硫酸盐侵蚀环境对CFRP-粘土砖界面粘结性能的影响

聂丹; 靳文强; 董磊; 赵坤; 张家玮

doi:10.13801/j.cnki.fhclxb.20230105.001

硫酸盐侵蚀环境对CFRP-粘土砖界面粘结性能的影响

doi: 10.13801/j.cnki.fhclxb.20230105.001

聂丹^1,,
靳文强^{2, 3, ,},
董磊²,
赵坤²,
张家玮^{2, 3}

1.
绵阳城市学院　建筑工程学院，绵阳 621000
2.
兰州交通大学　土木工程学院，兰州 730070
3.
兰州交通大学　道桥工程灾害防治技术国家地方联合工程实验室，兰州 730070

基金项目: 甘肃省建设科技攻关项目(JKR2021-07)

详细信息

通讯作者:
靳文强，博士，副教授，硕士生导师，研究方向为工程结构加固与性能提升　E-mail: 724813656@qq.com

中图分类号: TU362；TB333
计量
- 文章访问数: 423
- HTML全文浏览量: 264
- PDF下载量: 11
- 被引次数: 0
出版历程
- 收稿日期: 2022-10-13
- 修回日期: 2022-12-02
- 录用日期: 2022-12-21
- 网络出版日期: 2023-01-06
- 刊出日期: 2023-09-15

Effect of sulfate erosion on the bonding performance of CFRP-clay brick interface

NIE Dan^1
,,
JIN Wenqiang^{2, 3
, ,},
DONG Lei²,
ZHAO Kun²,
ZHANG Jiawei^{2, 3}

1.
College of Civil Engineering and Architecture, Mianyang City College, Mianyang 621000, China
2.
School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
3.
National and Provincial Joint Engineering Laboratory of Road & Bridge Disaster Prevention and Control, Lanzhou Jiaotong University, Lanzhou 730070, China

Funds: Gansu Province Construction Science and Technology Tackling Project (JKR2021-07)

摘要

摘要: 为探究硫酸盐浸泡环境下碳纤维增强复合材料(CFRP)-粘土砖界面粘结性能退化规律，试验采用质量分数为10wt%的硫酸盐溶液对CFRP-粘土砖试件进行加速腐蚀，并对材料性能进行测定，通过采集应变、承载力等参数，分析CFRP与粘土砖界面承载力能力与粘结强度变化规律。研究表明：硫酸浸泡对CFRP片材和树脂胶的力学性能无显著影响，但对粘土砖的抗压强度有明显影响，经过180天硫酸盐浸泡后，粘土砖抗压强度下降了34.50%。对于CFRP-粘土砖界面的极限承载力与粘结强度，研究发现CFRP的宽度对界面承载力和粘结强度均有影响，增加界面的宽度，可以增加界面的承载能力，但界面粘结强度会因此而下降，且粘结宽度越大，在硫酸盐持续浸泡作用下界面粘结性能退化越显著。在试验基础上引入硫酸盐综合影响系数，并对其采用两种不同方式进行计算，建立考虑硫酸盐浸泡影响的CFRP-粘土砖界面承载力关系模型，通过与试验值对比，本文提出的CFRP-粘土砖界面承载力能关系模型能够很好地预测硫酸盐持续浸泡对CFRP-粘土砖界面承载力退化情况。
- 硫酸盐环境 /
- 碳纤维增强树脂复合材料(CFRP)-粘土砖 /
- 单面剪切 /
- 极限承载力 /
- 粘结强度
Abstract: In order to investigate the degradation law of bonding performance of carbon fiber reinforced composite (CFRP)-clay brick interface under sulfate soaking environment, the test was conducted by accelerated corrosion of CFRP-clay brick specimens with 10wt% mass fraction of sulfate solution, and the material properties were measured, and the change law of bearing capacity and bonding strength of CFRP-clay brick interface was analyzed by collecting the parameters of strain and bearing capacity. The study shows that sulfuric acid immersion has no significant effect on the mechanical properties of CFRP sheet and resin adhesive, but has a significant effect on the compressive strength of clay brick, which decreases by 34.50% after 180 days sulfate immersion. For the ultimate bearing capacity and bond strength of CFRP-clay brick interface, it is found that the width of CFRP has an effect on both the bearing capacity and bond strength of the interface, increasing the width of the interface can increase the bearing capacity of the interface, but the bond strength of the interface will decrease as a result, and the larger the bond width is, the more significant the degradation of the bond performance of the interface under the effect of continuous sulfate immersion. Based on the test, the comprehensive influence coefficient of sulfate is introduced and calculated in two different ways to establish the CFRP-clay brick interfacial bearing capacity relationship model considering the influence of continuous sulfate soaking. The model can predict the degradation of the CFRP-clay brick interface by continuous sulfate soaking.
- sulfate immersion /
- carbon fiber reinforced composite (CFRP)-clay brick /
- unidirectional shear test /
- ultimate bearing capacity /
- bond strength

