Integral Abutment Bridges Research Articles

Integral Abutment Bridges: Current Practice in United States and Canada

Integral abutment bridges have been gaining popularity among bridge owners as cost-effective alternatives to bridges with conventional joints. They reduce initial construction costs and long-term maintenance expenses, improve seismic resistance, and extend long-term serviceability. New York has been building them since the late 1970s, with a wide variety of details, and they have been performing well. For further improvement of New York’s design practice, a comparative survey was undertaken across North America, focusing on design and construction of both substructures and superstructures. In all, 39 states and Canadian provinces responded, including 8 who said they had no experience with these bridges. Responses are analyzed and summarized in this report. Overall, integral abutment bridges are performing as well as, if not better than, conventional bridges, but no uniform national standards exist for their design. Design practices and assumptions concerning limits of thermal movement, soil pressure, and pile design vary considerably among responding agencies. These decisions are based largely on past experience. Validity of these assumptions needs investigation by testing and analysis to ensure efficient and reliable design.

Simplified Model for Computer-Aided Analysis of Integral Bridges

This paper presents a computer-aided approach for the design of integral-abutment bridges. An analysis procedure and a simplified structure model are proposed for the design of integral-abutment bridges considering their actual behavior and load distribution among their various components. A computer program, for the analysis of integral-abutment bridges, has been developed using the proposed analysis procedure and structure model. The program is capable of analyzing an integral-abutment bridge for each construction stage and carrying the effects of applied loads on the structure members from a previous construction stage to the next. The proposed analysis methods and structure models are compared with the conventional analysis method and structure model currently used by many structural engineers for the design of integral-abutment bridges. The benefits of using the proposed analysis method and simplified structure model for the design of integral-abutment bridges are discussed. It was concluded that it ...

Design and Performance of Jointless Bridges in Ontario: New Technical and Material Concepts

It is well recognized that leaking expansion joints at the ends of bridge decks have led to the premature deterioration of bridge components. The elimination of these maintenance-prone joints not only yields immediate economic benefits but also improves the long-term durability of bridges. In Ontario, Canada, “jointless” bridges have been used for many years. Recently, the use of two main types of these bridges has increased dramatically. The first type is an “integral abutment” bridge that comprises an integral deck and abutment system supported on flexible piles. The approach slabs are also continuous with the deck slab. The flexible foundation allows the anticipated deck movements to take place at the end of the approach slab. Control joint details have been developed to allow movements at this location. The second type is a “semi-integral abutment” bridge that also allows expansion joints to be eliminated from the end of the bridge deck. The approach slabs are continuous with the deck slab, and the abutments are supported on rigid foundations (spread footings). The superstructure is not continuous with the abutments, and conventional bearings are used to allow horizontal movements between the deck and the abutments. A control joint is provided at the end of the approach slab that is detailed to slide in between the wing walls. Some of the design methods and construction details that are used in Ontario for integral and semi-integral abutment bridges are summarized. A review of the actual performance of existing bridges is also presented.

Field Performance of Integral Abutment Bridge

The behavior of an integral abutment bridge near Rochester, Minnesota, was investigated from the beginning of construction through several years of service by monitoring more than 180 instruments that were installed in the bridge during construction. The instrumentation was used to measure abutment horizontal movement, abutment rotation, abutment pile strains, earth pressure behind abutments, pier pile strains, prestressed girder strains, concrete deck strains, thermal gradients, steel reinforcement strains, girder displacements, approach panel settlement, frost depth, and weather. In addition to determining the seasonal and daily trends of bridge behavior, live-load tests were conducted. All of the bridge components performed within the design parameters. The effects from the environmental loading of solar radiation and changing ambient temperature were found to be as large as or larger than live-load effects. The abutment was found to accommodate superstructure expansion and contraction through horizontal translation instead of rotation. The abutment piles appeared to be deforming in double curvature, with measured pile strains on the approach panel side of the piles indicating the onset of yielding.

A rational design approach for prestressed-concrete-girder integral bridges

This paper presents a rational design approach for prestressed-concrete-girder integral bridges. An analysis procedure and simplified analytical models are proposed for the design of integral bridges. The proposed design methodology is developed considering the actual behavior of integral bridges and load distribution among their various components. The methodology recommends the analysis of integral bridges for each construction stage. The earth pressure forces acting on integral bridge abutments are formulated in correlation with the effects of temperature variation. Some important design considerations for various integral bridge components are also highlighted. The benefits of using the proposed analysis method for the design of integral bridges are discussed. It was concluded that it may be possible to obtain more sound and economical designs for integral bridges using the proposed design method.

