斜铁路钢桥的高等动力有限元分析

介绍斜铁路钢桥动态分析的模型。给出一个有限元分析的案例及其与实际测量结果的对比。首先,通过不同模型的特征值分析,得到基础模型选型和桥梁频率,以及评估每个模型分析桥梁动态性能的能力。通过壳单元、梁单元以及组合单元对单跨、三跨和全比例桥梁建模。结果显示,桥梁基本动态特征数值分析结果与试验结果吻合。全比例桥梁模型用于分析特征值和动力时程分析。对不同列车时速和应变记录的分析与实际测量进行比较。疲劳评估通过选取桥梁某一位置的平均应力值也进行了比较研究。结果表明,采用梁单元和壳单元的组合单元的全比例尺模型,可以高效准确地预测桥梁的动力性能和疲劳破坏的平均应力值的范围。     

Dynamic stress analysis for fatigue damage prognosis of long-span bridges

For fatigue damage prognosis of a long-span steel bridge, the dynamic stress analysis of critical structural components of the bridge under the future dynamic vehicle loading is essential. This paper thus presents a framework of dynamic stress analysis for fatigue damage prognosis of long-span steel bridges under the future dynamic vehicle loading. The multi-scale finite element (FE) model of the bridge is first developed using shell/plate elements to simulate the critical structural components (local models) and using beam/truss elements to simulate the rest part of the bridge (global model). With the appropriate coupling of the global and local models, the multi-scale FE model can accurately capture simultaneously not only the global behavior in terms of displacement and acceleration but also the local behavior in terms of stress and strain. A vehicle traffic load model is then developed for forecasting the future vehicle loading based on the recorded weigh-in-motion (WIM) data and using the agent-based traffic flow microsimulation. The forecasted future vehicle loading is finally applied on the multi-scale model of a real long-span cable-stayed bridge for dynamic stress analysis and fatigue damage prognosis. The obtained results show that the proposed framework is effective and accurate for dynamic stress analysis and fatigue damage prognosis.     

Experimental and numerical analysis of the strain-rate effect on fully welded connections

This paper presents experimental and numerical results of dynamic cyclic tests carried out on two full-scale specimens of welded beam-to-column connections. In order to simulate the nonlinear dynamic behaviour of tested specimens, a fibre-based finite element beam is used to model beam and column members and a nonlinear rotational spring is also used to model welded connections. The effect of strain rate on beam and column behaviour is taken into account for each constitutive fibre using the Perzyna law. The effect of strain rate on welded connection is taken into account by extending the static Richard model to simulate its dynamic behaviour. The Krawinkler-Zoheri model, expressed as a function of normalized cumulative plastic strain, is introduced to quantify damage and degrading behaviour in terms of the strain-rate effect. The finite element Drain-2dx software is first upgraded for this purpose to carry out numerical investigations. The analytical results obtained from the numerical simulation, taking the strain rate effect and damage accumulation into account, predict well the structural dynamic behaviour up to failure of welded connections when compared with available experimental data.     

Remaining fatigue life of steel railway bridges under enhanced axle loads

In this study, various fatigue damage models proposed by researchers have been briefly discussed and found that the models are problem specific and their efficacy needs to be checked for high cyclic fatigue cases such as in railway bridges. Towards this, field studies were conducted to obtain the strain responses from a steel bridge during the passage of scheduled trains and test train formation with enhanced axle loading. Instrumentation was carried out at critical locations to obtain the responses from the girder. Three different scenarios have been considered to avoid the influence of noise. Further, numerical simulation of the bridge subjected to train loading at different speeds was carried out using ANSYS to obtain synthetic data of strain response from the validated finite element model. Analysis was carried out for normal as well as for futuristic speed of the trains. Responses obtained from field measurements as well as from numerical investigations were used to calculate the damage indices. Based on the damage indices, remaining fatigue life of the bridge was evaluated. The present study can be helpful in assessing the health condition of the railway bridges and to check the suitability of further increase in axle load or speed of trains.     

The vibrational behaviour of three composite beam-slab bridges

This paper describes field measurements of the vibrational frequencies of three bridges with prestressed concrete beams and in situ concrete deck slabs. In each bridge, the beams are simply supported over each span while the composite deck is continous over three or four spans with short, full width, crumple slabs between the beam diaphragms over each pier. Analytical analyses were also carried out and compared with the field measurements. Values are also given for the damping determined from the tests.     

