Integral Abutment Bridges Research Articles

Modelling of Soil Structure Interaction of Integral Abutment Bridges

Modelling of Soil Structure Interaction of Integral Abutment Bridges

Seven-Year Field Monitoring of Four Integral Abutment Bridges

Integral abutment bridges (IABs) are now a routine construction and design of choice for many DOTs as bridges are replaced or for new roadways. However, current design and analysis methodologies have not matured substantially because of a lack of available long-term field data. Often current analysis methods predict bridge behavior that is much different from observed. Because of thermal loading, time-dependent effects, and soil-structure interaction, significant irreversible abutment displacements and rotations occur. The primary objective of this paper is to report the actual in situ measurements obtained at four short to medium-long IABs and one weather station, all located in central Pennsylvania. A total of 240 instruments was installed on four IABs during bridge construction and monitored continuously. Monitoring duration at each bridge ranges from 2.5 years to nearly 7 years, having initiated the program in 2002 and continuing to the present. Because of a unique environmental issue, the bridges wer...

Parametric Study and Length Limitations for Prestressed Concrete Girder Integral Abutment Bridges

This study establishes a practical limit for the maximum length of prestressed concrete girder integral abutment bridges (IABs) and identifies potential distress in IABs at extreme lengths. The nonlinear numerical models developed using detailed three-dimensional solid elements include soil-pile interaction, abutment-pile interaction, and construction joint detail. The loads on IABs were ambient temperature, temperature gradient, time-dependent loads, and backfill pressure. A parametric study was performed with an initial bridge length of 305 m considering the effects of: (a) abutment height; (b) soil stiffness; (c) backwall to abutment stiffness; and (d) pile orientation on IAB response. Results of the parametric study showed that taller abutments, moderate construction joint stiffness, low soil stiffness, and strong axis pile orientation are best suited for IABs at extreme lengths. The length limitation study identifies that pile moments and concrete stress at the abutment/pile connection, concrete stress and transverse threading reinforcement shear stress at girder/backwall connection, and construction joint reinforcement are critical components in IAB responses and limit the bridge length. Finally, this study suggested a maximum length of 457 m on the basis of IAB critical responses.

Two New Earthquake Resistant Integral Abutments for Medium to Long Span Bridges

A wide field of study is open to new abutment configurations and design innovation as no unified procedure is available for the design and construction of integral abutment bridges (IABs). In this framework, an extended state-of the-art review on the configuration of IABs, with emphasis on the European Bridge Engineering, was done and two new integral abutments were studied. The primary feature of both integral abutments is the de coupling of the in-service response of the bridge from the backfill soil and the utilization of the backfill's resistance during earthquake, aiming at reducing the seismic demand on bridges. This objective was achieved by accommodating the in-service constraint movements of the deck through the flexibility of the IAB and via as small as possible clearances. During an earthquake the IABs interact with the backfill soil and reduce the displacements of the deck and thereby the seismic demand on bridge piers and foundations. Abutments will be useful in future design of intermediate to long-span bridges.

Load Testing and Modeling of Two Integral Abutment Bridges in Vermont, US

Load testing of two instrumented single-span integral abutment bridges (IABs) in Vermont, US, was conducted using loaded multiple tandem dump trucks. Data was used to validate finite element (FE) models of each structure. Field data and FE model results were compared to gain an understanding of the distribution of live load on completed integral bridges and resulting stresses and deformations in structural components. The superstructure of the two bridges consists of a concrete deck supported on steel I-girders that are cast integrally into concrete abutments at the bridge ends. Abutments are supported on H-piles oriented with their weak axis resisting deformations in the direction of bridge alignment. The spans of the two bridges are 43 and 37 m, with girders connected to the abutments perpendicularly and with a skew angle of 15°. Correlation of measured data, such as girder strains, pile strains and deflections, abutment displacements, and backfill pressures, with FE model values are presented. Important considerations in the interpretation of field data are presented, including evaluations of the degree of composite action in girders, effects of thermal fluctuations over the course of testing and challenges faced when using field data directly to compute live load distribution factors.

