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在钢筋混凝土或预应力混凝土T梁桥的腹板竖向裂缝中,有一些并非在施工时出现,而是在长达1-2 a后才逐渐出现。为解释这些T梁桥腹板竖向裂缝形成过程中具有时间依赖性的现象,研究了截面收缩、徐变不一致分布与T梁竖向开裂的相关性。根据T梁截面的特点,考虑结构截面不同部位实际的配筋与理论厚度对收缩、徐变的不同影响。根据轴力等效转换及截面钢筋和混凝土变形协调的原则,推导了钢筋对收缩、徐变应变影响的理论系数,采用截面分层的方法考虑截面理论厚度沿梁高的变化,最后依据截面应变的平截面假定,推导了T梁截面收缩、徐变非一致分布效应导致的截面收缩、徐变自应力及其随时间变化的分层计算方法。实桥参数计算结果表明,T梁梁体纤薄,其顶板、腹板和马蹄的配筋和理论厚度存在较大差异,收缩、徐变在截面上容易形成不同步或差异较大的不一致分布情况。T梁截面收缩、徐变非一致分布是导致腹板竖向裂缝具有时间依赖性的重要因素,利用本文方法得到的竖向裂缝在时间轴上的形成过程与实际桥梁的裂缝出现的时间和位置情况基本吻合,验证了本文方法的有效性,为结构设计中考虑此因素提供了理论工具。
Some of the vertical cracks in the webs of reinforced concrete or prestressed concrete T-Beam bridges do not appear during construction, but only gradually after 1-2 a. In order to explain the time-dependent phenomenon of the vertical cracks in the webs of T-Beams, the correlation between the cross-section shrinkage, the non-uniform distribution of creep and the vertical cracking of T-beams was studied. According to the characteristics of T-beam section, the different effects of actual reinforcement and theoretical thickness on shrinkage and creep are considered in different parts of the structure section. According to the principle of equivalent transformation of axial force and the coordination of deformation between steel bar and concrete, the theoretical coefficient of the influence of steel bar on shrinkage and creep strain is deduced. The thickness of the section along the beam height is taken into account by the method of section stratification. Finally, , The stratified calculation method of cross-section shrinkage, creep self-stress and its variation with time due to the non-uniform distribution of T-beam cross-section is deduced. The calculation results of actual bridge parameters show that the beam body of T-beam is thin, and the reinforcement and theoretical thickness of roof, web and horseshoe are quite different. Shrinkage and creep easily lead to inconsistent or large disparities in the cross-section Happening. The inconsistent distribution of shrinkage and creep of T-beams is an important factor that causes the time-dependent vertical cracks in the webs. The formation process of the vertical cracks on the time axis and the actual time and position of the cracks in the actual bridges are basically the same The results show that the proposed method is valid and provides a theoretical tool for the structural design to consider this factor.