Auto-parametric resonance of a continuous-beam-bridge model under two-point periodic excitation:an experimental investigation and stability analysis

The auto-parametric resonance of a continuous-beam bridge model subjected to a two-point periodic excitation is experimentally and numerically investigated in this study.An auto-parametric resonance experiment of the test model is conducted to observe and measure the auto-parametric resonance of a continuous beam under a two-point excitation on columns.The parametric vibration equation is established for the test model using the finite-element method.The auto-parametric resonance stability of the structure is analyzed by using Newmark's method and the energy-growth exponent method.The effects of the phase difference of the two-point excitation on the stability boundaries of auto-parametric resonance are studied for the test model.Compared with the experiment,the numerical instability predictions of auto-parametric resonance are consistent with the test phenomena,and the numerical stability boundaries of auto-parametric resonance agree with the experimental ones.For a continuous beam bridge,when the ratio of multipoint excitation frequency(applied to the columns)to natural frequency of the continuous girder is approximately equal to 2,the continuous beam may undergo a strong auto-parametric resonance.Combined with the present experiment and analysis,a hypothesis of Volgograd Bridge's serpentine vibration is discussed.

Application of Long-Span Continuous Bridge Technology in Bridge Construction

In order to promote the rapid development of urbanization in our country,it is necessary to improve the construction level and technology of bridge engineering.For long-span continuous bridge technology,it has the characteristics of wide application range,various applicable conditions,and short construction period.Therefore,it is necessary to pay attention to the application of long-span continuous bridge technology.This article mainly analyzes its application in bridge construction,hoping to provide some reference for future use.

Applicability of small resistance fastener on long-span continuous bridges of high-speed railway

Ballastless tracks have been widely applied in high-speed railway (HSR). The adaptability research between continuous welded rails (CWR) and long-span bridges of HSR is of great practical engineering significance. Based on the HSR long-span continuous bridges, the integrative spatial finite element model of track-bridge-pier-foundation system was established with the nonlinear spring element simulating the longitudinal resistance between track and bridge. Comparative study on the various additional longitudinal forces of CWR using the common fasteners and small resistance fasteners was carried out. Analysis results indicate that the additional expansion forces and additional rail-breaking forces in long-span ballastless continuous girders can be reduced evidently by 40% 50% after adopting small resistance fasteners, but lead to greater rail broken gap. The small resistance fasteners have little influence on the additional force only caused by vertical load, but can reduce the additional force caused by vertical load combined with braking load by over 10%. Besides, transient analysis method is proved to be more accurate and safe in calculating additional longitudinal forces when the train running or braking on the bridge, compared with the traditional static method.

Seismic analysis of long-span continuous rigid frame bridges in cold regions:a case study of Bridge 1 in north of international tourism resort in Changbai Mountain

It is helpful to improve the seismic design theory of long-span continuous bridges for studying the seismic performance of each cantilever construction state.Taking the Bridge 1 in the north of Changbai-Mountain international tourism resort as an example,the authors studied it in shutdown phase and the cantilever construction process,established the simulation model by using Midas / civil,and analyzed time-history of each construction stage for the bridge.The study shows that long-span bridge cantilever construction in northeastern China can be divided into two-year tasks for construction(suspending in winter).It is needed to think about seismic stability of the cantilever position in shut-down phase of winter.The effect of longitudinal vibration is the most disadvantageous influence to bridge,and its calculation results can provide reference for seismic design of similar bridges in the future.

