分离式公铁双层桥面桥梁-列车-风屏障系统气动效应风洞试验研究

为探究侧风作用下分离式公铁双层桥面桥梁上、下桥面间气动干扰效应对列车气动效应的影响,在无风屏障和设置风屏障两种情况下,分别针对单独铁路桥和标准间隔高度下的公铁双层桥面桥梁,通过大比例尺节段模型风洞试验测试了列车的气动力系数以及铁路桥面轨道上方的风速剖面变化规律。为了进一步探究公铁双层桥面间隔高度对列车气动效应的影响,测试了多种间隔高度下列车气动力系数以及铁路桥面轨道上方的风速剖面变化规律。结果表明,公铁双层桥面间气动干扰效应对列车气动效应有一定的影响,间隔高度的改变会引起铁路桥面风速剖面以及列车气动力系数的变化,对比分析可知,无风屏障时间隔高度仅需满足铁路桥梁基本建筑限界即可,设置风屏障后,当间隔高度≥15m时,铁路桥面风速剖面以及迎风侧轨道处列车气动力变化趋于平缓。     

Fatigue behavior and statistical evaluation of the stress category for a steel-concrete composite bridge deck

The maintenance cost of bridges is rapidly increasing since many existing bridges are deteriorating or reaching their design life all over the world. Moreover, as many long-span bridges are under construction and planning in Korea, research and development on bridge decks with high load-resistance capacity as well as high fatigue strength has become a growing concern. This research gives experimental results of the fatigue behavior of a new-type of steel-concrete composite bridge deck being developed under such circumstances. The proposed composite bridge deck consists of corrugated steel plate, welded steel ribs, stud shear connectors, and reinforced concrete filler. Fatigue tests were conducted under a four-point bending test with four different stress ranges in constant amplitude. In order to determine the influence of the concrete filling, fatigue tests on partial steel specimens containing only plain corrugated steel plates were performed in advance. The partial steel specimens and the steel-concrete composite deck specimens both showed fatigue failure in the tension part concerning the fillet welding part between the corrugated steel plate and steel rib. Finally, the stress category of the fillet welding part of each specimen is evaluated based on a statistical approach of Albrecht’s probability model. The research concludes that the fatigue behavior of such steel-concrete composite decks under sagging moment can be estimated based on the classical S-N approach, focusing on steel components.     

Investigation on aerodynamic stability of long-span suspension bridges under erection

The aerodynamic stability of long-span suspension bridge under erection, particularly at early erection stage, is more problematic than in the final state. It is influenced by the deck erection sequence and the nonlinear effects of wind-structure interactions. Considering the geometric nonlinearity of bridge structures and the nonlinear effects of wind-structure interactions, a method of nonlinear aerodynamic stability analysis is presented to predicate the aerodynamic stability limit (flutter speed) of long-span suspension bridges during erection. Taking the Yichang Bridge over the Yangtze River as example, evolutions of flutter speeds with the deck erected by different sequences are numerically generated. The sequences of pylons to midspan and the non-symmetrical deck erection are confirmed analytically to be aerodynamically favorable for the deck erection of long-span suspension bridges, particularly at early erection stages. The flutter speeds of long-span suspension bridges under erection are greatly decreased by the nonlinear effects of wind-structure interactions.     

悬索桥跨径的空气动力极限

桥梁建设已经进入了一个建造跨海大桥的新时代。在跨海大桥工程的可行性研究中存在许多技术方面的挑战 ,对于桥梁设计者来说 ,超大跨径悬索桥的气动稳定问题始终是必须十分关注的问题。本文首先研究超大跨径悬索桥的技术可行性及潜在的要求 ,然后讨论各种气动措施的性能 ,其中包括缆索系统的调整、中央开槽方案、垂直及水平稳定板以及振动控制措施等。从技术及航运要求出发 ,设计了一个接近极限跨径的主跨为5 0 0 0m的悬索桥方案 ,以此为基础研究并阐述解决其空气静动力稳定性的方法     

大跨径钢桥面铺装体系多目标优化设计

将大跨径钢桥的正交异性钢桥面和其上的铺装层作为钢桥面铺装体系整体进行多目标优化设计。取大跨径钢桥面铺装体系造价及铺装层表面极限应力最小化两类指标构造目标函数,在此基础上建立多目标优化设计的数学模型。采用评价函数中的线性加权和法进行求解,开发了钢桥面铺装体系结构多目标优化设计程序,以国内某大跨径钢桥为对象,采用多目标优化设计方法,给出钢桥面铺装体系中各参数的合理界限。应用国际通用有限元软件SPA93程序对其进行验证,结果表明,应用多目标优化设计方法对大跨径钢桥面铺装体系设计是可行的。研究成果可为大跨径钢桥面铺装体系结构的设计提供理论依据。     

