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Civil engineers focus on developing an optimum design that is cost-effective without compromising the performance. Experiences from optimizing airplane wings in aerospace engineering have been extensively made for the last decades where the aim is to maximize the lift-to-drag ratios. In civil engineering, shape optimization of tall buildings and bridge cross-sections is still an open research field where the aim is to enhance the aerodynamic behavior of these structures. The main challenge, however, is to develop bridge decks that avoid excessive deformations and ensure a sufficient structural reliability. Within this framework, the paper outlines the single and multi-objective shape optimization for static aerodynamic forces of a streamlined box section. Computational fluid dynamic simulation based on vortex particle method provides the quantities of interest which are approximately treated by a Kriging surrogate for the optimization. Later, the performance of the optimized structure is checked against flutter instability.

Fatal bridge collapses and accidents, climate change effects and critical maintenance condition of many bridges recently increased the interest among bridge owners worldwide to transition from preventive to more proactive bridge maintenance and support by digitalization. Analyzing maintenance information systematically contributes to successful maintenance management. Inspections and maintenance require organized, automated, open, and transparent digital processes. Worldwide Bridge Management Systems evolve, associated with the technological evolution, but are in urgent need for a digital upgrade, especially considering BIM technology. Existing BIM models must be enriched by assets obtained from inspection and maintenance processes. An Open BIM platform should be the goal and to this end IABSE Task Group 5.6 "BIM for Existing Structures" has defined its aim as helping to stimulate debate on this topic and give recommendations on how to address the issues raised.

A physics-informed machine learning model, in the form of a multi-output Gaussian process, is formulated using the Euler-Bernoulli beam equation. Given appropriate datasets, the model can be used to regress the analytical value of the structure’s bending stiffness, interpolate responses, and make probabilistic inferences on latent physical quantities. The developed model is applied on a numerically simulated cantilever beam, where the regressed bending stiffness is evaluated and the influence measurement noise on the prediction quality is investigated. Further, the regressed probabilistic stiffness distribution is used in a structural health monitoring context, where the Mahalanobis distance is employed to reason about the possible location and extent of damage in the structural system. To validate the developed framework, an experiment is conducted and measured heterogeneous datasets are used to update the assumed analytical structural model.

Many different approaches using modern digital technologies were recently developed to support engineers with the acquisition of visual inspection data, such as the usage of small unmanned aircraft systems (UAS) equipped with high-quality cameras. The images obtained are used, amongst others, for photogrammetric reconstruction methods or image-based anomaly detection, which leads to a high potential of automation in condition assessment, reducing time and costs. This article presents approaches for the integration of image-based inspection data sets into an automated workflow towards condition rating of damaged infrastructures. To this end, it is shown how 3D annotations are combined with information from a digital twin, such that further properties are assigned to the detected structural anomalies, in order to enrich the digital twin. Finally, the proposed methods are applied to a case study to show the feasibility in a practical use case.

The New Little Belt Bridge, designed by the consulting engineers Christian Ostenfeld and Wriborg Jønson, was to be Denmark's first suspension bridge. The construction of this Danish piece of engineering history took place between 1965 and 1970 and could only succeed with the help of tests on physical models. Most of the physical models have disappeared, only the three-dimensional dynamic model of the bridge has survived. This paper looks at the question which role the surviving and other models played in the planning process. The model still existing is a store of knowledge of engineering practice and shall be recorded and evaluated as one of the last witnesses of model statics. Therefore, the authors will create a digital twin of the model to examine aspects like boundary conditions, structural parameters of all bridge components and the well-documented research results.

