唐皇(1988-), 男, 博士, 主要从事桥梁时变可靠度评估, E-mail:
Tang Huang (1988-), PhD, main research interest: time-dependent reliability evaluation of bridge, E-mail:
彭建新(通信作者), 男, 博士, 教授, E-mail:
Peng Jianxin (corresponding author), PhD, professor, E-mail:
为了研究不同钢板加固方式对锈蚀钢筋混凝土梁承载性能的影响,探索不同钢板加固方式的加固效果,通过静力荷载试验对比研究了钢板抗弯加固、抗剪加固和抗弯-抗剪组合加固锈蚀RC梁在承载力、变形、破坏模式和延性等方面的特点,分析了不同加固方式的优缺点。研究结果表明:组合加固效果最明显,其极限承载力比锈蚀梁提高了107.7%;对于抗弯加固锈蚀梁,钢板厚度分别为3、4、5 mm时,厚度每增加1 mm,其极限承载力增加7~18 kN;组合加固锈蚀梁的抗变形能力最强,其次是抗弯加固锈蚀梁,且钢板厚度增加对抗弯加固锈蚀梁的抗变形能力有积极作用;组合加固较其他两种加固方式能更有效地提高锈蚀梁的延性,其延性相比锈蚀梁提高了320.4%,其次是抗剪加固锈蚀梁;抗弯加固锈蚀梁的延性比其他两种加固梁小,且随着钢板厚度增加,其延性先增加后减小。评价抗弯和抗剪加固锈蚀梁的加固效果时,需综合考虑抗变形能力和延性。
In order to explore the influence of different steel plate strengthening methods on the bearing capacity of corroded RC beams, the strengthening effect of different strengthening schemes is explored. The characteristics in the bearing capacity, deformation, failure mode and ductility of corroded RC beams strengthening by steel plate with flexural strengthening schemes, shear strengthening scheme, and flexure-shear combination strengthening scheme are compared, respectively, and the advantages and disadvantages of different strengthening schemes are analyzed. The results show that for the flexure-strengthened corroded beam which steel plate thickness are 3 mm, 4 mm and 5 mm, respectively, the ultimate bearing capacity increased by 7~18 kN with 1 mm increases of steel plate thickness. The effect of combined strengthening is most significant, and the ultimate bearing capacity increased by 107.7% compared with corroded beams. Combined strengthened corroded beams have the strongest deformation resistance, the following is flexure-strengthened corroded beams, and the increases of steel plate thickness has a positive effect on the deformation resistance of flexure-strengthened corroded beam. The combined strengthening scheme is more effective in improving the ductility of corroded beam than the other two strengthening schemes, the ductility of which is improved by 320.4% compared with corroded beam, followed by shear strengthened corroded beams. The ductility of flexure-strengthened corroded beam is smaller than other two kinds of strengthened beams, and it increases in the begining and then decreases with the increases of steel plate thickness. The deformation resistance and ductility should be considered comprehensively when evaluating the strengthening effect of flexural and shear-strengthened corroded beams.
钢筋锈蚀是引起钢筋混凝土(RC)结构承载性能退化的主要原因之一。中国现有公路桥梁中,超过15%的RC桥梁由于钢筋锈蚀导致了保护层剥落、混凝土开裂和钢筋断裂等病害[
作为一种施工方便、经济和效果明显的加固方法,钢板加固已经在RC结构加固工程中广泛应用,其中,主要加固方式分为抗弯加固、抗剪加固和抗弯-抗剪组合加固。学者们对于抗弯加固、抗剪加固和抗弯-抗剪组合加固不锈蚀RC梁的承载力、破坏模式和变形性能等力学指标进行了一系列研究[
笔者通过静力荷载试验研究锈蚀RC梁在不同钢板加固方式作用下的承载性能,对比分析了抗弯、抗剪和抗弯-抗剪组合加固锈蚀RC梁的破坏模式、裂缝分布、挠度、承载力和延性等力学指标,比较了不同加固方式的优缺点。
共设计8片RC梁,其设计参数如
试验试件设计参数
Properties of the tested beams