HTML全文

图 1 试件尺寸

Figure 1. Size of specimen

CFRP—Carbon fiber reinforced composite

下载: 全尺寸图片幻灯片

图 2 材料性能试验装置

Figure 2. Material property test device

下载: 全尺寸图片幻灯片

图 3 单剪试件示意图

Figure 3. Schematic diagram of single shear specimen

b_f—Width of CFRP

下载: 全尺寸图片幻灯片

图 4 应变片布置图

Figure 4. Strain gauge arrangement

b—Width of brick; L_f—Bond length; t_f—Thickness of CFRP

下载: 全尺寸图片幻灯片

图 5 加载装置

Figure 5. loading device

P—Applied load

下载: 全尺寸图片幻灯片

图 6 硫酸盐浸泡下粘土砖抗压强度变化规律

Figure 6. Change pattern of compressive strength of clay bricks under sulfate immersion

下载: 全尺寸图片幻灯片

图 7 各浸泡周期下CFRP-粘土砖试件的破坏形态

Figure 7. Damage patterns of CFRP-clay brick specimens under soaking cycle

下载: 全尺寸图片幻灯片

图 8 CFRP-粘土砖界面承载力变化趋势

Figure 8. Trend of bearing capacity of CFRP-clay brick interface

下载: 全尺寸图片幻灯片

图 9 CFRP-粘土砖界面承载力和粘结强度对比

Figure 9. Comparison of bearing capacity and bonding strength of CFRP-clay brick interface

下载: 全尺寸图片幻灯片

图 10 各浸泡周期下CFRP-粘土砖试件荷载-滑移曲线

Figure 10. Load-slip curves of CFRP-clay brick specimens at each immersion cycle

下载: 全尺寸图片幻灯片

图 11 不同粘结宽度CFRP-粘土砖极限承载力与硫酸盐侵蚀时间的关系曲线

Figure 11. Ultimate bearing capacity and sulfate immersion cycle relationship curves of CFRP-clay brick specimens with different bond widths

P_u(x)/P_u(0)—Ratio of the ultimate load capacity of the specimen under different sulfate immersion cycles to the ultimate load capacity under room temperature conditions

下载: 全尺寸图片幻灯片

图 12 CFRP-粘土砖极限承载力拟合曲线

Figure 12. Ultimate bearing capacity fitting curve of CFRP-clay brick

下载: 全尺寸图片幻灯片

图 13 CFRP-粘土砖承载力试验值与计算值误差分析

Figure 13. Error analysis between the test value of load bearing capacity and the calculated value of CFRP-clay brick

P_u(test)/P_u(cal)—Ratio of the test value to the calculated value of ultimate bearing capacity

下载: 全尺寸图片幻灯片

表 1 两种粘结宽度试件承载能力与粘结强度的变化幅度

Table 1. 1Changes of bearing capacity and bond strength of specimens with two bond widths

Soaking cycle/d	Average ultimate bearing capacity/kN		Change/%	Average bond strength/MPa		Change/%
Soaking cycle/d	70mm wide specimen	50mm wide specimen	Change/%	70mm wide specimen	50mm wide specimen	Change/%
0	16.37	12.05	-26.4	228.1	240.9	+5.3
30	14.12	10.63	-24.7	201.7	212.6	+5.1
60	12.96	10.31	-18.1	185.1	206.2	+12.8
90	12.11	10.14	-16.3	173.0	202.7	+14.7
120	11.54	9.67	-16.2	164.9	193.5	+14.8
150	10.87	9.32	-14.2	155.3	186.4	+16.7
180	10.23	8.85	-13.5	146.1	177.0	+17.5
Note: “-” represents a decrease, “+”represents an increase.