基于基频法的预应力混凝土箱梁疲劳刚度退化试验

开展了基于基频法的预应力混凝土箱梁桥模型疲劳试验; 详细介绍了基于基频法的疲劳多级变幅试验加载过程及疲劳加载方案和采集方案; 梳理了动刚度和静刚度的基本原理、基于基频的动刚度计算方法和基于挠度的静刚度计算方法; 对预应力混凝土箱梁的疲劳动刚度和静刚度退化规律进行了研究。结果表明:箱梁构件疲劳裂缝分布、裂缝走向和破坏敏感位置与矩形梁不同,模型梁均首先在腹板产生斜裂缝,腹板斜裂缝主要分布在从支座到1/4跨范围内,不断向顶板和底板斜向延伸; 预应力混凝土箱梁疲劳动刚度和静刚度二者退化规律相同,均呈现为先快速、后平稳的2阶段变化规律; 在疲劳初期,动刚度和静刚度退化率均在40%以上; 疲劳荷载上限值是桥梁结构疲劳刚度退化的一个重要影响因素,疲劳荷载上限值越大,动刚度和静刚度退化幅值就越大,且疲劳剩余刚度越小; 因为二者计算原理不同,所以计算的动静刚度数值也不同,但二者刚度退化规律相同,可相互对比、补充、验证,共同来探究预应力混凝土箱梁疲劳刚度的退化规律。     

Ermüdungsbeanspruchungen von Betonbrücken unter zunehmendem Schwerverkehr

Fatigue Life of Concrete Bridges under Consideration of Increasing Traffic Loads Increasing traffic loads lead to higher fatigue stresses on bridge structures. The effects on the stresses of the main load‐bearing structure depend on the load models representing weight and the ratio of the load model length to the bearing distance of the superstructure. Within a research project carried out on behalf of the Federal Ministry of Transport, Building and Urban Affairs several different bridge constructions (box girder bridge, skew slab construction, girder bridge with T‐beam elements) were analysed with respect to their fatigue strength. Hence, the stresses in concrete and steel components are examined on extensive numerical models in longitudinal and transversal direction. The fatigue investigations of these existing bridges are performed by specified load combinations according to the German Standard for the design of concrete bridges. Furthermore the future development of heavy traffic loads is included by calculating the effects of a 60to‐heavy traffic vehicle.     

Structural performance evaluation of a precast prefabricated bridge column under vehicle impact loading

In this study, the numerical analysis method was proposed to analyse the structural behaviour of bridge columns under various impact loading conditions. A parametric study of vehicle impact simulation was carried out to determine the impact loading-time functions. According to the impact simulation results, five-point piecewise linear approximation is proposed and validated. The proposed loading function was applied to the material nonlinear finite element analyses of two different types of bridge piers, the cast-in-place reinforced concrete bridge columns and the prefabricated bridge columns, which were designed under the same loading conditions. The dynamic performances of the considered bridge piers are compared using the results of dynamic numerical analyses. Also, the static design loadings of a vehicle crash defined in the Korean bridge design code and AASHTO LRFD Bridge Design Specifications were applied to analyse the results of the dynamic analyses of the piers.     

应变率对全焊节点影响的试验和数值分析

对2个梁柱焊接节点的足尺试件进行动力试验。为了模拟试件的非线性动力性能,用纤维梁单元模拟梁、柱,用非线性旋转弹簧模拟焊接节点。对每一纤维,均采用Perzyna准则考虑应变率对梁、柱性能的影响。通过改进Richard静力模型模拟动力性能,考虑应变率对焊接节点的影响。Krawin-kler-Zoheri模型是标准累积塑性应变的函数,可根据应变率影响量化损伤和退化性能。将有限元分析软件DRAIN-2DX升级,建立模型并进行数值分析。与试验结果比较可知,考虑应变率影响和损伤累积的数值模拟能很好预测结构动力性能,甚至能预测焊接节点的破坏模式。     

碳纤维拉索试验桥的有限元模型研究

本文以国内首座碳纤维拉索试验桥为研究对象,主要研究了碳纤维拉索斜拉桥空间有限元模型建立中的一些基础性问题。通过选取不同的单元类型,建立了三种全桥有限元模型。然后将有限元模型的分析结果与该桥静载试验的结果进行了对比。结果表明,三种模型的精度均能满足工程要求,其中壳单元模型要优于其余两种模型,具有较高的求解精度和求解效率。     

下承式钢管混凝土系杆拱桥的冲击系数研究

以泰兴滨江大桥为例,根据下承式钢管混凝土系杆拱桥的结构特点,采用大型通用有限元软件ANSYS对该桥进行有限元离散。采用梁单元beam4模拟钢管混凝土拱肋（内部混凝土及外部钢管）、系杆及横梁等构件,用杆单元Iinks模拟吊杆,用壳单元she1163模拟桥面铺装层,用实体单元solid45模拟桥面系的预制空心板部分,建立了系杆拱桥的空间计算的有限元模型,进行模态分析,得到各阶自振频率及振型。建立四分之一车辆模型作用下的拱桥车桥耦合振动模型,并利用MATLAB语言编制程序,分析了移动车辆荷载作用下下承式钢管混凝土系杆拱桥的响应,系统地得到了该桥在不同车速,不同车道,不同阻尼,不同路况的振动响应等力学性能。本文所得出的主要结论和有关研究成果可为大跨度钢管混凝土系杆拱桥设计时的冲击系数取值,研究车辆对系杆拱桥的冲击性能和后期桥梁养护确定荷载效应分析提供参考。     