Monitoring of a Swedish Integral Abutment Bridge

One of the most commonly discussed problems regarding bridges with integral abutments is the influence of longitudinal elongation of the superstructure as a result of seasonal temperature variations. A bridge built with integral abutments is often supported by a row of piles made of steel or concrete. The longitudinal elongation of the superstructure induces a displacement and a rotation at the top of the pile, which in turn may cause strains that exceeds the yield strain. Such seasonal variations may lead to low-cyclic fatigue failure in the pile. Therefore, it is of great interest to investigate the amplitude of these strains, as well as the general behaviour of the bridge. In 2005, the European R&D project, INTAB (RFSR-CT-2005-00041, “Economic and Durable Design of Bridges with Integral Abutments, 2005–2008”) was started. Within the INTAB project a composite bridge was built and monitored in Northern Sweden.

Deployment of a dense hybrid wireless sensing system for bridge assessment

Discussed in this paper is the deployment of a dense wireless sensor system on a short span integral abutment bridge superstructure located in St. Lawrence County, New York. The Wireless Sensor Solution (WSS) is designed specifically for diagnostic bridge monitoring providing independent conditioning for accelerometers and strain transducers. During deployment, strain measurements are obtained in real-time under ambient environmental and traffic loading. Strain transducers are placed at various locations along the girders, including the top and bottom flanges of a heavily instrumented interior girder at the mid-span and the abutment ends where the neutral axis location, section modulus, and girder moments are obtained. Results from the strain data analysis aid in quantifying the bridge response; notably, detection of end fixity, load distribution, and composite action between the girders and bridge deck. The measured responses are illustrated to propose a deterioration profile based on the level of capacity and demand.

Transition Slabs of Integral Abutment Bridges

Over the past decades, an increasing number of bridges with integral abutment have been built in Switzerland. This type of bridge offers various advantages over standard bridges with abutments, equipped with expansion joints and bearings that require regular inspection and maintenance. One main concern of integral abutment bridges is related to the soil-structure interaction, in particular between the transition slab and the embankment. To avoid any expansion joints, transition slabs are directly connected to the end of integral abutment bridges. They are therefore subject to large displacements of the bridge deck due to temperature effects and creep and shrinkage in concrete bridges. Consequently, detailing of transition slabs needs to be carefully considered. This paper investigates the behaviour of transition slabs, focusing on the settlement of the pavement at the end of the transition slab and on the cracking of the pavement between the bridge deck and transition slab. On that basis, a modified geometry of the transition slab and a new detail for the connection between the bridge deck and the transition slab are proposed. If these propositions are considered at an early stage in the design process, they will result in an improved long term performance of bridges with integral abutments without increasing the construction costs.

Predicting the Earth Pressure on Integral Bridge Abutments

The soil adjacent to integral bridge abutments experiences daily and annual temperature-induced cyclic loading due to expansion and contraction of the bridge deck. This causes a particular soil response and complicated soil-structure interaction problem, with considerable uncertainties in design. This paper describes a method of calculating the effects of thermal cycling by using the results of laboratory cyclic stress path testing within a numerical model. Samples of stiff clay and sand were tested in the triaxial apparatus under stress paths typical for behind an integral abutment. Distinct behavior was observed for the two soils, with stiff clay showing relatively little buildup of lateral stress with cycles, whereas for sand stresses continued to increase, exceeding at-rest and approaching full passive pressures. To explore the implications of these findings on the soil-abutment interaction and to estimate the lateral stresses acting on the abutment as a whole, a numerical (finite difference) model was developed with a soil model reproducing the sand behavior at element level. The numerical model gave good agreement with published centrifuge and field data, and indicated that the stress profile specified in some current standards is conservative. Influence of abutment stiffness and wall friction is also quantified.

