Pin and hanger assembly

A Pin and Hanger assembly is used to connect two plate girders of bridges. These assemblies are used when the space between two bridge piers is too wide to be spanned by a single set of girders. To overcome this, steel beams are set with one end resting on a bridge pier, while the other end is connected to adjacent steel beams that are cantilevered from the next pier. The two steel beams are connected using a pair of connecting plates (one on each side of the bridge joint). A pair of bolts are inserted through the plates and girder webbing: one through the cantilevered beam and one through the suspended beam. Exceptionally long spans may have two sets of girders cantilevered from opposite bridge piers with a third set of girders suspended by pin and hanger assemblies from both cantilevers.

afety concerns

Pin and hanger assemblies are considered fracture critical bridge components, meaning that the assemblies are non-redundant and failure of these systems could cause part or all of the bridge to collapse. The collapse of the Mianus River Bridge in Connecticut exposed potential flaws with pin and hanger bridges that could lead to catastrophic failures, if left unchecked. Because of this, state departments of transportation incur costly expenses on bridges with pin and hanger assemblies, as they require constant maintenance. As a result of these safety concerns, and advances in bridge design to allow longer spans, pin and hanger assemblies are no longer used on new bridges in the United States.