With the increasing spans and complex deck shapes, aerodynamic nonlinearity becomes a crucial concern in the design of long-span bridges. This paper investigates the nonlinear interaction between the gust-induced and motion-induced forces acting on bridge decks using the Vortex Particle Method (VPM) as a Computational Fluid Dynamics (CFD) method. This nonlinear interaction is complex and intractable by the conventional linear semi-analytical models that employ the superposition principle. To excite such interaction, a sinusoidally oscillating bridge deck is subjected to sinusoidal vertical gusts. Two distinct aspects are studied: The influence of large-scale sinusoidal vertical gusts on the shear layer of a moving body and the nonlinear dependence of the aerodynamic forces on the effective angle of attack. For the latter, the resultant aerodynamic forces based on a linear semi-analytical and a CFD model are compared for the same effective angle of attack due to sinusoidal gust and motion. The methodology is first employed to verify the linear behavior of a flat plate and then study the nonlinear behavior of two bridge decks. The results show that the linear superposition principle holds for streamlined bridge decks with minimal shear layer instability. However, this principle may not be valid for bluff bridge decks due to strong separation vortices that dictate the shear layer, which induces nonlinearity in the aerodynamic forces manifested through amplitude difference in the first harmonic and emergence of higher-order harmonics. The outcome of this study aims to provide a deeper understanding of the complex nonlinear fluid-structure interaction occurring for bluff bodies subjected to motion and free-stream gusts., 20 pages, 36 figures

IABSE Task Group 3.1 has the mandate to define reference results for the validation of methodologies and programs used to study both stability and buffeting responses of long-span bridges. These to...

This paper presents a coherent framework for automated unmanned aircraft system based inspections of large bridges to facilitate an automated condition assessment. Modern camera equipped unmanned aircraft systems are used to generate high-resolution digital image data of the structural surface. The flight path is automatically computed from a basic 3D model and ensures that the image set will satisfy defined quality parameters according to the desired information extraction. State-of-the-art photogrammetry and machine learning based feature detection methods are employed to automatically compute high-resolution geo-referenced 3D structural geometries and to identify typical damage patterns such as cracks. Further framework components dedicated to condition assessment allow the mapping of damages to structural parts and the calibration of mechanical numerical simulation models used to compute the internal structural demand under design loads. Data models are proposed that allow a consistent data storage and management to serve as a basis for all algorithmic components. The application of the framework to a large bridge structure showcases how the integration of digital systems and algorithms forms the basis for an intelligent and potentially autonomous safety assessment of very large infrastructures.

Independent protective structures supported by concrete-filled steel pipes have been widely used to protect bridge piers from vessel impact. In a high-energy impact scenario, such protective structures can absorb a large amount of energy through plastic deformation. Many previous studies are based on empirical static analysis which ignores important dynamic effects involved in an impact event. Finite-element simulation serves as an alternative approach which is commonly used for dynamic analysis of vessel collisions. However, finite-element simulation is expensive regarding both calculation time and computing resources. To conquer these problems, a simplified impact model considering soil-pile interactions and geometric non-linearity is developed in this paper based on the coupled multi-degree-of-freedom model previously proposed by the authors. The computational cost can be remarkably reduced by the simplified models. The influences of pile cross-section diameter, pipe thickness, pile length, free span of pile and soil properties on the energy dissipation capacity of pile-supported protective structures are investigated in this paper using the simplified models.

This paper presents the ongoing benchmark results of IABSE Task Group 3.1. The task of this working group is to create benchmark results for the validation of methodologies and software programs developed to assess the stability and the buffeting response of long span bridges. Indeed, accurate estimations of structural stability and response to strong winds are critical for the successful design of long-span bridges. While the first results of the benchmark, dealing with a section approach, have been already published, in this paper the ongoing activity and results of the task group are presented. The topic of these results is the numerical response of a full-bridge model under the actions of a multi-correlated wind field both in terms of aeroelastic stability and buffeting response.

