Integral Abutment Bridges (IABs) are jointless structures without bearings or expansion joints, which require minimum or zero maintenance. The barrier to the application of longspan IABs is the interaction of the abutment with the backfill soil during the thermal expansion and contraction of the bridge deck, i.e. serviceability, or when the bridge is subjected to dynamic loads, such as earthquakes. The interaction of the bridge with the backfill leads to settlements and ratcheting of the soil behind the abutment and, as a result, the soil pressures acting on the abutment build-up in the long-term. This paper provides a solution for the aforementioned challenges, by introducing a novel isolator that is a compressible inclusion (CI) of reused tyre derived aggregates (TDA) placed between the bridge abutment and the backfill. The compressibility of typical tyre derived aggregates was measured by laboratory tests and the compressible inclusion was designed accordingly. The CI was then applied to a typical integral frame abutment model, which was subjected to static and dynamic loads representing in-service and seismic loads correspondingly. The response of both the conventional and the isolated abutment was assessed based on the settlements of the backfill, the soil pressures and the actions of the abutment. The study of the isolated abutment showed that the achieved decoupling of the abutment from the backfill soil results in significant reductions of the settlements of the backfill and of the pressures acting on the abutment. Hence, the proposed research can be of use for extending the length limits of integral frame bridges subjected to earthquake excitations.
Abstract:Reuse of the 1.5 billion waste tyres that are produced annually is a one of the major worldwide challenges, as waste tyres are toxic and cause pollution to the environment. In recognition of this problem, this paper introduces the reuse of tyres, in the form of derived aggregates in mixtures with granulated soil materials, as previous studies indicated the potential benefits of these materials in the seismic performance of structures. The objective of the present research study is to investigate whether use of rubberised backfills benefits the seismic response of Integral Abutment Bridges (IABs) by enhancing soil-structure interaction (SSI) effects. Numerical models including typical integral abutments on surface foundation with nonlinear conventional backfill material and its alternative form as soil-rubber mixtures are analysed and their response parameters are compared. The research is conducted on the basis of parametric analysis, which aims to evaluate the influence of different rubber-soil mixtures on the dynamic response of the abutment-backfill system under various seismic excitations, accounting for dynamic soil-abutment interaction. The results provide evidence that the use of rubberised backfill leads to reductions in the backfill settlements, the horizontal displacements of the bridge deck, the residual horizontal displacements of the top of the abutment and the pressures acting on the abutment, up to 55%, 18%, 43% and 47% respectively, with respect to a conventional backfill comprising of clean sand. Considerable amount of decrease in bending moments and shear forces on the abutment wall is also observed. Therefore, rubberised backfills offer promising solution to mitigate the earthquake risk, towards economic design with minimal damage objectives for the resilience of transportation networks. Abstract 10Reuse of the 1.5 billion waste tyres that are produced annually is a one of the major worldwide challenges, as 11 waste tyres are toxic and cause pollution to the environment. In recognition of this problem, this paper 12 introduces the reuse of tyres, in the form of derived aggregates in mixtures with granulated soil materials, as 13 previous studies indicated the potential benefits of these materials in the seismic performance of structures. 14 The objective of the present research study is to investigate whether use of rubberised backfills benefits the 15 seismic response of Integral Abutment Bridges (IABs) by enhancing soil-structure interaction (SSI) effects. 16Numerical models including typical integral abutments on surface foundation with nonlinear conventional 17 backfill material and its alternative form as soil-rubber mixtures are analysed and their response parameters 18 are compared. The research is conducted on the basis of parametric analysis, which aims to evaluate the 19 influence of different rubber-soil mixtures on the dynamic response of the abutment-backfill system under 20 various seismic excitations, accounting for dynamic soil-abutment interaction. The results provid...
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