José N. Varandas

Universidade NOVA de Lisboa | NOVA · Department of Civil Engineering (CED)

The special issue on "Railway Infrastructure Resilience: Addressing Challenges and Ensuring Long-Term Sustainability" aims to bring together state-of-the-art research and advancements in the field of railway infrastructure, to tackle the challenges faced by this critical transport system and to ensure its long-term sustainability. Railways play a v...

Abrupt stiffness variations along the railway track may increase the geometrical and mechanical defects of railway lines. The conjunction points of a railway track with concrete and ballast pavements, which are called slab-ballasted track transitions, are one of the main areas where vertical track stiffness changes sharply. Therefore, the potential...

The complexity of the railway track system, in terms of its structural and material behaviour variability throughout its life cycle, has been an obstacle to the establishment of robust methods to predict its long-term behaviour. This work presents a computational implementation that incorporates some features for a more realistic reproduction of th...

The permanent railway track deformation caused by regular train traffic is important for infrastructure managers and railway contractors, as it determines the railway track quality. Although several successful approaches have been made to address the topic of the permanent railway track deformation, these have only been applied at specific location...

Transition zones between embankments and bridges or tunnels are examples of critical assets of the railway infrastructure. These locations often exhibit higher degradations rates, mostly due to the development of differential settlements, which amplify the dynamic train-track interaction, thus further accelerating the development of settlements and...

Railway track designers and maintenance entities have long been pursuing for a robust and reliable method to predict the track’s long-term behaviour. The complexity of this railway system, in terms of its changing structural and material behaviour throughout its life cycle, have hindered that quest. This paper presents a novel computer implementati...

The authors present a numerical study on railway track subgrade reinforcement using short soil-binder columns through injection, below the ballast layer. A 3D FEM program developed in MATLAB that considers the dynamic train–track interaction and the non-linear elastic behaviour of the ballast is used to study the response of the train–track–substru...

Transition zones to bridges and other structures are critical locations in railway tracks that frequently evidence poor long-term performance. Under sleeper pads (USPs) are reported to reduce ballast degradation and control the vertical stiffness of the track, which suggests that USPs can contribute to mitigating the frequent negative effects assoc...

ABRUPT TRACK VERTICAL STIFFNESS VARIATIONS ALONG RAILWAY TRACKS CAN LEAD TO INCREASED DYNAMIC LOADS, ASYMMETRIC DEFORMATIONS, DAM-AGED TRACK COMPONENTS, AND CONSEQUENTLY, INCREASED MAINTENANCE COSTS. THE JUNCTION OF SLAB TRACK AND BALLASTED TRACK IS ONE OF THE EXISTING AREAS WHERE VERTICAL TRACK STIFFNESS CAN SUDDENLY CHANGE, THEREFORE REQUIRING A...

Sudden changes in the structural and geotechnical properties of railway tracks along its course are normally associated with subgrade stiffness transitions, differential settlements and, ultimately, hanging sleepers that reduce the performance of the railway system. This paper aims at analysing and quantifying the impact of such situations, particu...

An abrupt change in the stiffness of railway tracks at the junction between slab track and ballasted track causes increased dynamic loads, asymmetric settlements, damage of track components, and, consequently, increased maintenance costs. Due to this, a transition zone is usually built at the junction between the ballasted and the ballastless track...

Transition zones corresponding to the passage from railway tracks on embankments to settlement free structures are frequently problematic for maintenance. Changing stiffness of the track and differential settlements are main causes for the degradation of tracks and foundations at transitions. This paper concentrates on a railway passage over a box-...

The resilient behaviour of the geomaterials used in railway tracks, particularly the ballast layer, is mostly non-linear and depends mainly on the loading stress path. However geomaterials are frequently considered as linear elastic in structural analyses, assuming that it somewhat reproduces the results of non-linear models for a given load amplit...

The long-term settlement of railway tracks is a consequence of permanent deformations taking place in the track granular layers and subgrade. In the ballast layer, which experiences the highest stress amplitudes during train passages, these permanent deformations strongly depend on the loading conditions, which in turn depend on several factors as...

At railway bridge approaches the track stiffness may vary rapidly and often differential settlements take place between the stiff structure and the approach section of the track. These differential settlements lead to uneven track profiles and the appearance of voids between the base of the sleepers and the ballast on the approach segment. The balla...

Transition zones corresponding to the passage from railway tracks on embankment to natural ground or settlement free structures are frequently problematic for maintenance. Changing stiffness of the track and differential settlements are the main causes for the degradation of tracks and foundations at transitions. This paper presents a methodology t...

Transition zones corresponding to the passage from railway tracks on embankment to settlement free structures are frequently problematic regions for maintenance. The paper presents a settlement model for ballast suited to be integrated in a methodology to predict the evolution of degradation in a transition zone due to train loadings. The settlemen...

The transient dynamic response of a beam supported on a foundation with sudden stiffness change and subjected to a force moving with constant velocity is analysed. The abrupt change is located at the mid-section of the beam of finite length. Two analytical approaches are implemented. In the first one, the response is obtained by finite integral tra...

10.4203/ccp.86.45

Palavras-chave: Comboios de alta velocidade, Variação brusca da rigidez de fundação, Análise dinâmica em regime transitório, Soluções analíticas Resumo. A variação rápida da rigidez das vias férreas, quer devido a mudança de solução estrutural, quer devido a alteração das condições geotécnicas pode induzir vibrações de amplitude excessiva à passage...