Bridge Section Research Articles

Analysis of self-excited forces for a box-girder bridge deck through unsteady RANS simulations

This paper presents the results of two-dimensional numerical simulations of the flow field around a trapezoidal box-girder bridge section with later cantilevers, experiencing small-amplitude heaving or pitching harmonic oscillations. Unsteady Reynolds-averaged Navier–Stokes equations are solved in conjunction with an eddy-viscosity and an explicit algebraic Reynolds stress model. Flutter derivatives are determined and compared with wind tunnel results, showing fairly good agreement. The degree of sharpness of the deck lower edges is found to play a key role in the aeroelastic behavior of the profile. In particular, the bridge section fully behaves as a bluff body and is prone to low-reduced-wind-speed torsional galloping in the case of perfectly sharp edges. By contrast, the presence of a small radius of curvature in the section lower corners changes the nature of the instability to coupled flutter and significantly postpones the stability threshold, in line with a quasi-streamlined body behavior. Moreover, a wide sensitivity study is carried out, investigating the influence on the self-excited forces of the amplitude of oscillation, mean angle of attack and Reynolds number. In particular, the numerical simulations for the geometry with smooth lower edges highlight the regime transition occurring when the Reynolds number is varied, with significant effects on the flutter derivatives. Finally, the numerical flow visualizations provide a physical explanation of some phenomena observed in the wind tunnel experiments.

Numerical wind tunnel for aerodynamic and aeroelastic characterization of bridge deck sections

The aim of the present study is to propose a reliable engineering procedure to analyze bridges subjected to wind loads by-passing the expensive wind tunnel tests thanks to numerical simulations. These exploit Kratos, a free multi-physic FEM code developed by the Kratos Team at CIMNE in Barcelona, and, specifically, an adaptation to the long-span bridge case of its numerical tool for simulation of in-wind ultra-lightweight structures developed within the uLites project (supported by the Research Executive Agency in the Seventh Framework Programme of the European Union, SP4-Capacities, Research for the benefit of SMEs, FP7-SME-2012 GA-314891, see http://www.cimne.com/websasp/ulites/). Time histories of the forces induced by the flow around the sections are used to calculate aerodynamic and aeroelastic parameters through statistical, frequencies extraction and fitting algorithms. Several analyses have been performed to derive rules for a reliable and stable evaluation of these aggregated parameters for engineering purposes. Results obtained for the sections of Great Belt Bridge (Denmark) and of the bridge on A31 highway over Adige river (Italy) are shown. Both static analyses (CFD procedure with fix boundaries) and imposed-displacements analyses (CFD with ALE) give results that are comparable with those coming from wind tunnel testing and from literature; evaluated parameters also manifest regular trends and values little influenced by CFD setting. These facts represent proofs of the reliability of the proposed procedure.

Field Static load Effect on Performance of Hollow Section Girder Bridge Subjected to Fire (Part A)

Hollow Bridge section inspection was carried out in this study and different reasons may cause major failure of bridge. The field inspection of bridge structural elements has been paying more attention of engineering academic researchers. The bridge has been exposed to fire accident in additional to the excessive load and environmental factors effects. This study dedicated for inspection the White River Bridge elements (Bai xi da Qiao/ China) including the essential damage in main girder , concrete spalling, deformation due to deflection and excessive stress and strain, deck slab and concrete cover, steel corrosion…..etc. The analysis of field test evaluates the performance of whole structure of bridge element under static load test. The investigation results shows that the bridge has minor defects through the substructures such as there is no major corrosion of reinforcement and the concrete in a good condition. The upper structure depending on analysis field test of deflection and strain at the critical section, that the main girder has no enough capacity and need to be strengthened.

Variation of aerodynamic coefficients with air flow parameters on long span bridge deck

Wind load is critical for bridges with high strength to weight ratio and determined experimentally using wind tunnel study that involves huge expenditure and time. In this study, behaviour of bridge deck is analysed by changing air flow parameters considering the structure submerged in turbulent flow using k-e turbulence model with boundary conditions calibrated to simulate neutral equilibrium atmospheric boundary layer. A computational model was considered to determine aerodynamic behaviour of bridge deck for different angle of attack of wind and results were compared with wind tunnel experiments keeping boundary conditions same. The aerodynamic behaviour of different bridge deck cross section are analysed using the computational model for different air flow parameters. The variation of aerodynamic coefficients are found and presented for box girder, plate girder, trapezoidal section and section of Great Belt East Bridge and attempt was made to select the optimum section to minimise the aerodynamic forces.

