版日期: 2022-05-11

Experimental on the shear behavior of pre-damaged RC beams strengthened by textile reinforced highly ductile concrete

Min ZHANG¹,
Mingke DENG^{1
, ,},
Aolong ZHI¹,
Xiangkun MA^{1, 2}

1.
School of Civil Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China
2.
China Fortune Land Development Co. Ltd., Xi’an 710055, China

摘要

摘要: 为研究二次受力对纤维织物增强高延性混凝土(TRHDC)加固钢筋混凝土(RC)梁受剪性能的影响，对8根TRHDC加固梁和1根对比梁进行了静载试验，分析了纤维织物层数、损伤程度及持载水平对梁破坏形态、荷载-挠度曲线、荷载-箍筋应变曲线及荷载-织物应变曲线的影响。试验结果表明：所有梁均发生了剪压破坏，仅一根梁出现剥离现象；TRHDC可有效限制斜裂缝的发展，延缓箍筋屈服和刚度退化；TRHDC加固显著地提高了梁的受剪承载力和变形能力，最高分别达67%和54%；加固效果未完全随纤维织物层数的增大而提高，与TRHDC面层利用率有关；原梁箍筋屈服之前，损伤程度对加固梁受剪性能的影响不明显，原梁箍筋屈服之后，加固梁受剪承载力随损伤程度的增大而降低；加固效果随持载水平的提高而降低；两层纤维织物的TRHDC可有效修复完全受损RC梁的受剪性能；建立了考虑二次受力的TRHDC加固RC梁受剪承载力的计算公式，且计算值与试验结果吻合较好。
- 纤维织物增强高延性混凝土 /
- 受损RC梁 /
- 受剪加固 /
- 二次受力 /
- 受剪承载力
Abstract: Static load tests were conducted on eight reinforced concrete (RC) beams strengthened by textile reinforced high ductile concrete (TRHDC) and one control beam to study the effect of secondary loading on the shear behavior of TRHDC-strengthened beams. The influence of the number of the textile layer, damage degree of beams, and different sustained loads on the failure mode, load-deflection curves, load-strain curves of stirrups, and load-strain curves of textile were analyzed. The results indicate that all beams fail in shear compression mode, and the debonding phenomenon is only observed in one beam. TRHDC can effectively restrain the development of shear cracks, delay the yielding of stirrups and the stiffness degradation. This strengthening method can significantly improve the shear strength and deformation capacity of RC beams by up to 67% and 54%, respectively. The strengthening effectiveness does not completely increase with the number of the textile layer increase, which is related to the utilization rate of the TRHDC layer. When the stirrup of the original beam does not reach its yielding strength, the damage degree has no obvious influence on the shear behavior of strengthened beams. On the contrary, the shear strength of strengthened beams decreases with the increase of the damage degree. The strengthening effectiveness decreases with the sustained load increasing. The completely damaged RC beams can be restored by the TRHDC with two numbers of the textile layer. A calculation formula for the shear strength of TRHDC-strengthened beams considering the secondary loading was proposed. The calculation values are in good agreement with the test results.
- textile reinforced high ductile concrete /
- pre-damaged RC beam /
- shear strengthening /
- secondary loading /
- shear strength

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图 1 RC梁试件截面尺寸及配筋(单位：mm)

Figure 1. Dimensions and rebar of RC beam specimens (Unit: mm)

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图 2 织物形式

Figure 2. Form of textile

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图 3 狗骨形试件尺寸(单位：mm)

Figure 3. Dimensions of dog bone specimens (Unit: mm)

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图 4 纤维织物增强高延性混凝土(TRHDC)的应力-应变曲线和开裂模式

Figure 4. Stress-strain curves and crack pattern of (textile reinforced high ductile concrete (TRHDC)

