World War Memorial Bridge

The World War Memorial Bridge, commonly referred to as theMemorial Bridge, is a vertical lift bridge over the Piscataqua River. It wasbuilt in 2013 and replaced a previous bridge of similar design. The name of thebridge itself is noteworthy, since it refers to the fact that the originalbridge was built after World War I, but before World War II. Constructionstarted in 1920, and the bridge opened in 1923, making this bridge an earlyexample of a vertical lift bridge. The lift span was a Warren through truss,and the approach spans were polygonal Warren trusses. The bridge requirednumerous repairs over its life, with poor safety ratings and structurallydeficient classifications beginning in 1994. Over the following years, repairswere made, but the weight limit continued to decrease. It was permanentlyclosed to vehicular traffic on July 27, 2011, when the inspection report saidthere were "too many problems in too many places". It was furtherclosed to pedestrians and cyclists on January 9, 2012, and the center span wasdemolished on February 8, 2012.

Plans for a rehabilitation project were underway, and thecontract was bid for construction in 2009. It was anticipated that the projectwould take approximately 2 years. However, the project was stalled when thewinning bid for the contract came in $15 million over the intended budget. Inearly 2010, it was decided that the bridge would be replaced instead. Thereplacement bridge was designed to be similar to the original structure,although it lost the elegant curves on the towers and trusses. The new bridge reusedthe original piers, so some sources call it a bridge rehabilitation instead ofa replacement. The new bridge was opened on August 8, 2013.

The original bridge had an extremely large and ornatesculpture mounted on the truss portal bracing. This sculpture was saved and wasmounted on the new bridge. It is one of the most ornate decorations found onany bridge in the United States.

This bridge is the first gusset-less truss bridge in the world.Gusset plates are typically steel plates, which the truss members are rivetedor bolted to. Properly designed gusset plates have been used on countlessstructures and have proven to be safe and reliable. However, improperlydesigned gusset plates led to the famous collapse of the I-35W Bridge inMinneapolis, MN in 2007. In addition, gusset plates are typically the firstelement to corrode and deteriorate on truss bridges. They can be tough to inspectand are tough to replace. This has led to a desire to reduce or eliminategusset plates. The Memorial Bridge was designed using splice plates instead ofgusset plates, which are easier to inspect and replace. The top and bottomcords were fabricated with bent plates and curved webs, and the bridge was fittogether like a puzzle.

In response to the vessel strike and collapse of the FrancisScott Key Bridge Collapse in 2024, the National Transportation Safety Board(NTSB) published a report identifying other bridges needing risk assessmentwith regards to a possible vessel strike. This report was published in March of2025, and identified 68 bridges, including the Memorial Bridge. At this time,the New Hampshire DOT has not published any plans to retrofit the bridge.