Behavior Of Integral Abutment Bridges Research Articles

Field Behavior of Integral Abutment Bridges under Thermal Loading

Integral abutment bridges (IABs) have become popular with departments of transportation throughout the United States due to their lower maintenance and construction costs and longer service life. Nevertheless, IAB design and construction vary widely across the country, and not all aspects of IAB behavior are fully understood. Research has previously been conducted on IABs, but primarily with a focus on substructure behavior. However, recent studies have shown that IAB superstructures may develop significant stresses, which warrant consideration in their design. The work reported herein addresses the need to better understand not only IAB substructure behavior but also superstructure behavior, with a goal of improving design and construction provisions for IABs. Two bridges were instrumented, with primary focus on superstructure behavior and more limited instrumentation of the substructure. Corresponding finite-element models were developed based on modeling techniques and findings from prior parametric studies. It was found that the IAB decks and girders (in the superstructure) and abutments and piles (in the substructure) generally show seasonal and even daily trends with respect to changes in temperature, with the exception of bottom-flange girder stresses that have wider variability not directly related to temperature change. Prior modeling assumptions regarding the rigidity of various IAB connections were also validated through the field monitoring data.

Behavior of integral abutment bridge with partially protruded piles

This study presents structural and parametric analyses on the behavior of an integrated and pile-bent abutment with mechanically stabilized earth wall (IPM) bridge. The IPM bridge is an integral abutment bridge (IAB) with partially protruded piles, which excludes earth pressure by means of a mechanically stabilized earth wall developed by the authors. The results of the analysis indicate that the IPM bridge, as any other IAB, is influenced to a large extent by temperature and time-dependent loads. When these loads are applied, the stress on a pile in the IPM bridge decreases as the displacement of the pile top increases, because the piles protrude from the ground surface and no soil reaction is generated on the protruded pile. Because the length of an IAB is restricted by the forces acting on its piles, the IPM bridge is an effective alternative to extend its length.

Parametric study of an integral abutment bridge supported by prestressed precast concrete piles

Integral abutment bridges (IABs) have been designed and constructed since the 1930s around the world. In these bridges, the water leaking problems and maintenance issues of expansion joints are minimized. However, the behaviors of IABs under temperature effects have not been completely understood. In the state of Louisiana, the first full IAB, i.e., the Caminada Bay Bridge, was built on the soft soil conditions in 2011. This paper presents a numerical investigation on the thermal performance of this bridge using ANSYS software. Based on the analysis studies, the numerical modeling methodology for IABs, i.e., temperature loadings, backfill–abutment interactions, and soil–pile interactions, is validated by comparing the bridge response with the field measurements. In addition, a parametric study is performed and demonstrated that the behavior of IABs is affected by temperature loadings, boundary support types, backfills behind abutments, soils surrounding piles, and pile–bent connections. It needs to balance all these parameters in designs so that the thermal deformation of slabs is appropriately accommodated without compromising the integrity of the superstructure and substructure.

Simple Approach to Calculate Displacements and Rotations in Integral Abutment Bridges

This paper presents a simple approach to calculate the displacements and the rotations induced by thermal loading in integral abutment bridges (IABs). The approach was derived from the results of a parametric study that investigated the effect of substructure stiffness on the performance of short- and medium-length steel IABs built on clay and sand under thermal load effects. Various parameters, such as pile size and orientation, pile material, and foundation soil stiffness, were considered in the study. Detailed three-dimensional (3-D) finite element (FE) models using the software LUSAS were developed to capture the overall behavior of IABs. The developed 3-D FE model was calibrated with field measurements obtained from a previous study. A parametric study was carried out with the calibrated models to study the effects of the above parameters on the performance of IABs under thermal loading using the AASHTO load and resistance factor design temperature ranges. The study showed that most parameters have significant effects on the displacement and rotation of the abutment and the supporting piles. Also, for relatively wide IABs, there were significant variations in the displacement and rotations in the substructure elements between interior and exterior locations. This approach, which used simple equations and charts and included parameters such as the length of the bridge, the stiffness of the foundation soil, and the pile location, provided results that were comparable with those of a detailed FE analysis.

