Design Of Integral Abutment Bridges Research Articles

Effect of Pre-Hole Filled with High-Damping Material on the Inelastic Response Spectrum of Integral Abutment Bridges

ABSTRACT This paper estimates the effect of a pre-hole filled with high-damping material on the inelastic response spectrum of Integral Abutment Bridges (IAB) with pile foundation. The hysteretic response of the pile, described by a Winkler beam model, is obtained from the piece-wise definition of the subgrade stiffness, calibrated on experimental data. The pre-hole with damping pre-hole determines a reduction of the demand spectral acceleration. The force modification factors of the acceleration response spectrum of the bridge superstructure under a large set of strong/motion earthquakes are estimated. The force-reduction factors for the elastic design of IABs with damping pre-hole are proposed.

An overview of integral abutments: Current practices, field monitoring and deck replacement measures

The use of integral abutments in bridges goes back many years to the late 1930’s in the United States. Over the years, integral bridges became more popular as more and more states built those bridges and more engineers became familiar with their design and construction. These bridges are being built in Europe since the 1980’s. An integral abutment bridge acts as a frame structure with a continuity connection between the superstructure and the substructure. The substructure is typically an integral cap supported on single row of piles that provides flexibility to accommodate thermal loads and displacements. The main advantage of integral abutment bridges is that they are built without expansion joints which eliminates maintenance costs and reduces construction costs. Because of the interaction between the soil and the integral abutment under the applied loads and the cyclic nature of thermal loads, the analysis and design of integral abutment bridges can be, in some cases, challenging especially when the designs falls outside the geometrical limits set by existing standards. This overview focus on field performance data reported in the literature and interpretation of this data. IT also highlights the needs for more test data during construction and for long term performance under cyclic thermal movements. Deck replacement requirements in integral abutments were investigated using analytical models and recommendations for deck replacement preparations are provided.

Seismic behavior assessment for design of integral abutment bridges in Illinois

Seismic behavior assessment for design of integral abutment bridges in Illinois

Longitudinal seismic response of integral abutment bridges

A finite-element (FE) investigation into the response of integral abutment bridges (IABs) to seismic loading in the longitudinal direction was conducted. An example multi-span reinforced concrete solid-slab bridge was designed and analysed using an elasto-plastic two-dimensional FE model. The bridge abutment was taken as supported on steel H-piles. The proposed FE model was found to have the capability of simulating both the bridge construction and the backfilling process using a multi-step numerical process. The bridge was examined considering various lengths and different backfill materials, and was subjected to earthquake loading. The analyses showed that the seismic response of IABs is notably affected by the bridge length. Longer bridges may be subject to higher pressures on the abutments and internal forces in the bridge structure. The stiffness and strength parameters of the backfill material may also markedly influence dynamic pressures on the abutments and internal forces in the structure. Backfill materials with greater stiffness and strength parameters may cause significant reductions in the seismic flexural stresses in both the abutments and the deck. Coupling seismic and thermal loads could be suggested for the design of IABs.

The Response Modification Factor for Seismic Design of Integral Abutment Bridges

The response modification factor (R factor) is a crucial parameter for calculating the design seismic forces applied to a bridge structure. This factor considers the nonlinear performance of bridges during strong ground motions. Conventional bridge structures rely on the substructure components to resist earthquake forces. Accordingly, there are R factors available in the design codes based on the type of bridge substructure system. Lateral load resisting system of Integral Abutment Bridges (IABs) in the longitudinal direction is more complex than ordinary bridges. It involves the contributions from soils behind the abutments and soil/structure interaction (SSI) in addition to existing rigid connection between the superstructure and abutments. There is no R factor available in any design code throughout the world for IABs in the longitudinal direction that considers all these parameters. In this research, the Federal Emergency Management Agency publication FEMA P695 methodology has been applied to estimate the R factor for IABs. It is found that 3.5 could be a safe and valid R factor in the longitudinal direction for seismic design of such bridges.

