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Editorial
Full text linkBridge engineering research and practice continuously pursue better understanding of engineering phenomena and delivery of innovative applications, pushing the boundaries of structural engineering. Among the topics that are included in bridge engineering activities, and that also characterise the topics covered by this Journal, there are several aspects related to innovation and research in the field. These can be interpreted both through theoretical research approaches and through the practical exemplification of innovative and challenging applications. This edition of Bridge Engineering actually reflects this dichotomy, and in fact the reader finds a first group of papers characterised by a greater abstractionism.
The first paper is an experimental endeavour backed by a 5-year experimental programme and validates experimentally numerical models used for estimating long-term deflections of reinforced concrete cantilevers. This laboratory study with significant practical applicability, also assesses the influence of heterogeneity on the long-term deflections of reinforced concrete components and aims at alleviating these deflections by making use of compression reinforcement and low-shrinkage concrete (ID38 – Sousa et al. 2020). The second paper studies specific models for the preliminary evaluation of the effect of cables in the stiffness of bridges supported by cables (ID28 – Tan et al. 2020). Equations are developed for preliminary estimates of longitudinal displacement in suspension bridges and the cable-spring effect and its longitudinal restraint stiffness on towers is quantified. Research papers in this edition also include a novel approach to improving the estimation of the local scour depth at bridge piers due to accumulated debris (ID45 – Ebrahimi et al. 2020). The method computes a debris factor based on the dimensions the debris blockage. The method takes one step ahead by applying the methodto a full-scale bridge in the UK that is suspected to have failed as a result of debris-induced scour.
On the more practical side of this edition there are contributions describing the most recent applications in the field of bridge engineering, which can represent examples in the field and challenges from which the reader can draw points of interest for new and future applicative developments. This peculiar aspect essentially characterises this journal and may probably be of special interest to professional engineers, which in their activities they have to cope with the implementation of creative and sometimes revolutionary solutions. Some examples are also given in this edition of the Journal, in particular the launch philosophy of the west flyover at Stockley airport junction (ID15 – Beavor et al. 2020), which includes the longest single-span constructed on the Great Western railway since Brunel’s Saltash Bridge in 1859. Between these two opposite but connected poles, in bridge engineering, intermediate studies can be found. For example, the preliminary study of special design works, such as the integral bridge concept herein presented for the third runway at Heathrow airport (ID44 – Sandberg et al. 2020), shown in Figure 1 below. At over 140 m in the total length, the adoption of an integral bridge of this length is in excess of most integral bridges in the UK. This paper presents a comprehensive SSI study to understand the behaviour of this long integral bridge during thermal deck movements
Physical simulation of the surface pressure field on a 5-storey residential building and application to natural ventilation
Full text linkChallenges and opportunities for the application of integral abutment bridges in earthquake-prone areas: A review
No full textIntegral Abutment Bridges (IABs) are robust structures without joints and bearings, hence they are less vulnerable to natural and manmade hazards, whilst they require minimal maintenance throughout their lifespan. As a result of these engineering advantages, IABs are appealing to road and railway agencies and consultants. Despite their advantages, IAB design and construction is challenging and the main barriers for extensive use of IABs originate from the interaction between the abutment and the backfill soil. This interaction causes permanent deflections of the backfill soil and enhanced soil pressures on the abutment of passive nature. Under strong earthquake excitations, the response of IABs is strongly affected by the aforementioned interaction. Surprisingly, no agreement has been reached to date in the international literature as to whether this is a beneficial or a detrimental effect. The reasons for acknowledged disagreements in the literature indicates a conceptual gap in IAB design and assessment and it, therefore, requires further investigation.To the best of the author's knowledge, the significance of this interaction in earthquake resistant IABs is dependent on a number of factors, such as the type and intensity of the earthquake, the type, length and condition of the bridge after a number of years of service, the type and height of the abutment, the bridge dynamic characteristics, e.g. stiffness, damping, mass and the type of the backfill soil, among others. Many of these competing and clashing, factors lead to worse or better IAB responses, and this depends on the additional inertia mass of the backfill soil, the additional input motion exerted on the bridge from dual paths e.g. the foundation of the abutment and the backfill soil, the dissipation capacity