An abundant amount of data gathered during wind tunnel testing and health monitoring of structures inspires the use of machine learning methods to replicate the wind forces. This paper presents a data-driven Gaussian Process-Nonlinear Finite Impulse Response (GP-NFIR) model of the nonlinear self-excited forces acting on structures. Constructed in a nondimensional form, the model takes the effective wind angle of attack as lagged exogenous input and outputs a probability distribution of the forces. The nonlinear input/output function is modeled by a GP regression. Consequently, the model is nonparametric, thereby circumventing to set up the function's structure a priori. The training input is designed as random harmonic motion consisting of vertical and rotational displacements. Once trained, the model can predict the aerodynamic forces for both prescribed input motion and aeroelastic analysis. The concept is first verified for a flat plate's analytical solution by predicting the self-excited forces and flutter velocity. Finally, the framework is applied to a streamlined and bluff bridge deck based on Computational Fluid Dynamics (CFD) data. The model's ability to predict nonlinear aerodynamic forces, flutter velocity, and post-flutter behavior are highlighted. Applications of the framework are foreseen in the structural analysis during the design and monitoring of slender line-like structures., 22 pages, 33 figures

Long-span bridges are prone to wind-induced vibrations. Therefore, a reliable representation of the aerodynamic forces acting on a bridge deck is of a major significance for the design of such structures. This paper presents a systematic study of the two-dimensional (2D) fluid-structure interaction of a bridge deck under smooth and turbulent wind conditions. Aerodynamic forces are modeled by two approaches: a computational fluid dynamics (CFD) model and six semi-analytical models. The vortex particle method is utilized for the CFD model and the free-stream turbulence is introduced by seeding vortex particles upstream of the deck with prescribed spectral characteristics. The employed semi-analytical models are based on the quasi-steady and linear unsteady assumptions and aerodynamic coefficients obtained from CFD analyses. The underlying assumptions of the semi-analytical aerodynamic models are used to interpret the results of buffeting forces and aeroelastic response due to a free-stream turbulence in comparison with the CFD model. Extensive discussions are provided to analyze the effect of linear fluid memory and quasi-steady nonlinearity from a CFD perspective. The outcome of the analyses indicates that the fluid memory is a governing effect in the buffeting forces and aeroelastic response, while the effect of the nonlinearity is overestimated by the quasi-steady models. Finally, flutter analyses are performed and the obtained critical velocities are further compared with wind tunnel results, followed by a brief examination of the post-flutter behavior. The results of this study provide a deeper understanding of the extent of which the applied models are able to replicate the physical processes for fluid-structure interaction phenomena in bridge aerodynamics and aeroelasticity.

Wind effects can be critical for the design of lifelines such as long-span bridges. The existence of a significant number of aerodynamic force models, used to assess the performance of bridges, poses an important question regarding their comparison and validation. This study utilizes a unified set of metrics for a quantitative comparison of time-histories in bridge aerodynamics with a host of characteristics. Accordingly, nine comparison metrics are included to quantify the discrepancies in local and global signal features such as phase, time-varying frequency and magnitude content, probability density, nonstationarity and nonlinearity. Among these, seven metrics available in the literature are introduced after recasting them for time-histories associated with bridge aerodynamics. Two additional metrics are established to overcome the shortcomings of the existing metrics. The performance of the comparison metrics is first assessed using generic signals with prescribed signal features. Subsequently, the metrics are applied to a practical example from bridge aerodynamics to quantify the discrepancies in the aerodynamic forces and response based on numerical and semi-analytical aerodynamic models. In this context, it is demonstrated how a discussion based on the set of comparison metrics presented here can aid a model evaluation by offering deeper insight. The outcome of the study is intended to provide a framework for quantitative comparison and validation of aerodynamic models based on the underlying physics of fluid-structure interaction. Immediate further applications are expected for the comparison of time-histories that are simulated by data-driven approaches.

IABSE Task Group 3.1 has the mandate to define reference results for the validation of methodologies and programs used to study both stability and buffeting responses of long-span bridges. To this ...

This paper presents a novel method for the simulation of aerodynamic admittance of turbulent wind on bluff line-like structures using a pseudo 3D model of Vortex Particle Method (VPM). The method i...