Dynamic Characteristics of a Curved Cable-stayed Bridge:Operational Modal Testing and FE Modeling

This paper summarizes the analytical and experimental dynamic analyses carried out to assess the actual dynamic behaviour of a curved cable-stayed bridge,recently erected in the commercial harbour of Porto Marghera ( Venice,Italy). Ambient vibration tests were carried out to determine the dynamic characteristics of the bridge and more than 20 modes were identified in the frequency range 0～10Hz. In the theoretical study,a 3D FE model of the bridge was developed using an integrated CAD-FEA approach; subsequen...     

Beam and shell element model for advanced analysis of steel structural members

Plastic zone method of advanced analysis, which uses shell elements to model the entire structure, is the most accurate method available to predict the ultimate strength and behavior of steel frames. The disadvantage of such full shell plastic zone models is that it is computationally expensive and hence its use is limited to small structures. Beam elements in commercial finite element packages can model residual stress and capture spread of plasticity, but cannot model local buckling of plates that the member is made up of, which leads to unloading and failure in steel frames. A hybrid model using shell elements only in the regions vulnerable to elastic or inelastic local buckling and beam elements in other locations could overcome this limitation of full beam element model. The issues in using this hybrid model are, knowing a priori the location and length of the shell element region and connecting the beam and shell regions without any artificial stress concentrations or incompatible displacements. In this study, in addition to addressing these issues, the hybrid model is systematically evaluated by studying its performance in structural elements. It is seen that the hybrid model strength predictions has an average error of only 0.91% but requires on an average 83% less computational time when compared to the full shell plastic zone models.     

Beam and shell element model for advanced analysis of steel structural members

Plastic zone method of advanced analysis, which uses shell elements to model the entire structure, is the most accurate method available to predict the ultimate strength and behavior of steel frames. The disadvantage of such full shell plastic zone models is that it is computationally expensive and hence its use is limited to small structures. Beam elements in commercial finite element packages can model residual stress and capture spread of plasticity, but cannot model local buckling of plates that the member is made up of, which leads to unloading and failure in steel frames. A hybrid model using shell elements only in the regions vulnerable to elastic or inelastic local buckling and beam elements in other locations could overcome this limitation of full beam element model. The issues in using this hybrid model are, knowing a priori the location and length of the shell element region and connecting the beam and shell regions without any artificial stress concentrations or incompatible displacements. In this study, in addition to addressing these issues, the hybrid model is systematically evaluated by studying its performance in structural elements. It is seen that the hybrid model strength predictions has an average error of only 0.91% but requires on an average 83% less computational time when compared to the full shell plastic zone models.     

New beam-to-beam joint with concrete embedding for composite bridges: Experimental study and finite element modelling

This paper deals with a new type of beam-to-beam joint used to connect continuously composite beams in small and medium span bridges. This new joint is realized by encasing totally the two composite beam ends into a massive composite reinforced concrete block. A direct contact between the ends of the bottom flanges of the steel girders over the support ensures the transfer of the compression forces. A half-scale joint specimen has been designed and fabricated. The specimen was first tested at the Structural Laboratory of INSA-Rennes under fatigue loading. Next, the load was monotonically increased up to the specimen failure. The main results of this experimental study are firstly presented. To allow an accurate interpretation of the test results and get a better insight into the joint behaviour, a numerical F.E. model has been developed. The numerical results are presented and compared against experimental ones. Besides, a parametric study has been carried out in order to investigate the influence of key parameters governing the joint behaviour. The influence of the behaviour of this type of joint on the global analysis of a continuous composite beam has then been studied. Finally, a worked example of a two-span continuous railway bridge is presented and effects of intermediate beam-to-beam joint characteristics on the bridge behaviour are discussed.     

Critical assessment of Eurocode approach to stability of metal cylindrical silos with corrugated walls and vertical stiffeners

The paper deals with stability of steel cylindrical silos composed of corrugated walls and vertical open-sectional stringers. Comprehensive three-dimensional finite element analyses were carried out with perfect slender, semi-slender and squat silos by means of a linear buckling approach. Corrugated walls were simulated as an equivalent orthotropic shell and vertical open-sectional stringers as beam elements. The FE results were compared with the Eurocode approach. In addition, comprehensive FE computations for axially compressed cylindrical shells composed of an orthotropic shell and stringers were carried out. An improvement of standard formulae was proposed.     

