Date of Award
Master of Science
Civil, Construction, and Environmental Engineering
Civil Engineerin g (Structural Engineering)
Throughout the year, seasonal and daily temperature fluctuations cause the materials within a bridge to shrink and swell, resulting in the expansion and contraction of the entire superstructure. If left unaccounted for, these movements result in structural damage to the bridge. Thus, implementing ways to safely accommodate this movement is a crucial part of ensuring a serviceable, long-term structure is designed and built. The most traditional approach to accommodating this movement involves the use of movement joints placed at the ends of the bridge deck. These movement joints are often fitted with a rubber device to prevent excess drainage from eroding key structural members underneath the deck. However, these movement joints create several additional issues, including a high risk for premature failure due to environmental factors. As a result, “moveable” jointless integral or semi-integral abutment, which directly connects the abutment to the bridge deck. In this case, the abutment rotates inward and outward with the deck’s expansion and contraction and moves the expansion joints farther away from the bridge deck, limiting the potential issues associated with movement joints.
The first part of this thesis investigates a common issue with strip seal expansion joints—their somewhat problematic performance on skewed bridges. A literature review and laboratory testing series were conducted to quantify and recommend appropriate movement ranges for the A2R-400 and A2R-XTRA expansion joint systems for use by the Iowa Department of Transportation (IDOT). In addition, tests were performed simulating issues related to debris entrance into the rubber expansion joint material. The conclusion of this research presents a series of acceptable movement guidelines, updated design table recommendations, and a sample set of design calculations. The second part of this thesis investigates settlement issues resulting from the use of jointless “moveable abutment” bridges connected to approach slabs via steel connection dowels. As the Iowa DOT prefers the use of this type of design detail over movement joints when possible, it is important to monitor and optimize their performance for long-term serviceability. The research performed for this thesis involves a literature review investigating best practices for moveable abutment design, the outline for a state-wide inventory of Iowa approach slabs, and three Finite Element investigations of different Iowa DOT bridges. Through in-situ observations and computational computer models, the goal of this project is to present a clearer understanding of the structural behavior of integrally-tied approach slabs when used as an alternative to expansion joints. Areas of emphasis focus on the effect of field conditions that result in premature serviceability issues in approach slabs: settlement, voiding, and erosion of the subbase beneath the approach slab.
Duffy, Conor, "Investigating serviceability issues related to thermal movement accommodation in bridges" (2020). Graduate Theses and Dissertations. 18121.