The impact of vessels straying out of control poses a serious hazard for bridge piers located in navigation waterways. In order to accurately predict the dynamic responses of the bridge piers subjected to barge impact and to design bridge piers which can resist such impact, the impact forces need to be accurately defined. Empirical formulas such as those provided by AASHTO Guide Specification are currently extensively used for predicting the equivalent static impact forces. Whilst such equivalent static methods cannot accurately reflect the actual dynamic phenomena in a barge impact event, sophisticated finite-element (FE) simulations are computationally expensive. This paper aims to establish a coupled model which can replicate the complex full barge impact model (FBIM) with sufficient accuracy. In this coupled model, the barge model is simplified into a mass-spring model (MSM) whilst the pier is modeled using discrete masses and discrete beam elements. The parameters introduced by MSM are determined using the proposed strategies in this paper. Linear elastic pier columns with fixed bases and cantilevered tops are employed to assess the prediction quality of the proposed coupled model for different impact scenarios.

The paper presents a numerical technique within the framework of two-dimensional Vortex Particle Methods to simulate pulsating flow by seeding pre-calculated vortex particles into the free stream flow. The interest is to investigate the performance of small-scale flutter-based energy harvesters, particularly under low-frequency periodic incoming flows. The proposed numerical extension utilizes the natural convection of the particles, regularly seeded from two distant seeding points near the upstream boundary. The seeding mechanism and the orientation of the particles are handled such that they induce only horizontal velocity components around the domain center while the vertical components are nearly canceled out. The sinusoidal periodic flow is modeled by seeding the particles of varied strength and orientation, correspondingly. Convergence studies are performed to validate the scheme. The quality of the modeled periodic flows is assessed and quantified. Finally, the studies are carried out to investigate the dynamic motion of a reference T-shaped harvester under steady and periodic incoming flows. The initiation of unstable flutter response is observed earlier in case of periodic incoming flows. The response amplitude and the pattern of limit cycle oscillations are found to be depending on the combination of frequency and intensity of the periodic flow.

Barge impact is a potential hazard for bridge piers located in navigation waterways. The dynamic impact process is influenced by many factors, including barge mass, impact velocity, oblique impact angle, water elevation, material properties of pier members, soil properties, etc. The uncertainties involved in these factors need to be considered for reliability analyses of bridge piers subjected to barge impact. Empirical formulas such as those provided by AASHTO Guide Specification are extensively used for estimating the impact loading. However, such equivalent static method ignores the important dynamic effects involved in the impact event. High-resolution finite-element (FE) simulation is another commonly-used strategy for analyzing the dynamic impact process. However, FE simulation is expensive regarding both calculation time and computing resources, especially when a large number of simulations are required. The coupled multi-degree-of-freedom model (CMM) previously proposed by the authors can transform the full barge impact model (FBIM) into a simplified model that is efficient for dynamic analyses of the pier subjected to barge impact. This paper aims to conduct reliability analyses of the RC pier subjected to barge impact using the simplified model developed on the basis of CMM considering soil-pile interactions. The randomness of barge mass, impact velocity, oblique impact angle, water elevation, material properties of pier members and soil properties are considered. Sensitivity analyses are conducted to figure out the sensitive random variables.

This paper presents a novel adaptive solution strategy for vortex particle methods that allows the efficient resolution of multiple scales that are characteristic of flows around bluff bodies with small structural details. The efficiency of the method arises from maintaining a sufficiently high spatial numerical discretisation near the fluid-solid interface and a progressive coarsening away from the bodies and their structural details. The control of the particle map is achieved through remeshing based on high-order interpolation kernels and ensures an accurate representation of the flow features of different scales whose resolution is critical to an accurate computation of the pressures on the immersed structure subjected to separated flows. As the required time step of the time integration is directly related to the spatial resolution, the adaptivity is further enhanced by a temporal adaptivity realized through a sub-stepping technique for controlling the frequency at which the particle convection and diffusion steps are performed. The validation of the proposed technique is performed by simulations of the impulsively started flow past a circular cylinder at Reynolds number 3000, where both the spatial and the temporal strategies are at first independently studied and then combined to full adaptivity. A substantially higher computational efficiency compared to equally accurate non-adaptive simulations is reported. Further studies of accuracy and efficiency are performed by simulating the flow past the cross section of a bridge arch geometry featuring small structural details. Solution properties studied include the resolution of local velocity profiles and global aerodynamic coefficients. These reveal how the application of the full adaptive strategy enables for the accurate and efficient prediction of the flow features. The results indicate speed-ups of up to factor 4 to 5 when comparing the new approach to the classical Vortex Particle Method.