下载: 导出CSV

表 1 硫酸盐浸泡下CFRP和树脂胶力学性能

Table 1. Mechanical properties of CFRP and resin adhesive under sulfate immersion

Material	Soaking cycle/d	Tensile strength/MPa	Change/%	Modulus of elasticity/GPa	Change/%	Elongation/%	Change/%
CFRP	0	3573	—	264.8	—	1.666	—
	30	3557	−0.45	263.2	−0.60	1.645	−1.26
	60	3518	−1.54	262.9	−0.72	1.630	−2.16
	90	3485	−2.46	261.8	−1.13	1.612	−3.24
	120	3463	−3.08	260.9	−1.47	1.604	−3.72
	150	3447	−3.53	260.5	−1.62	1.593	−4.38
	180	3427	−4.09	259.6	−1.96	1.589	−4.62
Resin glue	0	58.917	—	2707	—	2.294	—
	30	59.006	+0.15	2770	+2.33	2.354	+2.62
	60	57.926	−1.68	2628	−2.92	2.254	−1.74
	90	57.434	−2.52	2639	−2.51	2.241	−2.31
	120	55.983	−4.98	2610	−3.58	2.205	−3.88
	150	55.794	−5.30	2604	−3.80	2.202	−4.01
	180	55.262	−6.20	2589	−4.36	2.165	−5.62
Notes: The magnitude of change is compared with the results under 0 immersion cycles (room temperature conditions); “−”—Decrease; “+”—Increase.

下载: 导出CSV

表 2 各浸泡周期下CFRP-粘土砖试件基本参数及试验结果

Table 2. Basic parameters and test results of CFRP-clay brick specimens under each immersion cycle

Soaking cycle/d	Bonding width/mm	Specimen number	Ultimate load/kN	Average ultimate load/kN	Bond strength/MPa	Average bond strength/MPa
0	50	0-150×50-1	12.26	12.05	245.2	240.9
		0-150×50-2	11.32		226.4
		0-150×50-3	12.56		251.2
	70	0-150×70-1	15.39	16.37	219.9	228.1
		0-150×70-2	17.14		248.6
		0-150×70-3	15.11		215.9
30	50	30-150×50-1	11.78	10.63	235.6	212.6
		30-150×50-2	9.14		182.8
		30-150×50-3	10.97		219.4
	70	30-150×70-1	15.16	14.12	216.6	201.7
		30-150×70-2	14.05		200.7
		30-150×70-3	13.15		187.9
60	50	60-150×50-1	9.19	10.31	183.8	206.2
		60-150×50-2	12.02		240.4
		60-150×50-3	9.72		194.4
	70	60-150×70-1	11.03	12.96	157.6	185.1
		60-150×70-2	13.21		188.7
		60-150×70-3	14.64		209.1
90	50	90-150×50-1	10.24	10.14	204.8	202.7
		90-150×50-2	9.51		190.2
		90-150×50-3	10.66		213.2
	70	90-150×70-1	12.19	12.11	174.1	173.0
		90-150×70-2	10.62		151.7
		90-150×70-3	13.52		193.1
120	50	120-150×50-1	8.85	9.67	177.0	193.5
		120-150×50-2	9.51		190.2
		120-150×50-3	10.66		213.2
	70	120-150×70-1	11.68	11.54	166.9	164.9
		120-150×70-2	12.20		174.3
		120-150×70-3	10.74		153.4
150	50	150-150×50-1	8.76	9.32	175.2	186.4
		150-150×50-2	9.65		193.0
		150-150×50-3	9.55		191.0
	70	150-150×70-1	11.42	10.87	163.1	155.3
		150-150×70-2	10.97		156.7
		150-150×70-3	10.22		146.0
180	50	180-150×50-1	8.91	8.85	178.2	177.0
		180-150×50-2	9.17		183.4
		180-150×50-3	8.47		169.4
	70	180-150×70-1	10.77	10.23	153.8	146.1
		180-150×70-2	9.59		137.0
		180-150×70-3	10.33		147.6
Notes: Specimen number is soaking cycle - bond length × bond width - number of specimens; The change is compared with the results under 0 soaking cycles (room temperature conditions).

