拓宽T梁桥基础沉降差及低刚度支座应用研究

发布时间：2018-05-18 19:46

本文选题：拓宽T梁桥 + 容许沉降差　；参考：《长安大学》2017年硕士论文

【摘要】：公路桥梁改扩建日益增多,拓宽桥新旧部分连接后基础不均匀沉降致使上部结构产生附加应力,影响桥梁使用和安全。实际桥梁拓宽工程复杂多样,目前在公路拓宽桥的研究中,对沉降应力和控制标准都非常重要的沉降模式并没有被明确定义和分类,沉降控制标准主要集中在拓宽简支梁或连续梁桥,基本没有将二者的进行结合对比分析以适应实际工程。此外,应对拓宽桥基础不均匀沉降差的现行措施一般存在实施复杂、时间长或成本高等缺点,有待改进。为降低公路拓宽桥梁基础不均匀沉降给其造成的不利影响。将沉降模式划分为两类,依托某拓宽桥,建模计算分析了其基本受力性能,并在此基础上确定其沉降控制标准;最终提出一种新的沉降差应对措施,并分析了其合理性和优越性。论文主要研究如下:(1)基于部分典型拓宽桥沉降监测数据和已有研究结论,并分析了沉降模式差异的原因,将拓宽部分基础沉降简化分为两种,一是线性沉降,即拓宽部分基础由内侧向外侧沉降值逐渐增大,基本呈线性变化,最外侧沉降可视为一个累加值;二是均匀沉降,即拓宽部分基础沉降值基本接近,沉降可视为连接处新旧T梁的相对沉降值。(2)依托某拓宽T梁桥,采用Midas FEA和Midas Civil建模分析,得出T梁桥拓宽受力最不利位置在支点竖向截面接缝处上缘,新旧T梁最佳受力连接方式为接缝处跨内设置横隔板,而梁端不设置,桥墩最不利沉降工况为拓宽部分桥墩全部参与沉降。(3)采用前文得到的最不利沉降工况和最佳连接方式,以上部结构最大拉应力是否超过设计混凝土抗拉强度标准值作为控制标准,得出简支和连续T梁桥拓宽部分线性沉降下容许沉降差分别为8mm和7mm,均匀沉降下容许沉降差为3mm,均匀沉降情况即任意相邻两片T梁,尤其是接缝处新旧T梁间的相对沉降差要控制在3mm以内。(4)为提高拓宽T梁桥承受基础沉降差的能力,提出在旧桥连接中梁(原旧桥边梁)下设置轴向刚度略低的支座,并称为低刚度支座。应用低刚度支座后,其不利影响可以忽略,但是对拓宽T梁桥在典型沉降工况下的最大应力降低幅度达12.5%—38.1%,对简支和连续T梁桥拓宽部分线性沉降下容许沉降差均提高2mm分别至10mm和9mm,均匀沉降下均提高1mm至4mm,说明设置低刚度支座能够明显改善拓宽T梁桥基础沉降差对上部结构的不利影响,并且还具有实施简单、时间短和成本低等优点,值得推广应用。
[Abstract]:The construction and extension of highway bridges are increasing day by day. The uneven settlement of the foundation after widening the new and old parts of the bridges causes additional stress in the superstructure and affects the use and safety of the bridges. The actual bridge widening project is complex and diverse. At present, in the research of highway widening bridge, the settlement model, which is very important to settlement stress and control standard, has not been clearly defined and classified. The settlement control standard is mainly focused on widening simply supported beam or continuous beam bridge. In addition, the existing measures to widen the uneven settlement of the bridge foundation generally have the disadvantages of complex implementation, long time and high cost, which need to be improved. In order to reduce the adverse effect caused by uneven settlement of widening bridge foundation. The settlement mode is divided into two categories, and based on a widening bridge, the basic force performance of the bridge is modeled and analyzed, and the settlement control standard is determined on this basis. Finally, a new settlement difference response measure is put forward. Its rationality and superiority are analyzed. The main research contents are as follows: (1) based on the monitoring data of settlement of some typical widening bridges and the existing research conclusions, and analyzing the reasons for the difference of settlement modes, the settlement of widening part of foundation is simplified into two kinds, one is linear settlement, the other is linear settlement. That is to say, the settlement value of the widening part of the foundation increases gradually from the inside to the outside, showing a linear change, the most lateral settlement can be regarded as an accumulative value, the second is the uniform settlement, that is, the settlement value of the widening part of the foundation is close to that of the widening part. The settlement can be regarded as the relative settlement value of the old and new T-beam at the junction. Based on a widening T-beam bridge, by using Midas FEA and Midas Civil modeling and analysis, it is concluded that the most disadvantageous position of the widening force of the T-beam bridge is at the upper edge of the joint of the vertical section of the fulcrum. The best way of connecting the old and new T-beams is to set the transverse diaphragm at the joint, but not at the end of the beam. The most unfavorable settlement condition of the pier is to widen the partial pier to participate in the settlement. 3) the most unfavorable settlement condition and the best connection mode obtained from the previous paper are adopted. Whether the maximum tensile stress of the superstructure exceeds the standard value of the designed concrete tensile strength is taken as the control standard. It is obtained that the allowable settlement difference is 8mm and 7mm for the widening partial linear settlement of simply supported and continuous T-beam bridges, and 3mm for uniform settlement. In particular, the relative settlement difference between the new and old T-beams at the joint should be controlled within 3mm. 4) in order to improve the ability of widening the capacity of T-beam bridge to bear the settlement difference of foundation, it is proposed to set up a support with lower axial stiffness under the middle beam of the old bridge connection (the original side beam of the old bridge). They are called low stiffness supports. The adverse effects of the application of low stiffness bearings can be neglected. However, the maximum stress of widening T-beam bridge under typical settlement condition is 12.5-38.1. The allowable settlement difference of simply supported bridge and continuous T-beam bridge under widening partial linear settlement is increased to 10mm and 9mm, respectively, and even settlement is increased under uniform settlement. From 1mm to 4mm, it shows that setting low stiffness supports can obviously improve the adverse effect of widening T-beam bridge foundation settlement difference on the superstructure. It also has the advantages of simple implementation, short time and low cost, so it is worth popularizing and applying.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U443

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