Fur eine Abschatzung des Heizwarmebedarfs von Gebauden und Quartieren konnen thermisch-energetische Simulationen eingesetzt werden. Grundlage dieser Simulationen sind geometrische und physikalische Gebaudemodelle. Die Erstellung des geometrischen Modells erfolgt in der Regel auf Basis von Bauplanen oder Vor-Ort-Begehungen, was mit einem grosen Recherche- und Modellierungsaufwand verbunden ist. Spatere bauliche Veranderungen des Gebaudes mussen haufig manuell in das Modell eingearbeitet werden, was den Arbeitsaufwand zusatzlich erhoht. Das physikalische Modell stellt die Menge an Parametern und Randbedingungen dar, welche durch Materialeigenschaften, Lage und Umgebungs-einflusse gegeben sind. Die Verknupfung beider Modelle wird innerhalb der entsprechenden Simulations-software realisiert und ist meist nicht in andere Softwareprodukte uberfuhrbar. Mithilfe des Building Information Modeling (BIM) konnen Simulationsdaten sowohl konsistent gespeichert als auch uber Schnittstellen mit entsprechenden Anwendungen ausgetauscht werden. Hierfur wird eine Methode vorgestellt, die thermisch-energetische Simulationen auf Basis des standardisierten Ubergabe-formats Industry Foundation Classes (IFC) inklusive anschliesender Auswertungen ermoglicht. Dabei werden geometrische und physikalische Parameter direkt aus einem uber den gesamten Lebenszyklus aktuellen Gebaudemodell extrahiert und an die Simulation ubergeben. Dies beschleunigt den Simulations-prozess hinsichtlich der Gebaudemodellierung und nach spateren baulichen Veranderungen. Die erarbeite-te Methode beruht hierbei auf einfachen Modellierungskonventionen bei der Erstellung des Bauwerksinformationsmodells und stellt eine vollstandige Ubertragbarkeit der Eingangs- und Ausgangswerte sicher. Thermal building simulation based on BIM-models. Thermal energetic simulations are used for the estimation of the heating demand of buildings and districts. These simulations are based on building models containing geometrical and physical information. The creation of geometrical models is usually based on existing construction plans or in situ assessments which demand a comparatively big effort of investigation and modeling. Alterations, which are later applied to the structure, request manual changes of the related model, which increases the effort additionally. The physical model represents the total amount of parameters and boundary conditions that are influenced by material properties, location and environmental influences on the building. The link between both models is realized within the correspondent simulation soft-ware and is usually not transferable to other software products. By Applying Building Information Modeling (BIM) simulation data is stored consistently and an exchange to other software is enabled. Therefore, a method which allows a thermal energetic simulation based on the exchange format Industry Foundation Classes (IFC) including an evaluation is presented. All geometrical and physical information are extracted directly from the building model that is kept up-to-date during its life cycle and transferred to the simulation. This accelerates the simulation process regarding the geometrical modeling and adjustments after later changes of the building. The developed method is based on simple conventions for the creation of the building model and ensures a complete transfer of all simulation data.

This paper presents an analysis of the scalability and efficiency of a simulation framework based on the vortex particle method. The code is applied for the numerical aerodynamic analysis of line-like structures. The numerical code runs on multicore CPU and GPU architectures using OpenCL framework. The focus of this paper is the analysis of the parallel efficiency and scalability of the method being applied to an engineering test case, specifically the aeroelastic response of a long-span bridge girder at the construction stage. The target is to assess the optimal configuration and the required computer architecture, such that it becomes feasible to efficiently utilise the method within the computational resources available for a regular engineering office. The simulations and the scalability analysis are performed on a regular gaming type computer.

