大尺寸钢筋混凝土梁受剪试验研究
发布时间：2018-09-01 10:37
【摘要】：工程中常出现的大尺寸钢筋混凝土粱(非深梁)及厚板等是否安全会对整个结构的安全性产生重大影响。研究表明ACI规范及我国现行规范对大尺寸粱的截面尺寸效应考虑不足,偏于不安全。同时我国规范受剪承载力计算公式所依据的试验数据中大尺寸梁的数据不充分,因此有必要对大尺寸钢筋混凝土梁的受剪性能进行研究。本文结合国家自然科学基金项目(50778034)和国家自然科学基金重点项目(50838001),对大尺寸钢筋混凝土梁在集中荷载作用下的受剪性能展开了系统地试验研究和分析,主要内容总结如下： (1)通过集中荷载作用下的受剪试验,研究了截面高度对钢筋混凝土无腹筋梁受剪承载力的影响。结果表明,试件的开裂剪切强度和极限剪切强度都呈现出明显的尺寸效应现象。以截面高度500mm的试件为基准,当截面有效高度增加112%和158%时,开裂剪切强度减小31%和34%,极限剪切强度减小26%和41%。 (2)以纵筋配筋率为参数,研究了集中荷载作用下大尺寸钢筋混凝土无腹筋梁受剪承载力的影响。结果表明,在纵筋配筋率较低的情况下,纵筋率的变化对无腹筋梁受剪性能的影响较大。与纵筋率0.67%的试件相比,纵筋率1.10%的试件开裂剪切强度提高26%,极限剪切强度提高73%。 (3)对试件沿梁高配置水平纵向钢筋或按照最小配箍率配置箍筋,研究了不同的腹筋类型和腹筋配置对集中荷载作用下大尺寸钢筋混凝土梁受剪承载力的影响。研究表明,腹筋的配置能够提高试件的受剪承载力。与相同截面高度下的无腹筋梁相比,沿梁高配置水平纵向钢筋的试件,极限剪切强度提高14%；按照最小配箍率配置箍筋的梁,能够分散裂缝,极限剪切强度提高66%。 (4)研究了截面高度对斜裂缝间距的影响。研究表明,斜裂缝在纵筋重心高度处的平均裂缝间距与截面高度无关,与试件保护层相关；斜裂缝在截面一半高度处的平均裂缝间距与截面高度相关,表现出一定的尺寸效应。对比截面高度500mrn和1200mm的试件,二者在纵筋重心高度处的平均裂缝间距分别为258mm和243mm,为保护层厚度的4.3倍和4.1倍；二者在截面一半高度处的平均裂缝间距分别为192mm和450mm。 (5)研究了截面不同位置、截面高度、纵筋配筋率和腹筋对斜裂缝宽度和开展速度的影响。研究表明,在相同剪应力下,距梁顶0.5ho处的裂缝宽度和开展速度要大于裂缝尖端和纵筋重心位置处；试件斜裂缝的宽度和开展速度随着截面高度的增加和纵筋配筋率的降低而增大；相同截面高度的情况下,腹筋的配置能够有效的限制斜裂缝的宽度和开展速度。 (6)研究了无腹筋梁受压区混凝上在加载过程中提供的受剪承载力。结果表明,受压区混凝土提供的剪力占总剪力的比值,随着截面高度和纵筋配筋率的增加而减小。 (7)结合受剪试验数据库,在我国规范公式的基础上提出了经验公式,着重考虑了尺寸效应和纵筋配筋率的影响。分析结果表明,对于大尺寸梁和低纵筋率梁,经验公式的预测值精度较好,离散程度较小。 (8)通过截面分析,提出了大剪跨比钢筋混凝土无腹筋梁受剪承载力计算公式。在受剪试验数据库的基础上,利用对比分析法和缺陷点数分析法对GB50010-2010规范、ACI318-08规范、CSA A23.3-04规范和本文公式进行对比研究。结果表明,对于截面高度大于600mm和纵筋配筋率小于等于1.0%的无腹筋梁,GB50010-2010规范和ACI318-08规范计算结果偏于不安全。CSA A23.3-04规范和本文公式的预测结果较为准确,且离散程度较小。 (9)结合一起钢筋混凝土厚板桥梁的剪切破坏实例以及收集的大尺寸梁和厚板试验数据,对我国混凝土规范GB50010-2010的无腹筋构件抗剪计算公式的安全性进行了分析,探讨了最小配箍率和纵向分布钢筋对构件受剪承载力的影响。分析表明,规范公式虽然引入了尺寸效应系数,但尚不能充分考虑截面高度对受剪承载力的影响；规范规定的最小配箍率能够有效避免大尺寸构件发生剪切破坏,而纵向分布钢筋则不能有效避免高度大于1000mm的无腹筋构件的剪切破坏。
[Abstract]:The safety of large-size reinforced concrete beams (non-deep beams) and thick slabs, which often appear in engineering projects, will have a great impact on the safety of the whole structure. The research shows that ACI code and current code in China do not consider the size effect of large-size beams and are unsafe. It is necessary to study the shear behavior of large-size reinforced concrete beams because of insufficient data in the test data. In this paper, the shear behavior of large-size reinforced concrete beams under concentrated load is studied by combining the project of National Natural Science Foundation of China (50778034) and the key project of National Natural Science Foundation of China (50838001). The main contents are summarized as follows:
(1) The effect of section height on shear capacity of reinforced concrete beams without web reinforcement is studied by shear test under concentrated load. The results show that the cracking shear strength and ultimate shear strength of the specimens exhibit obvious size effect. The cracking shear strength decreased by 31% and 34% while the ultimate shear strength decreased by 26% and 41%. respectively.
