大跨度斜拉桥可靠度评估方法研究

针对大型复杂桥梁结构极限状态方程一般难以显式表达的特点,提出了基于神经网络的大跨度斜拉桥可靠度评估方法．通过Latinhypercube抽样技术对随机参数进行抽样,应用大跨度斜拉桥非线性有限元进行分析．通过对随机抽样的样本数据进行训练,应用神经网络的非线性映射和泛化技术,对大跨度斜拉桥的极限状态方程进行数值模拟．通过极限状态方程对随机变量的偏导数,求解结构可靠指标的优化问题,计算大跨度斜拉桥的可靠指标．结果表明：对于隐式极限状态方程的大跨度斜拉桥可靠度评估问题,本文方法具有较高的计算精度和较好的计算效率;荷载布置方式、作用位置等对斜拉桥可靠指标有很大影响;计入3种几何非线性效应后斜拉桥偏于不安全,其中斜拉索垂度非线性效应的影响最为显著．     

退化钢筋混凝土桥梁概率耐久性评估方法

提出了考虑时间、空间变异特性的退化钢筋混凝土桥梁耐久性概率评估的随机有限元方法.首先,通过考虑钢筋与混凝土之间时变的粘结滑移关系及腐蚀钢筋的应力应变关系,采用弥散裂纹方法对退化钢筋混凝土桥梁进行有限元分析.然后,提出了退化钢筋混凝土桥梁耐久性概率评估的随机有限元分析方法,基于文献及现场调查的数据,采用蒙特卡罗仿真方法对...     

基于Wiener过程和竞争失效分析的系统可靠性评估

考虑突发失效和性能退化之间的相关性和竞争关系,研究了基于竞争失效分析的产品可靠性评估问题.将突发失效的发生率视为性能退化量的函数,并采用Weibull分布加以描述;利用Wiener过程描述性能退化过程,采用极大似然估计法估计模型参数;提出了一种基于竞争失效分析的可靠性评估模型.以一种GaAs激光器性能退化和失效数据为例,验证模型及其求解方法的有效性.结果表明：若仅考虑退化失效将使得评估结果偏向乐观,突发失效与退化失效的相关性对可靠性评估的准确性有很大影响.     

多点激励下多跨斜拉桥缩尺模型的地震响应研究.部分1:振动台试验（英文）

研究目的:为多塔斜拉桥在一致激励和非一致激励下地震响应的研究提供地震模拟振动台全桥试验方法,并有助于加强多塔斜拉桥抗震性能和抗震设计的认识。创新要点:1.建立了地震模拟振动台多台阵试验方法,并首次将其应用于多塔斜拉桥全桥比例缩尺模型的地震响应分析之中;2.通过地震模拟振动台试验,揭示了多塔斜拉桥在多点一致激励和多点非一致激励的地震响应特性并提出了多塔斜拉桥在强震下的破坏模式。研究方法:1.基于动力相似理论,设计与制作了多塔斜拉桥的全桥比例缩尺模型(图2);2.利用地震模拟振动台多台阵试验,根据在不同地震波作用下和考虑行波效应后多塔斜拉桥模型的主梁和主塔响应,分析了多塔斜拉桥在多点一致激励和多点非一致激励的地震响应特性(图5~图8);3.根据在地震波不同强度作用下多塔斜拉桥模型的主梁和主塔响应,分析了多塔斜拉桥在强震下的破坏模式和地震响应(图9)。重要结论:1.江心波作用下该多塔斜拉桥的地震响应大于其他三种地震波;2.多塔斜拉桥在抗震设计时需要考虑行波效应的影响;3.在El-Centro波的加速度峰值高达4.0 m/s2时,多塔斜拉桥模型出现了支座破坏。     

随机车流作用下的斜拉桥恒载索力的提取（英文）

为了提取斜拉桥监测数据中的恒载索力,使用不同统计方法逐级剔除各类因素的影响.以南京长江三桥健康监测系统采集的索力传感器信息为依托,采用线性拟合剔除温度的影响;采用小波基函数为DB8的5级小波降噪方法剔除噪声信号;采用极值Ⅲ型分布拟合检验,取拟合的位置参数作为恒载索力.结果表明:索力和温度呈线性关系,有时温度效应较显著;噪声影响量较小;2007年交通状况下,车辆荷载影响量是温度影响量的2倍.多根拉索的计算结果验证了所提方法的可靠性和正确性.     

