【作者】 张珽；

【导师】 沈成武； 谢奇；

【作者基本信息】 武汉理工大学 ， 工程力学， 2003， 硕士

【摘要】 桥梁是一种复杂的空间结构，特别是预应力混凝土桥梁。在悬臂施工中，挠度的控制是施工成功与否的关键之一，而徐变引起的变形及内力重分布是挠度控制的一个难点。混凝土徐变的发生是受力混凝土对所受载荷的一种“屈服”，然而影响混凝土徐变的不仅仅是载荷，还有许多的不定因素、非线性因素，如预应力的施加及其损失等。考虑徐变后结构的挠度计算是极其复杂的，因为它包含了包括混凝土徐变在内的许多因素，而且即使计算出预拱度，在施工之前也应将计算数据并与设计值比较，从而发现问题。 在施工控制过程中，更应根据实测的标高数据调整施工过程，如立模标高、预应力索的张拉等。在每个施工阶段特别是在合拢前应计算出预应力损失以减少或消除合拢时所引起的不合理的附加内力。在超静定结构中，结构的变形和内力都会因徐变而随时间不断变化，对于实际的工程结构，结构的整体总是分阶段建造起来的，某些荷载(如自重)也是在结构建造过程中分阶段作用在不断生长的结构上的。根据徐变的基本特性可知，徐变在混凝土早期和加载初期发展较快，所以要较准确地确定结构的内力和变形，按照施工过程进行徐变分析才有可能。对于施工周期较长的大跨度桥梁，由于结构自重占整个长期荷载的大部分，各部分混凝土龄期差别很大，讨论施工过程的徐变受力分析，不论从结构的安全性还是从结构的适用性来考虑都是很有必要的。 为了使结构分析更接近桥梁结构的真实工作状况，最好把它们模拟成由三维实体元等组成的空间组合结构模型进行计算，给施工提供指导。现代计算机和软件系统的发展，为这种大计算量的分析工作提供了可能。在目前可采用有限元通用程序进行模拟，而这需要为其提供参数依据。因此，从试验及工程实际出发来研究混凝土的徐变性能，用得到的数据而来进行计算分析，从而达到对施工挠度进行监控的目的。事实证明，这一方法更直接有效。而且做好混凝土的徐变试验，对悬臂施工也是很有帮助的。本文将在徐变时效分析理论的基础上，结合实际施工情况，通过对不同龄期的混凝土徐变特性的试验，利用有限元软件进行节段的模拟分析，对施工起到良好的指导作用。更多还原

【Abstract】 The bridge is a kind of complicacy spatial structure, especially PC Bridge. The deflection’s control is very important during the cantilever’s construction. But the re-distribution of strain and inner force causing by creep caused difficulty to the deflection control. The occurrence of the concrete creep can be regarded as concrete "accept defeat" for the force. However not only the force influence concrete’s creep, but also many agents such as certain agent, nonlinear agent, latent agent, and with some interact agents such as prepare stress’s infliction and its loss. The deflection’s computation is complicacy when considered the agents included concrete creep. So we should compare the calculation results with design date before construction to find the problem.We should continually adjust the elevation date in construction control to reduce the error. In redundancy structure, the structure’s distortion and strain will change along with time because of creep. According to the characteristic of concrete’s creep, the creep grows quickly in the concrete’ earlier age. For the long of bridge’s construction period, the concrete’s age of different part are discrepantly. So it is necessary to analyze concrete’s creep in construction course.To make the structural analysis approach true condition, it is best to simulate the bridge structure to air space composite structure form, so it can offer instruction for construction. Modern calculating machine and developing of software system make the big computation possible. For supervising and controlling of the deflection of construction, we may use the date get from the test and practicality to have computation analysis with FEM. It proof that this device is more direct to validate. Based on the time effect theory of creep and combined the test and the actual construction circumstance, the paper may be helpful to construction for it is analyzed and simulated by FEM.更多还原