预应力RPC-RC柔性节段桩基础整体无缝桥的受荷性状和设计计算方法研究

Integral abutment and jointless bridge is one of the jointless bridges with the most advantages. Its foundation supporting abutment is usually flexible piles, such as H-shaped steel piles, in order to adapt the thermal deformation of superstructure. However, the steel pile does not conform to Chinese traditional RC pile. In addition, its corrosion-resistance and economic evaluation are not ensured yet. Therefore, this application proposes a new kind of so-called pre-stressed flexible and segmental pile consisting of upper RPC pile segment and lower normal RC pile segment, which is used as the supporting foundation for integral abutment. The upper part of the proposed combined pile has the properties of high-strength, high-ductility, high-corrosion resistance and high-hammering resistance which are comparable to steel pile or even better in terms of some key functions. This research first starts with the proportion design and manufacturing of a kind of RPC materials, followed by lab model experiment as well as in-situ full size experiment on the combined piles based on an equivalently trial design of a real bridge supported by H-shaped steel piles, in order to investigate the mechanical behavior and analytical calculation method of piles under vertical and horizontal loadings. Meanwhile, based on the various boundary conditions, the pile head will be mechanically connected to its supported superstructure to model the whole bridge structure. Based on that model, finally, a parametric analysis will be carried out to investigate the thermal deformation transfer path, internal force distribution and transfer mechanism, etc, in order to put forward the key design recommendations for both the pile foundation and the bridge supper structure as well as the simplified individual design methods for them. It is expected that this research outcomes will not only be a breakthrough of the bottleneck of integral abutment and jointless bridge engineering application, but also widening the RPC application towards underground engineering.

无缝桥中整体式桥台无缝桥梁的各种优点最多。为适应整体桥的各种纵向变形，一般以柔性H型钢桩作为桥台基础，但其抗腐蚀和经济性得不到保障，也不适于我国大量采用混凝土桩基础的实情。本项目提出一种由预应力超高性能混凝土（PRPC）桩与普通RC桩组合构成的柔性节段桩，充分利用其受压弯上段PRPC桩的高强、高韧、高耐腐和高抗锤击能力，达到不低于钢桩的主要使用功能。首先，优择一种可满足整体桥工作性能的RPC类材料，以一座整体桥的H型钢桩为原型，通过力学等代，试设计和制备柔性节段单桩模型；运用室内外加载试验和理论分析，研究其受荷特性；然后，将节段单桩与桥梁上部结构按不同约束边界条件进行联接，构建整桥力学分析模型；最后，以整桥的温变传递路径、内力分配与传递机制为控制目标，通过上下部结构的解耦，建立各自的简化计算方法和设计建议。研究结果将突破整体桥广泛应用的瓶颈，并为RPC类材料走向地下基础工程应用开辟新途径.

无缝桥中整体式桥台无缝桥梁的各种优点最多。为适应整体桥的各种纵向变形，一般以柔性H型钢桩作为桥台基础，但其抗腐蚀和经济性得不到保障，也不适于我国大量采用混凝土桩基础的实情。本项目提出一种由预应力超高性能混凝土（UHPC）桩与普通RC桩组合构成的柔性节段桩，充分利用其受压弯上段UHPC桩的高强、高韧、高耐腐和高抗锤击能力，达到不低于钢桩的主要使用功能。本研究将开展应用该概念的详细试设计，然后以试设计为原型，以UHPC-RC阶梯桩的水平恢复力滞回特性、水平位移吸纳和地震能量的耗散机理为重点，开展系统的试验和理论分析。研究主要内容包括（1）在正常使用极限状态下温度等变形的吸纳机理、桩土相互作用的传递方式和在上下桩段间的变形、内力分配关系；在低周循环往复荷载作用下结构的动力特性、地震响应及抗震机制；（2）采用室内动力模型试验的结果校准有限元分析模型，对主要设计参数进行敏感度分析，建立简化计算分析方式。.重要结果：（1）对于UHPC-RC阶梯桩，当UHPC段桩长比为16%~48%时水平受荷性能较好；阶梯桩上、下段桩身刚度比不宜小于0.25；UHPC截面厚度减小对水平承载能力、桩身内力和变形的影响均大于宽度影响；（2）HW-RC阶梯桩的桩身变形主要分布于上段桩，下段混凝土桩的变形较小，在变截面处会产生桩身应变的突变现象，且刚度比越小，应变突变越大，刚度比值增大，抗开裂能力变弱，建议阶梯桩的刚度比取0.5；（3）阶梯桩破坏位置均在变截面处，可通过设计使得变截面处为弯矩反弯点或采用节点加固构造，加固变截面延缓其开裂。.研究成果可为整体式无缝桥提供一种新型桩基形式，推动无缝桥梁设计理论的创新和完善，推动无缝桥在国内的应用与发展。