下载: 导出CSV

表 3 两种粘结宽度CFRP-粘土砖试件承载能力与粘结强度的变化幅度

Table 3. Changes of bearing capacity and bond strength of CFRP-clay brick specimens with two bond widths

Soaking cycle/d	Average ultimate bearing capacity/kN		Change/%	Average bond strength/MPa		Change/%
Soaking cycle/d	70 mm wide specimen	50 mm wide specimen	Change/%	70 mm wide specimen	50 mm wide specimen	Change/%
0	16.37	12.05	−26.4	228.1	240.9	+5.3
30	14.12	10.63	−24.7	201.7	212.6	+5.1
60	12.96	10.31	−18.1	185.1	206.2	+12.8
90	12.11	10.14	−16.3	173.0	202.7	+14.7
120	11.54	9.67	−16.2	164.9	193.5	+14.8
150	10.87	9.32	−14.2	155.3	186.4	+16.7
180	10.23	8.85	−13.5	146.1	177.0	+17.5

下载: 导出CSV

表 4 室温条件下不同粘结宽度CFRP-粘土砖试件的剥离承载力

Table 4. Peel bearing capacity of CFRP-clay brick specimens with different bond widths under standard maintenance conditions

Compressive strength of clay bricks/MPa	CFRP length/mm	CFRP width/mm	Test value/kN	Calculated value/kN	Ratio
17.39	150	30	7.62	7.72	0.987
	150	50	12.05	12.21	0.987
	150	70	16.37	16.58	0.987
	150	90	20.69	20.94	0.988

下载: 导出CSV

表 5 硫酸盐各浸泡周期下CFRP-粘土砖极限承载力计算结果与试验结果对比

Table 5. Comparison between calculated and experimental results of ultimate bearing capacity of CFRP-clay brick under each soaking cycle of sulfate

Soaking cycle/d	70 mm width specimen			50 mm width specimen
Soaking cycle/d	Test results/kN	Method 1 calculation results/kN	Method 2 calculation results/kN	Test results/kN	Method 1 calculation results/kN	Method 2 calculation results/kN
0	16.37	16.13	16.30	12.05	12.15	12.16
30	14.12	14.30	14.81	10.63	11.32	11.05
60	12.96	12.89	13.63	10.31	10.63	10.17
90	12.11	11.82	12.70	10.14	10.07	9.48
120	11.54	11.02	11.99	9.67	9.61	8.94
150	10.87	10.45	11.45	9.32	9.25	8.54
180	10.23	10.08	11.08	8.85	8.98	8.27

下载: 导出CSV

参考文献(28)

