混凝土桩基的桥台整体式无缝桥抗震性能与设计计算方法

There are no joints and bearings for Jointless Bridge while abutments integrate with girders, which make its structure simple and convenient to construct and maintain reasonably, and also make it sustainable and durable. Moreover, this type of bridge can provide a favorable integrality and seismic performance that the girders do not too easy to fall down under the impact of tsunami, flood and earthquake after monolithic with abutment. That is also to say light earthquake cannot damage Jointless bridge while rare earthquake cannot destroy and crush them. However, the piles of abutment are one of the most disadvantageous components compared to Joint Girder Bridges. Therefore, in order to accommodate with the requirement of seismic resistance, the piles of abutment are usually adopted H-shaped rolled steel in foreign developed countries. . Nevertheless, in our country, most of Jointless Bridges and huge numbers of medium or small Concrete Girder Bridges that are going to be integrated usually used concrete piles. The flexural stiffness and deformation behavior of concrete piles are different especially the damage modes under the effect of medium earthquake compare to rolled steel one, which are short of discussed thoroughly and systemically under seismic effect. The Guide Specifications for Seismic Bridge Design in our country do not present the method of how to design and calculate the seismic shear force yet. . Therefore, a kind of Integral Abutment Joint Bridge with concrete piles are selected as objective to study its seismic response and failure modes, and to reveal energy dissipative mechanism as well as seismic shear force distribution under the tests of dynamic interaction of structural abutment-piles-soils and shaking table tests of earthquake simulator of whole Jointless Bridge. Then, a displacement-based simplified calculation of response spectrum of equivalent stiffness and damping is presented based on the results of experiments and finite element method researches as well as theoretic analysis. Finally, a reasonable seismic conformation and configuration that embeds micro-piles into abutment and its soil is provided. . The results will have significant social meaning and application-value in the sustainability and durability of bridge, which also can present the technical support for the application and the basic theory foundation for the Guide Specification of this kind of Jointless Bridges in earthquake region.

无缝桥整体性好、行车舒适，后期养护维修少，地震作用下不易落梁，“小震不坏、大震不倒”，具有可持续、高耐久与较强的防灾减灾能力。不过，桥台桩基是此类型桥梁的最不利部位。国外无缝桥的桥台桩基多采用H型钢，然而，我国主要以混凝土桩为主，其在“中震可修与易损”性上存在一定差异。目前，对混凝土桩基的无缝桥抗震性能尚缺乏深入系统的研究，抗震规范也未给出相应的设计计算方法，影响了其应用与发展。为此，本项目以桥台混凝土桩基的整体式无缝桥为对象，通过对桥台结构-桩-土动力相互作用以及全桥的地震模拟振动台三台阵试验研究以及有限元分析，研究其抗震性能、耗能机理、破坏模式以及内力分配与传力机制，建立基于位移的等效刚度-阻尼反应谱简化计算方法，提出桥台微型桩的构造措施来提高其抗震性能。研究成果可望为此类型桥梁在地震区的应用提供技术支撑，为相关规范的制定提供理论依据，对我国桥梁可持续建设具有重要的社会意义和应用价值。

本项目以我国常用的混凝土桩基为对象，通过拟静力试验、振动台试验、理论推导和数值模拟等手段，深入研究基于位移的混凝土桩基整体桥受力性能和抗震设计计算方法。本项目开展了系列研究，如桩基材料（H型钢、RC混凝土桩、PC预应力混凝土桩、PHC高强混凝土管桩、CFST钢管混凝土桩、UHPC超高性能混凝土桩等）、截面类型（圆形、圆管形、矩形和H型等四种）以及配筋率、轴压比和预应力度等共计20余根模型桩的拟静力试验以及有限元研究，研究了桩-土体系的相互作用规律和桩基的抗震性能。同时，开展了整体式桥台-桩基-土相互作用拟静力试验，主要研究了桥台、桩基的滞回性能与变形规律以及桥台-桩基-土三者相互作用机理等。研究表明，往复水平位移作用下桥台桩基会产生累积变形；同时，在台背与桩顶的一定宽度和深度范围内存在土体脱空现象，对于实际工程中产生桥头跳车、搭板沉降的原因不仅与台后土体的特性相关，还与桥台结构的受力机理相关。在此基础上，提出了基于位移的桩-土相互作用剪力平衡简便抗震计算方法和桩基的水平等效刚度计算方法。同时，基于福州大学地震模拟振动台，开展了不同材料、截面形状以及土层、埋深和配筋率等为参数的10余根桩基的地震模拟振动台试验研究，分析了强震作用下液化砂土中桩基的动力响应特性，研究了桩-土体系的周期、频率、振型、阻尼比以及桩身应变、加速度、弯矩、变形、桩周土抗力等，给出了较实用的桩-土体系动力相互作用p-y曲线。此外，开展了无伸缩缝桥梁抗震性能地震模拟振动台三台阵试验和有限元研究。研究表明，无缝桥抗震性能明显要好于有缝桥，同时提出了合理的抗震设计与构造措施，为实际工程的应用提供了技术支撑。.本项目提出了基于位移的混凝土桩基整体桥抗震设计计算方法，获国家已授权发明专利10项、实用新型专利24项，专利应用技术成果转让3项，发表学术论文31篇（其中SCI/EI收录18篇），省级标准1项，出版专著1部。形成了以系列专利、论文、专著和技术标准等为支撑的创新性研究成果，取得了显著的社会、技术和经济效益。研究成果可望为我国地震区大量中小跨径桥梁的建设和改造时采用此类型桥梁的设计与应用提供理论基础，为无伸缩缝桥梁规范的制定提供参考与借鉴，并为推动无缝桥的技术创新提供科学依据，尤其是对于云贵川等地质灾害复杂地区和强震区并可能伴有海啸或洪水等次生灾害地区的桥梁建设具有重要的社会意义和应用价值。