Longitudinal force in continuously welded rail on long-span tied arch continuous bridge carrying multiple tracks

Considering arch rib, lateral brace, suspender, girder, pier and track position, the model for the interaction between long-span tied arch continuous bridge and multiple tracks was established by using steel-concrete composite section beam element to simulate concrete-filled steel tube(CFST) arch rib, using the beam element with rigid arm to simulate the prestressed concrete girder and using nonlinear bar element to simulate longitudinal constraint between track and bridge. Taking a(77+3×156.8+77) m tied arch continuous bridge with four tracks on the Harbin-Qiqihar Passenger Dedicated Line as an example, the arrangement of continuously welded rail(CWR) was explored. The longitudinal force in CWR on the tied arch continuous bridge, the pier top horizontal force and torque due to the unbalance load case, were analyzed under the action of temperature, vertical live load, train braking and wind load.Studies show that, it can significantly reduce track displacement to set the track expansion devices at main span arch springing on both sides; the track stress due to arch temperature variation can reach 40.8 MPa; the track stress, pier top horizontal force and torque are related to the number of loaded tracks and train running direction, and the bending force applied to unloaded track is close to the loaded track, while the braking force applied to unloaded track is 1/4 to 1/2 of the loaded track; the longitudinal force of track due to the wind load is up to 12.4 MPa, which should be considered.

Fatigue Safety Assessment of Concrete Continuous Rigid Frame Bridge Based on Rain Flow Counting Method and Health Monitoring Data

The fatigue of concrete structures will gradually appear after being subjected to alternating loads for a long time,and the accidents caused by fatigue failure of bridge structures also appear from time to time.Aiming at the problem of degradation of long-span continuous rigid frame bridges due to fatigue and environmental effects,this paper suggests a method to analyze the fatigue degradation mechanism of this type of bridge,which combines long-term in-site monitoring data collected by the health monitoring system(HMS)and fatigue theory.In the paper,the authors mainly carry out the research work in the following aspects:First of all,a long-span continuous rigid frame bridge installed with HMS is used as an example,and a large amount of health monitoring data have been acquired,which can provide efficient information for fatigue in terms of equivalent stress range and cumulative number of stress cycles;next,for calculating the cumulative fatigue damage of the bridge structure,fatigue stress spectrum got by rain flow counting method,S-N curves and damage criteria are used for fatigue damage analysis.Moreover,it was considered a linear accumulation damage through the Palmgren-Miner rule for the counting of stress cycles.The health monitoring data are adopted to obtain fatigue stress data and the rain flow counting method is used to count the amplitude varying fatigue stress.The proposed fatigue reliability approach in the paper can estimate the fatigue damage degree and its evolution law of bridge structures well,and also can help bridge engineers do the assessment of future service duration.

Longitudinal forces of continuously welded track on high-speed railway cable-stayed bridge considering impact of adjacent bridges

A proven beam-track contact model was used to analyze the track-structure interaction of CWR (continuously welded track) on bridge. Considering the impact of adjacent bridges, the tower-cable-track-beam-pier-pile finite element model of the cable-stayed bridge was established. Taking a bridge group including 40-32m simply-supported beam and (32+80+112)m single-tower cable-stayed bridge and 17-32m simply-supported beam on the Kunming-Shanghai high-speed railway as an example, the characteristics of CWR longitudinal force on the cable-stayed bridge were studied. It is shown that adjacent bridges must be considered in the calculation of the track expansion force and bending force on cable-stayed bridge. When the span amount of adjacent bridges is too numerous, it can be simplified as six spans; the fixed bearing of adjacent simply-supported beams should be placed on the side near the cable-stayed bridge; the track expansion device should be set at the bridge tower to reduce the track force near the bridge abutment.

Numerical analysis of dynamic response of vehicle–bridge coupled system on long-span continuous girder bridge

To systematically study the vehicle-bridge coupled dynamic response and its change rule with different parameters, a vehicle model with seven degrees of freedom was built and the total potential energy of vehicle space vibration system was deduced. Considering the stimulation of road roughness, the dynamic response equation of vehicle-bridge coupled system was established in accordance with the elastic system principle of total potential energy with stationary value and the ＂set-in-right-position＂ rule. On the basis of the self-compiled Fortran program and bridge engineering, the dynamic response of long- span continuous girder bridge under vehicle load was studied. This study also included the calculation of vehicle impact coefficient, evaluation of vibration comfort, and analysis of dynamic response parameters. Results show the impact coefficient changes with lane number and is larger than the value calculated by the ＂general code for design of highway bridges and culverts （China）＂. The Dieckmann index of bridge vibration is also related to lane number, and the vibration comfort evaluation is good in normal conditions. The relevant conclusions from parametric analyses have practical significance to dynamic design and daily operation of long-span continuous girder bridges in expressways. Safety and comfort are expected to improve significantly with further control of the vibration of vehicle-bridge system.

