Development of smart integral bridges

桥面和桥台墙相结合的整体桥梁的使用已经使用了几十年。然而，他们目前的设计很大程度上基于PD6694指南，这涉及到大量的经验主义和不确定性。这在很大程度上是由于未知的应力状态和桥台墙后回填土的应力-应变行为。随着桥梁跨度的增大，设计可以变得更加保守。同样值得注意的是，有轴承的老桥在其服务的后期可能会停止并像一个完整的桥梁一样，在桥台墙壁和后面的土壤回填上施加类似的载荷。减少桥梁的碳足迹，同时提供可持续的、有弹性的、在气候变化下强健的公路基础设施，这是一个公认的需求。本提案旨在研究桥梁和桥台的整体设计，最终目的是在这些桥梁的建设过程中通过适当部署智能仪器来改进设计，减少维护和增加检查间隔。根据这一观点，研究计划分为三个相互依存的阶段。第一阶段：在桥梁施工期间部署智能仪器：在这一阶段，桥梁业主、设计师、承包商、英国公路局、学者和研究人员等利益相关者齐聚一堂，设计智能仪器的部署，以帮助监测甲板热膨胀、桥台墙接缝上的弯矩和剪力、桥台墙后面的土压力、回填土中的应变等。采用这种智能仪器的选定桥梁将进行5至10年的长期监测，并将涉及许多热循环。第二阶段：物理和数值模拟的发展：整体桥梁和回填体的简化物理模型将被高度仪器化，并在剑桥10米直径的大型梁离心机中进行测试。回填土的应变将直接使用高分辨率成像和geo-PIV软件进行记录。计划对5到6台离心机模型进行试验，以改变回填土、使用桥台墙后的土工泡沫块等。离心机测试的费用估计约为每次测试6000英镑。离心机数据将与现场数据进行比较，这些数据将在适当的时间间隔内从项目的第一期流出。此外，将使用有限元方法进行数值模拟，并根据离心机测试数据对这些模型进行校准。此外，校准的FE分析结果将与第一阶段的现场监测数据进行比较。第三阶段：设计指南的制定：在这一阶段，验证当前设计指南的有效性。为了最大限度地减少碳足迹，并生产出能够应对气候变化问题的弹性桥梁结构，该指南将被更新，以用于未来的整体桥梁设计。此外，预计使用更精心选择的回填材料，使用土工泡沫或土工格栅，可以进一步优化设计，以尽量减少台墙移动，从而在回填中产生大的应变。将研究使用这些土工合成材料截面的最佳厚度来减少土壤应变和任何随后的土壤变形的可能性。

The use of integral bridges with a combined bridge deck and abutment walls has been in use for many decades. However their current design is largely based on PD6694 guidelines, which involves a significant amount of empiricism and uncertainty. This is largely due to the unknown stress state and the stress-strain behaviour of the backfill soil behind the abutment walls. The designs can get more conservative with an increase in the span of the bridges. It is also worth noting that older bridges that have bearings can cease up and act like an integral bridge during later years of their service, applying similar loads on the abutment walls and the soil backfill behind these. There is a well-recognised need to reduce the carbon footprint of bridges while delivering a sustainable and resilient highway infrastructure that is robust under climate change. This proposal is aimed at investigating the integral bridge and abutment design with the ultimate aim of improving the design, reduce maintenance and increase the inspection intervals with suitable deployment of smart instrumentation during the construction of these bridges. With this view, the research proposal is divided into three interdependent phases.Phase I: Deployment of smart instrumentation during bridge construction: In this phase the stakeholders such as the bridge owners, designers, contractors, Highways England, the academics and the research staff are brought together to design the deployment of smart instrumentation that can help with monitoring of thermal expansion of decks, bending moments and shear forces on the deck-abutment wall joints, earth pressures behind the abutment wall, strains mobilised in the backfill soil etc. The selected bridges with this smart instrumentation will be monitored over a long period of 5 to 10 years and will involve many thermal cycles.Phase II: Development of physical and numerical modelling: Simplified physical models of the integral bridges and the backfill that are highly instrumented will be developed and tested in the large 10m diameter beam centrifuge at Cambridge. Soil strains in the backfill will be recorded directly using highresolution imaging and use of the geo-PIV software. It is planned that about 5 to 6 centrifuge models will be tested varying the backfill soils, use of geo-foam blocks behind the abutment wall etc. The cost of the centrifuge testing is estimated at about £6k per test. The centrifuge data will be compared to field data, flowing from Phase I of the project at appropriate intervals. In addition, numerical modelling using the finite element method will be carried out and these models will be calibrated against the centrifuge test data. Also the results from the calibrated FE analyses will be compared to field monitoring data flowing from Phase I.Phase III: Development of design guidelines: In this phase the validity of the current design guidelines is verified. With the view of minimising the carbon footprint and producing a resilient bridge structure that can cope with climate change concerns, the guidelines will be updated for use in future integral bridge design. It is also anticipated that use of more carefully chosen backfill materials with use of geofoams or geo-grids, the designs can be further optimised to minimise the abutment wall movement inducing large strains in the backfill. The possibility of using an optimal thickness of these geo-synthetic material sections to reduce soil strains and any subsequent soil deformation will be investigated.