The Review about Continuous Rigid Frame Bridge in Guizhou Mountain Area

Based on Guizhou mountain area, the characteristic of Guizhou mountain area and the characteristic of continuous rigid frame bridge were thought. An analysis about the advantage of this bridge type and the reason why this bridge type had energetic development in Guizhou mountain area was made. According to the collected literature and design information, the development status, including construction features, building materials, design theory and method, the key technique of construction and development prospect were revealed. Firstly, a review about the achievement of this bridge type in Guizhou mountain area was made. Then an induction and conclusion were given. In construction features, the parameter of bridge span and section was mainly introduced and a conclusion for the choice of this parameter was given. In materials, the characteristic and problem of present materials were analyzed, and then an outlook and advice for new materials, including lightweight and ultra high strength concrete and fiber reinforced composites, were given. In design, the method and key point in continuous rigid frame bridge design were reviewed; then mainly focusing on the durableness design, the limitation of the old bridge design specifications was concluded, and some ideas and an outlook were put forward for the new bridge design specifications. In construction, the construction method, the key step in construction, the common problems and solution were focused on. And the method, the affect and value of construction control in continuous rigid frame bridge were then simply introduced. In the end, the development of continuous rigid frame bridge is looking forward the future. This paper is expecting making some contribution for bridge construction in Guizhou mountain area and offering some basic information for beginners in bridge engineering.

Framework for sensitivity and uncertainty quantification in the flutter assessment of bridges

The phenomenon of aerodynamic instability caused by wind is usually a major design criterion for long-span cable-supported bridges. If the wind speed exceeds the critical flutter speed of the bridge, this constitutes an Ultimate Limit State. The prediction of the flutter boundary therefore requires accurate and robust models. The state-of-the-art theory concerning determination of the flutter stability limit is presented. Usually bridge decks are bluff and therefore the aeroelastic forces under wind action have to be experimentally evaluated in wind tunnels or numerically computed through Computational Fluid Dynamics (CFD) simulations. The self-excited forces are modelled using aerodynamic derivatives obtained through CFD forced vibration simulations on a section model. The two-degree-of-freedom flutter limit is computed by solving the Eigenvalue problem.A probabilistic flutter analysis utilizing a meta-modelling technique is used to evaluate the effect of parameter uncertainty. A bridge section is numerically modelled in the CFD simulations. Here flutter derivatives are considered as random variables. A methodology for carrying out sensitivity analysis of the flutter phenomenon is developed. The sensitivity with respect to the uncertainty of flutter derivatives and structural parameters is considered by taking into account the probability distribution of the flutter limit. A significant influence on the flutter limit is found by including uncertainties of the flutter derivatives due to different interpretations of scatter in the CFD simulations. The results indicate that the proposed probabilistic flutter analysis provides extended information concerning the accuracy in the prediction of flutter limits.The final aim is to set up a method to estimate the flutter limit with probabilistic input parameters. Such a tool could be useful for bridge engineers at early design stages. This study shows the difficulties in this regard which have to be overcome but also highlights some interesting and promising results.

Thermal Bridges At Wood Frame Construction

Abstract The paper presents the results of numerical analysis on the effects of thermal bridges at wood frame buildings with or without thermal insulation placed on the exterior surface of the wall. The heat flow crossing the wooden thermal bridges, respectively the linear heat transfer coefficients ψ and the temperature factors fRsi, can be established based on the plane temperature field in stationary thermal regime. The “PSIPLAN” computer program used to determine the temperature field, derived from the original program “CIMPLAN” with its first version developed in 1980. The program allows graphic description of the plane section of a thermal bridge and discretizes automatically the section on both axes in accordance with the stipulations of the EN ISO 10211-1:1995 standard and EN ISO 10211:2007 standard. The computer program generates automatically the system of equations that is solved using iterative methods until the heat flows on the two surfaces of the section are balanced. The calculation results are presented with numerical values and in a graphical manner by isothermal surfaces. The program has various libraries that include several types of wood thermal bridges.

