Igor Kavrakov

University of Cambridge | Cam

Machine learning models trained with structural health monitoring data have become a powerful tool for system identification. This paper presents a physics-informed Gaussian process (GP) model for Timoshenko beam elements. The model is constructed as a multi-output GP with covariance and cross-covariance kernels analytically derived based on the di...

Long-span bridges are subjected to a multitude of dynamic excitations during their lifespan. To account for their effects on the structural system, several load models are used during design to simulate the conditions the structure is likely to experience. These models are based on different simplifying assumptions and are generally guided by param...

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 quantiti...

Long-span bridges are subjected to a multitude of dynamic excitations during their lifespan. To account for their effects on the structural system, several load models are used during design to simulate the conditions that the structure is likely to experience. These models are based on different simplifying assumptions and are generally guided by...

In the last years, extreme climate events as thunderstorm and downburst are becoming increasingly frequent and widespread. These phenomena could significantly impact on the dynamic response of super long-span bridges since they are typically characterized by a sudden variations of the mean wind speed combined with large vertical angles of attack. T...

Aerodynamic stability and buffeting response due to turbulent wind have a fundamental importance for long-span bridge design. However, there are no benchmark cases that can be used as a reference estimate for an independent validation of the numerical methods and theoretical approximations. Therefore, the IABSE Task Group 3.1 proposal is to fill th...

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. T...

Wind-induced response governs the design of the long-span bridges. The shape of the deck is one of the most important factors that not only affects the mechanical properties but greatly influences the aerodynamic performance of the bridge. An efficient framework is proposed to perform aerodynamic shape optimization of a bridge deck using Computatio...

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...

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 quantiti...

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. T...

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. These forces are critical for both the design and life-cycle assessment of lifeline structures such as bridges. This paper presents a data-driven Gaussian Process-Nonlinear Fin...

p>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 s...

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-hi...

The assessment of wind-induced vibrations is considered vital for the design of long-span bridges. The aim of this research is to develop a methodological framework for robust and efficient prediction strategies for complex aerodynamic phenomena using hybrid models that employ numerical analyses as well as meta-models. Here, an approach to predict...

The paper presents numerical extensions of Vortex Particle Methods (VPM) for aeroelastic analysis of line-like structures such as long-span bridges. The pseudo-3D VPM is a coupled algorithm that considers the structural behaviour in 3D with flow modelled in 2D. This multi-strip model is able to predict the changes in vorticity flow due to the varia...

Wind-induced vibrations often represent a major design criterion for long-span bridges. This work deals with the assessment and development of models for aerodynamic and aeroelastic analyses of long-span bridges. Computational Fluid Dynamics (CFD) and semi-analytical aerodynamic models are employed to compute the bridge response due to both turbule...

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 end, the working group set up a benchmark procedure consisting of several steps with increasing complexity to define reference results useful for this va...

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 tools for the simulation of the aeroelastic behaviour are fundamental in the safe design of bridges and they should be validated. The working group decided...

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 ve...

The accurate description of the aerodynamic forces due to free-stream turbulence acting on a stationary bridge deck represents a challenging task. This paper presents a Computational Fluid Dynamics (CFD) approach based on the two-dimensional (2D) Vortex Particle Method (VPM) for simulation of a six-component complex aerodynamic admittance. Determin...

Structural optimization has gained considerable attention in the design of structural engineering structures, especially in the preliminary phase. This study introduces an unconventional approach for structural optimization by utilizing the Energy method with Integral Material Behavior (EIM), based on the Lagrange’s principle of minimum potential e...

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...

Reliable modelling in structural engineering is crucial for the serviceability and safety of structures. A huge variety of aerodynamic models for aeroelastic analyses of bridges poses natural questions on their complexity and thus, quality. Moreover, a direct comparison of aerodynamic models is typically either not possible or senseless, as the mod...

p>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 comparis...

The accurate representation of aerodynamic forces is essential for a safe, yet reasonable design of long-span bridges subjected to wind effects. In this paper, a novel extension of the Pseudo-three-dimensional Vortex Particle Method (Pseudo-3D VPM) is presented for Computational Fluid Dynamics (CFD) buffeting analysis of line-like structures. This...

Long-span bridges are sensitive to wind-induced forces. In this paper, we evaluate the influence of the assumptions in the semi-analytical aerodynamic models on the dynamic response of a bridge deck using comparison metrics. These metrics are constructed in such way to evaluate the differences in the signal properties of the time-dependent response...

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 c...

The accurate description of the aerodynamic forces due to free-stream turbulence acting on a stationary bridge deck represents a challenging task. This paper presents a numerical approach based on the vortex particle method for the simulation of a two-dimensional complex aerodynamic admittance. Wakes of two fictitious airfoils are replicated by rel...

Die Modellbildung zu der Berechnung von Tragwerken ist eine wichtige Aufgabe im konstruktiven Ingenieurbau. Die Prognosen eines Modells hängen stets von getroffenen Annahmen und Vereinfachungen ab, weshalb die Abschätzung der notwendigen Detailliertheit bei der Modellentwicklung häufig im Mittelpunkt steht. Der vorliegende Beitrag widmet sich der F...

p>The IABSE Task Group 10 (super-long span bridge aerodynamics) has the mandate to create a standard procedure for validation of methodology and software programs applied for stability and buffeting response analyses of super-long span bridges. Precise estimations of structural stability and response to strong winds are critical for the successful...

Wind-induced vibrations commonly represent the leading criterion in the design of long-span bridges. The aerodynamic forces in bridge aerodynamics are mainly based on the quasi-steady and linear unsteady theory. This paper aims to investigate different formulations of self-excited and buffeting forces in the time domain by comparing the dynamic res...

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 follow...

Wind-induced vibrations are commonly the leading action in the ultimate and serviceability state of the long-span bridges. There is a multitude of aerodynamic models for simulating wind action on a bridge deck based on various theories. Within this study, the influence of the implied assumptions in the aerodynamic models is studied regarding the Wi...

With the ongoing expansion of railway systems in Europe, spun-cast reinforced concrete poles have become one of the most prevalent civil engineering structures. In this study, three spun-cast reinforced concrete poles along a new high-speed railway track in Germany have been instrumented with a structural monitoring system to capture the structural...

Wind-induced vibrations commonly are the leading design criterion for long-span bridges. This article presents a comparative study between a recently developed quasi-3D turbulent Computational Fluid Dynamics (CFD) scheme based on the Vortex Particle Method (VPM) and various semi-analytical models based on a flat-plate aerodynamics. The models are c...

Wind-induced vibrations commonly represent the leading criterion in the design of long-span bridges. By well accepted classification, the aerodynamic forces are categorized into static, self-excited and buffeting forces for which different formulations apply based on the quasi-steady and the linear unsteady air-foil theory. This paper aims to inves...

The authors propose to replace a reinforced concrete (RC) slab with a cross-laminated timber (CLT) floor panel as a method to increase the use of timber in moderate- or large-scale buildings. The advantages of using CLT floor panels are as follows: 1) the weight of the building is reduced, 2) an environmental value is established, 3) forest resourc...

With the advances of the computer technology, structural optimization has become a prominent field in structural engineering. In this study an unconventional approach of structural optimization is presented which utilize the Energy method with Integral Material behaviour (EIM), based on the Lagrange’s principle of minimum potential energy. The equi...