Dynamic performance of cable-stayed bridge tower with multi-stage pendulum mass damper under wind excitations——I:Theory

In this paper, wind-induced vibration control of a single column tower of a cable-stayed bridge with a multi- stage pendulum mass damper （MSPMD） is investigated. Special attention is given to overcoming space limitations for installing the control device in the tower and the effect of varying natural frequency of the towers during construction. First, the finite element model of the bridge during its construction and the basic equation of motion of the MSPMD are introduced. The equation of motion of the bridge with the MSPMD under along-wind excitation is then established. Finally, a numerical simulation and parametric study are conducted to assess the effectiveness of the control system for reducing the wind-induced vibration of the bridge towers during construction. The numerical simulation results show that the MSPMD is practical and effective for reducing the along-wind response of the single column tower, can be installed in a small area of the tower, and complies with the time-variant characteristics of the bridge during its entire construction stage.

Dynamic performance of cable-stayed bridge tower with multi-stage pendulum mass damper under wind excitations—Ⅱ: Experiment

The possibility of using a multi-stage pendulum mass damper （MSPMD） to control wind-induced vibration of a single column tower of a cable-stayed bridge during construction was studied theoretically in part I of this work. In this paper, the performance of the MSPMD for reducing bridge tower vibration is studied experimentally. A MSPMD model and a tower model of the bridge with geometry scaling of 1：100 were designed and manufactured. Calibration of the MSPMD model with different wire lengths is conducted to verify the analytical model of the damper. A series of tests for the uncontrolled freestanding tower, tower with cables, and tower with MSPMD model are then performed under harmonic and white noise excitations. The experimental results show that the responses of the tower model significantly decrease with the installation of the MSPMD model, which demonstrates the effectiveness of the M SPMD to mitigate the vibration of the bridge tower.

Shake table experimental study of cable-stayed bridges with two different design strategies of H-shaped towers

As one of the main load-carrying components of cable-stayed bridges,bridge towers are typically required to remain elastic even when subjected to severe ground motions with a 2%-3%probability of exceedance in 50 years.To fulfill this special requirement imposed by current seismic design codes,reinforcement ratios in the bridge towers have to be kept significantly higher than if limited ductility behavior of the tower is allowed.In addition,since the foundation capacity is closely related to the moment and shear capacities of the bridge tower,a large increase in bridge construction cost for elastically designed cable-stayed bridge is inevitable.To further investigate the possibility of limited ductility bridge tower design strategies,a new 1/20-scale cable-stayed bridge model with H-shaped bridge towers designed according to strong strut-weak tower column design was tested.The shake table experimental results are compared with a previous strong tower column-weak strut designed full bridge model.A comparison of the results show that ductility design with plastic hinges located on tower columns,i.e.,strong strut-weak tower column design,is another effective seismic design strategy that results in only small residual displacement at the top of the tower column,even under very severe earthquake excitations.

Comprehensive Optimal Control on Seismic Response of a Single-Tower Self-Anchored Suspension Bridge

Earthquake may cause severe damage to all kinds of bridge such as the falling down of the girder; therefore,effective measures should be employed to control the seismic displacement. In this paper,the method of comprehensive optimal control,com-bined with analytic hierarchy process,is employed to investigate the seismic response control of the Nanjing Jiangxinzhou Bridge,which is a single-tower self-anchored suspension bridge （SSSB）. Also,3-dimensional nonlinear seismic response analyses are con-ducted. Three types of practical connection measures for seismic response control of SSSB are investigated,and the optimal pa-rameters of the connection devices are achieved by this method. Results show that both the elastic connection devices and the damp-ers with rational parameters can reduce the seismic displacement of the bridge effectively,but the elastic connection devices will in-crease the seismic force of the tower. When all factors are consid-ered,the optimal measure is by using the elastic connection devices and the dampers together. These results can provide references for seismic response control of SSSBs.

桥梁刚度变化对高速铁路独塔斜拉桥车⁃桥耦合振动的影响分析

以高速铁路独塔斜拉桥为研究对象,建立车-轨-桥耦合系统的空间多体动力学分析模型,开展高速铁路斜拉桥的车-轨-桥耦合振动的仿真分析。通过改变材料弹性模量的方式调整桥塔和主梁刚度,研究桥梁刚度变化对桥梁车-桥-耦合振动的影响规律。研究结果表明,随着桥塔刚度的增大,主梁跨中竖向和塔顶纵向位移响应逐渐减小,其峰值减幅分别为7.57%和10%;随着主梁刚度的减小,主梁跨中竖向位移和塔顶纵向位移峰值呈逐渐递增趋势,主梁刚度变化对车体竖向加速度和Sperling竖向舒适度指标影响相对较大;相比于桥塔刚度的变化,主梁刚度变化对车-桥振动响应的影响更大;整体上,列车运行的安全性和平稳性指标满足规范要求。

Study on seismic response control of a single-tower self-anchored suspension bridge with elastic-plastic steel damper

