Numerical modelling of integral abutment bridges under seasonal thermal cycles

Abstract

The interest in Integral Abutment Bridges (IABs) from the industry has increased in recent years. IABs are robust bridges without joints and bearings hence they are durable and virtually maintenance-free; moreover, the resulting cost-saving associated with their construction is significant, a fact that makes IABs appealing to Agencies, Contractors and Consultants. However, their use in long-span bridges is limited by the complex Soil-Structure Interaction (SSI) which is developed between the structure and the backfill soil. Thermal movements, horizontal loads and dynamic actions are transferred directly to the backfill soil, leading to settlements, ratcheting effects and high earth pressures, hence deteriorating the serviceability of the structure and leading to poor driving conditions for the end-users. The longer the integral bridge the greater the challenge, as movements are increased and so are the aforementioned SSI phenomena. This is an acknowledged gap in IAB design philosophy and even though many solutions have been proposed in the international literature, the emphasis is placed on the understanding of the mechanisms developed within the soil, rather than on the efficient design of the involved components. This is the gap that this research fills. This paper provides an extended review of the techniques used in the international literature and in practice to alleviate the interaction between the bridge abutment and the backfill. Subsequently, the performance of an innovative isolation system for IABs using recycled tyres as a compressible inclusion is studied using detailed numerical models of a representative three span IAB. The inclusion decouples the response of the abutments and the backfill soil under static and dynamic loads. Regarding the methodology followed for assessing the performance of the IAB with the TDA isolator, initially, a conventional IAB is subjected to realistic temperature time histories and amplitudes essentially providing an envelope of the thermal cycles for 120 years of the bridge service and then a second IAB, isolated from the backfill, is subjected to the same loading. The two bridges, i.e. conventional and isolated, are then analysed for different initial restraint conditions, in order to determine the effect of initial temperature on the development of pressures behind the abutment walls. The comparison of the responses showed that the proposed isolation scheme is an effective and sustainable method to isolate the structure from the backfill soil, reducing the pressures experienced by the abutments and the residual vertical displacements of the backfill soil. The proposed research can be of use for extending the length limits of integral abutment bridges, delivering in this way long lasting and more sustainable infrastructure for future highways.

Integral bridge abutments in response to seasonal temperature changes: State of knowledge and recent advances

“…Frontiers in Built Environment frontiersin.org inclusion (e.g., EPS foam, tire shred, or tire-derived aggregates) has been placed between the abutment and the backfill to reduce the horizontal earth pressures behind the abutment and the pile moment (Hoppe, 2005;Caristo et al, 2018;Duda and Siwowski, 2020;Liu et al, 2021a;Zadehmohamad et al, 2021). Arsoy (2000) indicated that flexible piles were beneficial to prevent damages of pileabutment connections.…”

On the seismic performance of straight integral abutment bridges: From advanced numerical modelling to a practice‐oriented analysis method

“…Several research studies focused on the evaluation of the soil-structure contact pressures exchanged along the abutment front wall accounting for the cyclic thermal deformations in the deck. [13][14][15][16][17] Thermal expansion may produce important interaction forces in the abutments and at their connection with the deck, depending on the deformability of the soil-abutment system, that may limit the use of an integral abutment-deck connection to short-and medium-span bridges. 18,19 This drawback can be overcome by designing a deformable abutment, supported by a single pile row, capable to accommodate the thermal deformation of the deck, 20 and in fact, design recommendations to this effect were published by the UK Highways Agency in its publication BA42/96 21 and in its Amendment No.…”

“…Despite the large experience gained worldwide, the design of IABs is still affected by several uncertainties, which are mainly related to the assessment of the effects induced by the soil on the structural members, under both static and dynamic conditions. Several research studies focused on the evaluation of the soil‐structure contact pressures exchanged along the abutment front wall accounting for the cyclic thermal deformations in the deck 13–17 . Thermal expansion may produce important interaction forces in the abutments and at their connection with the deck, depending on the deformability of the soil‐abutment system, that may limit the use of an integral abutment‐deck connection to short‐ and medium‐span bridges 18,19 .…”

Integral abutment bridges: Investigation of seismic soil‐structure interaction effects by shaking table testing

“…From a structural point of view, the use of a monolithically cast frame superstructure has several advantages over traditional designs such as reduced sagging moment at mid‐span, smaller girders and smaller intermediate supports 7,8 . Furthermore, these designs are characterised by improved durability (i.e., reduced corrosion and material degradation at the joints), lower costs associated with construction and maintenance 9 and improved driving comfort. On the other hand, thermal and lateral loads induce high stresses in the structure due to the rigidity of the deck‐abutment connection 10 .…”