Design

Environmental Suitability of Weathering Steel Structures in Florida – Materials Selection, Phase 2

For the purpose of establishing guidelines for selection of weathering steel material for bridges in Florida, data were collected to help establish appropriate guidelines. There were 30 monitoring stations set up for direct (weight loss) measurements and weather data. Data indicated that the corrosion rates in Florida are generally low for weathering steel. The use of weathering steel material for bridges in Florida in the context of adjusted guidelines is very favorable. Consideration should be given to increasing the allowable deposition rate of chloride to approximately 13 mg·m–2·d–1 corresponding to 4 miles from the shoreline. An alternative direct assessment at the site considered is recommended for determining the advisability for uncoated weathering steel in this manner: (1) Expose several plate specimens and collect monthly for a minimum of 4 months. (2) Directly compare the time series weight losses to known corrosion studies. ISO methods permit this alternative. Additionally, estimates of chloride and sulfur compound depositions can be obtained from the same exposed panels by analyses of panel wash water prior to oxide removal, if desired. The advantage of direct assessment is that no environmental factor will likely be neglected, such as pH, ammonia, fertilizer, ozone, exposure/sheltering, or unanticipated factors (positive or negative).

Download the Weathering Steel Study Report (.pdf)

Residual Dye (Lubricant) on Galvanized Fasteners – How much is too much?

The nuts of galvanized fasteners used on bridges are coated with a wax-based lubricant that contains a dye. Once installed, the fasteners are cleaned to remove the wax prior to painting. Cleaning is typically accomplished using a combination of solvents and hand tools, but questions are often raised as to how much residual dye on the surface is acceptable for painting. To gain better insight into this issue, the Florida Department of Transportation (FDOT) commissioned a research project to evaluate the performance of a bridge paint system applied to mechanically galvanized and hot dip galvanized fasteners after removal of various amounts of lubricant. A paper was written summarizing the research that was undertaken and the results.

Read the Summary Paper (.docx)

FHWA and AASHTO Release Findings on Dimensions of ET-Plus Guardrail End Terminal

The Federal Highway Administration (FHWA) and the American Association of State Highway and Transportation Officials (AASHTO) have released the findings of a joint task force which evaluated field measurement data collected by FHWA engineers from more than 1,000 4-inch ET-Plus devices installed on roadways throughout the country.

The joint task force concluded that:

• There is no evidence to suggest there are multiple versions (i.e., ET-Plus 4-inch devices with markedly different dimensions) on our nation’s roadways, and
• The end terminals crash tested at the Southwest Research Institute (SwRI) between December 2014 and January 2015 are representative of the devices installed across the country.

Read the FHWA Press Release