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Expansion and contraction of bridge decks move integral bridge abutments (IABs) toward and away from the backfill, resulting in high horizontal earth pressures, backfill surface settlements, and abutment toe movements away from the backfill. Geofoam can reduce relative abutment movements to the backfill when the abutment moves toward the backfill due to bridge deck expansion. Geosynthetic reinforcement can improve the stability of the backfill, thus reducing backfill surface settlements when the abutment moves away from the backfill due to bridge deck contraction. Numerical analysis was utilized in this study to investigate mechanisms of geosynthetic reinforcement and geofoam and effects of key parameters, such as the thickness and elastic modulus of geofoam and the length and vertical spacing of geosynthetic reinforcement. Increasing the thickness and/or reducing the elastic modulus of geofoam could reduce maximum horizontal earth pressures in the backfill. However, the effects of geofoam to reduce backfill surface settlements were not significant. In addition, geosynthetic reinforcement reduced surface settlements of the backfill away from the abutment but increased surface settlements of the backfill right behind the abutment. By connecting the front ends of geosynthetic reinforcements with the abutment, settlements of reinforced backfill decreased at the expense of large settlements of unreinforced backfill. Furthermore, geofoam together with geosynthetic reinforcement with wrap-around facing could significantly minimize seasonal temperature change-induced problems for IABs.

Exterior shear keys are used in bridge abutments to provide lateral restraints to the bridge superstructure under normal service loads and moderate earthquake forces. They also serve as a structural fuse to protect the abutment piles from damage in the event of a major earthquake. These shear keys are conventionally constructed monolithic with the stem walls in bridge abutments and are referred to as non-isolated shear keys. Past experimental data have shown that the failure of these shear keys under lateral seismic forces tends to be governed by diagonal shear cracks in the stem walls. This type of failure can be sudden, resulting in non-ductile behavior and costly post-earthquake repairs. This paper presents a design method that prevents the diagonal shear failure of the stem wall and allows for a more predictable failure mechanism governed by the horizontal sliding of the shear key. Analytical formulas are presented for design. The design method has been validated by the tests of three shear key-stem wall assemblies. Keywords: bridge abutment; concrete cracks; diagonal cracks; monolithic; non-isolated; shear keys; shear sliding.

The construction of integral bridges is one of the most effective methods to reduce bridges’ construction and in-service costs. However, there are associated geotechnical problems with their abutments backfill due to the integrated abutments. The main goal of this study is to evaluate and quantify the benefits of geogrid reinforcement for reducing the backfill’s geotechnical problems. For this purpose, using small-scale physical modeling, the benefits of geogrid reinforcing of the backfill of an integral abutment bridge subjected to cyclic movements are evaluated. The results are then compared with a previous study performed on unreinforced backfill and two types of geocells. In this study, 120 loading cycles are applied to geogrid-reinforced soil to simulate the cyclic loadings on integral abutment backfill due to seasonal abutment displacement. The horizontal reaction load at the top of the wall, changes in pressure behind the wall, and deformation in backfill soil are measured during the test. Then the results are discussed in terms of equivalent peak lateral soil coefficient (Kpeak), lateral earth pressure coefficient (K*), and normalized settlement behind the wall (Sg/H). The derived lateral soil coefficients and settlement behind the abutment show that geogrid substantially reduces pressure and settlements after 120 cyclic loads. Based on the results, Kpeak and K* of the geogrid-reinforced backfill decrease by up to 36%, and Sg/H behind the wall decreases by 62%. In addition, the comparison of the results for geogrid with two geocell types shows that geogrid is more efficient in terms of lateral soil coefficients.

Integral abutment bridges (IABs) are increasingly adopted in transportation infrastructure due to their durability, reduced maintenance needs, and cost-effectiveness compared to conventional bridges. However, their reliable performance under live loads is strongly influenced by the nonlinear soil–structure interaction (SSI) at the pile–abutment joint, which remains challenging to quantify using conventional analysis methods. This study develops simplified spring-based models to capture the SSI behavior of pile–abutment joints in short-span IABs. Predictive equations for joint rotation, deflection, moment, and shear are formulated using Linear Regression (LR) and Response Surface Methodology (RSM). Unlike prior studies relying solely on FEM or traditional p–y curves, the novelty of this work lies in deriving regression-based spring constants calibrated against FEM analyses, which can be directly implemented in standard structural software. This approach significantly reduces computational demands while maintaining predictive accuracy, enabling efficient assessment of pile contributions and global bridge response. Validation against finite element method (FEM) results confirms the reliability of the simplified models, with RSM outperforming LR in representing nonlinear parameter interactions.

The flexibility of the foundation system significantly affects the seismic and operational performance of integral abutment bridges (IAB). The so-called pile isolation system can lead to higher flexibility in pile foundations. It consists in backfilling the pile hole with high-damping materials up to a certain depth from the surface level. However, the impact of this solution in increasing the lateral flexibility and reducing the seismic demand strongly depends on the scale factor and pile diameter. Most investigations on this topic are based on experimental tests on scaled pile specimens. This paper explores the pile isolation system’s effectiveness by conducting a multivariate sensitivity analysis of the seismic demand of an IAB structural archetype. The IAB archetype is modelled as a Winkler beam with a piece-wise definition of the subgrade stiffness and equivalent viscous damping, simulating the responses of the soil and high-damping particles. The simulated data are then used to calibrate a probabilistic formulation of the seismic demand reduction due to the pre-hole. The formulation, calibrated following a Bayesian approach, is used to derive estimates of the q -factor associated with the damping pre-hole for possible use in engineering practice. The analyses demonstrate that pile isolation with high-damping material can be effective but possesses a limited dissipating capacity, with a seismic reduction factor of approximately 1 and 2.

