Numerical analysis on bearing capacity of middle pylon caisson foundation of Taizhou Bridge

Because of the computation difficulty of the bearing capacity of large underwater caisson foundation on thick overburden layer ground, the geotechnical software FLAC3D was utilized in the 3D numerical analysis on the bearing capacity of middle pylon foundation. From the computational results, it is concluded that the caisson foundation has a good bearing capacity on thick overburden layer ground and the bearing capacity can be improved assuming that the soil near the area of basal corner is reinforced.     

Introduction to steel pylon hoisting of Taizhou Yangtze Bridge

Taizhou Yangtze River Bridge is the first three-pylon two-span suspension bridge in the world. The middle pylon adopts deep water caisson foundation. The superstructure of the middle pylon employs herringbone shape along the bridge, and portal shape in the transverse direction for the first time in China. In this paper, the basic construction procedure, equipment, construction steps, the key construction technologies and methods of steel pylon are introduced.     

Taizhou Yangtze River Bridge—the first kilometer level three-pylon two-span suspension bridge in the world

Taizhou Bridge, located at the middle of Jiangsu Province, connecting Taizhou City and Zhenjiang City, started in Dec. 2007. The bridge is the first kilometer level three-pylon suspension bridge in the world, and it adopts longitudinal herringbone shape steel middle pylon for the first time in the world. The foundation of the middle tower is the deepest underwater caisson in soil on earth. A great many of technical innovations such as the design techniques of three-pylon suspension bridge,precisely locating and bottom-sealing techniques of the large scale caisson foundation, manufacturing, combination techniques of steel and concrete in the middle tower, welding of extra thick steel plate, manufacture and control techniques of abnormal sections of the middle tower and so on were introduced.     

Research on dynamic characteristics model test scheme for middle pylon of multi pylon multi span suspension bridges

Multi-pylon multi-span suspension bridge is a new type super flexible structure system, and the rigidity design of middle pylon is one of the main difficult technical issues. Due to the requirements of longitudinal rigidity, the structural form and the corresponding foundation type of middle pylon are different from those of the ordinary steel pylon, and the complicated dynamic characteristics make the calculation quite difficult. In this article, exploration has been made in selection of similarity ratio, selection of model materials, section simulation, restriction conditions simulation, fixing of mass blocks, fabrication scheme and testing method by taking into account different construction and working conditions such as restriction conditions and working environment of a 3-pylon suspension bridge, to conduct the test experimental design of the dynamic behavior of the middle pylon, with the purpose to reveal its dynamic characteristics and make comparison and analysis with theoretical assumptions, to provide basis for anti-wind and anti-seismic design and as a reference for the design and research of 3-pylon 2-span suspension bridges in the future.     

水泥搅拌桩在淤泥质软土路基中的试验与应用研究

用水泥搅拌桩对湖州市创业大道跨长湖申线大桥工程东引桥桥头软土路基进行了处理,随机抽取3根水泥搅拌桩进行了桩基静载试验,并对桥头段2个断面工后变形进行了监测。试验及监测结果表明:桩基各参数均符合地基处理的力学要求,地基承载力得到了有效的提高;路基沉降较缓慢,且变形速率在施工之后几个月逐渐变小,符合桥头地基的变形要求。     

陆上特大型沉井施工技术

泰州大桥主桥采用主跨2×1 080 m三塔两跨两锚碇悬索桥,其中南、北锚碇基础为特大型沉井,矩形平面尺寸为67.9 m×52.0 m,高度分别为41 m,57 m。针对锚碇基础覆盖层深厚、基础尺寸巨大、沉井下沉深度深等特点,通过施工技术的攻关,顺利完成了砂桩复合地基处理、沉井制作和拼装、钢壳沉井混凝土填充、混凝土沉井接高施工、水力机械冲吸式排水下沉和空气吸泥机吸泥下沉等多项施工工序,为今后陆上特大型沉井施工提供了借鉴。文章简要介绍了南、北锚碇陆上特大型沉井的施工技术。     

Research on key technologies in design of middle pylon of Taizhou Bridge

At the middle pylon of a three-pylon two-span suspension bridge, the effect of unbalanced loads on the adjacent spans may result in a series of technical bottlenecks in design, such as stability and anti-slippage between saddles and main cables. This article presents the researches conducted on structure selection and behavior characteristics of middle pylon, interaction mechanism between main cables and saddles and their anti-slippage safety performance, elastic and plastic stability analysis and safety assessment of steel middle pylon, and fatigue design load and method for steel pylon of Taizhou Bridge. According to the research results, a longitudinal inverted Y shape steel middle pylon is used in design, effectively solving many technical difficulties, and this type of pylon has become a suitable middle pylon structural form for many three-pylon two-span suspension bridges.     