试验梁编号 | 加固前设计锈蚀率/% | 实际锈蚀率/% | 加固钢板厚度/mm | 加固钢板宽度/mm |
P1 | 00 | 00.0 | 无 | 无 |
P2 | 10 | 08.5 | 无 | 无 |
PSC-0 | 00 | 00.0 | 5 | 100 |
PSC-1 | 10 | 07.4 | 3 | 100 |
PSC-2 | 10 | 10.3 | 4 | 100 |
PSC-3 | 10 | 10.9 | 5 | 100 |
PUC | 10 | 10.4 | 3(U型箍) | 50(U型箍) |
PSU | 10 | 10.3 | 3(U型箍)、5(底钢板) | 50(U型箍)、100(底钢板) |
试验梁配筋图(单位:mm)
Reinforcement layout of thetested beams (units: mm)
试验梁电化学腐蚀
Electrochemical corrosion of RC beam
不同钢板加固方式(单位:mm)
Different strengthening schemes (units: mm)
试验梁制作完毕后,在标准养护条件下养护7 d,然后利用500 kN千斤顶进行加载。试验中,分别在梁支座、1/4点处和跨中处安装百分表测量试验梁挠度。混凝土应变由沿梁高粘贴的6个电阻应变片测得,应变片间距为50 mm。钢板的应变由两锚钉之间的应变片测得。试验梁加载如
试验梁加载程序(单位:cm)
Loading set-up of beam specimen (units: cm)
所有试验梁的试验结果见
试验梁试验结果
Test results of the tested beams
试验梁 | 抗弯规范值/kN | 抗剪规范值/kN | 提高量/% | 破坏模式 | ||||||
注:F表示弯曲破坏;DT为斜拉破坏;SF为支座破坏 | ||||||||||
P1 | 22 | 090 | 140 | 130 | 130 | 165 | 1.07 | 05.7 | F | |
P2 | 20 | 065 | 117 | 120 | 120 | 165 | 0.98 | 05.1 | F | |
PSC-0 | 70 | 105 | 215 | 220 | 307 | 165 | 0.98 | 053.6 | 08.7 | DT |
PSC-1 | 40 | 100 | 165 | 169 | 271 | 165 | 0.98 | 041.0 | 09.8 | DT |
PSC-2 | 50 | 090 | 172 | 177 | 289 | 165 | 0.97 | 047.0 | 10.2 | DT |
PSC-3 | 55 | 090 | 190 | 196 | 304 | 165 | 0.97 | 062.4 | 09.0 | DT |
PUC | 20 | 085 | 171 | 168 | 125 | 343 | 1.01 | 046.2 | 11.6 | F |
PSU | 56 | 080 | 243 | 256 | 303 | 343 | 0.94 | 107.7 | 09.1 | SF |
式中:
由于抗弯加固梁是斜拉破坏,极限荷载由抗剪承载力控制,文献[
对于梁PUC和梁PSU,文献[
从
试验梁的破坏模式
Failure modes of the beam specimens
从
在
试验梁沿梁高混凝土应变
Concrete strain along the beam height of tested beams
试验梁底面钢板应变
Steel plate strain of tested beams on the bottom
从
试验梁裂缝分布
Crack distribution of tested beams
试验梁荷载挠度曲线
Load-deformation curves of tested beams
Keheyroddin等[
1) 加载过程中,试验误差会引起加载点微小的变化。
2) 整个加载过程,左右两加载点的微小不均匀性。
3) 曲率在纯弯矩区变化,存在波动,由于拉伸-刚度效应,曲率峰值在离散开裂处不能精确确定。
上述原因导致纯弯段曲率的量测受塑性铰的影响,用纯弯段曲率来衡量试验梁之间的延性存在问题,特别是当钢筋屈服后进入塑性阶段,曲率更加难以确定。另一个方面,梁跨中挠度曲线反映的是沿梁长曲率的集合,使用荷载挠度曲线评价试验梁延性更为可靠。
试验梁延性
Ductility of the tested beams
试验梁 | 韧性模量/(kN·mm) | 比对比梁提高量/% |
P1 | 0 738.0 | |
P2 | 0 589.4 | |
PSC-0 | 1 811.4 | 145.4 |
PSC-1 | 1 230.9 | 108.8 |
PSC-2 | 1 359.6 | 130.7 |
PSC-3 | 1 220.7 | 107.1 |
PUC | 1 660.9 | 181.8 |
PSU | 2 477.8 | 320.4 |
结合荷载挠度分析结果可以看出,虽然同一荷载下,梁PUC的抗变形能力低于梁PSU和梁PSC-3,但其整体延性比梁PSC-3要大。另外,钢板厚度的增加对抗弯加固锈蚀梁的抗变形能力有积极作用,但整体延性却是随钢板厚度增加先增后减。因此可以表明,对于抗变形能力弱的抗剪加固锈蚀梁,其整体延性并不一定比其他加固梁弱,钢板厚度增加并不能始终有利于抗弯加固锈蚀梁的承载性能,评价其加固效果时需综合考虑抗变形能力和延性。
通过静力荷载试验对比分析了钢板抗弯加固、抗剪加固和抗弯-抗剪组合加固锈蚀RC梁在承载力、变形、破坏模式和延性等方面的特点,分析了不同加固方式的优缺点,根据试验和分析结果,得到如下结论:
1) 与锈蚀梁和不锈蚀梁相比,钢板加固能有效提高梁的极限承载力。组合加固效果最明显,其极限承载力比锈蚀梁提高了107.7%。抗弯加固锈蚀梁钢板厚度分别为3、4、5 mm时, 厚度每增加1 mm, 其极承载力增加7~18 kN。
2) 每种加固方式都能提高锈蚀梁的抗变形性能,组合加固锈蚀梁的抗变形能力最强,其次是抗弯加固锈蚀梁,同时,钢板厚度的增加对抗弯加固锈蚀梁的抗变形能力有积极作用。
3) 组合加固比其他两种加固方式能更有效地提高锈蚀梁的延性,相比锈蚀梁延性提高达320.4%,其次是抗剪加固锈蚀梁。抗弯加固锈蚀梁的延性相比前两种梁都要小,并且随着钢板厚度的增加先增加后减小。评价抗弯和抗剪加固锈蚀梁的加固效果时需综合考虑抗变形能力和延性。
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