Elastic-plastic steel damper(EPSD) is a new device controlling seismic responses.The mechanical principle of EPSD was presented and a comparison was conducted between the theoretical formulas and finite element(FE) simulation of damper units.The verified force-displacement hysteretic curve of the damper system was obtained with reference to tests.The Nanjing Jiangxinzhou Bridge(NJB) was subsequently taken as the case to investigate the seismic response control effect of EPSDs on single-tower self-anchored suspension bridges.A 3-dimensional FE model of the bridge was established in ANSYS and the dynamic and static analyses of the bridge were conducted,the control effect of EPSDs under different seismic waves was further investigated through nonlinear time-history analysis based on the validated model.Results showed that both the simplified theoretical and FE simulation methods can preferable reflect the mechanical performance of EPSD,and that seismic responses of NJB with EPSDs are better than those with elastic connection device or fluid viscous damper.However,the control effect of EPSDs is influenced by seismic wave characteristics.

跨铁路独塔斜拉桥索塔平转施工技术与监测研究

某跨铁路独塔斜拉桥索塔高85 m,左右塔柱内倾81.22°,采用翻模+平面转体法施工,逆时针转体93°,转体质量约18 500 t。因此,针对该桥塔因转体质量大、重心高所带来的水平转体施工安全问题,开展了独塔斜拉桥索塔平转施工技术分析、实桥跟踪测试,得到了称重、配重、姿态监测与调整等技术要点。得出的主要结论包括:沿桥塔下横梁与0号梁段上对称平衡配重50 t,可降低桥塔重心;平转过程受不平衡力矩和偏心距的影响较为敏感,桥塔称重与配重误差需严格控制;索塔姿态调整前移出配重,并通过临时支墩锁定索塔姿态;转体前、后垂直度应尽量保持一致。

单塔双索面大跨径斜拉桥荷载试验技术研究

斜拉桥作为大跨径桥梁的主要形式,具有跨越能力强、结构轻巧、造型美观的特点,斜拉桥的荷载试验是通过对斜拉桥结构直接施加荷载后进行有关检测、数据分析,从而了解斜拉桥结构在试验荷载作用下的实际工作状况,进而评定桥梁结构施工质量和使用状况。通过桥梁的荷载测试,可以对桥梁的施工质量和结构受力性能做出判断,根据测试结果推断桥梁结构的实际承载能力,确定斜拉桥的实际运营情况和使用状况,为桥梁的验收、后期的运营使用提供科学有效的依据。论文通过某斜拉桥的主桥为例,对单塔不等跨斜拉桥荷载试验过程及要点进行研究分析。

空间索面独塔钢箱梁斜拉桥索力优化

空间索面斜拉桥由于结构特殊性,索力相互影响复杂,其合理成桥索力以及施工张拉力调整是需要解决的关键问题.为对以上问题进行研究,以石家庄市学府路斜拉桥为工程背景,将结构的弯曲和拉压应变能之和最小作为目标函数,通过控制主梁的挠度、弯矩和斜拉索索力等条件,采用影响矩阵法求解了成桥索力.结合钢箱梁斜拉桥先梁后索的施工特点,研究了不同斜拉索张拉方案的可行性.结果表明,求解得到的最优索力与设计索力误差很小,索力分布合理;通过正装迭代法求解得到不同方案的斜拉索张拉力及成桥索力,分析确定了最优的斜拉索张拉方案,为工程实际提供参考.

大跨度单索面地锚式悬索桥异形主塔施工技术研究

为了探究大跨度单索面悬索桥异形主塔的受力变形机理与施工控制成果,本研究以南宁英华大桥为背景,采用数值计算与现场监测的方法对其异形浮吊施工的主塔进行了研究。结果表明:在20℃设计基准温度条件的成桥永久荷载作用下,其稳定性和受力均满足相关规范要求。经过现场实测可知:主塔施工过程中,线形良好,合龙精度满足规范要求。

非对称独塔部分斜拉桥索道管精准定位控制研究

以沪苏湖铁路苏湖特大桥(35+168+136+35)m非对称独塔部分斜拉桥为工程背景,进行了斜拉索索道管精准定位控制研究。考虑影响索道管空间位置的主要因素,对每个影响因素进行了具体的研究分析,确定了索道管精准定位的修正方法。采用该方法确定索道管两端最终的三维坐标和倾角,并以理论计算的空间坐标对施工中索道管进行监控测量,通过实测位置与理论坐标的对比来进行施工控制。结果表明桥梁施工中索道管定位控制良好,符合预期要求。