Aerodynamic stability of cable-stayed bridge with new Vierendeel-type girder

An aerodynamic study is described showing the stability of a new type of double deck cable-stayed bridge having both upper and lower flat, shallow, streamlined box girder decks connected by vertical members only. In long span, cable-stayed bridges the longer the span, the more important the aerodynamic stability of the structure becomes. Even though cable-stayed bridges evidence structural damping, the measure of the aerodynamic stability of such a bridge is whether or not a cross-sectional shape of the suspended structure is stable against flutter oscillation and vortex-excited oscillation. The experiments presented in this paper, therefore, focus on the aerodynamic stability against these phenomena in a partial scale model of a cable-stayed bridge of new design. The three aerodynamic components of force have also been measured. For comparison, a wind-tunnel experiment has been carried out using a partial model of a conventional suspended structure of a typical truss type double deck cable-stayed bridge. It is shown that the new system is superior to the truss type from an aerodynamic stability viewpoint.     

Parametric study on the aerodynamic stability of a long-span suspension bridge

The aerodynamic stability becomes a governing factor in designing long-span suspension bridges. In this paper, using the method of three-dimensional nonlinear aerodynamic stability analysis, parametric analyses on the aerodynamic stability of the Runyang bridge over the Yangtze River are performed including the structural system, the cable sag, the side span length, the depth, dead load and supporting system of the deck, etc. Some important design parameters that affect the aerodynamic stability of the bridge are pointed out, and the favorable structural system of the bridge is also discussed based on the wind stability.     

Experimental study of aerodynamic interference effects on aerostatic coefficients of twin deck bridges

The aerodynamic interference effects on aerostatic coefficients of twin deck bridges with large span were investigated in detail by means of wind tunnel test. The distances between the twin decks and wind attack angles were changed during the wind tunnel test to study the effects on aerodynamic interferences of aerostatic coefficients of twin decks. The research results have shown that the drag coefficients of the leeward deck are much smaller than that of a single leeward deck. The drag coefficients of a windward deck decrease slightly compared with that of a single deck. The lift and torque coefficients of windward and leeward decks are also affected slightly by the aerodynamic interference of twin decks. And the aerodynamic interference effects on lift and torque coefficients of twin decks can be neglected.     

Monitoring the dynamic characteristics of an urban bridge before,during and after widening

The dynamic characteristics of a multi-span pre-stressed concrete urban bridge before, during and after widening operations have been studied. The widening operations have been carried out by adding two new bridges on the either sides of the old bridge. The decks of the new bridges have been structurally separated from the old one by two longitudinal joints on the either side of the old bridge. The dynamic characteristics have been extracted from operational modal tests in three phases during different stages of the widening operations. The dynamic interaction between the new parts and the old part of the bridge has also been investigated. The results show that after the completion of the widening works, and when the whole bridge was placed in service condition, this interaction affects the natural frequencies of almost all the vibration modes of the bridge. It was also found that the longitudinal joints were unable to effectively isolate the new parts from the old part. Finally, in order to achieve a consistent behaviour in the first bending mode of the new and old bridges, a geometrical index has been introduced. This index includes both the effects of stiffness and mass properties of the bridge deck. In widening projects, where the span lengths, material properties and support conditions of the two bridges are taken the same, adopting equal geometrical indices leads to almost equal values of the natural frequencies and similar mode shapes in the first bending mode. The proposed index can be used in the initial design stage for such projects.     