Aerodynamic interference and vortex-induced vibrations on parallel bridges: The Ewijk bridge during different stages of refurbishment

This paper presents the results of sectional wind tunnel studies of the Ewijk bridge, a 270m span cable-stayed bridge crossing over the river Waal in Netherlands, which during its refurbishment was doubled with a close parallel bridge. The aerodynamics of parallel bridges may be complex and unpredictable, therefore specific wind tunnel tests were conducted.The tests were performed with sectional models in a 1:50 scale with the aim of identifying the aerodynamic interference effects between the two decks, in terms of aeroelastic stability, vortex-induced vibrations, and stationary aerodynamic loads. Several configurations were tested, since during various stages of refurbishment, the profile, the eigen-frequencies, the mass, and the relative position of the deck change.Results show that for the considered case, the interference effect is characterized by a significant change in the steady aerodynamic coefficients, vortex-induced vibrations of the upstream box-girder and forcing of the downstream bridge section, and no stability problems.

Cross-spectral recognition method of bridge deck aerodynamic admittance function

This study proposes a new identification algorithm about the admittance function, which can estimate the full set of six aerodynamic admittance functions considering cross power spectral density functions about the forces and the turbulence components. The method was first numerically validated through Monte Carlo simulations, and then adopted to estimate the aerodynamic admittance of a streamlined bridge deck. The identification method was further validated through a comparison between the numerical calculation and wind tunnel tests on a moving bridge section.

Effect of temperature difference load of 32 m simply supported box beam bridge on track vertical irregularity

In order to study the effect of temperature difference load (TDL) along the vertical direction of a simply supported beam bridge section on the vertical irregularity, a rail-bridge-piers calculation model was established. Taking 32 m simply supported box beam bridge which is widely used in the construction of passenger dedicated line in China as an example, influences of the temperature variation between the bottom and top of the bridge, temperature curve index, type of temperature gradient, and beam height on track vertical irregularity were analyzed with the model. The results show that TDL has more effects on long wave track irregularity than on short one, and the wavelength mainly affected is approximately equal to the beam span. The amplitude of irregularity caused by TDL is largely affected by the temperature variation, temperature curve index, and type of temperature gradient, so it is necessary to monitor the temperature distribution of bridges in different regions to provide accurate calculation parameters. In order to avoid the irregularity exceeding the limit values, the height of 32, 48, and 64 m simply supported box beam bridges must not be less than 2.15, 3.2, and 4.05 m, respectively.

Numerical evaluation of the mid-span assumption in the calculation of total load effects in railway bridges

Maximum load effects in simply supported railway bridges traversed by trains are generally investigated at the mid-span section. However, this assumption is not necessarily correct. The true maximum load effect might occur at some other bridge section and its magnitude could be significantly greater. This paper quantifies the underestimation of the load effects as a result of exclusively considering the middle section, with special emphasis on resonant situations. A 2D numerical model of a vehicle–track–bridge system was used to evaluate different vehicle velocities, bridge properties and track irregularity conditions. The error due to the mid-span assumption depends on the particular case considered but can be related to the relative energy content of the higher modes of vibration. The results show that the error is greatest for accelerations, smaller for bending moments and is almost negligible for displacements.

On estimating the aerodynamic admittance of bridge sections by a mesh-free vortex method

A stochastic method of generating a synthetic turbulent flow field is combined with a 2D mesh-free vortex method to simulate the effect of an oncoming turbulent flow on a bridge deck cross-section within the atmospheric boundary layer. The mesh-free vortex method is found to be capable of preserving the a priori specified statistics as well as anisotropic characteristics of the synthesised turbulent flow field. From the simulation, the aerodynamic admittance is estimated and the instantaneous effect of a time varying angle of attack is briefly investigated. The obtained aerodynamic admittance of four aerodynamically different bridge sections is compared to available wind tunnel data, showing good agreement between the two.

