Category Archives: Bridges and Structures

Updating Load Ratings for Shingle Creek Slab-Span Bridges

Detours around bridges in a critical freight transportation route create costs to the trucking industry, taxpayers and state economy. New load rating factors for the slab-span bridges across Shingle Creek will give MnDOT more flexibility in managing truck traffic and keeping freight moving efficiently.

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Estimating Corrosion of Embedded Steel Rebars in Bridge Structures

Corrosion of steel reinforcement in bridge structures creates uncertainty in the structural capacity. A new prediction tool will help estimate rebar section loss to accurately plan for appropriate bridge maintenance repairs. 

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Nondestructive Detection of Pile Length for High-Mast Light Towers

A new testing method will allow MnDOT to determine the underground foundation pile depths of high-mast light towers (HMLTs) without digging or dismantling. HMLTs need to meet design standards to ensure load-bearing stability. By using the new method to evaluate pile depth, MnDOT could avoid costly retrofits or replacements, and prioritize light towers in need of redesign.  

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Managing Building Assets With Scanning and Reality Modeling

MnDOT owns and maintains approximately 900 buildings across Minnesota, and the Building Services Section is responsible for planning repairs, renovations or expansions. Architects, engineers and other specialists involved in these activities require data regarding building and site conditions. Collecting this data is often a multidisciplinary and laborious effort that can be time-consuming and expensive. Alternative technologies, however, can gather and process large amounts of accurate information more comprehensively, safely and cost-effectively. 

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New Project: Bridge Low Slump Concrete Overlay Mix Design for Mobile Mixers

In recent years, MnDOT has seen an increase in cracking of low slump overlays. Cracking of overlays allows chlorides to get into the bridge deck which leads to deterioration of the reinforcement and eventual delamination or spalling.  This means that the bridge deck needs to be repaired or even replaced before the service life has been reached. 

What is a low slump overlay? A low slump overlay is a technique used by DOTs to extend the life of bridge decks. They are typically 2″ thick and designed to provide low permeability.

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Monitoring System Provides Decade of Data From I-35W Bridge

This article was originally published in Catalyst, August 2020.

On August 1, 2007, the I-35W Saint Anthony Falls Bridge collapsed in Minneapolis. Its replacement, open to traffic just over a year later, was instrumented with more than 500 sensors to record the new structure’s behavior and evaluate the effectiveness of different monitoring strategies. A 10-year review of the bridge’s monitoring system is now available from U of M researchers.

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GFRP Rebar Shows Promise for Use in Bridge Decks

Reinforced concrete bridges are built to handle heavy loads and routine traffic for 75 years or more. But bridges in climates like Minnesota’s are exposed to moisture and chlorides from road salts that may penetrate these structures and corrode the steel.

In a recently completed research project, funded by MnDOT and the Local Road Research Board, researchers studied a rural bridge built in 2017 near Elgin, MN, that used glass fiber–reinforced polymer (GFRP) rebar in the bridge deck. They found that GFRP performed well, proving sufficiently strong for use as an alternative to corrosion-susceptible steel rebar.

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