In this paper, a two-dimensional non-linear finite element model is proposed for seismic analysis of integral abutment bridges (IABs). The model captures the soil-pile-structure interaction and includes far-field soil inertia effects and piles non-linear behavior. The compression-only (gap) elements behind abutments were used to detect possible soil wall separation phases during earthquakes. The gap stiffness parameter was studied, and a recommendation is given for its value. To validate the proposed model, several ground motion time histories were applied to pile supported single cantilever walls with free-field soil and gap elements. The active/passive seismic earth pressures exerted on the wall were compared with the conventional Mononobe-Okabe method, which is often used by practicing engineers. The results indicate that the proposed FE model is appropriate for seismic analysis of IABs and captures the soil-pile-structure interaction effects with acceptable accuracy in all phases of ground motions.

The reinforced concrete piles (RC) in integral abutment bridges (IABs) are challenging to meet the longitudinal deformation of bridges with significant lateral stiffness. The H-shaped steel (HS) piles are costly and prone to corrosion. This paper proposes a new form of pile comprised of HS and RC piles in series to meet the longitudinal deformation demand of IABs. Tests were conducted for one HS pile under reciprocating low-cycle pseudo-static test and two HS-RC stepped piles with different bending stiffness ratios of HS/RC (0.25 and 0.5) using the HS-RC pile test model,. The influence of the stiffness ratio on the mechanical behavior of stepped pile-soil was studied. The mechanical behavior of the stepped pile was also compared with single HS and RC piles. and the applicability of the m and p - y curve methods to the calculation of horizontal displacement of stepped pile is discussed. The results show that the elastic deformation range of the HS pile is 2 mm to 25 mm, and its horizontal deformation capacity and bearing capacity are excellent. As the stiffness ratio increases, the stepped pile-soil system’s yield displacement and yield load increased. The stiffness ratio has no significant effect on the failure mode of the piles. The hysteretic ring of the stepped pile shows a squeezing shape at the initial loading stage, but becomes a full spindle in the later loading stage. The stepped pile shows an excellent energy consumption effect and a horizontal deformation ability, indicating it is suitable for IABs. The m method has better accuracy only up to 2 mm displacement, while the p - y curve method still has higher accuracy within 15 mm.

Integral bridges are a class of bridges with integral or semi-integral abutments, designed without expansion joints in the bridge deck of the superstructure. The significance of an integral bridge design is that it avoids durability and recurring maintenance issues with bridge joints, and maybe bearings, which are prevalent in traditional bridges. Integral bridges are less costly to construct. They require less maintenance and therefore cause less traffic disruptions that incur socio-economic costs. As a consequence, integral bridges are becoming the first choice of bridge design for short-to-medium length bridges in many countries, including the UK, USA, Europe, Australia, New Zealand and many other Asian countries. However, integral bridge designs are not without challenges: issues that concern concrete creep, shrinkage, temperature effects, bridge skew, structural constraints, as well as soil–structure interactions are amplified in integral bridges. The increased cyclic soil–structure interactions between the bridge structure and soil will lead to adverse soil ratcheting and settlement bump at the bridge approach. If movements from bridge superstructures were also transferred to pile-supported substructures, there is a risk that the pile–soil interactions may lead to pile fatigue failure. These issues complicate the geotechnical aspects of integral bridges. The aim of this paper is to present a comprehensive review of current geotechnical design practices and the amelioration of soil–structure interactions of integral bridges.

The flow's velocity field with the lateral contraction and expansion in an open channel around bridge abutment was measured with laser Doppler anemometry (LDA), and the free-surface profile was determined using a limnimeter for two flow discharges. Basic equations of fluid flow are solved by the ANSYS Fluent program based on the finite volume method for the same experimental flow conditions. In the numerical simulations, the detached eddy simulation (DES) model is used to simulate the turbulence, and the free-surface profile is calculated using the volume of fluid method (VOF). Computational results for free-surface profiles and horizontal velocity component are compared with measured data for the two cases. The length of the separation zone formed in the downstream region of the bridge abutments is considerably larger than in the upstream region. The length of this region downstream ( L s ) is greatest at the channel bottom and is approximately 14 d (d: length of the bridge abutment perpendicular to the flow). The thickness of the separation zone was similar around both piers. In the contraction region, the horizontal maximum velocity component ( u max ) occurred at z / z max  =  ± 0.5, not in the central axis. Moreover, the u max is larger in the downstream region than in the upstream region, u max  = 1.5 u o and u max  = 2u o for Cases 1 and 2, respectively. The experimental and numerical results indicate that the DES model accurately predicts the velocity field and free-surface profiles under the present flow conditions.

In an integral abutment bridge (IAB), the superstructure and the abutment are constructed monolithically at their junction without the presence of any bearing or expansion joint. This leads to a significant reduction in the maintenance cost of the bridge. However, integral connection at deck-abutment junction causes a significant change in the bridge behavior under thermal loading and earthquake shaking as the superstructure (along with bridge deck and girders), abutment, foundation, wingwall, and approach slab may act like a single unit. Different countries and the respective Highway Agencies have adopted different guidelines for design and construction of IABs. Though many advancement in construction of IAB have been made, still there are many aspects which require additional attention. The aim of the present paper is to review the past studies on seismic behavior of IABs performed in the last three decades incorporating seismic soil-structure interaction. A few features are also highlighted which need to be addressed through further studies.