Impact coefficient and reliability of mid-span continuous beam bridge under action of extra heavy vehicle with low speed

To analyze the dynamic response and reliability of a continuous beam bridge under the action of an extra heavy vehicle, a vehicle–bridge coupled vibration model was established based on the virtual work principle and vehicle–bridge displacement compatibility equation, which can accurately simulate the dynamic characteristics of the vehicle and bridge. Results show that deck roughness has an important function in the effect of the vehicle on the bridge. When an extra heavy vehicle passes through the continuous beam bridge at a low speed of 5 km/h, the impact coefficient reaches a high value, which should not be disregarded in bridge safety assessments. Considering that no specific law exists between the impact coefficient and vehicle speed, vehicle speed should not be unduly limited and deck roughness repairing should be paid considerable attention. Deck roughness has a significant influence on the reliability index, which decreases as deck roughness increases. For the continuous beam bridge in this work, the reliability index of each control section is greater than the minimum reliability index. No reinforcement measures are required for over-sized transport.

Damage assessment of a continuous beam bridge based on the strain mode

Based on the method of strain mode, damage identification of continuous beam bridges by comparing the variance of several curves of strain modes difference is studied. Three cases of numerical simulation demonstrate that the proposed method is applicable to detecting many a damage in a continuous beam bridge, which accurately identifies the damaged positions of the bridge, and detects the damage severity of an element by its according peak value of the curve of strain modes difference that is found to increase with the increasing damage severity.

风屏障透风率对强风作用下重载铁路刚构-连续梁车桥耦合振动响应的影响

为探究风屏障透风率对强风作用下重载铁路刚构-连续梁车桥耦合振动的影响,先通过节段模型风洞试验获取桥上设置0%,20%,40%,60%和无风屏障5种不同透风率风屏障时车桥系统的三分力系数,再根据弹性系统动力学总势能不变原理建立风-车-桥耦合振动仿真计算分析模型,对不同车速下重载货运列车通过设置不同透风率风屏障刚构-连续梁桥开展风-车-桥系统动力学仿真计算与分析研究。结果表明:在列车上桥初期,桥梁横向位移峰值随透风率的增大而明显减小,而当列车运行趋于满布桥梁时,桥梁的横向位移峰值随透风率的增大变化不明显;列车的动力响应峰值随风屏障透风率的增大而增大,相比于满载编组列车,空载和轻重混编编组列车的动力响应对风屏障透风率的变化更加敏感。综合桥梁动力响应和列车走行安全性评价指标(脱轨系数和轮重减载率),该桥梁应设置40%透风率的风屏障。

高铁大跨连续梁不同约束体系下抗震性能研究

研究目的:为研究不同抗震约束体系对高速铁路大跨度连续梁桥纵向抗震性能的影响,以一座跨径为(60+100+60)m的高速铁路连续梁桥为工程背景,采用OpenSees软件对全桥进行非线性时程分析,针对不同的设防烈度,从动力特性、桥墩墩底弯矩、墩顶位移、支座位移等方面,对比分析延性体系、减隔震体系以及延性体系加减隔震体系多种工况下桥梁的地震响应差别。研究结论:(1)与延性体系相比,减隔震体系可显著延长桥梁结构的自振周期;(2)对于墩高20 m的高铁大跨连续梁按罕遇地震设防时,在Ⅶ度区及以上设防烈度时,桥墩会进入延性,且位移延性系数随着桥墩配筋率的增大而减小;(3)采用延性抗震体系的高铁大跨连续梁,可通过增大配筋率和设置阻尼器减轻桥墩的损伤,使其处于轻微损伤状态;(4)采用减隔震体系可保证高烈度地震区的高铁大跨连续梁桥的桥墩在罕遇地震下处于弹性工作状态,结构的减震率可超过80%;(5)摩擦摆支座体系减震效果好,但需要通过附加阻尼的形式来满足支座设计位移需要;(6)本研究成果可为高铁大跨连续梁桥的抗震设计提供参考。

