Print Case Study
Connecticut Department of Transportation
When the Connecticut Department of Transportation (CTDOT) examined a 50 year old 8’-10” span by 6’-1” rise steel structural plate pipe arch that carries an unnamed brook under I-91 in Middletown, CT, they found a corroded structure that had served its purpose since the original construction of the interstate in 1964. During a routine inspection, a visual examination determined the general condition of the culvert. The inspectors recorded measurements of the culvert’s cross section at select distances along the culvert and used a template with predefined points in order to measure size and shape of the culvert. Local deformations were recorded separately. Beginning in 2015, the condition of the culverts was found to have worsened to the point where DOT personnel were restricted from entering them. It was in dire need of immediate repair or replacement.
The CTDOT considered using grouted, metal pipe to slip-line the culvert. This option was rejected because it required workers to access the entire culvert before it was lined. Because significant portions of the invert had to be removed before the liner could be placed, this option was not safe or feasible. To provide protection for workers inside the culvert while advancing a liner, they selected 2-Flange Aluminum Tunnel Liner Plate (TLP) manufactured by Contech Engineered Solutions as the optimal solution. The heavy gage aluminum, pressed into a corrugated profile, 18 inches wide, provided the structural capacity to support 20 feet of fill above the culvert. These sections were assembled inside the culvert and spliced together with lap-type joints to form closed rings in a shape very similar to the host pipe.
The project was designed using AASHTO LRFD structural design methodology. Due to the advanced deterioration, the CTDOT quickly awarded a contract to Arborio Corporation using the emergency declaration process. Installation included the full removal of the invert along one-third of the length, while all travel lanes and the shoulders of the Interstate remained operational 20’ above the work. The tunnel liner plate method allowed for safe construction practices and a full structural rehabilitation. The estimated savings using TLP was more than $3M.
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