Exploratory Study: Influence of Thermal Gradients Induced by Southwest Desert Climate on Bridge Durability

The desert climate of the southwestern United States can induce extreme daily and seasonal variations in temperature. Daytime solar radiation raises the temperature of the top surface of a bridge, inducing a thermal gradient (temperature differential) from top to bottom of a bridge deck. These thermal gradients are found in bridges throughout the US, but are much more severe in the drier southwestern states where the lack of cloud cover increases the solar radiation received at the surface during daytime hours. These same conditions (clear skies, particularly those at high altitude) can lead to excessive cooling at night and negative thermal gradients can be induced in the early morning hours. Bridges are more susceptible to losing heat than surrounding roadways, causing a safety hazard if the bridge is unexpectedly icy when the approach road is dry. Severe nonlinear thermal gradients are believed responsible for severe cracking and deterioration or even failure of structures in service or under construction. One aspect that has not received much attention is the daily redistribution of bearing loads due to diurnal fluctuations in temperature and corresponding fluctuations in curvature of the bridge superstructure. This redistribution can be significant with some bearings being subjected to much higher loads than anticipated. This phenomenon may explain the poor performance of some bearings and/or unexpected bearing failures. Since bridge joints and bearing performance are a dominant component of bridge maintenance, the influence of nonlinear thermal gradients on bearing loads is worth investigating, particularly in the southwestern states where these gradients are more severe than elsewhere in the US. An exploratory study will be conducted to better understand how extreme temperatures might be affecting the long term performance of bridges, especially bridge bearings, in the consortium states. The research objective is to predict the influence of thermal gradients on representative existing bridges that have been exposed to temperature extremes in the southwest. Two or three case study bridges will analyzed for deformations, stresses, moments and bearings loads under thermal loading, and the analysis results will be interpreted in light of the bridge maintenance records.

Language

• English

Project

• Status: Completed
• Sponsor Organizations:

  Office of the Assistant Secretary for Research and Technology

  University Transportation Centers Program
  Department of Transportation
  Washington, DC  United States  20590
• Managing Organizations:

  University of Nevada, Reno

  College of Engineering
  Reno, NV  United States  89557
• Performing Organizations:

  University of Nevada, Reno

  College of Engineering
  Reno, NV  United States  89557
• Principal Investigators:

  Ryan, Keri

• Start Date: 20160601
• Expected Completion Date: 20170531
• Actual Completion Date: 20170701

Subject/Index Terms

• TRT Terms: Bridges; Climate; Cracking; Deserts; Deterioration; Durability; Failure; Heat; Ice; Solar radiation; Thermal fatigue
• Geographic Terms: Southwestern States
• Subject Areas: Bridges and other structures; Environment; Highways;

Filing Info

• Accession Number: 01596020
• Record Type: Research project
• Source Agency: Center for Advanced Transportation Education and Research (CATER)
• Files: UTC, RIP
• Created Date: Apr 13 2016 4:21PM