Applicability of URANS and DES Simulations of Flow Past Rectangular Cylinders and Bridge Sections

This paper discusses the results of computational fluid dynamics simulations carried out for rectangular cylinders with various side ratios of interest for many civil engineering structures. A bridge deck of common cross-section geometry was also considered. Unsteady Reynolds-averaged Navier–Stokes (URANS) equations were solved in conjunction with either an eddy viscosity or a linearized explicit algebraic Reynolds stress model. The analysis showed that for the case studies considered, the 2D URANS approach was able to give reasonable results if coupled with an advanced turbulence model and a suitable computational mesh. The simulations even reproduced, at least qualitatively, complex phenomena observed in the wind tunnel, such as Reynolds number effects for a sharp-edged geometry. The study focused both on stationary and harmonically oscillating bodies. For the latter, self-excited forces and flutter derivatives were calculated and compared to experimental data. In the particular case of a benchmark rectangular 5:1 cylinder, 3D detached eddy simulations were also carried out, highlighting the improvement in the accuracy of the results with respect to both 2D and 3D URANS calculations. All of the computations were performed with the Tau code, a non-commercial unstructured solver developed by the German Aerospace Center.

Study on seismic disaster mechanism of irregular C-shaped curved bridge with high piers

Based on multi-support excitation theory, an irregular C-shaped curved bridge model with high piers was made by taking scale proportion of 1:20 to conduct the seismic simulation shaking table test in this paper. Failure mode of high flexible piers and earthquake damage mechanism of the curved bridge with high piers in action of different seismic wave spectrum, different peak acceleration, and different local topography effect were studied. The results showed that the failure mode of high flexible pier presents obvious distributional flexible characteristics, #1 pier's cracks concentrated in range of 0.125L–0.46L (L is the height of the piers) from the bottom of the pier, while #2 and #3 pier's cracks concentrated in range of 0.07L–0.625L from the bottom of the piers. Pier elevation difference significantly affected pier cracks development and bridges dynamic response. Accompanied with increase of load, the fundamental frequency curve presented decline in leveling off, while the damping increased gradually and the capacity of seismic energy dissipation of the structure enhanced. Dynamic responses of the curved bridge are different and presented different law when four different seismic waves were applied. When seismic loads increased from 120 gal to 360 gal, peak dynamic response basically presented linear growth. When seismic loads increased from 480 gal to 960 gal, considering the local topography effect, peak dynamic response significantly presented nonlinear growth. In action of seismic load of 960 gal, the displacements at the top of the #1 and #3 piers were up to 32.3 mm, showing that the seismic response was relatively large at head and tail section of bridge thus prone to cause beam dropping down.

Odin’s Bridge—Europe’s Longest Twin Swing Bridge, Denmark

Odin’s Bridge is a 900 m long bridge closing a gap in a circular road that is an integral part of the infrastructure of the city of Odense, Denmark. The bridge comprises a 194 m swing bridge crossing a 80 m wide navigation canal. The swing bridge consists of two equal rotating parts designed as monoplane structures in steel. The outstanding feature of the swing bridge is the new concept of the 12 m diameter sliding bearings on which the swing bridge sections rotate. The design commenced in September 2009 and the bridge was inaugurated for service in June 2014.

Motion response of immersing tunnel element under random waves

The Hong Kong–Zhuhai–Macau Link project crosses the ocean water of Ling Ding Yang and includes a 10 km long bridge section and a 6 km submerged tube tunnel section. The submerged tube tunnel is to be placed in the base trench at the seabed under 40 m water depth (d). Each tunnel element is 180 m in length, 11.4 m in height and weighs 72,000 tons in air. All tunnel elements are to be constructed on yards onshore, towed to the site location, linked to two stabilising floating pontoons and then ballasted and immersed at the site location with an exposed open wave environment. To ensure that the tunnel element can be immersed and then landed safely and accurately on the base trench during the process, an experimental study with scale model tests was performed to investigate the motion responses of the immersing tunnel element linked to the floating pontoons under random waves. The experimental measurements revealed quantitatively the motion behaviour under different wave climates, immersion depths and negative ballasted buoyancy. The results also demonstrated that the dynamic response of the tunnel element was most severe during the stage of freeboard elimination. The experimental measurements during the freeboard elimination stage were also compared to the numerical simulations for further analysis. Overall, an important conclusion from this study is that the freeboard elimination scenario should be checked against cable breakages and the stability of the tunnel element in the design stage, which has not been highlighted in the literature so far. Also, with the quantitative information, the study illustrates how the weather window for the tunnel element immersion can be determined.