Evaluation on the behavior of abutment–pile connection in integral abutment bridge

Integral abutment bridges can reduce the amount and cost of construction and maintenance work since they do not have expansion joints and shoes in order to increase stability and durability of the bridges’ system. Integral abutment bridges normally have single-row H-pile systems to resist the behaviors under service loading conditions such as thermal loading. In order to transfer member forces between abutments and H-pile, the abutment–pile connection in the integral abutment bridge should have rigid behavior. Therefore, the installation of reinforcing bars and minimum installed length of the piles in the concrete abutment are required to resist bearing force and deformation caused by shear forces and bending moments. This study examines the abutment–pile connections in the integral abutment bridge to improve the shear and bearing resistance of concrete abutment and constructability of abutment–pile connections for the single-row H-pile system with weak axis. Three types of new abutment–pile connections are proposed in this study. They feature transverse reinforcing bars perforated in H-pile, stud connectors, and perfobond rib connectors on the flange of H-pile, respectively. They are intended to increase the stiffness and strength so that they will better resist the bearing force caused by deformations and rotations at abutment H-pile concrete. Loading tests and FE analysis were conducted to evaluate the stiffness and behaviors of proposed connections for half scale abutment–H-pile connection specimens. From the test results, proposed abutment–H-pile connections were evaluated to secure sufficient stiffness, rotational stiffness, and bearing strength.

Soil Structure Interaction for Integral Abutment Bridge Using Spring Analogy Approach

The reaction of the backfill behind the abutments and adjacent to the piles plays a significant role in the behavior of the Integral bridge. The handling of soil-structure interaction in the analysis and design of integral abutment bridges has always been problematic due to its complexity. This study describes the implementation of a 2-D finite element model of IAB system which explicitly incorporates the soil response. The superstructure members and the pile have been represented by means of three-node isoperimetric beam elements with three degree of freedom per node. The Eight node isoperimetric quadrilateral element has been used to model the abutment. The backfill was idealized by uncoupled 'Winkler' spring. The applic1ability of this model is demonstrated by analyzing a single span IA bridge. The results have shown that the shear forces at the tops of the supported piles were only 12% to 16% of the load which at the top of abutment.

Rigidity of abutments in integral abutment bridges

In this article, we present the results from a numerical and an experimental analysis of the Scotch Road integral abutment bridge located in Trenton, New Jersey. A three-dimensional, non-linear finite element (FE) model of the bridge has been developed to study the effect of thermal loading on pile–soil interaction. The abutment, pile and soil were modelled using solid elements. Material non-linearity is accounted for both, the piles and the soil. The bridge substructure was fully instrumented. An analysis of the pile-soil system was performed using the finite difference software LPILE. Field data were used to verify the results obtained from the FE and finite difference (FD) analyses. We found that the integral abutments are not behaving rigidly as was assumed and a plastic hinge is formed at the connection between the piles and the abutment at a lateral displacement of 0.06 m which is greater than the maximum displacement of 0.023 m that the bridge can experience as a result of a maximum expected temperature change of±26.7°C during the life time of the bridge. Therefore, the 0.6 m embedment of the piles inside the integral abutment is adequate for maintaining their fixity inside the abutment.

Parametric and pushover analyses on integral abutment bridge

Abstract Integral abutment bridges (IABs) are jointless bridges where the girder or the deck is continuous and monolithically connected to the abutments. A usual and important problem in the design of IABs is how to deal with the soil–structure interaction behind the abutments and next to the foundation piles: this can be considered as a fundamental aspect to reach a thorough understanding of this type of structure, which requires iterative and nonlinear analysis. In this paper, a 2D simplified finite-element model of a real 400-metre-long IAB, built in the Province of Verona-Italy, is implemented and used to perform non-linear analyses on the bridge, the structural response of which is then examined in detail. A parametric study based on the variation of the soil properties behind the back-walls and around the piles is then performed. Furthermore, a temperature pushover analysis (non linear static analysis for positive and negative temperature variations) is carried out to assess the failure pattern of the bridge caused by a temperature change, considered as one of the key parameters in IAB design. Lastly, the effect of abutment stiffness is also discussed.