典型矮塔斜拉桥地震风险概率评估方法研究

鉴于矮塔斜拉桥受力性能的特殊性,引入增量动力分析（IDA）和拉丁超立方体抽样（LHS）评估该结构在地震激励下发生损伤的风险概率。首先采用LHS考虑桥梁构件材料的随机性,与事先选取的地震波相结合形成桥梁-地震动样本集合;其次在确定桥梁有限元模型主要构件损伤指标的基础上采用基于蒙特卡罗（MC）抽样的IDA进行地震易损性分析和地震风险概率评估。为验证方法的正确性和有效性,对一预应力混凝土独塔双索面矮塔斜拉桥结构模型进行地震风险概率评估,结果表明:该方法既充分考虑了材料和地震输入双重随机性又避免了繁琐的积分过程,同时也提高了工程计算的效率及精度。     

多点激励下多跨斜拉桥缩尺模型的地震响应研究．部分1：振动台试验

研究目的：创新要点：为多塔斜拉桥在一致激励和非一致激励下地震响应的研究提供地震模拟振动台全桥试验方法,并有助于加强多塔斜拉桥抗震性能和抗震设计的认识。1．建立了地震模拟振动台多台阵试验方法,并首次将其应用于多塔斜拉桥全桥比例缩尺模型的地震响应分析之中;2．通过地震模拟振动台试验,揭示了多塔斜拉桥在多点一致激励和多点非一致激励的地震响应特性并提出了多塔斜拉桥在强震下的破坏模式。研究方法：1．基于动力相似理论,设计与制作了多塔斜拉桥的全桥比例缩尺模型（图2）;2．利用地震模拟振动台多台阵试验,根据在不同地震波作用下和考虑行波效应后多塔斜拉桥模型的主梁和主塔响应,分析了多塔斜拉桥在多点一致激励和多点非一致激励的地震响应特性（图5～图8）;3．根据在地震波不同强度作用下多塔斜拉桥模型的主梁和主塔响虚,分析了多塔斜拉桥在强震下的破坏模式和地震响应（图9）。重要结论：1．江心波作用下该多塔斜拉桥的地震响应大于其他三种地震波;2．多塔斜拉桥在抗震设计时需要考虑行波效应的影响;3．在El-Centro波的加速度峰值高达4．0m／s^2时,多塔斜拉桥模型出现了支座破坏。     

1860级钢绞线断丝效应精细化分析

为研究钢绞线其中一根断丝后对其他丝应力分布的影响,在SolidWorks中建立1×7的1860级钢绞线实体模型,利用HyperMesh进行网格划分,利用ANSYS Workbench对钢绞线进行受力分析.分别通过不同边界条件和几何模型模拟侧丝断丝和中丝断丝效应,并将计算结果与现有文献进行对比,验证了有限元模型的正确性....     

大跨径斜拉桥施工过程中无应力状态控制法

为了满足大跨径斜拉桥目标成桥状态,得到大跨径斜拉桥在施工过程中拉索的张拉力,提出了大跨径斜拉桥在施工过程中的拉索索力计算调整拉索无应力长度的降温法。倒退分析法和传统无应力状态控制法在计算大跨径斜拉桥施工过程中存在缺陷,在传统无应力状态控制法的基础上,提出了调整拉索无应力长度的降温法。该方法可用于计算大跨径斜拉桥且计算方法简单,计算结果精度较高,能够满足工程要求。     

三塔斜拉桥地震响应分析

文章以山东济南建邦三塔斜拉桥为研究对象,采用有限元软件建立该桥有桩和无桩两种模型,进行了动力特性分析,并在不同工况下进行反应谱和弹性时程分析。两种模型的地震响应的结果表明,桩土效应对结构位移和内力影响较大,在对大跨度支撑体系斜拉桥进行抗震分析时,应该考虑桩土效应。     

Dynamic responses of cable-stayed bridges to vehicular loading including the effects of the local vibration of cables

Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexibility which increases with the span of the bridge. This makes stay cables vulnerable to local vibrations which may have significant effects on the dynamic responses of long-span CSBs. Hence, it is essential to account for these effects in the assessment of the dynamics CSBs. In this paper, the dynamic responses of CSBs under vehicular loads are studied using the finite element method (FEM), while the local vibration of stay cables is analyzed using the substructure method. A case study of a cable-stayed steel bridge with a center span of 448 m demonstrates that stay cables undergo large displacements in the primary mode of the whole bridge although, in general, a cable’s local vibrations are not obvious. The road surface roughness has significant effects on the interaction force between the deck and vehicle but little effect on the global response of the bridge. Load impact factors of the main girder and tower are small, and the impact factors of the tension of cables are larger than those of the displacements of girders and towers.     

不确定型层次分析在斜拉桥状态评估中的应用

为了确保大跨度斜拉桥的安全运营,保证桥梁的使用寿命,采用不确定型层次分析法对桥梁的状态进行评估.介绍了不确定型层次分析法的相关理论和应用对象,在众多计算区间数判断矩阵的方法中,经过对比分析选用了最优传递矩阵理论,因为其计算结果精确可靠.以哈尔滨松花江斜拉桥为背景桥,利用不确定型层次分析法建立了该桥状态评估的指标体系和评估模型,确定了评估指标的权重并通过计算得到该桥最终的状态评估值,证明了该方法的可行性与实用性.这种评估方法的应用将会为大跨度斜拉桥的养护管理提供更加科学的依据.     

