【作者】 孙尧州；

【导师】 张耀庭；

【作者基本信息】 华中科技大学 ， 结构工程， 2006， 硕士

【摘要】 随着预应力技术的发展,预应力混凝土结构在土木工程中的应用日益广泛。预应力混凝土梁与普通钢筋混凝土梁相比,由于结构采用了高强度材料,显得更加纤细,因而其挠度计算尤为重要。有关预应力混凝土梁的挠度计算,国内外学者提出了不少计算方法,但几乎都是以满足工程要求为前提的近似经验公式。因此,对预应力混凝土梁的挠度和刚度问题开展深入研究显得十分必要。论文首先采用我国《混凝土结构设计规范》(GB50010-2002)和《美国混凝土房屋建筑规范》(ACI318-99)建议的挠度公式,对预应力混凝土梁进行了计算,并将计算结果与试验结果进行了对比。计算表明:GB50010-2002公式的计算结果在梁未开裂时与试验结果比较吻合,美国ACI318-99中的计算公式对开裂后的计算相对准确。但这两种规范对处于开裂荷载附近的计算均不是很理想,而且,对于钢筋屈服后的挠度计算,上述规范公式的计算值均不能很好地与试验结果吻合。随后利用大型有限元程序ANSYS对梁进行了全过程非线性分析,模拟结果与试验结果吻合较好,但在梁接近破坏时也存在较大误差,主要原因是模拟约束与试验条件之间存在差异。因此,寻求合理的支座约束需要做进一步的研究。针对规范经验公式和ANSYS分析所存在的问题,论文采用试验、数值分析和理论分析相结合的方法,考虑几何非线性和材料非线性对预应力梁挠度的影响,研究预应力混凝土梁挠度及短期刚度的计算方法,最终推导了基于有效惯性矩法的挠度计算公式。该公式能较好地模拟三折线荷载挠度曲线,但是在开裂荷载和屈服荷载附近的计算并不是很理想,而且计算公式过于复杂,需要作进一步简化。更多还原

【Abstract】 With the development of prestressing, more and more prestressed concrete structures were extensively used in civil engineering. Compared with reinforced concrete beams, the prestressed ones are more slimmer due to the usage of high strength materials, so it is very important to study their deflection. Many methods on calculation of deflection of prestressed concrete beams have been proposed both at home and abroad, most of which were empirical formulas for approximate engineering calculation. Thus, further study on deflection and stiffness of the prestressed beams is necessary.First, formulas on calculation of deflection specified in both the Chinese Concrete Design Code GB50010-2002 and ACI318-99 were adopted, and then compared calculation results with test results. It is found that calculation results from formulas specified in GB50010-2002 agree with the test results on uncracked prestressed concrete beams to a great extent, and formulas specified in ACI318-99 are more suitable for calculation of those postcracked prestressed concrete beams, but formulas in both codes are not ideal for the calculation of beams which are subjected to loads near the crack ones or ultimate ones. Subsequently, the whole process nonlinear analysis for prestressed concrete beams was carried out by finite element analysis software ANSYS, and results indicated that deflection simulated by ANSYS agreed with test results well except data near the ultimate loads. Error is mainly due to difference between restraints simulated by ANSYS and in experiments, so it’s need to search for more rational restraints.According to deficiency of empirical formulas in codes and analysis in ANSYS, the paper combined tests, theories and numerical analysis, took into account influence of geometrical non-linearity and material non-linearity on deflection. The method of calculating deflection and short-term stiffness on prestressed reinforced concrete beams was presented, and then formulas on deflection based on effective inertia method were induced. Compared with test results, it is found that formulas proposed in this paper could simulate tri-linear load-deflection curves to a great extent, but are not ideal for calculation of beams under loads near the crack ones and the yield ones too. Also, those formulas are so complex that they need to be simplified.更多还原