Predicting the phenomenon of aerodynamic instability is essential for the analysis and design of long-span cable-supported bridges. This paper reviews the history and development of aerodynamic analysis techniques and state-of-the-art numerical and experimental methods for flutter stability analysis. A discussion of the flutter phenomenon is followed by a literature review. This study provides a perspective on self-excited aerodynamic force models, identification of aerodynamic derivatives and methods for determining aerodynamic instability of long-span bridges in two dimensions and three dimensions. Computational fluid dynamics (CFD) techniques for modelling the flow past bluff bodies are also covered. Different model combination techniques are presented, utilising analytical, numerical and experimental approaches to predict the flutter limit. The effect of different parameters on the flutter stability limit is also highlighted. Furthermore, an overview of the complementary relationship between wind tunnel testing and CFD is provided. Finally, this paper also describes the engineering solutions adopted as countermeasures to prevent flutter instabilities.

The following paper presents a framework for an assessment of energy performance of buildings based on the identification of physical parameters characterizing a building regarding its thermal behavior. Data acquisition within this framework is performed primarily by using UAS, equipped with RGB-camera and thermography-camera for a simultaneous application during the flight. To ensure a reproducible flight for the parallel acquisition of thermography and RGB data, a flight path automatically computed from a basic three-dimensional model is used. An estimation of U-value is applied to the thermography data obtained, allowing the derivation of a probable material set of the investigated structure. The framework also proposes suitable data models for data storage and management to act as a foundation for all algorithmic components, including numerical assessment of energy performance of buildings. Conclusively the framework is applied on a school building illustrating the previously defined methods. The validation of the Building Performance Simulation (BPS) performed within this framework shows an oscillation of Mean Bias Error (MBE) for the heat demand between −6.4% and 6.3%.

During the life-cycle of constructions various influences induce material defects that could affect the behavior of the structural system. Therefore, anomalies that affect heavily stressed constructions, such as bridges, need to be inspected and evaluated regarding their impact on the structural capacity. By using new technologies in the field of damage detection, e.g. laser scanners or unmanned aircraft systems (UAS), this process can be facilitated. However, the classification and assessment of detected anomalies must still be performed in a manual way by human experts due to the lack of machine-processable evaluation methods. In this paper an approach is proposed towards a machine-based damage evaluation, applying semantic web technologies on a new developed method for damage detection on constructions. Thereby, anomalies are detected based on a large amount of high-resolution images from which georeferenced point clouds are calculated by using photogrammetric methods. Using the geometric relations among the image positions and reconstructed points, image features such as anomalies are localized on a 3 dimensional surface. Based on these image features, a web ontology as semantic representation of the recorded damages is generated and linked with an ontology that contains information about the affected construction and its environment. By using predefined rules based on expert knowledge, the detected anomalies are classified and assessed automatically. The inferred information is then used to generate damage representations in a structural analysis model. Furthermore, the geometrical data, which are represented in a model created according to Building Information Modeling (BIM) standards, the semantic data as well as the structural data are linked by utilizing the Multimodel approach.

In the last two decades, the problem of compressive membrane action (CMA) in laterally restrained reinforced concrete (RC) slabs has been widely under research due to significant strength enhancement and reserve strength it can provide in resisting progressive collapse. Besides, it is well known that reliability of a structure subjected to extreme loading scenarios is a function of uncertainty propagation in the ultimate load-bearing capacity of structural components. This paper is concerned with probabilistic assessment of the ultimate load-bearing capacity of laterally restrained RC slabs considering the contribution of CMA. Using global variance-based sensitivity analysis, uncertainties in material properties, geometrical properties and mechanical properties are studied. Moreover, the influence of different modeling strategies on uncertainty propagation is investigated for the available analytical and numerical approaches to provide a basis in terms of probabilistic model quality. Mesh sensitivity and parametric studies are also performed to shed light on the influence of finite element discretization, reinforcing steel configuration, and in-plan aspect ratio on uncertainty propagation in the ultimate load-bearing capacity. Following the sensitivity studies, non-influential parameters are fixed at their mean values, and the probability of failure is estimated for the investigated modeling strategies using a full-probabilistic approach.