独塔双索面斜拉桥荷载试验研究

为准确评估斜拉桥成桥时的承载能力及工作状态,检验桥梁结构是否达到设计及有关规范规定的要求,为桥梁交工验收提供技术依据,以沥桂大桥(独塔双索面预应力混凝土斜拉桥)为研究对象,采用Midas Civil建立了斜拉桥有限元模型,介绍了斜拉桥荷载试验检测的主要测试断面及测试内容,对比分析了主梁应变、挠度、主塔塔顶纵桥向水平位移、索力增量等静力理论计算值与实测数据,并对该桥的自振特性及动力特性等动力荷载试验进行了分析。结果表明:1)该桥各项静载试验参数、校验系数均在规范要求的合理范围内,相对残余均小于20%;2)结构的自振频率、阻尼比及动力响应均处于正常工作状态,该桥整体处于弹性工作状态,受力状态良好,满足设计荷载及有关规范的使用要求。

四肢异形独塔斜拉桥桥塔设计

邓州市穰城跨湍河大桥为主跨90m+90m的空间框架式独塔钢-混凝土组合梁斜拉桥,主塔采用四肢异形空间框架式独塔,桥塔设计总高75.5m,四根塔柱倾斜角度较大,且上塔柱为空间曲线结构,塔柱受弯、剪、扭效应明显。结合MIDAS Civil对桥塔进行静、动力分析。索塔上采用多种形式的横梁,针对不同位置的横梁选择相对最优的衔接位置、锚固方式来优化设计。总结四肢异形独塔斜拉桥在桥塔设计中遇到的重难点,为类似桥塔设计提供参考。

异型独塔斜拉桥纵向水平力平衡措施分析

文章以花山大桥为例,首先介绍了其概况,随后针对花山大桥的建设条件,展开了其纵向不平衡水平力控制措施的选择及设计,包括控制措施对比、抗推支座设置位置研究及主梁纵向抗推措施设计三方面。以景观因素为主导,选择以墩塔设置纵向限位装置的方式解决不平衡水平力问题,保障了花山大桥受力合理、结构安全,可以为类似桥梁的设计提供参考。

隧洞内钢箱梁架设施工技术

绿汁江特大桥是国内外首座单塔单跨钢箱梁悬索桥,主跨780m,楚雄岸未设置主塔,且山体为绝壁陡崖,设计将主跨钢箱梁直接伸入到相接的隧道内18m。因受楚雄岸悬崖绝壁地形条件限制,隧洞内架设空间狭小,盲区大,缆索吊机难以将钢箱梁直接吊装至隧洞内。本文结合现场实际施工情况,剖析本工程的施工难点,首创一种隧洞内钢梁架设方法(绝壁托架+缆索吊60m辅助牵引+洞内18m滑移)。此种方法成功的运用节省了洞内钢梁的吊装时间,缩短了钢梁架设总体工期,提前了绿汁江特大桥的合龙时间。

大温差环境下钢制桥塔施工线形测控关键技术研究

随着交通建设的快速发展,钢制桥塔在桥梁工程中得到越来越广泛的应用。文章以昆山西路与304国道连通-高架桥工程为研究案例,聚焦大温差环境下钢制桥塔施工的难点问题,深入分析光照、环境温度等外部因素对钢制桥塔不均匀变形的影响以及温度变化对线形的影响,探讨了温度-位移数据处理在施工中的核心作用,提出了一套切实可行的线形测控方法。研究可为钢制桥塔施工质量和安全性保障提供研究依据和技术支持。

独塔斜拉桥边跨压重施工方案优化研究

在独塔斜拉桥施工过程中,辅助墩出现负支反力会导致结构受力状态变化,使辅助墩支座受力不均或脱空,进而损害支座。文章以降低压重混凝土用量和避免辅助墩出现负支反力为优化目标,提出压重施加工序不变且支架分批拆除和压重分批施加且支架分批拆除两种施工改进方案。通过对比分析不同方案下的辅助墩支反力、施工过程中主梁应力、钢管支架立柱最大应力和成桥状态,确定合理的辅助墩施工方案。

单塔式缆索吊在大跨度钢拱桥吊装施工中的应用

本文主要介绍了在新安江大桥钢拱桥施工中,针对钢拱桥结构型式及桥址区域地质状况及地形条件,通过采用单塔式缆索吊的施工方法,从而很好地解决了大跨度钢拱桥拱肋吊装的难题,保证了大吨位吊装的安全性,提高了拱肋安装的精确度。利用有利地形条件,采用单塔缆索吊,不但降低了施工措施费用,而且减少了对周边地形的扰动,最大限度地保护了新安江两岸的生态环境,为类似施工提供相关经验。

双层钢桁梁独塔斜拉桥荷载试验

为了准确评价双层钢桁梁独塔斜拉桥成桥时的工作性能和承载能力,以联石湾大桥为对象,建立有限元模型,并对桥梁结构进行静、动载试验测试,测试内容包括主桁挠度、截面应变、主塔纵桥向水平位移、斜拉索索力增量以及结构模态、冲击系数等参数,旨在评估该桥的结构状态。同时,将试验结果与理论分析结果进行了对比,表明:联石湾特大桥各控制截面的应变、挠度及位移均满足技术规范的要求,且该桥各阶振型实测频率均大于理论频率,结构整体刚度符合设计要求;大桥受力状态良好,整体处于弹性工作状态,满足设计荷载正常使用的要求。