预应力混凝土梁受剪性能研究

发布时间：2018-10-13 17:13

【摘要】：根据对大跨径预应力混凝土箱梁桥的病害调查可知,跨中下挠过大和腹板斜裂缝问题常常是“并发症”。腹板斜裂缝是结构性裂缝,属于受剪基本理论范畴。目前,国内外已有的混凝土受剪性能试验均偏重于承载力研究,对于斜裂缝出现之后的剪切变形影响关注较少,且没有一个统一的理论能够完整地反映混凝土结构的受剪性能。本文从混凝土结构的受剪基本理论入手,同时开展钢筋混凝土和预应力混凝土梁的受剪承载力研究,重点探究斜向开裂后剪切变形对预应力混凝土梁跨中挠度的影响,最后在有限元软件中定量分析了斜裂缝开展对实桥跨中挠度的影响。本文研究主要取得了如下成果：(1)收集了216根钢筋混凝土有腹筋梁剪切试验数据,分析讨论了受剪承载力随着剪跨比、截面有效高度、混凝土抗压强度、纵筋率、配箍特征值等因素变化的基本规律。基于桁架-拱模型,考虑变形协调条件,推导了能够考虑全剪跨比影响的钢筋混凝土梁受剪承载力计算公式。采用统计特征值法、影响因素法对建议方法以及各国设计规范计算结果进行了分析比较,结果表明建议方法预测精度较高。(2)基于桁架-拱模型,分别考虑预应力以及受压翼缘对受剪承载力的提高作用,推导了预应力混凝土有腹筋梁受剪承载力计算公式。收集了115根预应力混凝土有腹筋梁剪切试验数据,分析讨论了受剪承载力随剪跨比、截面有效高度、混凝土抗压强度、纵筋率、配箍特征值以及截面形心处预压应力等因素变化的基本规律。采用统计特征值法、影响因素法对建议方法以及各国设计规范的计算结果进行了分析比较,结果表明建议方法预测精度较高。(3)考虑了斜裂缝间混凝土拉应力影响,推导了预应力混凝土梁有效剪切刚度计算公式。根据项目组以往开展的6根预应力混凝土矩形梁和文献中的4根工字型试验梁的剪切性能试验,验证了建议有效剪切刚度计算方法的适用性,并与规范GB 50010-2010计算的弯曲变形进行了比较。在对试验梁各阶段变形比的分析结果表明,对于预应力混凝土薄腹梁,斜向开裂后的剪切变形对挠度的影响不可忽略。此外,分析评估了曲线预应力筋角度、普通钢筋配筋率、剪跨比、跨高比、有效预应力、混凝土抗压强度及配箍率等因素对斜裂缝出现之后的剪切变形的影响。(4)以苏通大桥辅桥预应力混凝土连续刚构为背景,采用有限元分析软件MIDAS/Civil,比较分析了混凝土收缩徐变、预应力损失及斜裂缝开展对大跨箱梁桥跨中挠度的影响。分析结果表明,收缩徐变模式的选取对跨中挠度的影响较大,预应力束中悬臂束的预应力损失对跨中挠度的影响最为明显,而斜裂缝出现之后的剪切变形对跨中挠度的影响不可忽略。
[Abstract]:According to the disease investigation of long span prestressed concrete box girder bridge, it is often a "complication" that the overlong span deflection and the inclined crack of web plate are often "complications". The web oblique crack is a structural crack, which belongs to the basic theory of shear. At present, the existing tests of shear behavior of concrete at home and abroad focus on the research of bearing capacity, pay little attention to the influence of shear deformation after the occurrence of oblique cracks, and there is no unified theory to reflect the shear behavior of concrete structures completely. In this paper, the shear capacity of reinforced concrete and prestressed concrete beams is studied based on the basic shear theory of concrete structures, and the influence of shear deformation on the deflection of prestressed concrete beams is studied. Finally, the effect of inclined crack development on the deflection of real bridge span is quantitatively analyzed in finite element software. The main achievements of this paper are as follows: (1) the shear test data of 216 reinforced concrete beams with web reinforcement are collected, and the shear bearing capacity with shear span ratio, effective height of section, compressive strength of concrete and ratio of longitudinal reinforcement are analyzed and discussed. The basic law of the change of the hoop characteristic value and other factors. Based on the truss-arch model and considering the condition of deformation coordination, a formula for calculating the shear capacity of reinforced concrete beams considering the effect of total shear span ratio is derived. The statistical eigenvalue method and the influence factor method are used to analyze and compare the calculation results of the suggested method and the design codes of various countries. The results show that the proposed method has a high prediction accuracy. (2) based on truss-arch model, the proposed method is based on the truss-arch model. Considering the effect of prestress and compression flange on the shear capacity, the formulas for calculating the shear capacity of prestressed concrete beams with web reinforcement are derived. The shear test data of 115 prestressed concrete beams with web reinforcement are collected, and the shear bearing capacity with shear span ratio, the effective height of section, the compressive strength of concrete and the ratio of longitudinal reinforcement are analyzed and discussed. The basic law of the change of the characteristic value of the hoop and the preloading stress at the center of the cross section. The statistical eigenvalue method and the influence factor method are used to analyze and compare the calculation results of the suggested method and the design codes of various countries. The results show that the proposed method has a high prediction accuracy. (3) the effect of tensile stress on concrete between inclined cracks is taken into account. The formula of effective shear stiffness of prestressed concrete beam is derived. According to the shear behavior tests of 6 prestressed concrete rectangular beams and 4 I-shaped test beams in the literature, the applicability of the proposed effective shear stiffness calculation method is verified. The bending deformation calculated by GB 50010-2010 is compared with that calculated by code GB 50010-2010. The results show that the shear deformation of prestressed concrete thin web beam after diagonal cracking can not be ignored. In addition, the angle of curved prestressed reinforcement, the ratio of reinforcement to reinforcement, the ratio of shear span to span, the ratio of span to height, the effective prestressing force are analyzed and evaluated. The influence of concrete compressive strength and hoop ratio on the shear deformation after the occurrence of oblique cracks. (4) taking the continuous rigid frame of prestressed concrete of Sutong Bridge as the background, the shrinkage and creep of concrete are compared and analyzed by using the finite element analysis software MIDAS/Civil,. The influence of prestress loss and inclined crack development on the midspan deflection of long span box girder bridge. The results show that the selection of shrinkage and creep mode has a great influence on the deflection in the span, and the prestress loss of the cantilever in the prestressing beam has the most obvious effect on the deflection in the span. However, the influence of shear deformation on the deflection in the span can not be ignored after the oblique crack appears.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU378.2

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