钢-混凝土组合简支桥面连续结构横向应力分析

针对钢-混组合简支梁桥的桥面连续结构开裂等病害,围绕桥面连接板的横桥向应力问题,采用线弹性理论和板的偏微分方程进行分析,得出了桥面连接板挠度和应力的分布函数,建立非线性有限元模型,并进行实桥荷载试验.通过比较理论解、有限元解和实测试验结果,证实了理论解和有限元的有效性.根据得到的分布函数,发现横桥向和纵桥向上的最大拉应力出现在钢梁端部位置的连接板的上缘.此外,还分析了连接板区域尺寸变化对横桥向应力峰值的影响,包括纵梁端部距支座的长度、纵梁的间距以及连接板区域整体尺寸变化.结果表明:较小的纵梁间距和较长的纵梁端部与支撑之间的距离会导致连接板中的横向拉应力峰值增加,并提高横向拉应力在总应力中的占比,从而导致桥面连接板早于设计荷载开裂.因此对于纵梁间距较小、梁端长度较长的钢-混组合简支梁桥桥面连续结构,仅计算其纵桥向受力性能会导致计算结果偏危险,建议按照本文方法考虑横桥向应力对桥面连接板的影响.

基于绝对位移法的曲线梁桥多维多点弹塑性随机响应分析

针对当前地震动空间效应下曲线梁桥地震反应分析多采用确定性激励输入且忽略桥梁非线性的情况,采用了多维多点非平稳随机激励对曲线连续梁桥进行弹塑性响应分析。建立非线性有限元模型并降维解耦非平稳地震动非平稳演化功率谱(energy power spectral density,EPSD)矩阵,采用绝对位移法对桥梁进行非线性时程分析。考虑不同视波速、场地条件、相干性以及平稳与非平稳地震激励,综合分析了曲线连续梁桥的随机响应及其频域特性和时域特性。结果表明,地震动空间效应和地震动的非平稳性对曲线梁桥随机响应影响很大,其中地震动空间效应对桥梁随机响应大小及其频域分布有显著影响,而非平稳性会对随机响应大小及其时变响应趋势产生重要影响。因此,在曲线连续梁桥抗震分析中需充分考虑地震动空间效应和地震动非平稳性,以避免错误估计桥梁抗震性能。提供了全面的分析结果,对加强曲线连续梁桥的抗震设计和评估,从而提高其抗震性能和可靠性具有重要意义。

曲线条件大跨度拱加劲连续梁设计

贵南高铁二塘双线特大桥采用90m+180m+90m拱加劲连续梁结构。大桥位于曲线上,梁体采用分段直线布置,悬灌施工;主拱采用哑铃形钢管混凝土拱肋,钢管直径1 m,拱肋全高3 m;采用整束挤压钢绞线吊杆,全桥拱设置36组吊杆;纵向活动主墩通过构造措施,形成半刚构结构体系,限制部分梁体问题伸缩变形;大桥采用先悬灌主梁,后在主梁上搭设支架原位拼装拱肋方式施工。经论文研究计算结果表明,该桥刚度、受力等均满足规范要求。