Deck Slab Stresses in Integral Abutment Bridges

This study deals with the stress distribution in concrete deck slabs on composite steel beams used with integral abutment bridges. The applied loading is composed of one or more side-by-side HS20-44 trucks. The finite-element method is used to analyze two bridge structures with different numbers of beams, beam spacings, and supporting piles. The transverse and longitudinal slab stresses in the deck slab are investigated in the positive and negative bending regions near and away from the integral abutment. The slab stresses in the integral abutment bridges are compared with the corresponding stresses induced in the slab of equivalent jointed bridges. The results indicate that integral abutment bridges distribute the loads in the deck slab more uniformly than their jointed counterparts. The maximum stresses in the transverse direction of the slab can be 25–50% lower in the integral bridges than in their corresponding simply supported ones.

Centrifuge Modeling of Spread-Base Integral Bridge Abutments

Integral bridge abutments are attracting increasing interest in many countries around the world. Maintenance costs due to damage from assorted agents to bearings and expansion joints can be greatly reduced. However, adverse temperature effects on the performance of these bridges are of concern to many engineers. This paper describes some centrifuge model tests on, and numerical modeling of, spread-based integral bridge abutments subjected to cyclic deformation, which simulated the expansion and contraction of the bridge deck as effective temperature of the bridge deck changed. Significant settlements were observed behind the abutment resulting from soil densification, “strain” ratchetting, horizontal sliding, and the rocking motion of the abutment. The measured lateral earth pressure increased with the amplitude of the passive displacements and the number of cycles, but at a decreasing rate. Under the serviceability and ultimate limit conditions, the measured lateral earth pressure was less than the \iK\i\dp value, although the measured value was significantly higher than \iK\i\do. A triangular failure wedge developed behind the abutment wall under the ultimate limit conditions.

Soil-Structure Interaction of Spread-Base Integral Bridge Abutments

ABSTRACT To reduce long-term maintenance costs arising from the deterioration of concrete bridges due to leaky expansion joints, integral bridges have been becoming increasingly popular in many countries. Abandoning expansion joints leads to complex soil-structure interaction problems including those caused by cyclic temperature changes in the deck. These have adverse effects on the performance of integral bridges in terms of deformation mechanisms, lateral earth pressures acting on the abutment wall, bending moment and axial stress in the deck. All these are of great concern to engineers. Centrifuge model tests were conducted on spread-base integral bridge abutments to simulate these temperature effects on the soil-structure interaction. Thermal expansion and contraction of the deck were modelled by imposing controlled cyclic displacements at the top of the abutment wall. Substantial horizontal sliding and the rocking of the abutment due to soil densification and “strain” ratchetting were observed. The measured lateral earth pressure increased with the amplitude of the displacements into the fill (in the passive sense) and the number of cycles, but at a decreasing rate. For the ultimate limit state and the 1 in 120 years return event, the measured lateral earth pressure coefficient was 3.7 and 4.2 for the abutment backfilled with dense and loose sand respectively. The measured bending moments varied fairly linearly with depth, rather than varying as a cubic function with depth as would be expected for a relatively flexible wall subjected to a triangular distribution of lateral pressure. The measured value appeared to reach the design bending capacity of the reinforced concrete wall and base for the 1 in 120 years return event.

Pile Forces in Integral Abutment Bridges Subjected to Truck Loads

Interest in the use of integral bridges has increased in recent years because of their economy, reliability, and strength. However, most of the published research on integral bridges has been concerned with determination of the thermal effect, creep analysis, and seismic behavior. Few studies on live load analysis of integral abutment bridges have been carried out. The pile load behavior of integral abutments supporting composite steel superstructures subjected to gravity loads is investigated. The applied loading is composed of one or more side-by-side HS20-44 trucks. The finite element method is used to analyze the three-dimensional bridge system and determine forces in the piles. A parametric study is performed to obtain the effects of the number of trucks and their location, superstructure geometry, pile spacing and stiffness, pile connection type, and wingwall length on the pile loads. A simple, approximate procedure for computing pile loads is developed on the basis of the findings of the finite element analysis. The results indicate that the abutment-wingwall system does not behave as a rigid block as in the conventional case of a footing on flexible piles. Also, the generated bending moment in the piles caused by gravity load is significant and cannot be neglected in design.

