This paper presents an efficient mathematical model for studying the global buckling behavior of concrete-filled steel tubular (CFST) columns with compliant interfaces. The present mathematical model is used to evaluate exact critical buckling loads and modes of CFST columns for the first time. The results prove that the presence of finite interface compliance may significantly reduce the critical buckling load of CFST columns. A good agreement between analytical and experimental buckling loads of circular CFST columns is obtained if at least one among longitudinal and radial interfacial stiffnesses is high. The design methods compared in the paper give conservative results in comparison with the experimental results and analytical results for almost perfectly bonded layers. The parametric study reveals that critical buckling loads of CFST columns are very much affected by the diameter-to-depth ratio and concrete elastic modulus. Moreover, a material nonlinearity has a pronounced effect for short CFST columns, and a negligible effect for slender ones. The paper is categorized as an important achievement A’.
COBISS.SI-ID: 7151457
The paper presents a simplified model for coupled heat and moisture transfer and charring behaviour of timber exposed to fire. A numerical method to calculate temperature, bound water, water vapour and pressure distribution over two dimensional domain in timber specimen exposed to fire was developed. In the model, a modified description of sorption for the temperatures above the boiling point is proposed. In addition, the model also accounts the char formation. Due to the non-linear system of governing equations describing coupled heat and moisture transport, together with the char formation, the solution is obtained numerically with the finite element method. Finally, the result from the numerical analysis are validated against experimental measurements. The paper is categorized as an important achievement A’.
COBISS.SI-ID: 7062369
Highway operators around the world are using automated vehicle identification (AVI)-based techniques as a technological input for travel time estimation on highways. Various AVI technologies provide various travel time measurement samples: some of them are able to identify only personal cars (e.g. tolling tags), while others provide mixed samples of all vehicle classes (e.g. license plate matching). As the adequate information on travel times should concern the personal cars, the influence of heavy vehicles (HVs) should be eliminated from the samples, which is not feasible with the use of existing travel time estimation algorithms. It was observed that also during congestion travel times of personal cars and HVs remain dispersed. The motivation for the present study was to introduce an algorithm that would be able to exclude the influence of slower HVs in travel time estimation for technologies, providing mixed samples of travel time measurements. This was achieved by the use of robust statistics. The results of the study could be used by all highway agencies and operators who are encountering problems with unreasonably extended estimations of travel times because of the presence of slow HVs in the traffic flow. The paper is categorized as an exceptional achievement A’’.
COBISS.SI-ID: 6803553
The paper presents an automatic procedure for the correction of bridge weigh-in-motion (B-WIM) measurements, which are used to determine the axle loads of heavy vehicles using instrumented bridges. According to the European specifications for weigh-in-motion criteria, using this procedure the weighing results could be improved by up to one accuracy class. Whereas measurements performed on steel structures provide reliable information about the global behaviour of individual bridges, which is accounted for in the B-WIM algorithms, cracks that are present in concrete structures can, depending on their locations with respect to installed strain transducers, amplify or reduce the response. In the present work special care was taken to detect and calibrate any strain transducer which showed a disproportional response. The accuracy of the method was investigated numerically in relation to the extensive data which were available in the case of a reinforced concrete bridge (motorway underpass), located near Ljubljana, Slovenia, and then validated by a one-to-one comparison of the B-WIM weighing results and the statically weighed test vehicles. The paper is categorized as an important achievement A’.
COBISS.SI-ID: 7254113
A new finite element model for the analysis of the restrained curved reinforced-concrete (RC) beams simultaneously exposed to mechanical and extreme fire-like thermal loading is presented. The moisture and heat transfer through concrete is considered to be uncoupled with the deformation and the shape change of the beam. The hygro–thermo-mechanical analysis is performed in two separate steps, the first one starting with the coupled moisture and heat transfer analysis, and the next one continuing with the mechanical stress–strain analysis. A novel, strain-based finite element formulation of the curved planar beam has been developed for the mechanical part of the fire analysis. The unilateral soil–concrete beam contact is modelled with the set of discrete non-linear springs situated at nodes of the finite element mesh at the soil–beam contact. The model is verified by the numerical results of a full three-dimensional solid finite element model created in the LUSAS finite element analysis software and they are in good agreement with the present solution. In the subsequent parametric studies, the effects of material parameters of soil dictating the unilateral restraining forces to the beam, the load magnitude and the boundary conditions on the behaviour of the curved reinforced-concrete RC beam exposed to fire are investigated. The paper is categorized as an important achievement A’.