Assessment on Thermal Displacement of a Cable-Stayed Footbridge

The thermal displacement of a large scale footbridge is investigated in this study through numerical simulation. With appropriate assumption, the temperature field of the footbridge is simplified and divided into several components. Fine finite element models are constructed for the deck plate, bridge section, and bridge tower to calculate the structural thermal effects. The made observations indicate that the thermal deformation of the bridge tower is much larger than that of the deck due to the cable sag under temperature increase.

Design and Realization of the 3D Electronic Chart Based on GIS and Virtual Reality Technology

Two-dimensional electronic chart system can’t intuitively express the various information of 3D navigation environment, and the existing 3D electronic chart system lacks comprehensive display and scientific quantitative analysis. In that context, designed a 3D electronic chart system framework based on GIS and virtual reality technology (VR technology) and studied the key technologies such as visualization of 3D navigation environment, numerical simulation of water current and dynamic ship information display. Consequently, a 3D electronic chart system has been developed for Sutong Bridge section of Yangtze River waterway and it is verified to be feasible and reliable for ensuring safety of navigation.

The influence of vehicles on the flutter stability of a long-span suspension bridge

The presence of traffic on a slender long-span bridge deck will modify the cross-section profile of the bridge, which may influence the flutter derivatives and in turn, the critical flutter wind velocity of the bridge. Studies on the influence of vehicles on the flutter derivatives and the critical flutter wind velocity of bridges are rather rare as compared to the investigations on the coupled buffeting vibration of the wind-vehicle-bridge system. A typical streamlined cross-section for long-span bridges is adopted for both experimental and analytical studies. The scaled bridge section model with vehicle models distributed on the bridge deck considering different traffic flow scenarios has been tested in the wind tunnel. The flutter derivatives of the modified bridge cross section have been identified using forced vibration method and the results suggest that the influence of vehicles on the flutter derivatives of the typical streamlined cross-section cannot be ignored. Based on the identified flutter derivatives, the influence of vehicles on the flutter stability of the bridge is investigated. The results show that the effect of vehicles on the flutter wind velocity is obvious.

Análise da Influência da Presença de Veículos de Grande Porte no Comportamento Aerodinâmico e Aeroelástico de Estrutura de Ponte

Estruturas de pontes flexíveis são frequentemente suscetíveis à ação dinâmica do vento, apresentando os chamados fenômenos aeroelásticos causados pela interação entre as forças inerciais, elásticas e as aerodinâmicas. A ocorrência desse tipo de oscilação pode gerar danos estruturais e desconforto aos usuários. Tradicionalmente, o estudo dos efeitos dinâmicos do vento em estruturas era feito apenas por meio de experimentos em túneis de vento. Atualmente, utilizam-se também análises com modelos numéricos por meio da fluidodinâmica computacional (CFD – ComputationalFluid Dynamics).Utilizando uma ferramenta computacional em Dinâmica dos Fluidos, avaliam-se, no presente trabalho, os efeitos do vento no comportamento aerodinâmico da ponte Rio-Niterói, quando esta tem seu perfil não aerodinâmico alterado pela presença de veículos de grande porte. A comparação entre registros de grandes oscilações da ponte sugere que a alteração do seu perfil pela presença de veículos de grande porte pode contribuir para tornar mais intensa a oscilação induzida pelo desprendimento cadenciado de vórtices. Primeiramente, apresentam-se os resultados para as estruturas em repouso sob a ação do vento. Consideram-se os perfis da ponte, de dois tipos de veículos e do conjunto ponte mais veículo. Na sequência, apresentam-se os resultados para a seção da ponte, com e sem veículo, em movimento, em termos das histórias no tempo de amplitude de vibração em função das velocidades de vento. Os resultados obtidos para a seção dos veículos e para a ponte sem veículo, tanto em repouso quanto em movimento, compararam-se bem com os respectivos resultados experimentais. Isto permitiu a avaliação do comportamento aerodinâmico da ponte com os veículos, atestando que este perfil contribui para o aumento das vibrações com a ação do vento.