NON-LINEAR ANALYSIS OF AN INTEGRAL BRIDGE

This study describes the implementation of a 2‐D finite element model of an integral abutment bridge (IAB) system which explicitly incorporates the nonlinear soil response. The superstructure members have been represented by means of three‐node isoparametric beam elements with three degrees of freedom per node. The soil mass is idealized by eight node isoperimetric quadrilateral element at near field and five node isoparametric infinite element to simulate the far field behavior of the soil media. The non‐linearity of the soil mass has been represented by using the Duncan and Chang hyperbolic model. The applicability of this model was demonstrated by analyzing a single span IAB. This study has shown that the soil nonlinearity has significant effect on the response of the structure, where the displacement that have been obtained on basis of nonlinear analysis is 1.5–2.0 times higher than that obtained from linear analysis. The stress magnitudes in the nonlinear analysis are also higher where in some point the difference reached almost 3 times. Santrauka Straipsnyje aprašoma, kaip taikomas 2‐D baigtiniu elementu metodas tilto sistemai su integraliniais ramtais analizuoti, apimant ir netiesine grunto elgsena. Antžemines tilto dalies laikantieji elementai modeliuojami taikant triju mazgu izoparametrinius strypinius elementus su trimis laisves laipsniais kiekviename mazge. Grunto masyvui modeliuoti taikomi aštuoniu mazgu izoparametriniai ketursieniai elementai arti tilto esančioje aplinkoje ir penkiu mazgu izoparametriniai begaliniai elementai, imituojantys grunto terpes elgsena nuo tilto nutolusiose srityse. Grunto masyvo elgsenos netiesiškumas ivertinamas Duncan ir Chang hiperboliniu modeliu. Jo tinkamumas aiškinamas analizuojant vieno tarpatramio integralini tilta. Atlikti tyrimai parode, kad grunto savybiu netiesiškumas turi didele itaka tilto konstrukciju elgsenai. Tilto poslinkiai, nustatyti taikant netiesine analize, yra 1,5–2,0 karto didesni už poslinkius, nustatytus taikant tiesine analize. Atlikus netiesine analize nustatyti itempiai taip pat yra didesni, o kai kuriais atvejais skirtumas siekia beveik tris kartus.

Integral Abutment Bridges: The European Way

Integral abutment bridges are becoming more popular in Europe, but the traditions differ from country to country. This leads to different technical solutions for the same problem in each country. A European survey was conducted in early 2007 to illustrate the design criteria used by each different country for integral abutment bridges. The survey requested information useful to a designer comparing the design requirements and restrictions of various European countries. As an added measure of comparison, these results were compared to some recently conducted surveys of state agencies within the United States. When looking at the results of the European survey responses and past surveys of U.S. transportation agencies, it is clear that there are many similarities in design assumptions and construction practices. Yet, there are also significant differences.

Numerical analysis method for long-term behavior of integral abutment bridges

Many engineering uncertainties exist in the prediction of integral abutment bridge (IAB) long-term behavior. This paper reports on the development of numerical modeling methodologies formulated on the basis of an extensive field monitoring program and results obtained from four IABs on I-99 in central Pennsylvania. The proposed numerical modeling methodologies allow long-term bridge response prediction, recognizing that an IAB has significant time-dependent response changes as a result of irreversible soil–structure interaction and time-dependent effects of the superstructure in the case of prestressed concrete girders. Both measured and numerical responses indicate that soil–structure interaction and time-dependent effects significantly influence long-term IAB behavior. In addition, relatively low rotational stiffness and nonlinear behavior of common abutment-to-backwall connections influence long-term response. The proposed numerical modeling methodologies are practical and reasonably predict long-term IAB behavior and response under thermal loading.

Effect of superstructure-abutment continuity on live load distribution in integral abutment bridge girders

In this study, the effect of superstructure-abutment continuity on the distribution of live load effects among the girders of integral abutment bridges (IABs) is investigated. For this purpose, two and three dimensional finite element models of several single-span, symmetrical integral abutment and simply supported (jointed) bridges (SSBs) are built and analyzed. In the analyses, the effect of various superstructure properties such as span length, number of design lanes, girder size and spacing as well as slab thickness are considered. The results from the analyses of two and three dimensional finite element models are then used to calculate the live load distribution factors (LLDFs) for the girders of IABs and SSBs as a function of the above mentioned parameters. LLDFs for the girders are also calculated using the AASHTO formulae developed for SSBs. Comparison of the analyses results revealed that the superstructure-abutment continuity in IABs produces a better distribution of live load effects among the girders compared to SSBs. The continuity effects become more predominant for short span IABs. Furthermore, AASHTO live load distribution formulae developed for SSBs lead to conservative estimates of live load girder moments and shears for short-span IABs.

