Pin and hanger assembly

A pair of large steel pins through the plates and girder webbing provide the hinges, holding up the suspended span while allowing it to move longitudinally.

Because of this, state departments of transportation incur costly expenses on bridges with pin and hanger assemblies, as they require constant inspection and maintenance.

Retrofits that add redundancy to pin and hanger assemblies include adding a "catcher's mitt"‍—‌a short steel beam attached to the bottom of the cantilevered girder that extends out beneath the suspended girder to "catch" the suspended girder should the pin and hanger assembly fail.

Another redundancy is connecting the cantilevered and suspended girders at the pin and hanger assembly with welded blocks and tie rods.

Replacement options include bolted splices (gusset plates) plus shear connectors; a link slab; a ship-lap joint; and a new pin and hanger assembly with improved materials.