COBISS.SI-ID: 6877281
The article presents a possibility of using a non-destructive ultrasonic shear wave reflection technique for monitoring hardening process of bitumen. The technique relies on the use of a new measuring instrument called USWR-4 Hardening meter, which was developed to be applicable directly in situ and has been effectively used for cement-based materials so far. It works on the principle of continuous measurement of change of a shear wave reflection coefficient. Three different types of paving grade and two polymer-modified bitumens were used. Results show that the presented ultrasound technique can effectively track a temperature-dependent hardening process of bitumen. The paper is categorized as an important achievement A’.
COBISS.SI-ID: 7360097
Travel time is considered the most useful travel related information as it is the best indicator of the level of service on the road stretch and is completely understandable to all users. Various technologies for measuring traffic flow parameters provide the optimal background for the implementation of data fusion schemes to gain the maximum accuracy from the combination of the available data. The objective of the data fusion is to gain knowledge of predicted departure based travel time from the two outdated accurate measurements. In this paper a new and simple algorithm is proposed for short-term highway travel time prediction by fusing direct travel time measurements estimated by vehicle reidentification, indirect travel time estimated by the extrapolation of spot speed measurements and additional qualitative data in terms of the level of service. The proposed algorithm has been in operation on the A1 highway in Slovenia for more than two years and has shown robust behaviour in the real world environment. The algorithm is capable of providing short-term travel time prediction in real time with a 9 % better accuracy than the presently used travel time prediction algorithms. The paper is categorized as an exceptional achievement A’’.
COBISS.SI-ID: 7590497
When some critical condition is reached at a material point of a solid body, a localized strain starts developing which makes the strain field discontinuous and highly accelerates local damaging of material. The present paper addresses this kind of strain localization in spatial geometrically exact beams. Here we propose a new beam finite element formulation which accounts for softening of material by applying the embedded strong strain discontinuity technology. The formulation is essentially an extension of the original strain-based formulation, upgraded such to allow for detecting the onset of strain localization and to introduce additional equations for evaluating singular strain peaks and jumps of displacements and rotations at the localized section in further deformation. The paper is categorized as an important achievement A’.
COBISS.SI-ID: 7933537
In the paper we present a novel original finite-element formulation for the dynamic analysis of geometrically exact three-dimensional beams. We focus our studies on implicit time-integration schemes and possible approaches for increasing their robustness and numerical stability. In contrast to standard displacement-rotation based approach we present a spatial and temporal discretization based on velocities and angular velocities. To describe the rotational degrees of freedom quaternions are used which elegantly avoids the singularities present in any the three-component parametrization of rotation. The time-integration scheme and the governing equations of the three-dimensional beam are modified accordingly. In the numerical implementation the Galerkin-type discretization is employed to obtain the finite-element formulation of the problem. The result of our studies is accurate, efficient and robust numerical model. Long term stability of calculations without any additional measures taken is an important characteristic of this approach. The paper is categorized as an important achievement A’.
COBISS.SI-ID: 7582305
In this paper, we present a coupled dynamic analysis of a moving particle on a deformable three-dimensional frame. The presented numerical model is capable of considering arbitrary curved and twisted initial geometry of the beam and takes into account geometric non-linearity of the structure. Coupled with dynamic equations of the structure, the equations of moving particle are solved. The moving particle represents the dynamic load and varies the mass distribution of the structure and at the same time its path is adapting due to deformability of the structure. A coupled geometrically non-linear behaviour of beam and particle is studied. The equation of motion of the particle is added to the system of the beam dynamic equations and an additional unknown representing the coordinate of the curvilinear path of the particle is introduced. The specially designed finite-element formulation of the three-dimensional beam based on the weak form of consistency conditions is employed where only the boundary conditions are affected by the contact forces. The paper is categorized as an important achievement A’.
COBISS.SI-ID: 8198753