Design of integral abutment bridges for combined thermal and seismic loads

Integral abutment bridges have many advantages over bridges with expansion joints in terms of economy and maintenance costs. However, in the design of abutments of integral bridges temperature loads play a crucial role. In addition, seismic loads are readily transferred to the substructure and affect the design of these components significantly. Currently, the European and American bridge design codes consider these two load cases separately in their recommended design load combinations. In this paper, the importance and necessity of combining the thermal and seismic loads is investigated for integral bridges. A 2D finite element combined pile-soil-structure interactive model is used in this evaluation. Nonlinear behavior is assumed for near field soil behind the abutments. The soil around the piles is modeled by nonlinear springs based on p-y curves. The uniform temperature changes occurring at the time of some significant earthquakes around the world are gathered and applied simultaneously with the corresponding earthquake time history ground motions. By comparing the results of these analyses to prescribed AASHTO LRFD load combinations it is observed that pile forces and abutment stresses are affected by this new load combination. This effect is more severe for contraction mode which is caused by negative uniform temperature changes.

Performance-based seismic design of integral abutment bridges

Integral abutment bridges (IAB) are experiencing increasing diffusion in the short to mid-range lengths, where they offer some advantages over traditional girder bridges with non-monolithic connection at the abutments. One challenging problem with their analysis and design is that consideration of the interaction between foundation soil, structure and backfill is unavoidable, also for the deck design. Further, the end of the construction is only one of the conditions that need to be verified during design. Cyclic deformations, such as those occurring during ground shaking, typically lead to an increase in stresses in the abutments and connections, due to progressive compaction (ratcheting) of the backfill soil. This problem is magnified when the bridge is comprised between two embankments, whose response may amplify the input motion and drive the deformation of the bridge. Performance-based design aims at superseding current design procedures by explicitly checking that the target performances set out are achieved, and not overly exceeded. Such a design paradigm naturally calls, on the one hand, for improved accuracy in response determination and more refined analyses, and, on the other, for taking into account the uncertainties entering into the problem by means of an explicitly probabilistic approach. With this objective in mind, the paper presents an inelastic dynamic model for the seismic analysis and design of IABs. The model, that features a balanced compromise between the setup and evaluation effort on one hand, and accuracy on the other, has been developed for implementation in typical commercial analysis packages. It builds on 1D site-response analysis and on inelastic Winkler-like modeling, to reproduce the main physical aspects of the seismic response of IABs. One example application to a highway overpass in Italy illustrates the model and the relevance of a fully probabilistic approach to performance-based design. The application offers also important insight into the choice of an efficient intensity measure for this type of structure.

Applications, Behaviour and Design of Composite Steel-Concrete Structures

The behaviour of composite steel-concrete beams subjected to pure flexure and the presence of flexure and shear is fairly well understood and provisions do exist in international codes of practice for their design, however in most instances the influence of the concrete slab is not included in the strength design of the composite beam in shear. Combined internal actions including the presence of torsion and flexure have also been considered of late. These actions combine to occur in edge beams and curved composite beams and thus are of significant practical interest. Of increasing interest has become the presence of axial force and flexure in composite beams. These internal actions need to be considered in the design of raking beams of stadia, elevated approach spans for bridges and interchanges and in the design of integral abutment bridges and cable stayed bridges. Furthermore, composite beams in floor systems for braced multi-storey buildings are often required to resist axial force, flexure and shear force. This paper considers the effects of the presence of axial force in conventional composite beams. The effects of different forms of axial force and flexure combinations are considered in this paper. An analytical treatment, experiments and design approaches are given in this paper which is useful for structural engineers. Furthermore research in this area is also discussed. This paper will also present the results of an extensive experimental series to study the behaviour of high performance steel sections subjected to transverse impact loads which are able to simulate either a collision or blast. The experimental program has considered both mild structural steel and stainless steel hollow sections both filled and unfilled being tested. The purpose of the tests was to identify the potential advantages of using concrete infill to increase the energy absorption capability of steel hollow sections.