Computer Modeling and Parametric Study of Thermal Effects in Integral Abutment Bridge

Structural behavior of concrete integral abutment bridge subjected to temperature rise was investigated through a numerical modeling and parametric study. Long-term, field monitoring through the summer was performed on Industrial Park Bridge located in Heilongjiang province, China from June 13, 2010 until June 28, 2010. The collected data was used to validate the accuracy of a 3D-finite element model of the bridge which took into account soil-structure interaction. Based on the calibrated finite element model a parametric study considered two parameters, bridge length and abutment height, was carried out to investigate the effects of this parameters on structural behavior of integral abutment bridge subject to temperature rise. It was determined that Thermal load in the superstructure of the integral bridge develop significant magnitudes of bending and axial forces in the superstructure. The largest magnitude of thermally induced moment always occurs near the abutment, and axial force is constant across the length of each span. For bridge thermal expansion, longer bridges and taller abutments cause larger thermally induced superstructure axial force due to development of higher backfill pressure. Generally span length has a higher influence for thermally induced superstructure forces in terms of axial force and bending moment than the abutment height.

Effect of Substructure Stiffness on Performance of Steel Integral Abutment Bridges under Thermal Loads

This paper presents a study that investigated the effect of substructure stiffness on the performance of short- and medium-length steel integral abutment bridges (IABs) built on clay under thermal load effects. Various parameters, such as pile size and orientation, pile type, and foundation soil stiffness, were considered in the study. Detailed, three-dimensional (3-D), finite element (FE) models were developed to capture the behavior of IABs. Field measurements from a IAB were used to validate the 3-D FE model developed with LUSAS software. With the use of validated models, a parametric study was carried out to study the effect of these parameters on the performance of IABs under thermal loading with AASHTO load and resistance factor design temperature ranges. The study showed that the substructure stiffness had a significant effect on the stress level induced by thermal loads in various components of the substructure and superstructure. The results also showed significant variations in displacement and stress between interior and exterior locations in relatively wide IABs. The study showed that prestressed concrete piles could form a viable alternative to steel H-piles for short-span bridges. The stress level from thermal loading in the various components of the bridge could be reduced significantly if the top part of the pile were placed in an enclosure filled with crushed stone or loose sand.

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.

Parametric Study of Concrete Integral Abutment Bridges

A parametric study was conducted to extend the results of an experimental program on a concrete integral abutment (IA) bridge in Rochester, MN to other integral abutment bridges with different design variables including pile type, size, orientation, depth of fixity, and type of surrounding soil, fixity of the connection between the abutment pile cap and abutment diaphragm, bridge span and length, and size and orientation of the wingwalls. The numerical results indicated that bridge length and soil types surrounding the piles had a significant impact on the behavior of IA bridges. To select pile type and orientation, there is a need to balance the stresses in the piles with the stresses in the superstructure for long IA bridges or IA bridges in stiff soils. Plastic hinge formation is possible at the pile section near the pile head for combined critical variables, such as long span, compliant piles in weak axis bending, deep girders, and stiff soils. Because large pile curvatures or stresses may be caused due to the rotation of the pile cap during temperature increases, hinged connections between the abutment pile cap and diaphragm are not recommended for the practice of IA bridges. Cast-in-place piles are recommended only for short-span IA bridges because their relatively large bending stiffness can cause large superstructure concrete stresses during temperature changes.

Time-Dependent Behavior of a Concrete Integral Abutment Bridge

Time-dependent behavior of an integral abutment bridge near Rochester, Minnesota, was investigated from the beginning of construction through 7 years of service by using field data collected from more than 150 instruments installed in the bridge during construction. Long-term bridge shortening was observed from the readings of horizontal extensometers installed behind the abutments. Measured pile curvatures steadily increased with time. To understand this unexpected bridge behavior better, a time-dependent numerical study using the creep and shrinkage models from American Concrete Institute Committee 209 was conducted. The results obtained in this research indicate that concrete creep and shrinkage had a significant effect on the behavior of the concrete integral abutment bridge over the course of the 7-year study.