The assessment of the condition of structures subjected to ageing and extreme loading conditions becomes increasingly important. Highly accurate sensor technologies and advanced structural identification methods can help to detect critical structural conditions and thus prevent collapse. The paper presents a general methodology for the evaluation of the measurement quality of sensor setups based on the identification of target structural properties like section forces, deflections or stresses. The target quantities that are relevant for the structural assessment will be identified from readily measurable deformation quantities such as inclinations. The proposed framework includes considerations of uncertainty in load pattern and uses mathematical optimisation techniques to relate the measured quantities to the range of target properties and thus to the ability of identifying critical structural conditions. The methods are applied to sample structures and the effect of uncertainty in the loading and uncertainty in the measurement process are studied for an inclinometer-based monitoring system. The quality of competing sensor setups will be evaluated for a single target quantity and expanded to multiple target properties. The methodology developed can be used for optimising sensor setups in the context of detection systems.

Material non-linearity of pier members is an important factor that needs to be considered for dynamic analysis of the bridge pier subjected to barge impact. However, many existing studies pertaining to barge impact on the bridge pier are based on the assumption that the pier is rigid or elastic. High-resolution finite-element simulation serves as the main strategy for dynamic analysis of the bridge pier subjected to barge impact considering material non-linearity of pier members. However, high-resolution finite-element simulations are expensive regarding both calculation time and computing resources, thus efficient models are often required. This paper develops the numerical model of the square RC pier column with fixed base. By coupling the simplified mass-spring model developed by the authors previously with the RC pier column at the impact position using fibre beam elements, the efficient model is developed to predict the impact force time-history and dynamic responses of the RC pier column subjected to barge impact. The studies in this paper show that the prediction quality of the proposed efficient model is adequate for different impact scenarios.

This paper presents a numerical method for analysing the aero-elastic response of bluff line-like structures subjected to turbulent wind. Simulating the buffeting response of line-like structures such as bridges and towers requires accurate modelling of atmospheric turbulence, the cross-sectional aerodynamic behaviour and the structural dynamics. Here the fluid–structure interaction problem is solved considering a three-dimensional structural model coupled with a series of two-dimensional Computational Fluid Dynamics simulation slices, utilising the Vortex Particle Method. The coupled set of simulation slices accounts for the three-dimensional dynamic characteristics of the structure and the turbulent inflow conditions. This pseudo three-dimensional approach is presented as an accurate, yet computationally cheaper alternative to fully three-dimensional simulations of the fluid–structure interaction problem. For the inflow conditions in each simulation slice, the characteristics of the turbulent wind are modelled through pseudo-random velocity time-histories that satisfy the mean velocity profile, spectral properties and spatial coherence of the three-dimensional turbulent wind assumed. The wind field is modelled through vorticity injected at the upstream boundary of the simulation domain. The different components of the method are presented and validated. Finally, the method is applied to the study of a cable-stayed bridge, and the results are validated against wind tunnel measurements.

The article presents a two-dimensional fully coupled fluid–structure interaction model for simulating aeroelastic instabilities to evaluate and optimize the performance of flutter-based electromagn...

In the last decade, a great care is exercised in progressive collapse analysis of structures to avoid the catastrophic consequences of such a system-level problem. The majority of the previous research works dealt with the quantification of resisting mechanisms such as the compressive arching action using two-dimensional frameworks. The three-dimensional (3D) studies are also limited to considering the initial damage as instantaneous removal of one or simultaneous removal of multiple supporting elements. This paper studies the 3D nonlinear dynamic response of reinforced concrete structures subjected to sequential column removal scenarios. A sequential nonlinear time-history analysis algorithm alongside with a macro modeling approach is utilized to predict the dynamic redistribution of the gravity loads. The efficiency of such a numerical framework is verified through comparison of computational results with the available experimental data from a past 3D half-scale test. Good agreement is observed for the global and for the local response quantities. Furthermore, a practical strengthening technique is applied into the computational model of the structural system for artificially activating the catenary mechanism. Analysis results show that strengthening of peripheral beams with externally bonded steel plates significantly increases the rotational ductility at beam-sections and in turn, enables the damaged structure to accommodate larger deformations. Finally, the influence of the removal sequence on the 3D force redistribution mechanism is investigated. Permanent plastic deformations and maximum sectional forces of a sequential removal scenario are found to be larger on average compared with those obtained from an at-once removal scenario. It is demonstrated that the time-lag between the column removals considerably affects the 3D redistribution of gravity loads, and shall not be neglected in case of considering an extreme initial damage.