Parametric study on the thermal response of curved integral abutment bridges

Integral abutment bridges (IABs) are a common structural system for short to moderate span bridges. Construction of curved IABs, however, is limited partly due to lack of quantified performance. Many departments of transportation (DOTs) in the USA therefore restrict or even prohibit the design of curved IABs with curved steel girders. However, the application of design concepts of in-plan curved superstructure geometry and integral abutments can offer various advantages. Often the design of IABs considers the response of structural components separately without considering the connectivity between them and simplifies design to a two dimensional analysis. Therefore, this analysis method fails to capture the system response of curved IAB bridges which requires an accurate estimate of the temperature induced displacement/stresses and the effects of the curvilinear alignment. In this paper, a research program using finite element (FE) modeling to simulate the abutment–pile and abutment–superstructure connections in curved IABs is reported. A detailed, three dimensional, FE model of a curved IAB located in Stockbridge, Vermont, USA was used as a prototype to evaluate the behavior of curved IABs under thermal loading. A parametric study was carried out to investigate the effects of bridge curvature and abutment backfill soil type. Moreover, additional FE models were created to investigate the effect of degree of lateral restraint provided by the U-shaped wingwalls integral with abutments and the interior pier. The results, including abutment displacements, moments at abutment piles, earth pressures on abutments and wingwall, and bridge superstructure forces, are reported and compared with the responses of conventional curved bridges containing expansion joints.

프리스트레스트 콘크리트 거더 일체식 교량의 교대 거동 해석과 예측

이 연구는 교량의 생애 동안의 온도 변화와 콘크리트의 시간 의존 영향을 고려하여 PSC 거더 일체식 교량의 해석 방법과 교대의 변위를 예측하는 모델 개발에 관한 것이다. 비선형 수치 해석 모델은 지반-구조물의 상호작용을 고려하며, 재료의 비선형 또한 고려되었다. 개발된 수치 해석 모델을 이용하여 총 243가지의 경우에 대하여 변수 연구를 하였다. 고려된 변수는 (1) 열팽창 계수, (2) 교량 길이, (3) 뒤채움재의 높이, (4) 뒤채움재의 강성, 그리고 (5) 말뚝-지반 강성이다. 변수 연구의 결과는 열팽창 계수, 교량 길이, 말뚝-지반의 강성이 지배적인 영향을 나타내는 것으로 드러났다. 또한, 교량의 길이는 교대의 윗부분의 변위에 지배적인 영향을 미치며 자유팽창·수축과 유사하였다. 하부의 변위에는 다른 변수들의 영향으로 추정이 쉽지 않았다. 개발된 교대의 변위 추정 모델은 기본 설계시에 사용될 수 있을 것이다.

A Methodology for Modelling the Integral Abutment Behaviour of Non-Symmetrically Loaded Bridges

Integral abutment bridges (IABs) are an economical option to design appealing single-span bridges. However, more experience is needed, as the main difference in the design of IAB compared with conventional bridges is the restraint of the frame corner, caused by the fact that the superstructure and the abutments are one monolithic structure. This requires modification in design regarding the internal forces and deformations as well as the detailing of the frame corner itself.IABs are generally designed as frames using grid models with idealised superstructure. This calculation involves sophisticated models and is considered to be time consuming. Also conventional single-spa n bridges are designed with the help of grid models, for which experience and various design software tools exist, especially when simply supported structures are considered.Main problem in the transfer of frame systems into simply supported structures are the interactions between superstructure and sub-structure. By separating the superstructure from the sub-structure, the implementation of IAB design through existing software tools is possible. However, to take into account the superstructure–abutment interaction, the superstructure needs to be restrained by rotational springs. As a result of sway effects in the original frame, the boundary conditions (horizontal position of the frame corner) for the determination of the rotational spring stiffness vary. Therefore these springs have to be non-linear, and do not comply with the demand for load case superposition.This paper presents a new approach to separate the superstructure from the sub-structure with provision for possible superposition of the load cases. The approach is based on the division of the non-linear springs into two linear springs, one for symmetric loading and the other for antimetric loading, from which a modification factor kmgk has been derived. This factor is defined as adjusting the single-span model with a single rotational linear spring to the original grid model system. On the basis of this approach and the kmgk factor, the use of conventional design tools for IABs has been made possible.To further close the gap in experience on IAB, design and detailing recommendations are given.

