表面内嵌FRP筋加固混凝土T形梁受弯性能研究

发布时间：2018-01-09 05:29

本文关键词：表面内嵌FRP筋加固混凝土T形梁受弯性能研究　出处：《沈阳建筑大学》2015年硕士论文　论文类型：学位论文

【摘要】：目前我国城市当中混凝土危桥数量约占桥梁总数的14%,并且比例仍在逐年增加,人们的生活起居和安全受到影响,所以需对这些正在服役当中的危桥进行加固。纤维增强复合材料(Fiber Reinforced Polymer, FRP)是一种轻质、高强、耐腐蚀的新型材料,被广泛应用于混凝土结构的加固当中。表面内嵌FRP筋加固法是一种新型的加固方法,其是在需要加固的混凝土结构构件的表面(混凝土保护层厚度内)开槽,然后嵌入FRP筋,并用黏结剂(改性环氧树脂类胶体)进行黏结,提高构件承载力的一种加固方法。相比传统的加固方法,其具有施工简便、耐火、耐高温和耐久性好等优点。为此对采用表面内嵌FRP筋加固的混凝土T形梁进行试验研究,研究加固前后混凝土T形梁裂缝发展、破坏模式和受弯性能的变化规律,同时分析不同混凝土强度等级、钢筋配筋率、有无附加锚固、FRP筋表面特征、FRP筋直径和FRP筋类型这些参数影响下加固试件受弯性能的变化规律,最后根据规范以及试验的结果,给出修正后的表面内嵌FRP筋加固混凝土T形梁的受弯承载力计算公式。研究的主要内容如下：为对比研究混凝土T形梁加固前后的裂缝发展及破坏模式的变化规律,对10根加固试件和3根标准试件进行受弯静力试验。研究结果表明,加固试件裂缝数量多、间距小、宽度窄,且底部有树根状的45°斜向裂缝和纵向裂缝,同时发展速度有所延缓。附加锚固可以防止GFRP筋加固试件产生混凝土纵向剥离裂缝；光圆GFRP筋加固试件裂缝发展速度相对较快；随着GFRP筋直径的增加,裂缝数量逐渐增加,而间距与宽度逐渐减小；CFRP筋加固试件更易产生混凝土纵向剥离裂缝。有附加锚固的加固试件发生弯曲破坏,无附加锚固的加固试件发生混凝土剥离破坏。螺纹GFRP筋加固试件的破坏模式为弯曲破坏,光圆GFRP筋加固试件的破坏模式为FRP—胶体界面破坏。FRP筋直径不宜大于槽深及槽宽的1/2,否则易发生FRP—胶体界面破坏。CFRP筋加固试件更易发生混凝土剥离破坏。为对比研究混凝土T形梁加固前后的抗弯刚度、承载力、跨中位移、延性、跨中钢筋应变的变化规律,对试验结果进行了研究。研究结果表明,加固试件开裂阶段的抗弯刚度基本没有提高,屈服阶段和破坏阶段的抗弯刚度有所提高,并且破坏阶段提高的更为显著。加固试件的开裂荷载基本没有提高,屈服荷载提高15.32%-67.07%,极限荷载提高16.3%-76.17%,并且极限荷载提高的更为显著。加固试件开裂阶段的跨中位移基本没有减小,屈服阶段和破坏阶段的跨中位移有所减小,并且破坏阶段的跨中位移减小的更为显著。加固试件的延性有所降低。加固试件开裂阶段钢筋的应变基本没有得到限制,屈服阶段和破坏阶段钢筋的应变有所限制,并且对破坏阶段钢筋应变的限制更为显著。为研究混凝土强度等级、钢筋配筋率、附加锚固、FRP筋表面特征、FRP筋直径和FRP筋类型对加固试件的抗弯刚度、承载力、跨中位移、延性、跨中FRP筋应变和钢筋应变的影响规律,对10根加固试件的试验结果进行了研究。研究结果表明,混凝土强度等级对屈服荷载提高率和极限荷载提高率影响较为显著,对其它的基本没有影响。钢筋配筋率较大的加固试件的抗弯刚度、屈服荷载、极限荷载和跨中屈服位移较大,屈服荷载提高率、极限荷载提高率和延性较低,其它的基本没有差别。附加锚固主要在加固试件的破坏阶段起到重要作用,有附加锚固加固试件的跨中钢筋应变较小,其它的均较大。螺纹GFRP筋加固试件的抗弯刚度、极限荷载、极限荷载提高率、跨中FRP筋应变和FRP筋利用率较大,而跨中屈服位移、极限位移、延性和跨中钢筋应变较小,其它的基本没有差别。随着GFRP筋直径的增大,加固试件的抗弯刚度、极限荷载和极限荷载提高率逐渐增大,跨中钢筋应变逐渐减小,其它的基本没有差别；但当FRP筋直径过大时,虽然跨中屈服位移和极限位移较大,但跨中FRP筋应变和FRP筋利用率较低。CFRP筋加固试件的抗弯刚度、屈服荷载、屈服荷载提高率、极限荷载、极限荷载提高率较大,跨中极限位移、延性、跨中FRP筋应变和FRP筋利用率较小,其它的基本没有差别。为验证表面内嵌FRP筋加固混凝土T形梁的受弯承载力计算公式是否适用,首先根据《混凝土结构加固设计规范》GB 50367-2006中的表面粘贴FRP构件的受弯承载力计算公式,并且结合《混凝土结构设计规范》GB 50010-2010中的T形截面构件的受弯承载力计算公式,给出了表面内嵌FRP筋加固混凝土T形梁受弯承载力计算公式。然后根据发生弯曲破坏的4根加固试件的承载力试验结果与理论公式计算结果的对比,通过二元线性回归的方法对计算公式中的折减系数Km进行了修正。最后经过修正以后的表面内嵌FRP筋加固混凝土T形梁的受弯承载力计算公式与试验结果值吻合较好。
[Abstract]:At present our country city among the number of concrete bridges accounted for about 14% of the total number of bridges, and the proportion is still increasing year by year, living and safety of affected people, so these are serving the dangerous bridge reinforcement. Fiber reinforced composites (Fiber Reinforced, Polymer, FRP) is a kind of lightweight, high strength, model corrosion resistant material, is widely used in reinforced concrete structures. The surface strengthening method of embedded FRP bar is a new reinforcement method, which is on the surface of concrete structure reinforcement (the concrete protective layer thickness) slot, and then embedded FRP tendons, and binder (modified epoxy resin colloid) bonding a strengthening method, improve the bearing capacity of specimens. Compared with the traditional reinforcement methods, which has simple construction, fire resistance, resistance to high temperature and good durability. Therefore the embedded FRP reinforced surface