[1]	李莉. 传统砌体房屋病害分析及结构加固[D]. 邯郸: 河北工程大学, 2018. LI Li. Disease analysis and structural seismic strengthening of traditional masonry buildings[D]. Handan: Hebei University of Engineering, 2018(in Chinese).
[2]	叶列平, 冯鹏. FRP在工程结构中的应用与发展[J]. 土木工程学报, 2006, 39(3):24-34. doi: 10.3321/j.issn:1000-131X.2006.03.004 YE Lieping, FENG Peng. Applications and development of fiber-reinforced polymer in engineering structures[J]. China Civil Engineering Journal,2006,39(3):24-34(in Chinese). doi: 10.3321/j.issn:1000-131X.2006.03.004
[3]	王作虎, 申书洋, 杨菊, 等. FRP布加固结构粘结界面耐久性的研究进展[J]. 复合材料科学与工程, 2020(7):117-122. WANG Zuohu, SHEN Shuyang, YANG Ju, et al. Research progress on durability of bond interface of FRP sheet reinforced structures[J]. Composites Science and Engineering,2020(7):117-122(in Chinese).
[4]	JI Y C, KIM Y J. Effects of sulfuric acid on durability characteristics of CFRP composite sheets[J]. Journal of Materials in Civil Engineering,2017,29(10):04017159. doi: 10.1061/(ASCE)MT.1943-5533.0002008
[5]	ZINNO A, LIGNOLA G P, PROTA A, et al. Influence of free edge stress concentration on effectiveness of FRP confinement[J]. Composites Part B: Engineering,2010,41(7):523-532. doi: 10.1016/j.compositesb.2010.07.003
[6]	张祥顺, 谷倩, 管克俭, 等. 碳纤维布加固砌体结构试验研究[J]. 武汉理工大学学报, 2002, 24(11):29-32. ZHANG Shunxiang, GU Qian, GUAN Kejian, et al. Experimental study of masonry walls strengthened by CFRP[J]. Journal of Wuhan University of Technology,2002,24(11):29-32(in Chinese).
[7]	ALECCI V, BATI S B, RANOCCHIAI G. Study of brick masonry columns confined with CFRP composite[J]. Journal of Composites for Construction,2009,13(3):179-187. doi: 10.1061/(ASCE)1090-0268(2009)13:3(179)
[8]	YARIGARRAVESH M, TOUFIGH V, MOFID M. Experimental and analytical evaluation of FRPs bonded to masonry-long term[J]. Surface and Coatings Technology,2018,344:729-741.
[9]	陶毅, 古金本, 信任, 等. CFRP网格修复后多层砌体结构墙体的抗震性能[J]. 西南交通大学学报, 2019, 54(6):1258-1267. doi: 10.3969/j.issn.0258-2724.20170491 TAO Yi, GU Jinben, XIN Ren, et al. Seismic performance of multi-storey masonry wall repaired by carbon fiber reinforced polymer grids[J]. Journal of Southwest Jiaotong University,2019,54(6):1258-1267(in Chinese). doi: 10.3969/j.issn.0258-2724.20170491
[10]	雷真, 白柳, 郭洪波, 等. FRP加固砌体结构的界面粘结性能综述[J]. 材料科学, 2018, 8(11):1038-1046. doi: 10.12677/MS.2018.811124 LEI Zhen, BAI Liu, GUO Hongbo, et al. A review of interfacial adhesion properties between FRP and masonry structures reinforced with FRP[J]. Material Sciences,2018,8(11):1038-1046(in Chinese). doi: 10.12677/MS.2018.811124
[11]	KASHYAP J, WILLIS C R, GRIFFITH M C, et al. Debonding resistance of FRP-to-clay brick masonry joints[J]. Engi-neering Structures,2012,41(8):186-198.
[12]	宦文娟. 多因素耦合作用下砖及其砌体的性能劣化规律与机理研究[D]. 南京: 东南大学, 2013. HUAN Wenjuan. Investigation of deterioration and mechanism of brick and masonry subjected to multi-factor coupling effect[D]. Nanjing: Southeast University, 2013(in Chinese).
[13]	王作虎, 王江北, 申书洋, 等. 冻融循环对FRP片材-砌块界面粘结性能的影响[J]. 复合材料学报, 2022, 39(11):5275-5286. doi: 10.13801/j.cnki.fhclxb.20220110.003 WANG Zuohu, WANG Jiangbei, SHEN Shuyang, et al. Effect of freeze-thaw cycles on bond properties of FRP sheet-brick[J]. Acta Materiae Compositae Sinica,2022,39(11):5275-5286(in Chinese). doi: 10.13801/j.cnki.fhclxb.20220110.003
[14]	靳文强, 赵建昌, 王琦, 等. 冻融循环对CFRP-烧结粘土砖界面粘结性能影响[J]. 复合材料学报, 2020, 37(9):2294-2302. doi: 10.13801/j.cnki.fhclxb.20200111.002 JIN Wenqiang, ZHAO Jianchang, WANG Qi, et al. Effects of freeze-thaw cycles on interfacial bonding property of CFRP-sintered clay brick[J]. Acta Materiae Compositae Sinica,2020,37(9):2294-2302(in Chinese). doi: 10.13801/j.cnki.fhclxb.20200111.002