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图 5 试验装置

Figure 5. Test setup

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图 6 测点布置

Figure 6. Measuring points

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图 7 各RC梁试件的破坏形态

Figure 7. Failure modes of RC beam specimens

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图 8 各RC梁荷载-跨中挠度曲线

Figure 8. Load-midspan deflection curves of RC beams

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图 9 各RC梁荷载-箍筋应变曲线

Figure 9. Load-strain curves of stirrups of RC beams

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图 10 试件CL-3的荷载-织物应变曲线

Figure 10. Load- textile strain curves of specimen CL-3

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图 11 RC梁拉-压杆模型

Figure 11. Strut-and-tie model of RC beams

$ {f_1} $ and $ {f_2} $—Principal tensile and compressive stresses at the node B zone, respectively; $ {\theta _{\text{s}}} $—Angle between the longitudinal tension reinforcement and the diagonal strut; h—Depth of RC beams; $ {d_{\text{c}}} $—Distance from the centroid of the nodal A zone to the centroid of the nodal B zone; $ {l_{\text{d}}} $ and $ {l_{\text{c}}} $—Depths of the nodal A and B zones, respectively; a—Distance from loading point to support; $ {l_{\text{b}}} $—Width of the nodal B zone; $ {V_{{\text{RC}}}} $—Shear strength of RC beams; $ {C_{\text{C}}} $ —Compressive force of the concrete in the shear compression zone; $ {T_{\text{s}}} $—Tensile force of longitudinal reinforcements; $ {F_{\text{c}}} $ —Compressive force of the concrete diagonal struts.

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表 1 钢筋混凝土(RC)梁试件加固参数

Table 1. Strengthening parameters of reinforced concrete (RC) beam specimens

Specimen	Damage degree	Unloading level	Number of the textile layer in TRHDC
L-0	–	–	–
CL-1	–	–	1
CL-2	–	–	2
CL-3	–	–	3
SCL-1	Shear cracks occurred (47%P_u,0)	Unloading completely	2
SCL-2	Stirrups yielded (56%P_u,0)	Unloading completely	2
SCL-3	Failure (the load drops to 85%P_u,0)	Unloading completely	2
XCL-1	Shear cracks occurred (47%P_u,0)	Unloading 23.5%P_u,0	2
XCL-2	Shear cracks occurred (47%P_u,0)	Not unloading	2
Notes: P_u,0—Peak load of the control beam； L—Control beam; CL—Strengthened beams without initial stress; SCL—Strengthened beams with different damage degrees; XCL—Strengthened beams under sustained loads.

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表 2 钢筋力学性能

Table 2. Mechanical properties of reinforcement

Type	Diameter/mm	Yielding strength/MPa	Ultimate strength/MPa
HPB300	6	343	508
HRB400	18	438	610
HRB400	25	450	620

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表 3 织物力学性能

Table 3. Mechanical properties of textile

Type of textile	f_t/MPa	E_f/GPa	$ {\varepsilon _{\text{t}}} $/%	$ {\rho _{\text{f}}} $/(g·cm⁻³)	A/(mm²·bundle⁻¹)
Carbon	3600	230	1.5	1.74	0.88
Notes: f_t is the tensile strength; E_f is the elastic modulus; $ {\varepsilon _{\text{t}}} $ is the tensile elongation; $ {\rho _{\text{f}}} $ is the density; A is the cross-sectional area of each bundle of yarns.

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表 4 高延性混凝土(HDC)的基体配合比(kg/m³)

Table 4. Mixed proportions of matrices in high ductile concrete (HDC) (kg/m³)

Cement	Flyash	Mineral powder	River sand	Water	Water reducer
235	764	177	424	376	8

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表 5 聚乙烯醇(PVA)纤维的力学性能指标

Table 5. Mechanical properties of polyvinyl alcohol (PVA) fibers

Fiber type	L/mm	D/μm	E/GPa	f/MPa	$ \varepsilon $/%	$ \rho $/(g·cm⁻³)
PVA	12	39	40	1600	7	1.3
Notes: L is the length; D is the diameter; E is the elastic modulus; f is the tensile strength; $ \varepsilon $ is the tensile elongation; $ \rho $ is the density.