大跨径钢桥面铺装设计理论与方法研究

结合南京长江第二大桥、舟山桃夭门大桥、润扬长江公路大桥和杭州湾大桥等大型桥梁桥面铺装的研究与设计 ,对大跨径钢桥面铺装设计理论与方法 ,包括铺装材料与结构、钢桥面铺装体系受力特性、疲劳特性、热塑性沥青混合料铺装车辙、设计指标、轴载换算方法、设计方法等关键技术进行系统的分析与研究 ,研究成果已在多座大跨径钢箱梁桥面铺装设计和铺装工程中应用     

Zur Effizienz von Queraussteifungen und unteren Verbänden bei breiten Straßendeckbrücken

Efficiency of diaphragms and horicontal bracings of highway deck bridges with multiple girders. This paper deals with different structural systems of a multispan composite highway bridge with spans of about 70 meters. The basis is a highway bridge which had to be strengthened. It has two seperate bridge decks, consisting of single boxed girders with a bottom bracing. Beside this structural system a connection of both decks with cross bracings and a completion to a multicellular deck with three cells is studied. For comparison also the system with two seperate decks composed of two plate girders and a multiple plate girder bridge deck are considered. Also the variation of the stiffness of the bracings and the number of cross bracings is studied. For every structural system the results in form of vertical deflections, influence lines and stresses in representative sections are presented and compared. On this basis the efficiency of bracings can be evaluated and the most economic structural system for the strengthening of two isolated bridge decks can be found. Also the material effort of the different structural systems for a new bridge with a wide deck is shown.     

正交异性钢桥面板纵肋与桥面板连接细节的疲劳评估及修复措施

正交异性钢桥面板由于具有自重轻、极限承载力大等优点目前广泛应用于大、中跨径桥梁中,我国已建和在建的大跨径桥梁也大多采用正交异性钢桥面板.但由于正交异性钢桥面板结构构造复杂,受焊接残余应力影响大,钢桥面板直接位于车轮荷载的作用下,一些构造细节处极易发生疲劳开裂.以国内某大桥正交异性钢桥面板为例,针对纵肋与桥面板之间的疲劳...     

主桁弦杆盖板栓接处与桥面不等厚对接焊的疲劳性能研究

<正>交异性板整体桥面具备诸多良好性能,正越来越多地应用于高速铁路桥梁建设。由于国内尚无建成高速铁路桥梁的成熟经验,钢整体桥面又是疲劳裂纹高发部位,因此,对其构造细节必须进行充分的分析与研究。其中,主桁下弦杆连接处的盖板与桥面板不等厚对接交叉焊缝构造,是一种栓焊混合结构。该部位由对接焊缝和高强螺栓同时承受外力,应力分布比较复杂。针对其受力特点,设计试验试件,在试验室模拟实桥受力进行静载试验和疲劳试验,对该构造的疲劳寿命进行评估。应用ANSYS有限元软件对该构造细节进行应力分析。最后在有限元分析的基础上,针对该构造疲劳性能较差的薄弱点,提出补强措施。     

Wind tunnel: a fundamental tool for long-span bridge design

An overview of wind tunnel activities and methodologies to support the design of long-span suspension bridges is proposed. The most important aspects of the wind-bridge interaction are investigated considering the aerodynamic phenomena affecting the different parts of the bridge (mainly deck and towers). The experimental activities and results are proposed in the framework of a synergic approach between numerical and experimental methodologies that represent the common practice in defining the full scale aeroelastic behaviour of the bridge starting from scaled reproduction of the wind-bridge interaction. Static and dynamic wind loads, aeroelastic stability, vortex-induced vibrations will be investigated.     

Direct identification of flutter derivatives and aerodynamic admittances of bridge decks

Flutter derivatives and aerodynamic admittances provide basis of predicting the critical wind speed in flutter and buffeting analysis of long-span cable-supported bridges. In this paper, one popular stochastic system identification technique, covariance-driven stochastic subspace identification (SSI in short), is first presented for estimation of the flutter derivatives and aerodynamic admittances of bridge decks from their random responses in turbulent flow. Numerical simulations of an ideal thin plate are adopted to extract these aerodynamic parameters to evaluate the applicability of the present method. Then wind tunnel tests of a streamlined thin plate model and a Π type blunt bridge section model were conducted in turbulent flow and the flutter derivatives and aerodynamic admittances are determined by the SSI technique. The identified aerodynamic parameters are compared with the theoretical ones and the results indicate the applicability of the current method.     