Integral abutment bridge response under thermal loading

This paper presents a parametric study and approximate integral abutment bridge (IAB) response prediction models. IABs are complex structures due to the nonlinearity and uncertainties in bridge materials and soil boundaries. Current design specifications and guides do not provide clearly defined analysis methods; therefore, there is a need for easily implemented preliminary analysis and accurate two-dimensional (2D) analysis methods. Based on a calibrated, nonlinear, 2D numerical modeling methodology including backfill–abutment interaction, soil–pile interaction and critical construction joints, a parametric study of 243 analysis cases was performed, consistent with the AASHTO 75-year bridge life. Analyses were performed under thermal load and gradient, and backfill pressure with time-dependent effects of concrete creep and shrinkage and prestressing steel relaxation included. The parametric study considered five parameters: (1) thermal expansion coefficient, (2) bridge length, (3) backfill height, (4) backfill stiffness, and (5) pile soil stiffness. Each of the five parameters was evaluated at three distinct magnitudes to cover the normal range of bridge construction. The parametric study revealed that the thermal expansion coefficient, bridge length and pile soil stiffness significantly influence the IAB response as measured by: (1) girder axial force, (2) girder bending moment, (3) pile lateral force, (4) pile bending moment, and (5) pile head/abutment displacement. The influences of backfill height and backfill stiffness are not relatively significant. The study results provide practical, preliminary estimates of the bridge response and ranges for preliminary IAB design and analysis.

Seismic Analysis of Integral Abutment Bridge in Tennessee, Including Soil–Structure Interaction

Integral abutment bridges are jointless bridges in which the deck is continuous and connected monolithically with the abutment walls, supported typically by a single row of piles. Part of the research results from an ongoing project focus on the effects of two major parameters on the seismic behavior of an integral abutment bridge in Tennessee. The soil–structure interaction around the piles and in back of the abutments is considered, namely, clay stiffness (medium versus hard) around the piles and level of compaction (loose versus dense) of the abutment wall backfilling. Modal and nonlinear time-history analyses were performed on a three-dimensional detailed bridge model with the commercial software SAP2000. These analyses clearly showed that (a) compacting the backfilling of the abutment wall will increase the dominant bridge longitudinal natural frequency considerably more than increasing the foundation clay stiffness; (b) the maximum deflection and bending moment in the piles under seismic loading will occur at the pile–abutment interface; (c) under seismic loading, densely compacted backfilling of the abutment wall is generally recommended because it will reduce the pile moments considerably, the pile deflection, the abutment displacement, and the moments in the steel girder, except for girder moments at the abutments when the piles are in medium clay; and (d) under seismic loading, when the abutment backfilling is loosely compacted, steel girder moments at the abutments will increase considerably with the foundation clay stiffness.

Field-Measured Response of an Integral Abutment Bridge with Short Steel H-Piles

Integral abutment bridges (IABs) with short steel H-pile (HP) supported foundations ( ⩽4 m of pile depth) are economical for many environmentally sensitive sites with shallow bedrock. However, such short piles may not develop an assumed, fixed-end support condition at some depth below the pile cap, which is inconsistent with traditional pile design assumptions involving an equivalent length for bending behavior of the pile. In this study, the response of an IAB with short HP-supported foundations and no special pile tip details such as drilling and socketing is investigated. Instrumentation of a single-span IAB with 4-m-long piles at one abutment and 6.2- to 8.7-m-long piles at the second abutment is described. Instrumentation includes pile strain gauging, pile inclinometers, extensometers to measure abutment movement, earth pressure cells, and thermistors. Pile and bridge response during construction, under controlled live load testing, and due to seasonal movements are presented and discussed. Abutment ...