Analytical Formulation for Limit Length of Integral Abutment Bridges

The integral abutment bridge concept has recently become a topic of remarkable interest among bridge engineers, not only for newly built bridges but also for refurbishment processes. The super-structure of integral abutment bridges (IABs) is made continuous through composite cast-in-place concrete deck slabs over pre-stressed concrete or steel girders. The system constituted by the substructure and the super-structure can achieve a composite action responding as a single structural unit; this principle is applicable also while converting existing simply supported bridges into IABs.Several guidelines for the design of IABs have been published in the last few years. The main idea is to introduce designers to this kind of structures thereby limiting the total length, skewness and inclination of the deck.The maximum length usually recommended for this kind of structures is around 100 m or less. This limitation is derived from the difficulties introduced by the need to control the soil–structure interaction for imposed temperature variations: this is the main factor affecting increasing of the overall length of the structure.Achieving the maximum length attainable with this kind of structures is intrinsically related to a thorough understanding of the soil–structure interaction behind the abutments or next to the foundation piles. It has been proved that the maximum allowed length for IABs is 400 m. The world record for the longest IAB, which represents the transformation of a simply supported flyover in Verona, Italy, will be discussed in this paper together with the non-linear parametric analyses carried out to determine the solution presented. The paper will deal with the possibility of achieving super-long IABs using standard pre-fabricated cross sections and typical reinforcement ratios for foundation elements and super-structure.

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.

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.

Time-Dependent Behavior of Continuous Composite Integral Abutment Bridges

Integral abutment bridges provide bridge engineers with an economical and attractive design alternative to traditional bridges with thermal expansion joints. Very limited design and construction guidelines are available and no unified design procedures exist, hence there is a lack of enthusiasm to adopt integral abutment bridges for long spans. Time-dependent effects of creep, shrinkage, and temperature on composite superstructure, soil pressure from abutment backfill, and soil-substructure-superstructure interaction are the main parameters governing the design. Analytical models and numerical procedures are developed for predicting instantaneous linear and nonlinear time-dependent long-term behavior of continuous composite integral abutment bridges. The redistributions of moments due to temperature gradient, creep, shrinkage, and restraints provided by abutment foundation and backfill have been considered in the analysis. The substructure system is modeled as discrete springs for translational and rotational degrees of freedom. A numerical design example is illustrated showing the deformations and stresses due to time-dependent effects on a continuous composite deck due to typical sustained loads and compared with those of the conventional bridge system on seat-type abutments. The axial forces and moments on the piles supporting the abutment were used to analyze the behavior of the laterally loaded piles. Recommendations are presented for the analysis and design of integral abutment bridges.

Nonlinear Analysis of Integral Bridges: Finite-Element Model

Integral abutment bridges (IABs) are jointless bridges where the deck is continuous and connected monolithically with the abutment walls. The biggest uncertainty in the design of these bridges is the reaction of the soil behind the abutments and next to the foundation piles, especially during thermal expansion. This lateral soil reaction is inherently nonlinear and is a function of the magnitude and nature of the wall displacement. Handling the soil-structure interaction in the design of IABs has always been problematic, usually requiring iterative, equivalent linear analysis. This paper describes the implementation of a full 3D finite-element model of an IAB system which explicitly incorporates the nonlinear soil response. This paper also presents the results from a small parametric study on a sample bridge where the soil compaction levels in the cohesionless soils behind the wall and adjacent to the piles were varied. These results show that the level of compaction in the granular backfill strongly dominates the overall soil reaction, and that this reaction greatly impacts the overall structural response of the bridge system.