【摘要】：工程中常出現(xiàn)的大尺寸鋼筋混凝土粱(非深梁)及厚板等是否安全會(huì)對(duì)整個(gè)結(jié)構(gòu)的安全性產(chǎn)生重大影響。研究表明ACI規(guī)范及我國現(xiàn)行規(guī)范對(duì)大尺寸粱的截面尺寸效應(yīng)考慮不足,偏于不安全。同時(shí)我國規(guī)范受剪承載力計(jì)算公式所依據(jù)的試驗(yàn)數(shù)據(jù)中大尺寸梁的數(shù)據(jù)不充分,因此有必要對(duì)大尺寸鋼筋混凝土梁的受剪性能進(jìn)行研究。本文結(jié)合國家自然科學(xué)基金項(xiàng)目(50778034)和國家自然科學(xué)基金重點(diǎn)項(xiàng)目(50838001),對(duì)大尺寸鋼筋混凝土梁在集中荷載作用下的受剪性能展開了系統(tǒng)地試驗(yàn)研究和分析,主要內(nèi)容總結(jié)如下： (1)通過集中荷載作用下的受剪試驗(yàn),研究了截面高度對(duì)鋼筋混凝土無腹筋梁受剪承載力的影響。結(jié)果表明,試件的開裂剪切強(qiáng)度和極限剪切強(qiáng)度都呈現(xiàn)出明顯的尺寸效應(yīng)現(xiàn)象。以截面高度500mm的試件為基準(zhǔn),當(dāng)截面有效高度增加112%和158%時(shí),開裂剪切強(qiáng)度減小31%和34%,極限剪切強(qiáng)度減小26%和41%。 (2)以縱筋配筋率為參數(shù),研究了集中荷載作用下大尺寸鋼筋混凝土無腹筋梁受剪承載力的影響。結(jié)果表明,在縱筋配筋率較低的情況下,縱筋率的變化對(duì)無腹筋梁受剪性能的影響較大。與縱筋率0.67%的試件相比,縱筋率1.10%的試件開裂剪切強(qiáng)度提高26%,極限剪切強(qiáng)度提高73%。 (3)對(duì)試件沿梁高配置水平縱向鋼筋或按照最小配箍率配置箍筋,研究了不同的腹筋類型和腹筋配置對(duì)集中荷載作用下大尺寸鋼筋混凝土梁受剪承載力的影響。研究表明,腹筋的配置能夠提高試件的受剪承載力。與相同截面高度下的無腹筋梁相比,沿梁高配置水平縱向鋼筋的試件,極限剪切強(qiáng)度提高14%；按照最小配箍率配置箍筋的梁,能夠分散裂縫,極限剪切強(qiáng)度提高66%。 (4)研究了截面高度對(duì)斜裂縫間距的影響。研究表明,斜裂縫在縱筋重心高度處的平均裂縫間距與截面高度無關(guān),與試件保護(hù)層相關(guān)；斜裂縫在截面一半高度處的平均裂縫間距與截面高度相關(guān),表現(xiàn)出一定的尺寸效應(yīng)。對(duì)比截面高度500mrn和1200mm的試件,二者在縱筋重心高度處的平均裂縫間距分別為258mm和243mm,為保護(hù)層厚度的4.3倍和4.1倍；二者在截面一半高度處的平均裂縫間距分別為192mm和450mm。 (5)研究了截面不同位置、截面高度、縱筋配筋率和腹筋對(duì)斜裂縫寬度和開展速度的影響。研究表明,在相同剪應(yīng)力下,距梁頂0.5ho處的裂縫寬度和開展速度要大于裂縫尖端和縱筋重心位置處；試件斜裂縫的寬度和開展速度隨著截面高度的增加和縱筋配筋率的降低而增大；相同截面高度的情況下,腹筋的配置能夠有效的限制斜裂縫的寬度和開展速度。 (6)研究了無腹筋梁受壓區(qū)混凝上在加載過程中提供的受剪承載力。結(jié)果表明,受壓區(qū)混凝土提供的剪力占總剪力的比值,隨著截面高度和縱筋配筋率的增加而減小。 (7)結(jié)合受剪試驗(yàn)數(shù)據(jù)庫,在我國規(guī)范公式的基礎(chǔ)上提出了經(jīng)驗(yàn)公式,著重考慮了尺寸效應(yīng)和縱筋配筋率的影響。分析結(jié)果表明,對(duì)于大尺寸梁和低縱筋率梁,經(jīng)驗(yàn)公式的預(yù)測(cè)值精度較好,離散程度較小。 (8)通過截面分析,提出了大剪跨比鋼筋混凝土無腹筋梁受剪承載力計(jì)算公式。在受剪試驗(yàn)數(shù)據(jù)庫的基礎(chǔ)上,利用對(duì)比分析法和缺陷點(diǎn)數(shù)分析法對(duì)GB50010-2010規(guī)范、ACI318-08規(guī)范、CSA A23.3-04規(guī)范和本文公式進(jìn)行對(duì)比研究。結(jié)果表明,對(duì)于截面高度大于600mm和縱筋配筋率小于等于1.0%的無腹筋梁,GB50010-2010規(guī)范和ACI318-08規(guī)范計(jì)算結(jié)果偏于不安全。CSA A23.3-04規(guī)范和本文公式的預(yù)測(cè)結(jié)果較為準(zhǔn)確,且離散程度較小。 (9)結(jié)合一起鋼筋混凝土厚板橋梁的剪切破壞實(shí)例以及收集的大尺寸梁和厚板試驗(yàn)數(shù)據(jù),對(duì)我國混凝土規(guī)范GB50010-2010的無腹筋構(gòu)件抗剪計(jì)算公式的安全性進(jìn)行了分析,探討了最小配箍率和縱向分布鋼筋對(duì)構(gòu)件受剪承載力的影響。分析表明,規(guī)范公式雖然引入了尺寸效應(yīng)系數(shù),但尚不能充分考慮截面高度對(duì)受剪承載力的影響；規(guī)范規(guī)定的最小配箍率能夠有效避免大尺寸構(gòu)件發(fā)生剪切破壞,而縱向分布鋼筋則不能有效避免高度大于1000mm的無腹筋構(gòu)件的剪切破壞。
[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.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU375.1

【引證文獻(xiàn)】

相關(guān)期刊論文 前1條

1 車軼;于磊;;剪力作用下鋼筋混凝土大尺寸無腹筋構(gòu)件安全性研究[J];建筑結(jié)構(gòu)學(xué)報(bào);2014年02期

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本文編號(hào)：2216933