Estimating Early-age Thermally-induced Stresses in Concrete Bridge Decks

Open Access
Author:
Hopper, Travis Alan
Graduate Program:
Civil Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 04, 2015
Committee Members:
  • Gordon Patrick Warn, Thesis Advisor
  • Aleksandra Z Radlinska, Thesis Advisor
  • Farshad Rajabipour, Thesis Advisor
Keywords:
  • bridge deck
  • early age
  • thermal stress
Abstract:
Early-age cracking has been identified as a significant contributor to increased life cycle cost and decreased service life of concrete bridge decks. Newly placed concrete is susceptible to cracking due its low tensile strength at an early age, commonly considered to be within a few months post concrete placement. Temperature variations within the deck caused by environmental conditions as well as heat of hydration have been identified as potential contributors to early-age cracking. Adjusting the placement time to avoid the adverse effects of different environmental factors could be a strategy to further mitigate early-age cracking. However, there is inconclusive guidance regarding the time of deck placement and corresponding environmental conditions that would effectively limit tensile stresses within the deck at an early-age. In this study, an investigation of the effect of environmental conditions, such as ambient air temperature and solar radiation, and early-age concrete properties, such as heat of hydration and elastic modulus development, on the principle tensile stresses within a concrete deck during the first 29 hours after concrete placement (including an assumed 5 hour set time from placement) is summarized. The investigation was conducted using thermo-mechanical finite element modeling to analyze the stresses in a composite concrete deck-steel girder bridge system for different environmental and design scenarios. The results of this study showed that reducing the concrete heat of hydration within the deck was most effective at limiting the maximum principle tensile stresses within the deck during the first 29 hours following placement of the concrete deck.