Aerodynamic stability of cable-supported bridges using CFRP cables

To gain understanding of the applicability of carbon fiber reinforced polymer (CFRP) cable in cable-supported bridges, based on the Runyang Bridge and Jinsha Bridge, a suspension bridge using CFRP cables and a cable-stayed bridge using CFRP stay cables are designed, in which the cable’s cross-sectional area is determined by the principle of equivalent axial stiffness. Numerical investigations on the aerodynamic stability of the two bridges are conducted by 3D nonlinear aerodynamic stability analysis. The results showed that as CFRP cables are used in cable-supported bridges, for suspension bridge, its aerodynamic stability is superior to that of the case using steel cables due to the great increase of the torsional frequency; for cable-stayed bridge, its aerodynamic stability is basically the same as that of the case using steel stay cables. Therefore as far as the wind stability is considered, the use of CFRP cables in cable-supported bridges is feasible, and the cable’s cross-sectional area should be deter-mined by the principle of equivalent axial stiffness.     

Comparison of various procedures for progressive collapse analysis of cable-stayed bridges

Alternate path(AP) method is the most widely used method for the progressive collapse analysis,and its application in frame structures has been well proved.However,the application of AP method for other structures,especially for cable-stayed structures,should be further developed.The four analytical procedures,i.e.,linear static,nonlinear static,linear dynamic,and nonlinear dynamic were firstly improved by taking into account the initial state.Then a cable-stayed structure was studied using the four improved methods.Furthermore,the losses of both one cable and two cables were discussed.The results show that for static and dynamic analyses of the cable-stayed bridges,there is large difference between the results obtained from simulations starting with either a deformed or a nondeformed configuration at the time of cable loss.The static results are conservative in the vicinity of the ruptured cable,but the dynamic effect of the cable loss in the area farther away from the loss-cable cannot be considered.Moreover,the dynamic amplification factor of 2.0 is found to be a good estimate for static analysis procedures,since linear static and linear dynamic procedures yield approximately the same maximum vertical deflection.The results of the comprehensive evaluation of the cable failure show that the tread of the progressive failure of the cable-stayed bridges decreases when the location of the failed cables is closer to the pylon.     

Parametrically excited oscillation of stay cable and its control in cable-stayed bridges

This paper presents a nonlinear dynamic model for simulation and analysis of a kind of parametrically excited vibration of stay cable caused by support motion in cable-stayed bridges. The sag, inclination angle of the stay cable are considered in the model, based on which, the oscillation mechanism and dynamic response characteristics of this kind of vibration are analyzed through numerical, calculation. It is noted that parametrically excited oscillation of a stay cable with certain, sag, inclination angle and initial static tension force may occur in cable-stayed bridges due to deck vibration under the condition that the natural frequency of a cable approaches to about half of the, first model frequency of the bridge deck system. A new vibration control system installed on the cable anchorage is proposed as a possible damping system to suppress, the cable parametric oscillation. The numerical calculation results showed that with the use of this damping system, the cable oscillation due to the vibration of the deck and/or towers will be considerably reduced. Project supported by National Natural Science Foundation of China (No. 59978044)     

Nonlinear Dynamic Reliability of Coupled Stay Cables and Bridge Tower

Nonlinear vibration can cause serious problems in long span cable-stayed bridges.When the internal resonance threshold is reached between the excitation frequency and natural frequency,large amplitudes occur in the cable.Based on the current situation of lacking corresponding constraint criteria,a model was presented for analyzing the dynamic reliability of coupling oscillation between the cable and tower in a cable-stayed bridge.First of all,in the case of cable sag,the d'Alembert principle is applied to studying the nonlinear dynamic behavior of the structure,and resonance failure interval of parametric oscillation is calculated accordingly.Then the dynamic reliability model is set up using the JC method.An application of this model has been developed for the preliminary design of one cable-stayed bridge located on Hai River in Tianjin,and time histories analysis as well as reliability indexes have been obtained.When frequency ratio between the cable and tower is approaching 1∶2,the reliability index is 0.98,indicating high failure probability.And this is consistent with theoretical derivation and experimental results in reference.This model,which is capable of computing the reliability index of resonance failure,provides theoretical basis for the establishment of corresponding rule.     

双边轮式斜拉桥悬索检测机器人设计与分析(英文)

为了检测斜拉桥圆柱形悬索内部钢丝情况,设计了一种新型的双边轮式悬索爬升机器人,简述了其机械结构及运动方式,建立了爬升模型,分析了其机构的静态特性,并以直径为139 mm的悬索为例给出了相关设计参数.为使机构在电路系统故障时能安全回收,提出了一种基于反电动势理论的安全节能回收方法,应用曲柄滑块驱动气缸设计了气体阻尼机构,以消耗机构下降时因重力作用产生的多余动能,并建立了机构数学模型来仿真下降速度.试验结果表明,所设计的机器人能携带3.5 kg重物沿直径为65～205 mm的悬索平稳运行,满足了悬索检测的实用要求.