Experimental study of concrete T beam structure, research before and after the reinforcement of concrete T beam crack development, failure mode and the variation of bending performance, and analysis of different strength grade of concrete, reinforcement ratio, there is no additional anchorage, the surface characteristics of FRP bars, FRP bars and FRP bars diameter of these types of parameters under the influence of reinforcement the specimen bending performance changes, according to the specification and test results, given the modified surface of FRP embedded reinforcement concrete T shaped by the calculation formula of flexural capacity of the beam. The main contents are as follows: for the comparative study of the change of concrete T beam before and after reinforcement of crack development and failure mode on the 10, specimens and 3 standard specimens are static bending test. The results show that the reinforcement of the crack number, small spacing, narrow width, and the bottom root shaped 45 degree oblique cracks and longitudinal cracks, At the same time, the development speed slowed. Additional anchorage can prevent GFRP reinforcement produced avulse cracks in concrete specimen; round GFRP reinforcement crack development speed is relatively fast; with the increase of diameter of GFRP bar, the number of cracks increases gradually, while the spacing and width decrease; CFRP reinforcement specimens are more susceptible to longitudinal concrete there are additional anchorage stripping cracks. Specimens of bending failure, no additional anchorage reinforcement concrete specimen debonding. Thread GFRP reinforcement failure mode of specimen is bending failure, round GFRP reinforcement failure mode of specimen is FRP - colloid interface failure.FRP bar diameter should not be greater than the depth of the groove and the groove the width of the 1/2, or prone to FRP colloid interface failure.CFRP reinforcement concrete specimen is more likely to happen. The debonding failure for the comparative study of concrete T beam before and after reinforcement of flexural stiffness, bearing Cross force, displacement ductility, variation of cross strain in the steel, the results of the test are studied. The results show that the reinforced specimen cracking stage the flexural rigidity of the basic does not increase, the stiffness increases the flexural yielding stage and failure stage, and failure stage increased more significantly. Reinforcement the basic cracking load was not increased, the yield load increases 15.32%-67.07%, 16.3%-76.17% and increase the ultimate load, ultimate load increase is more significant. The reinforcement specimen cracking stage cross displacement without decreasing the yield stage and destruction stage of the midspan displacement decreases, and the damage stage of midspan displacement decreases more significant ductility decreases. The reinforcement strain specimen cracking stage of steel does not limit, limit strain yield stage and failure stage of steel, and destruction of the order The steel strain limit is more