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表 6 各RC梁试验结果

Table 6. Test results of RC beams

Specimen number	$ {P_{{\text{cr}}}} $/kN	$\dfrac{ { {P_{ {\text{cr} } } } } }{ { {P_{ {\text{cr,0} } } } } }$	$ {P_{\text{r}}} $/kN	$\dfrac{ { {P_{\text{r} } } }}{ { {P_{ {\text{r,0} } } } } }$	$ {P_{\text{u}}} $/kN	$\dfrac{ { {P_{\text{u} } } }}{ { {P_{ {\text{u,0} } } } } }$	$ {\Delta _{\text{u}}} $/mm	$\dfrac{ { {\Delta _{\text{u} } } }}{ { {\Delta _{ {\text{u,0} } } } } }$	Failure mode
L-0	42	—	172	—	367.56	—	5.88	—	S
CL-1	250	5.95	335	1.95	585.54	1.59	9.05	1.54	S
CL-2	190	4.52	330	1.92	563.90	1.53	6.96	1.18	S
CL-3	300	7.14	410	2.38	615.49	1.67	7.97	1.36	S+PD
SCL-1	180	4.29	300	1.74	528.38	1.44	6.71(0.63)	1.14	S
SCL-2	165	3.93	280	1.63	565.22	1.54	6.60(0.61)	1.12	S
SCL-3	160	3.81	223	1.30	434.91	1.18	6.71(2.59)	1.14	S
XCL-1	210	5.00	320	1.86	498.76	1.36	5.62(1.29)	0.96	S
XCL-2	200	4.76	280	1.63	485.03	1.32	5.24(1.86)	0.89	S
Notes: $ {P_{{\text{cr}}}} $ and $ {P_{{\text{cr,0}}}} $ are the cracking load of the strengthened beam and control beam, respectively. $ {P_{\text{r}}} $ and $ {P_{{\text{r,0}}}} $ are the loads corresponding to the yielding of stirrups of the strengthened beam and control beam, respectively. $ {P_{\text{u}}} $ and $ {P_{{\text{u,0}}}} $ are the peak load of the strengthened beam and control beam, respectively. $ {\Delta _{\text{u}}} $ and $ {\Delta _{{\text{u,0}}}} $ are the ultimate deflection corresponding to the load dropping to 85% of the peak load of the strengthened beam and control beam, respectively. The $ {\Delta _{\text{u}}} $ of specimens SCL-1, SCL-2, SCL-3, XCL-1, and XCL-2 is the midspan deflection under secondary loading, while the values in parentheses are the residual midspan deflection before secondary loading. S denotes the shear-compression failure, and PD denotes the debonding failure between the concrete and the TRHDC layer.

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表 7 各RC梁受剪承载力计算值与试验值比较

Table 7. Comparison for the calculation values and test results of shear strength of RC beams

Resource	Strengthening method	Specimen number	$ {P_{{\text{u,t}}}} $/kN	$ {P_{{\text{u,cal}}}} $/kN	$\dfrac{ { {P_{ {\text{u,cal} } } } } }{ { {P_{ {\text{u,t} } } } } }$
This study	—	L-0	183.78	218.02	1.19
	Non-damaged strengthened beams	CL-1	292.77	259.43	0.89
		CL-2	281.95	281.50	1.00
		CL-3	307.74	301.64	0.98
	Pre-damaged strengthened beams	SCL-1	264.19	281.50	1.06
		SCL-2	282.61	281.50	1.00
		SCL-3	217.45	217.40	1.00
	Pre-damaged strengthened beams under sustained load	XCL-1	249.38	242.53	0.97
	Pre-damaged strengthened beams under sustained load	XCL-2	242.52	242.53	1.00
Literature [32]	Pre-damaged strengthened beams	J3 B	212	200.89	0.95
		J3 C	200	189.78	0.95
		J3 D	178	178.86	1.00
	Pre-damaged strengthened beams under sustained load	J6 C	166	175.64	1.06
	Pre-damaged strengthened beams under sustained load	J6 D	160	171.20	1.07
Literature [33]	Pre-damaged strengthened beams under sustained load	L₁Rd₂P₂A₂₁₂-70	342.00	288.20	0.84
		L₁Rd₂P₂A₂₁₁-70	410.50	332.95	0.81
		L₂Rd₂P₂A₂₁₂-70	344.50	275.033	0.80
		L₂Rd₂P₂A₂₁₁-70	440.50	323.608	0.74
Notes: $ {P_{{\text{u,t}}}} $ is the experimental value of the specimen; $ {P_{{\text{u,cal}}}} $ is the calculated value of the specimen.

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