BRIDGE RESCUE: Longer to live

Nov. 13, 2014

Louisiana focuses on bridge preservation

With more than 12,800 bridges comprising 100 million sq ft of deck area, Louisiana has a very unique and complex bridge system.

Our current inventory contains approximately 10% structurally deficient and 14% functionally obsolete bridges, many of which are off the state system. We rank first in the nation for the most movable bridges and second for the most timber bridges. Managing this volume of structures is a task the Louisiana Department of Transportation and Development (DOTD) takes very seriously.

DOTD’s Bridge Maintenance and Bridge Design Sections are responsible for maintaining the safety and serviceability of Louisiana’s bridges. Bridge inspections play an important role in determining the condition of our bridge inventory. DOTD’s Maintenance Sections utilize 81 highly experienced bridge inspectors who yearly average 8,100 inspections and are also responsible for performing minor routine maintenance and repair work. And this fall, DOTD will participate in a peer-exchange program with Georgia.

Recently, DOTD has incorporated new technologies into bridge inspections such as amphibious vehicles to reduce traffic impacts, and the use of infrared thermography, ultrasonic surface waves and impulse response non-destructive testing for bridge decks.

Moreover, in an effort to maintain accuracy and consistency in inspections, reports and inventory, an appropriate quality control and quality assurance (QC/QA) process is followed. The process involves a two-step QC method consisting of a review of the reports from the district bridge inspector supervisor and the bridge inspection engineer. Additionally, a QA process is followed in which a group performs independent random or select inspections on previously inspected structures to assure the inspections are representative, repeatable and meet applicable standards. These inspections are performed by the most experienced inspectors on the QA inspection team.

After inspections, the next step is a thorough and continuous load-capacity analysis to determine if a bridge should be rehabilitated or replaced. Since weight limits are required on all bridges found to be structurally deficient, DOTD utilizes regulatory weight-limit signs for all bridges incapable of bearing the state’s statutory legal limit.

When issues arise, constant interaction and communication between the bridge sections and the districts are the norm. To assess the needs and priorities, quarterly bridge team meetings are held between the design, maintenance, construction, management and research sections. It is at these meetings that major issues are discussed and resolved.

DOTD’s Bridge Design Section is responsible for bridge rating and preparing projects for bridge rehabilitation, replacement and preventive maintenance projects.

As a major component of bridge preservation, preventive maintenance is a strategy for extending the service life by applying cost-effective treatments to bridges. These types of projects comprise 5-10% of the bridge program.

Louisiana’s plethora of timber bridges requires keeping up with repairs in a severe environment that is time- and resource-intensive. Our Bridge Design and Maintenance Sections are in the process of standardizing engineered solutions to timber bridge repairs using both new and old technologies in order to better manage our inventory.

Communication, ingenuity and teamwork help DOTD extend the life of its structures, and it is these values that will continue to aid us moving forward.R&B

About The Author: Mumphrey is the assistant bridge design administrator with the DOTD.

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