significant. For the study of the grade of concrete strength, reinforcement ratio, anchorage and surface characteristics of FRP bars, FRP bars and FRP bars of diameter type specimens of the flexural stiffness, bearing capacity, displacement ductility, cross, cross effects of FRP reinforcement strain and steel strain the 10 specimens test results were studied. The results show that the concrete strength of the yield load and ultimate load increase rate of increase rate has remarkable effect, has no effect on the other. The basic reinforcement ratio of reinforcement bending specimens of larger stiffness, yield load, ultimate load and cross yield larger displacement, yield load rate, ultimate load and ductility increase rate is low, the other basically no difference. The main anchorage reinforcement in failure phase plays an important role, with additional anchorage reinforcement test cross strain in the steel parts Small, other are large. Thread GFRP reinforcement the flexural rigidity, ultimate load, ultimate load increase rate, cross FRP reinforcement strain and FRP bars utilization rate is larger, and the cross in the yield displacement, ultimate displacement, ductility and cross strain in the steel is smaller, the other had no distinct difference with. Increasing the diameter of GFRP bar, strengthening the flexural rigidity, ultimate load and ultimate load increase rate increased gradually, the cross strain in the steel decreases gradually, the other has no difference; but when the diameter of FRP bar is too large, although the midspan yield displacement and ultimate displacement of large span, but in FRP and reinforcement strain the low utilization rate of.CFRP FRP reinforced reinforcement specimens flexural stiffness, yield load, yield load rate, ultimate load, ultimate load increase rate of large span limit displacement, ductility, span FRP reinforcement strain and FRP bars using rate is low, the other basically no difference. In order to verify the table The surface embedded FRP reinforcement concrete T beam the calculation formulas of the applicability of the flexural capacity, according to the first FRP component is stuck to the surface of reinforced concrete structure design specification of >GB 50367-2006 in the calculation formula of flexural bearing capacity, and the combination of "code for design of concrete structures >GB 50010-2010 in the T section member by the calculation formula of bearing capacity bending, gives concrete reinforcement T surface embedded FRP rib beam flexural capacity calculation. Then according to the comparison of bending failure of 4 reinforced specimen loading test results and theoretical calculation results, through the method of two linear regression formulas of the reduction coefficient Km is modified. Finally after surface modified FRP embedded reinforcement concrete T beam by formula and the test results are in good agreement with the values of flexural bearing capacity.

【学位授予单位】：沈阳建筑大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU37

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