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Development of General Guidelines On The Effects Of Bridge Span Range

PI: Susan Faraji
Institution: University of Massachusetts Lowell
PI Email:
PI Phone: Office: 978-934-2276


Integral Abutment Bridges (IABs) are single or multiple span continuous deck bridges. Instead of movable expansion joints between spans and bearings at the abutments, IABs have continuous decks and relatively flexible integral abutment walls and foundations. The IAB concept has become increasingly popular in USA, especially in the northeast, due to reduced maintenance costs associated with the expansion joints and abutment bearings.

Over the past 30 years, there has been much research on the behavior, analysis, and design of IABs. The increase in the construction of IABs and their reported good performance has led to a number of departments of transportation developing standard details and design guidelines. There have emerged many design recommendations, ranging from state to state, such as limiting span length or skew angle. Building more IABs will improve the durability and extend the life of highway bridges. Even though back fill soil stiffness plays an important role in the behavior of IABs, the bridge span and skew angle are the predominant influences on their behavior, especially under thermal expansions and contractions. These can cause combinations of axial forces and bending moments in the girders, which can in turn cause concrete cracking at the girder connections to the abutment / pier. That is the reason for limiting the span length and skew angles.


There is a need to streamline the guidelines regarding the behavior, analysis, and design of IABs. This will be done in phases. In phase I, this proposed project aims to improve the analysis, design and construction of IABs by investigating the impact of the span range, skew angle range, and soil-structure interaction on IABs:

  • Study of the effect of ranges of skew angle on axial and bending stresses in the superstructure (pre-stressed girders, steel girders, concrete slab);
  • Study of the effect of axial and bending stresses in the superstructure (pre-stressed girders, steel girders, concrete slab) caused by thermal expansion and contraction for range of bridge spans;
  • Development of general guideline regarding the proper modeling, design and construction of the superstructure and substructure of IABs.
Variation of vertical displacement for abutment #1under thermal loading (a) normal to the abutment wall); (b) longitudinal direction for Bridge


  • December 30, 2019: The completed finite element modeling of five sample bridges provided by VTrans has been used to study the effect of the roadway profile grade on substructure, the constructability of pile supported IABs at a site with shallow bedrock, and the effect of range span and of skew angle on axial and bending stresses in the superstructure and substructure.
  • Professor Susan Faraji, Ph.D., Civil and Environmental Engineering