The fire resistance of concrete members is controlled by the temperature distribution of the considered cross section. The thermal analysis can be performed with the advanced temperature dependent physical properties provided by EN 1992-1-2. But the recalculation of laboratory tests on columns from TU Braunschweig shows, that there are deviations between the calculated and measured temperatures. Therefore it can be assumed, that the mathematical formulation of these thermal properties could be improved. A sensitivity analysis is performed to identify the governing parameters of the temperature calculation and a nonlinear optimization method is used to enhance the formulation of the thermal properties. The proposed simplified properties are partly validated by the recalculation of measured temperatures of concrete columns. These first results show, that the scatter of the differences from the calculated to the measured temperatures can be reduced by the proposed simple model for the thermal analysis of concrete.

The risk of vehicle accidents and discomfort under wind actions is key in the serviceability assessment of long-span bridges. This paper presents a complete wind-vehicle-bridge interaction (W-VBI) framework in which the pavement irregularities are simulated as random surfaces that include the bridge joints instead of traditional one-dimensional (1D) road profiles. The methodology includes a new approach to assess the safety and comfort of all the users of the bridge, including those in the vehicles and on the deck, and to account for the variability of the response. The application of the proposed W-VBI framework in the study of a long cable-stayed bridge demonstrated that the driving safety and the pedestrians’ comfort cannot be based on the analysis of a single record, and guidance is proposed to obtain results with statistical significance. Moreover, it is observed for the first time that 1D road irregularity models can significantly underpredict the risk of discomfort and of driving instabilities in bridges subjected to crosswinds. Finally, the direct connection between the quality of the road and the comfort in the vehicles is clearly established, which has potential implications on pavement monitoring programmes.

This paper is part of a series of publications aimed at the divulgation of the results of the 3-step benchmark proposed by the IABSE Task Group 3.1 to define reference results for the validation of the software that simulate the aeroelastic stability and the response to the turbulent wind of super-long span bridges. Step 1 is a numerical comparison of different numerical models both a sectional model (Step 1.1) and a full bridge (Step 1.2) are studied. Step 2 will be the comparison of predicted results and experimental tests in wind tunnel. Step 3 will be a comparison against full scale measurements.The results of Step 1.1 related to the response of a sectional model were presented to the last IABSE Symposium in Nantes 2018. In this paper, the results of Step 1.2 related to the response long-span full bridge are presented in this paper both in terms of aeroelastic stability and buffeting response, comparing the results coming from several TG members.

In the design of super-long-span bridges, the wind actions are commonly a governing criterion. Critical design checks for wind-induced vibrations involve experimental and numerical procedures for determination of the flutter instability threshold, commonly under laminar free-stream. The influence of free-stream turbulence on the critical flutter velocity of bridge decks still represents an open topic in bridge aerodynamics. This paper presents an investigation of the influence of free-stream deterministic gusts on the critical flutter velocity using Computational Fluid Dynamics (CFD). Deterministic free-stream harmonic gusts are simulated by modelling the wake of two flapping airfoils using the two-dimensional Vortex Particle Method (VPM). These gusts are then applied to a streamlined bridge deck and the oscillation amplitudes are studied for various gust amplitudes and frequencies. The results indicate that the critical flutter velocity is reduced for harmonic gusts with a frequency similar to the critical frequency under laminar free-stream, while it is not in affect for gust frequencies corresponding to the structural frequencies. By dissecting the random free-stream into harmonic gusts, this study aims to provide a deeper understanding of the physical processes occurring in the fluid-structure interaction near the instability threshold.