Aerodynamic interference effects and mitigation measures on vortex-induced vibrations of two adjacent cable-stayed bridges

By examining the two neighboring Haihe Bridges with semi- and full-closed bridge decks, the aerodynamic interference between the two decks on the vortex-induced vibration (VIV) and the corresponding aerodynamic mitigation measures are investigated via a series of wind tunnel tests with a spring-suspended sectional model aided with computational fluid dynamics (CFD) method. The results show that the VIV responses of both bridges can be significantly affected by the aerodynamic interference and that the extent of the influence varies with the shapes of the windward and leeward decks. The VIV amplitudes of the windward bridge are often fairly close to those of the single bridge. However, those of the leeward bridge are magnified substantially by aerodynamic interference if the same structural and aerodynamic configurations are adopted for the two bridges. Otherwise, the VIV responses are not significantly increased and may even be reduced by the aerodynamic interference if different configurations are employed for the two bridges. Furthermore, an effective combined measure of adding wind barriers and sharpening the wind fairing noses of the two box decks is presented for mitigating both the vertical and torsional VIV responses of the windward and leeward bridges.     

Wind suction effect on long-span stiffened steel truss bridges during erection

During the erection of long-span steel truss bridges, the bridge decks and the steel truss girders are commonly constructed simultaneously in order to shorten the construction period, leading to wind suction effect on the decks when wind strikes. This effect may have a remarkable influence on the wind-resistant behavior of stiffened steel truss bridges which hold long-span cantilevers during erection, as wind suction can act together with the gravity load to increase the structural response. However, neither current codes nor studies have taken this effect into account. This paper is intended to investigate the wind suction effect and its influence on the static wind-resistant behavior of stiffened steel truss bridges during construction. Two wind tunnel tests, including a high-frequency base balance (H-FBB) test and a synchronous multi-pressure sensing system (SM-PSS) test, were carried out with the world's longest arch-stiffened steel truss bridge as a model. On the basis of the experimental results, two net pressure coefficients which could be used to determine the wind suction are proposed. A finite element analysis considering the wind suction effect is also performed, through which the wind suction influence on the model bridge during erection is obtained.     

Study of super long span cable-stayed bridges with CFRP components

This paper introduces new types of cable-stayed bridges with carbon fiber reinforced polymers (CFRP) stay cables and/or a CFRP bridge deck. For each of the two CFRP components, namely, CFRP stay cables and CFRP bridge deck, the key design parameters and design strategies were determined and the appropriate value of each key design parameter was suggested. Using the suggested parameter values, six types of cable-stayed bridges with a main span length of 1400 m were selected and modeled with the finite element method, through which the procedures of designing composite cable-stayed bridges with CFRP components were presented in details. From a mechanical-behavior viewpoint (static and dynamic) a comparative study of composite cable-stayed bridges with different CFRP components was performed through numerical simulations. The economical behavior of each type of cable-stayed bridges was also comparatively studied considering the varying material price. With the high strength-to-weight ratio and other advantages of CFRP materials, it was proven in this study that the use of CFRP stay cables and CFRP bridge decks in super long span cable-stayed bridges is feasible and these types of composite cable-stayed bridges could become an excellent alternative to steel cable-stayed bridges where super long spans are desired.     

安装过程中风吸力对大跨加劲钢桁桥的影响

在大跨钢桁桥的安装过程中,为缩短工期,桥面板和钢桁梁常同时施工,这将导致风吸力对桥面板产生影响,从而影响安装过程中含大跨悬臂梁的加劲钢桁桥的抗风性能,因为风吸力与自重共同作用会增大结构响应。然而,现有规范和研究都没有考虑这种影响,故需研究风吸力对安装过程中加劲钢桁桥的抗风静力性能的影响。以世界最长的拱加劲钢桁桥为模型,进行2个风洞试验:高频底座天平试验和同步多点压力传感系统试验。基于试验结果,建立2个净压力系数以确定风吸力。通过确定安装过程中风吸力对桥梁的影响,建立了考虑风吸力的有限元模型。     

Experimental study of aerodynamic interference effects on aerostatic coefficients of twin deck bridges

The aerodynamic interference effects on aerostatic coefficients of twin deck bridges with large span were investigated in detail by means of wind tunnel test. The distances between the twin decks and wind attack angles were changed during the wind tunnel test to study the effects on aerodynamic interferences of aerostatic coefficients of twin decks. The research results have shown that the drag coefficients of the leeward deck are much smaller than that of a single leeward deck. The drag coefficients of a windward deck decrease slightly compared with that of a single deck. The lift and torque coefficients of windward and leeward decks are also affected slightly by the aerodynamic interference of twin decks. And the aerodynamic interference effects on lift and torque coefficients of twin decks can be neglected. __________ Translated from Journal of Hunan University (Natural Science), 2008, 35(1): 16–20 [译自: 湖南大学学报(自然科学版)]