(2) The influence of longitudinal reinforcement ratio on shear capacity of large reinforced concrete beams without web reinforcement under concentrated load is studied. The results show that the change of longitudinal reinforcement ratio has a greater influence on shear performance of beams without web reinforcement under the condition of low longitudinal reinforcement ratio. The shear strength increased by 26%, and the ultimate shear strength increased by 73%.
(3) The influence of different types of web reinforcement and web reinforcement configuration on shear capacity of large-size reinforced concrete beams under concentrated load is studied for the specimens with horizontal longitudinal reinforcement along the beam height or hoops at the minimum hoop ratio. The ultimate shear strength of beams with horizontal longitudinal reinforcement along the beam height is increased by 14% and that of beams with stirrups according to the minimum stirrup ratio can disperse cracks and increase the ultimate shear strength by 66%.
(4) The effect of section height on the spacing of diagonal cracks is studied. The results show that the average spacing of diagonal cracks at the height of barycenter of longitudinal reinforcement is independent of section height and is related to the protective layer of specimens. The average spacing of diagonal cracks at half height of section is related to the height of section, showing a certain size effect. The average crack spacing at the center of gravity of longitudinal bars is 258 mm and 243 mm respectively, which is 4.3 times and 4.1 times of the thickness of protective layer, and the average crack spacing at half height of section is 192 mm and 450 mm respectively.
(5) The effects of different section positions, section heights, longitudinal reinforcement ratio and web reinforcement on the width and development velocity of inclined cracks were studied. With the increase of reinforcement ratio and the decrease of longitudinal reinforcement ratio, the width and velocity of inclined crack can be effectively limited by the arrangement of web reinforcement at the same section height.
(6) The shear capacity provided by concrete in the compression zone of beams without web reinforcement during loading is studied. The results show that the shear ratio of concrete in the compression zone decreases with the increase of section height and longitudinal reinforcement ratio.
(7) Combining with the shear test database, an empirical formula is proposed on the basis of the Chinese code formula, with emphasis on the size effect and longitudinal reinforcement ratio.
(8) Based on the cross-section analysis, a formula for calculating the shear capacity of reinforced concrete beams with large shear span ratio without web reinforcement is proposed. Based on the shear test database, the GB50010-2010 code, ACI318-08 code, CSA A23.3-04 code and the formula in this paper are compared and studied by using the comparative analysis method and defect number analysis method. The results of GB50010-2010 code and AC318-08 code are unsafe. The predicted results of CSA A23.3-04 code and the formula in this paper are more accurate and less discrete.