Prestressed Concrete Piles in Jointless Bridges

The purpose of this investigation is to determine the feasibility of using precast, prestressed concrete piles in jointless bridges and to develop design criteria and pile-abutment joint details that can be used in practice. This phase of the project comprised an experimental and analytical study of load-deflection behavior of HP 10-42 and 12x12 in. (305x305 mm) precast, prestressed piles, and a computer analysis of the pile-soil interaction. The test results show that the proposed joint would allow the use of concrete piles in integral abutment bridges of lengths comparable to those with steel piles. A field investigation to study the performance of two prestressed concrete piles in a full-scale integral abutment bridge is currently being carried out.

Thermal Expansion of Concretes: Case Study in Iowa

To control the effect of concrete expansion or contraction on the integrity of concrete bridge structures, the thermal coefficient of expansion of concrete is often incorporated into design equations. Current practice is to use the value recommended by the Association of American State Highway and Transportation Officials of 11 parts per million per °C (6 parts per million per °F) change. Historically this has been used without considering the effect of local material properties on the overall expansion of concrete. This paper summarizes research findings on the thermal behavior of structural bridge concretes in Iowa. The thermal coefficient of expansion of limestone aggregates, gravel aggregates, mortar, corresponding limestone aggregate concretes, and gravel aggregate concretes were determined in the laboratory. Laboratory results were compared to actual bridge expansion data from field studies and the results from an empirical equation for determining concrete expansion. Results of the laboratory study compared very favorably to field data and results from the empirical equation. Results also indicated that the coefficients of expansion obtained in this study were lower than the Association of American State Highway and Transportation Officials suggested design value. These lower values of thermal coefficient of expansion affect the design length of integral abutment bridges in Iowa.

Design Model for Piles in Jointless Bridges

Piles in integral abutment bridges (jointless bridges) are subjected to lateral movement due to thermal expansion and contraction of the superstructure. The reduction in vertical load‐carrying capacity of the piles due to lateral movement is an important parameter in designing the piles and in setting length limits for the jointless bridge. A simplified design method for analyzing piles in integral abutment bridges is presented. The model was developed from previous analytical models and observations of pile behavior. Two failure modes for a pile are examined: the slip mechanism, where the pile slips through the soil; and the lateral mechanism where the failure of the soil‐pile system is associated with lateral movement of the pile. Equations for determining the ultimate load for the pile for each mechanism are obtained. Results predicted by the simplified model are compared to results from a nonlinear finite element program and shown to be conservative with respect to the finite element model.

Finite element model for soil-pile interaction in integral abutment bridges

An algorithm based on a nonlinear finite element procedure is developed and used to study piling stresses and pile-soil interaction in integral abutment bridges. The finite element idealization consists of beam-column elements with geometric and material nonlinearities for the pile and nonlinear springs for the soil. An idealized soil model (modified Ramberg-Osgood model) is introduced in this investigation to obtain the tangent stiffness of the nonlinear spring elements. Several numerical examples are presented to establish the reliability of the finite element model and the computer software developed.

Nonlinear Analysis of Integral Abutment Bridges

A state-of-the-art, three-dimensional, nonlinear finite element algorithm is developed and used to study piling stresses and pile-soil interaction in integral abutment bridges. The finite element idealization consists of beam-column elements with geometric and material nonlinearities for the pile, and nonlinear springs for the soil. An idealized soil model (a modified Ramberg-Osgood cyclic model) was introduced in this investigation to obtain the tangent stiffness of the nonlinear spring elements. Several numerical examples, including results on an existing bridge, are presented. The finite element model and the computer software developed are found to give reliable methods.

Effects of Predrilling and Layered Soils on Piles

A state-of-the-art nonlinear finite element algorithm for pile-soil interaction has been developed and implemented in a modular computer program to study the effects of predrilled oversize holes and layered soils on the vertical load carrying capacity of piles in integral abutment bridges where thermally induced lateral movements occur. A 40-ft (12 m) H pile embedded in very stiff clay is used to study the effect of a predrilled oversize hole with or without sand fill. Numerical results showed that the vertical load carrying capacity of H piles is significantly affected by predrilling. The study of layered soils included the case where compacted soil (50 or more blow counts in standard penetration tests) is used as a fill on top of different layers of natural soil. For such cases, the numerical results indicated that the type of failure is greatly influenced by depth of the compacted soil.