可液化河谷场地不同形式梁式桥的地震反应

场地液化对河谷场地中不同结构体系、不同基础形式的梁式桥的地震反应可能具有不同程度的影响.针对该问题,以典型可液化河谷场地三跨梁式桥为背景,建立了二维场地-桥梁结构一体化有限元模型,包括群桩基础简支梁桥、群桩基础连续梁桥和桩柱式基础简支梁桥3种桥型,并进行非线性地震反应分析.从场地和桥梁震后变形、桩基础变形分布、桥墩漂移率、滑动支座位移和桥台伸缩缝位移等方面,探究不同形式梁桥的地震反应规律,重点揭示场地液化对不同形式梁式桥地震反应的影响规律.结果表明:场地液化会显著增大群桩基础简支梁桥的落梁风险,群桩基础连续梁桥受场地液化的影响次之,桥台处的落梁、台梁碰撞风险也较大,而桩柱式基础简支梁桥受场地液化的影响较小.     

沉箱-钢管桩逆作法复合基础试验

为研究逆作法复合基础的荷载与沉降关系、桩土荷载分担特性以及钢管桩受力性能,进行了单桩、沉箱及沉箱-钢管桩逆作法复合基础系列模型试验.结果表明:采用沉箱-钢管桩逆作法复合基础,先施工沉箱及部分上部结构,而后续进行钢管桩的压、封桩能充分利用土体的承载能力,压桩前土体与沉箱底板保持严密接触,上部结构荷载全部由地基土承担;压桩后,土体得到了加固,沉降减小,承载力提高;封桩后,继续增加的荷载主要由桩体承担,直至桩达到极限承载能力;由于沉箱的影响,使桩身上部轴力衰减平缓,桩侧摩阻力被削弱,同时使桩身中下部轴力衰减加剧,侧摩阻力发挥得到增强;6倍桩距时,可不考虑群桩效应对逆作法复合基础的影响.     

箱简型基础防波堤结构受力模式及合理尺度

防波堤向深水区域发展时,抛石堤、抛石基床和半圆体混合堤等传统结构基底宽度呈倍数增加,同时还必须对软土地基进行处理,工程造价大幅上升．针对天津港淤泥质软土地基情况,开发了一种不需要进行地基处理的防波堤结构——箱筒型基础防波堤结构．本结构由插入到地基土中的箱筒型基础结构和上部的挡浪结构组成,利用周边软土的黏聚力和摩擦阻力来保证结构的抗滑和抗倾稳定性,利用插入埋深来提高基底的承载力和整体稳定性,可预制且可重复利用．对结构抗滑、抗倾和地基承载力稳定性系数进行了计算研究,得出了优化的合理结构尺度,为箱筒型基础防波堤的实际工程应用奠定了基础,也为软土地基上新型深水防波堤的计算模式提供了借鉴．经比较,采用箱筒型基础防波堤结构较其他方案节省工程投资25．8％．     

塔底铰接型独塔斜拉桥施工阶段力学特性分析

为了研究塔底铰接型独塔斜拉桥施工阶段的力学行为,通过有限元软件建立空间梁格的数值模型,研究了该结构在各个施工阶段桥塔、主梁的位移、内力和应力变化情况,并对塔底铰接和固结两种设计方案的整体力学行为进行对比分析。结果表明:桥塔最大弯矩位置随着施工阶段不同斜拉索的张拉而发生改变;张拉主梁拉索时,主梁曲率半径外侧受拉,内侧受压;塔底铰接对结构整体受力更加有利。可见塔底铰接型独塔斜拉桥与常规斜拉桥施工阶段的力学行为不同,研究结论可以为未来类似结构的设计、施工和监控提供参考。     

Key technology for construction of connection between steel pylon and concrete pile cap of middle pylon of Taizhou Bridge

Taizhou Yangtze River Bridge is a suspension bridge with three pylons and two 1080m main spans. The middle pylon is a steel frame with longitudinal herringbone shape and lateral gate shape. The connection between steel pylon and concrete pile cap is a key part to transfer the huge inner force from the pylon to the foundation. Its construction quality is a critical factor to the overall structural loading of the whole bridge, therefore the contact ratio between the bearing steel plate of pylon and concrete pile cap is required to be over 75%. The inclined joint surface in two directions, longitudinally at 39/1920 and laterally at 1/4, posted a challenge to the construction works. Technological tests were carried out to find an optimal construction method by comparison, and finally the Post-Injection method was selected as it can meet the requirement of concrete strength and contact ratio at the connection. The successfully application of the Post-Injection method at Taizhou Yangtze River Bridge has provided an example and reference for similar projects in the future.     