(9) Combining with a shear failure example of reinforced concrete thick slab bridge and the experimental data of large-scale beams and thick slabs collected, the safety of shear calculation formulas for non-Web reinforcement members in Chinese code GB50010-2010 is analyzed, and the influence of minimum stirrup ratio and longitudinal distribution of reinforcement on shear capacity of members is discussed. It is shown that the influence of section height on shear capacity can not be fully considered in the code, although the dimension effect coefficient is introduced in the code. The minimum stirrup ratio stipulated in the code can effectively avoid shear failure of large-scale members, while the longitudinal distributed steel bars can not effectively avoid shear failure of non-webbed members with height greater than 1000mm.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU375.1
本文编号：2216933
[Abstract]:The safety of large-size reinforced concrete beams (non-deep beams) and thick slabs, which often appear in engineering projects, will have a great impact on the safety of the whole structure. The research shows that ACI code and current code in China do not consider the size effect of large-size beams and are unsafe. It is necessary to study the shear behavior of large-size reinforced concrete beams because of insufficient data in the test data. In this paper, the shear behavior of large-size reinforced concrete beams under concentrated load is studied by combining the project of National Natural Science Foundation of China (50778034) and the key project of National Natural Science Foundation of China (50838001). The main contents are summarized as follows:
(1) The effect of section height on shear capacity of reinforced concrete beams without web reinforcement is studied by shear test under concentrated load. The results show that the cracking shear strength and ultimate shear strength of the specimens exhibit obvious size effect. The cracking shear strength decreased by 31% and 34% while the ultimate shear strength decreased by 26% and 41%. respectively.
(2) The influence of longitudinal reinforcement ratio on shear capacity of large reinforced concrete beams without web reinforcement under concentrated load is studied. The results show that the change of longitudinal reinforcement ratio has a greater influence on shear performance of beams without web reinforcement under the condition of low longitudinal reinforcement ratio. The shear strength increased by 26%, and the ultimate shear strength increased by 73%.
(3) The influence of different types of web reinforcement and web reinforcement configuration on shear capacity of large-size reinforced concrete beams under concentrated load is studied for the specimens with horizontal longitudinal reinforcement along the beam height or hoops at the minimum hoop ratio. The ultimate shear strength of beams with horizontal longitudinal reinforcement along the beam height is increased by 14% and that of beams with stirrups according to the minimum stirrup ratio can disperse cracks and increase the ultimate shear strength by 66%.
(4) The effect of section height on the spacing of diagonal cracks is studied. The results show that the average spacing of diagonal cracks at the height of barycenter of longitudinal reinforcement is independent of section height and is related to the protective layer of specimens. The average spacing of diagonal cracks at half height of section is related to the height of section, showing a certain size effect. The average crack spacing at the center of gravity of longitudinal bars is 258 mm and 243 mm respectively, which is 4.3 times and 4.1 times of the thickness of protective layer, and the average crack spacing at half height of section is 192 mm and 450 mm respectively.
(5) The effects of different section positions, section heights, longitudinal reinforcement ratio and web reinforcement on the width and development velocity of inclined cracks were studied. With the increase of reinforcement ratio and the decrease of longitudinal reinforcement ratio, the width and velocity of inclined crack can be effectively limited by the arrangement of web reinforcement at the same section height.
(6) The shear capacity provided by concrete in the compression zone of beams without web reinforcement during loading is studied. The results show that the shear ratio of concrete in the compression zone decreases with the increase of section height and longitudinal reinforcement ratio.
(7) Combining with the shear test database, an empirical formula is proposed on the basis of the Chinese code formula, with emphasis on the size effect and longitudinal reinforcement ratio.
(8) Based on the cross-section analysis, a formula for calculating the shear capacity of reinforced concrete beams with large shear span ratio without web reinforcement is proposed. Based on the shear test database, the GB50010-2010 code, ACI318-08 code, CSA A23.3-04 code and the formula in this paper are compared and studied by using the comparative analysis method and defect number analysis method. The results of GB50010-2010 code and AC318-08 code are unsafe. The predicted results of CSA A23.3-04 code and the formula in this paper are more accurate and less discrete.
(9) Combining with a shear failure example of reinforced concrete thick slab bridge and the experimental data of large-scale beams and thick slabs collected, the safety of shear calculation formulas for non-Web reinforcement members in Chinese code GB50010-2010 is analyzed, and the influence of minimum stirrup ratio and longitudinal distribution of reinforcement on shear capacity of members is discussed. It is shown that the influence of section height on shear capacity can not be fully considered in the code, although the dimension effect coefficient is introduced in the code. The minimum stirrup ratio stipulated in the code can effectively avoid shear failure of large-scale members, while the longitudinal distributed steel bars can not effectively avoid shear failure of non-webbed members with height greater than 1000mm.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU375.1
【引证文献】
相关期刊论文 前1条
1 车轶;于磊;;剪力作用下钢筋混凝土大尺寸无腹筋构件安全性研究[J];建筑结构学报;2014年02期
，本文编号：2216933
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