and stiffness of the abutment and backfill soil. With the aim of better understanding the seismic response of IABs and opine with regard to the importance of the abutment and backfill soil on the seismic response of IABs, a comprehensive state of the art review is conducted in this paper. The review includes all the aspects relevant to the IAB-backfill interaction, with emphasis on IABs subjected to earthquake excitations. The research-based evidence provided here postulates a very complex interaction effect, which may have a positive or negative effect on IAB seismic responses. The evidence gathered also suggests a minimal understanding of the potential benefits of the IAB-backfill interaction, yet a reasonable understanding of the aggravated seismic response due to the same interaction in other instances. The paper includes literature-based evidence and inferences on IAB seismic designs and concludes with the results of an extended numerical study, which was conducted to provide further evidence with regard to the effect of the bridge-backfill interaction on the seismic response and design of IABs. A representative IAB was utilised as the base model and a comprehensive parametric study was conducted varying the abutment type and height, the bridge length and the backfill soil properties. The results are evidence that, indeed, the backfill soil predominantly benefits the bridge as it reduces its bending moments and pier drifts, and which potentially can lead to more economic designs. However, the IAB-backfill interaction is strongly case-dependent and therefore meticulous and detailed modelling of the backfill soil is believed to be important to avoid underestimation of bridge stress resultants and consequent under-designs.•Comprehensive state-of-the-art-review on the seismic response of Integral Abutment Bridges (IABs).•Challenges in earthquake-resistant IABs are discussed with the view of promoting innovation in IAB design and construction.•Opinion, based on new findings, on the benefits and detriments of the bridge-backfill interaction in IABs.•For the analysed IABs, the dynamic bridge-backfill interaction reduced, in most cases, the pier bending moments and drifts.•The backfill soil seems to increase significantly the mass in shorter IABs and also increase the stiffness in longer IABs
Response of integral abutment bridges under a sequence of thermal loading and seismic shaking
No full textFragility of transport assets exposed to multiple hazards: State-of-the-art review toward infrastructural resilience
No full textUplift of Bearings in Isolated Bridges Subjected to Longitudinal Seismic Actions
No full textBearings are used to isolate bridge substructures from the lateral forces induced by creep, shrinkage and seismic displacements. They are set in one or two support lines parallel to the transverse axis of the pier cap and are typically anchored to the deck and to the pier cap. This detailing makes them susceptible to possible tensile loading. During an earthquake, the longitudinal displacements of the deck induce rotations to the pier caps about a transverse axis, which in turn cause tensile (uplift) and compressive displacements to the bearings. Tensile displacements of bearings, due to the pier rotations, have not been addressed before and questions about the severity of this uplift effect arise, because tensile loading of bearings is strongly related to elastomer cavitation and ruptures. An extended parametric study revealed that bearing uplift may occur in isolated bridges, while uplift effect is more critical for the bearings on shorter piers. Tensile displacements of bearings were found to be significantly increased when the isolators were eccentrically placed with respect to the axis of the pier and when flexible isolators were used for the isolation of the bridge. The results of this study cannot be generalised as bridge response is strongly case-dependent and the approach has limitations, which are related to the modelling approach and to the fact that emphasis was placed on the longitudinal response of bridges
Control of long-term deflections of RC beams using reinforcements and low-shrinkage concrete
No full textAn experimentally based programme was conducted to assess the influence of heterogeneity on the long-term deflection of reinforced concrete (RC) elements with compression reinforcement and low-shrinkage concrete. These two structural measures are usually employed by designers to mitigate deflection of concrete beams, slabs and bridge decks due to creep and shrinkage effects. Control of creep and shrinkage deflections is important for successful design of concrete elements as the deflections influence their sizing and thus the associated costs. A 5 year experimental study was undertaken to address the most common alternative design approaches to alleviate long-term deflections of concrete. These included variable reinforcement ratios within the compressive zone, variable tensile reinforcement ratios, low-shrinkage concrete within the compressive zone and a combination of these measures. In total, 12 cantilever beam specimens were tested in the laboratory under controlled environmental conditions, supported by a time-dependent finite-element model. Both numerical and experimental results showed RC beam deflection reductions of up to 85% could be achieved when both compressive reinforcement and low-shrinkage concrete were employed
Fragility of bridges exposed to multiple hazards and impact on transport network resilience
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