连续梁桥跳车冲击下车桥耦合振动响应分析

为研究车辆在不同工况下发生跳车对变截面连续梁桥动力响应的影响,文章选用1/4车辆模型,采用D’Alembert原理建立车辆振动平衡方程;基于Euler-Bernoulli梁理论将变截面连续梁划分成多个微段并进行受力分析,建立桥梁振动平衡方程,采用模态坐标法考虑振型的正交性对方程进行简化,与车辆振动方程联立得到车桥耦合振动方程,最终理论推导出跳车冲击过程中的车桥耦合振动平衡方程;利用MATLAB自编程序求解车桥耦合振动方程,得出车桥耦合动力响应。研究表明:当跳车高度不断增加时,桥梁动力响应持续加重,位移最大值逐渐增加;当不同桥跨跨中发生跳车时,跳车跨位移响应最大,距离跳车跨越远,位移响应越小。

基于Dynamo模式+Revit二次开发的变截面连续梁桥初步设计研究

针对变截梁桥建模困难、效率低下、精确度不足等问题,以鄂州市东沟大桥为工程背景,基于Revit+Dynamo模式提出一套搭建变截面梁桥参数化模型方案,成功搭建全桥三维模型,验证了该参数化模型方案具有可行性。并在此模型基础上,通过Revit API程序接口进行二次开发创建0#节段箱梁钢筋参数化模型,实现了桥梁工程参数化、自动化建模效果,期望能为同类型和其他类型桥梁参数化设计提供一些思路和参考。

小半径曲线梁桥的无缝线路有限元模型简化研究

为更简便地建立小半径曲线梁桥的无缝线路有限元模型,降低计算成本并保证计算精度的可靠性,本文比较分析不同简化程度的模型。首先,依据已有桥上无缝线路模型的形式,通过不同程度简化桥梁上部结构,由简到繁确立了单刚臂模型、多刚臂模型、准梁格模型、平面壳模型、空间壳模型、实体模型共6种模型,并通过扣件横向和纵向阻力试验取得了模型的关键参数;其次,以曲线半径为200 m的(40+50+50+40) m连续梁桥为实例,计算了桥上无缝线路在伸缩、挠曲、制动和断轨等其他组合工况下的结果;最后,以实体模型的计算结果为基准,将前5种模型的计算结果与实体模型的进行对比,通过欧几里得距离量化分析了各模型的计算精度。研究结果表明:综合考虑模型复杂程度和计算精度,多刚臂模型和准梁格模型相比于空间壳模型性价比更高,梁格法在桥梁工程中被大量用于异形桥梁计算,且支座分布以及边界条件更符合实际情况。因此,推荐在进行小半径曲线梁桥的无缝线路计算时采用准梁格模型。

高铁大跨双肢墩连续刚构桥减震系梁地震易损性分析

为了解地震作用下减震系梁对高铁大跨双肢墩连续刚构桥的减震效果,以某主跨180 m的山区高铁双肢墩连续刚构桥为背景,分别建立采用钢筋混凝土(RC)系梁、2种新型减震系梁(可屈服钢系梁与斜交筒式黏弹性阻尼器系梁)方案的全桥有限元模型,对比分析不同系梁方案下的结构损伤、桥面平顺性指标等。结果表明:2种新型减震系梁均不会在地震作用下出现负刚度,新型减震系梁方案较RC系梁方案能有效降低系梁和主墩的结构损伤概率,主墩最大压应变降低83.3%;但减震系梁对震后桥面平顺性指标无明显改善,需采用更具针对性的技术措施。

基于GNSS的五塔连续斜拉桥主梁上CPⅢ平面网快速测量方法试验研究及应用

大跨度桥梁的长大连续梁会随着温度的变化,产生较大的纵向和竖向位移,导致连续梁桥上CPⅢ点坐标存在多值性,设站精度无法满足高铁对轨道板测量相关精度要求。本文提出了一种基于GNSS静态测量的连续梁上CPⅢ点平面坐标快速测量新方法,并依托郑济高铁长清黄河特大桥,设计了实际测量试验,并对新方法的可行性进行了验证。试验结果表明,这种基于GNSS的CPⅢ点平面坐标快速测量方法,在观测时长为30 min的情况下就能达到大跨度桥梁上底座板、轨道板等施工对CPⅢ平面网相关测量精度的要求。