钢桥面沥青混合料铺装体系疲劳特性的损伤力学分析

用损伤力学原理及方法,从力学近似法角度分析了单纯的沥青混合料铺装层矩形截面梁疲劳损伤特性,推导出梁的应变场和疲劳寿命预测公式。按抗弯刚度等效简化原则,将疲劳试验复合梁模型中的实际桥面用钢板简化为沥青混合料铺装层叠加到下面的沥青混合料铺装层上,共同组成准单纯的沥青混合料铺装层矩形截面梁,应用该原理及方法推导出梁底缘的应变场,以南京长江第二大桥钢桥面环氧沥青混凝土铺装体系复合梁疲劳试验为例,进一步推导出复合梁的疲劳寿命预测公式。通过实例分析,表明损伤力学原理及方法可用于分析钢桥面沥青混合料铺装体系疲劳特性,其疲劳寿命预测结果是较为精确的,它的实际应用还需给出相应的修正,此外指出了环氧沥青混凝土铺装具有很好的抗疲劳性能。     

Assessment of the dynamic and fatigue behaviour of the Panaro railway steel bridge

The functionality maintenance of European infrastructures like bridges is acquiring more and more importance due to the huge economic losses related to the interruption of their regular service. In particular, fatigue represents one of the most common failure modes occurring in steel and steel–concrete composite bridges: most failures in steel structures are related to fracture and fatigue. Railway bridges endure millions of stress cycles during their life and they are expected to be highly vulnerable to such phenomena. Phenomena like ‘vibration induced’ and ‘distortion induced’ fatigue are still partially uncovered by actual design codes and they represent critical aspects for the assessment of existing bridge remaining life and for the design of new bridges. The European research project FADLESS ‘Fatigue damage control and assessment for railways bridges’, funded by the Research Fund for Coal and Steel, aims at defining innovative technical guidelines for the assessment and control of existing and new bridges with regard to fatigue phenomena induced by vibrations and distortions produced by train passages. The project combines experimental and numerical techniques to study fatigue cracking induced by vibration and distortion phenomena taking into account the dynamic train–bridge interaction effects and the actual traffic spectra on European railway lines. In the present paper, preliminary analyses performed on the Italian case study, the Panaro Bridge, are being reported upon. Results obtained by standard fatigue assessment according to Eurocode rules were compared with the actual fatigue cracks found in the deck secondary components. A preliminary critical review of adopted fatigue assessment methodologies was carried out. Moreover, experimental tests were designed and performed on the bridge in order to identify global and local vibration modes and to evaluate the strain time-histories under train passages of critical details. Finally, experimental global/local mode shapes were compared to numerical results from the preliminary FE bridge model.     

延性节点钢框架结构的抗震性能分析

为简化延性耗能节点钢框架结构的数值计算,利用延性耗能节点简化理论模型分别对6层、12层的翼缘削弱型节点钢框架和盖板加强型节点钢框架进行简化,并对框架简化模型和实际框架模型进行模态分析;提取框架结构的前3阶基本周期并计算阻尼比,并对框架结构简化模型和实际模型开展El Centro波和Taft波2种地震波下的动力时程分析,将框架简化模型计算得到的框架基本周期、柱顶位移和柱底剪力时程曲线与实际框架模型的数值计算结果进行对比。结果表明:整体上框架简化模型和实际框架模型的数值计算结果吻合较好,翼缘削弱型节点框架简化模型计算的框架基本周期比实际模型计算值稍小,相对误差在8.5%以内,而盖板加强型节点框架简化模型计算的框架基本周期比实际模型计算值稍大,相对误差在4.0%以内;柱顶位移和柱底剪力时程曲线吻合较好。延性节点简化理论模型用于框架结构动力计算具有极高的计算精度,可有效分析延性节点钢框架结构的抗震性能。     

Numerical solution of curved pipes submitted to in-plane loading conditions

An alternative formulation to current meshes dealing with finite shell elements is presented to solve the problem of stress analysis of curved pipes subjected to in-plane bending forces. The solution is based on finite curved elements, where displacements are defined from a total set of trigonometric functions or a fifth-order polynomial, combined with Fourier series. Global shell displacements are achieved through the one associated with curved arch bending and the other referred to the toroidal thin-walled shell distortion. Beam-type displacement and in-plane rotation are uncoupled and separately formulated, using trigonometric shape functions, as in Timoshenko or Mindlin beam theory. To build up the solution, a simple deformation model was adopted, based on the semi-membrane concept of the doubly curved shells behaviour. Several studies are presented and compared with experimental and numerical analyses reported by other authors.