[15]	王复生, 孙瑞莲, 秦晓鹃. 察尔汗盐湖条件下水泥混凝土耐久性调查研究[J]. 硅酸盐通报, 2002, 21(4):16-21,35. doi: 10.3969/j.issn.1001-1625.2002.04.004 WANG Fusheng, SUN Ruilian, QIN Xiaojuan. The investigation of concrete durability under natural condition of Ca Er Han salt lake[J]. Bulletin of the Chinese Ceramic Society,2002,21(4):16-21,35(in Chinese). doi: 10.3969/j.issn.1001-1625.2002.04.004
[16]	刘生纬. 硫酸盐环境下CFRP-混凝土界面粘结性能退化规律及劣化机理研究[D]. 兰州: 兰州交通大学, 2018. LIU Shengwei. Research on degradation law and mechanism of CFRP sheet-concrete interfacial bonding performance under sulfate environment[D]. Lanzhou: Lanzhou jiaotong University, 2018(in Chinese).
[17]	余红发. 盐湖地区高性能混凝土的耐久性、机理与使用寿命预测方法[D]. 南京: 东南大学, 2004. YU Hongfa. Study on high performance concrete in salt lake: durability, mechanism and service life prediction[D]. Nanjing: Southeast University, 2004(in Chinese).
[18]	张家玮, 邵利君, 刘生纬, 等. 硫酸盐环境中CFRP约束劣化混凝土柱的力学性能[J]. 复合材料学报, 2021, 38(3):966-978. doi: 10.13801/j.cnki.fhclxb.20201210.002 ZHANG Jiawei, SHAO Lijun, LIU Shengwei, et al. Mechani-cal properties of CFRP confined pre-damaged concrete columns in sulfate environment[J]. Acta Materiae Compositae Sinica,2021,38(3):966-978(in Chinese). doi: 10.13801/j.cnki.fhclxb.20201210.002
[19]	中国国家标准化管理委员会. 纤维增强塑料性能试验方法总则: GB/T 1446—2005[S]. 北京: 中国标准出版社, 2005. Standardization Administration of the People’s Republic of China. Fiber-reinforced plastics composites-The generals for determination of properties: GB/T 1446—2005[S]. Beijing: China Standards Press, 2005(in Chinese).
[20]	中国国家标准化管理委员会. 定向纤维增强聚合物基复合材料拉伸性能试验方法: GB/T 3354—2014[S]. 北京: 中国标准出版社, 2015. Standardization Administration of the People’s Republic of China. Test method for tensile properties of orientation fiber reinforced polymer matrix composite materials: GB/T 3354—2014[S]. Beijing: China Standards Press, 2005(in Chinese).
[21]	中国国家标准化管理委员会. 树脂浇铸体性能试验方法: GB/T 2567—2021[S]. 北京: 中国标准出版社, 2021. Standardization Administration of the People’s Republic of China. Test methods for properties of resin casting boby: GB/T 2567—2021[S]. Beijing: China Standards Press, 2021(in Chinese).
[22]	中国国家标准化管理委员会. 烧结普通砖: GB/T 5101—2017[S]. 北京: 中国标准出版社, 2017. Standardization Administration of the People’s Republic of China. Fired common bricks: GB/T 5101—2017[S]. Beijing: China Standards Press, 2017(in Chinese).
[23]	黄奕辉. FRP与砖界面行为及其应用研究[D]. 泉州: 华侨大学, 2008. HUANG Yihui. Studies on FRP-brick interface and it application[D]. Quanzhou: Hua Qiao University, 2008(in Chinese).
[24]	王全凤, 陈莹, 黄奕辉, 等. GFRP复合材料与粘土砖单剪粘结试验研究[J]. 建筑结构, 2008, 38(5):106-108. WANG Quanfeng, CHEN Ying, HUANG Yihui, et al. Experimental study on single shear strength between GFRP and clay brick[J]. Building Structure,2008,38(5):106-108(in Chinese).
[25]	钱长根. 纤维增强复合材料(FRP)与烧结普通砖粘结性能的试验研究[D]. 泉州: 华侨大学, 2007. QIAN Changgen. Experimental research on bonded pro-perty of interface between FRP and fired common brick[D]. Quanzhou: Hua Qiao University, 2007(in Chinese).
[26]	郑怡, 李莉, 刘明, 等. FRP与砌体界面的粘结承载力[J]. 沈阳建筑大学学报(自然科学版), 2010, 26(1):27-30. ZHENG Yi, LI Li, LIU Ming, et al. Study on anchorage strength models for FRP attached to masonry[J]. Journal of Shenyang Jianzhu University (Natural Science),2010,26(1):27-30(in Chinese).
[27]	YUAN H, TENG J G, SERACINO R, et al. Full-range behavior of FRP-to-concrete bonded joints[J]. Engineering Structures,2004,26(5):553-565. doi: 10.1016/j.engstruct.2003.11.006
[28]	NAKABA K, KANAKUBO T, FURUTA T, et al. Bond behavior between fiber-reinforced polymer laminates and concrete[J]. ACI Structural Journal,2001,98(3):359-367.