斜拉桥异型主塔稳定性研究

斜拉桥体系中,主塔是受压构件,对于异型主塔,结构重心偏离中轴线位置,空间受力和稳定性比较薄弱,稳定性分析显得极其必要．针对长青沙二桥施工过程中主塔的不同状态,建立主塔有限元分析模型进行稳定性分析;在悬臂施工阶段对比主塔稳定性计算方法,确定了斜拉索保向力对主塔稳定性的贡献．     

软土地基三维固结分析及其工程应用

采用非线性比奥（Biot)固结有限元法研究软土地基的固结变形,推导了有关公式,编制了相应的计算程序,并对某工程大型沉井封底后沉井的变位和地基应力、孔隙水压力的分布及消散过程进行了研究。结果表明,天然地基下,通车后沉井有南倾趋势;地基应力不大,应力水平较低,地基土不会发生塑性剪切破坏;孔压逐渐减小,地基固结度逐渐增大。     

独塔部分地锚式PC斜拉桥经济及设计参数研究

为得到独塔部分地锚式PC斜拉桥的合理设计参数范围,通过对拉索、主塔、锚碇、主梁的材料用量和造价进行计算,建立了全桥总造价及单位桥长造价公式,据此开展了独塔部分地锚式PC斜拉桥合理背索自锚比例、锚碇主跨长度比、边主跨比及塔跨比的研究,并与其他斜拉桥型进行了对比。结果表明:考虑全桥跨越能力时,背索自锚比例宜取0.336~0.487范围内的大值,边主跨比宜取0.487~0.544范围内的小值,考虑单跨跨越能力时反之;当主跨跨度较小时,可取适当小于依据上原则的取值,当主跨跨度较大时反之;塔跨比宜取0.372左右,对应的主跨边索倾角为20.4°左右,跨径较小时取较大值,跨径较大时取较小值,与其他斜拉桥型无明显区别。独塔部分地锚式PC斜拉桥仅在边跨自锚段空间受地形条件限制时经济性能优于独塔常规斜拉桥,在常规地形并无优势。     

吸力式沉箱基础抗拔破坏标准研究

为了得到吸力式沉箱基础的抗拔破坏标准,针对长径比为4的吸力式沉箱基础开展了倾斜抗拔承载力模型试验。试验中考虑了不同荷载作用角度的影响。试验结果表明:荷载作用角度较小时,吸力式沉箱基础的荷载-位移曲线可分为位移平缓段和突变段,且有明显的拐点。依据荷载-位移曲线上的拐点所对应的位移,提出了一个确定吸力式沉箱基础破坏位移的公式。对于荷载作用角度为90°的情况,吸力式沉箱基础被拔出前发生的位移非常小,无法用位移来判断吸力式沉箱基础是否发生破坏,建议从控制外荷载大小的角度预防其破坏的发生。     

超大跨度V塔斜拉桥的经济与力学特性

建立了超大跨度V塔斜拉桥和常规直立索塔斜拉桥的有限元分析模型.通过对比研究,给出了V塔斜拉桥的一些经济、力学特性.和常规直立索塔体系斜拉桥相比,当V塔斜拉桥的塔柱倾角为对应跨最外侧拉索倾角之半时,节省量最优,但此时塔柱材料用量仅节省6%,拉索用量节省1%,总节省量并不大.V塔斜拉桥能够降低塔高,减小拉索悬挂长度,增大拉索倾角,使得结构整体刚度增加,稳定性系数得以提高,算例中塔根弯矩比常规体系小26%左右.另外,V塔体系能更好地抵抗横向风荷载的作用,满足斜拉桥向更大跨度方向发展的需求.     

土层相对位置对桶形基础承载力的影响

为了研究双土层情况下土层相对位置不同时桶形基础地基土在单一荷载作用下的极限承载力,采用南水土体本构模型进行ABAQUS有限元建模。在分析过程中,首先采用位移控制法,通过计算地基的p-s曲线确定相应的地基极限承载力,然后以单一加载情况下的地基极限承载力为基准进行归一化,最后提出土层相对位置修正系数的概念,从而获得土层相对位置不同时的地基极限承载力表达式。分析结果表明:土层由单一黏土层向单一淤泥层变化的过程中,竖向承载力、水平承载力和力矩承载力都逐渐减小,且减小幅度最大的是竖向承载力,其次是水平承载力,最后是力矩承载力;当土层相对位置比分别达到0.33,0.25和0.2时,竖向承载力、水平承载力、力矩承载力依次趋于稳定。     

深厚覆盖层下锚碇沉井基础的极限承载力及其长期稳定性研究进展

评述深厚覆盖层下锚碇沉井基础的极限承载力及其长期稳定性问题的国内外研究进展,重点讨论锚碇沉井基础的极限承载力、短期和长期变位以及稳定性的基本理论和研究方法,详细阐述在该领域的研究现状和存在问题,并提出了未来研究重点和发展趋势。     

Key technology and innovation of Sutong Bridge

Sutong Bridge is a cable-stayed bridge across Yangtze River with the main span of 1088m. This article outlines technical challenges, key technology and innovation in the design and construction such as scour protection, lowering steel cofferdam, construction platform establishment, construction and control of pylons, fabrication and damping of long cables, erection and control of steel box girders.