The Mianus River Bridge is a span that carries

Interstate 95 Interstate 95 (I-95) is the main north–south Interstate Highway on the East Coast of the United States, running from U.S. Route 1, US Route 1 (US 1) in Miami, Miami, Florida, to the Houlton–Woodstock Border Crossing between M ...

(

Connecticut Turnpike The Connecticut Turnpike (officially the Governor John Davis Lodge Turnpike) is a controlled-access highway and former toll road in the U.S. state of Connecticut; it is maintained by the Connecticut Department of Transportation (ConnDOT). Span ...

) over the

Mianus River The Mianus River is a river in Westchester County, New York, and Fairfield County, Connecticut, in the United States. It begins in the town of North Castle, New York (east of Armonk) in a series of ponds at about altitude. Flowing northeast i ...

, between

Cos Cob Cos Cob is a neighborhood and census-designated place in the town of Greenwich, Connecticut. It is located on the Connecticut shoreline in southern Fairfield County. It had a population of 6,770 at the 2010 census. Cos Cob is located on the west ...

and

Riverside, Connecticut Riverside is a neighborhood/section in the town of Greenwich in Fairfield County, Connecticut, United States. As of the 2010 census, it had a population of 8,416. The town of Greenwich is one political and taxing body, but consists of several d ...

. It is the second bridge on the site. The original bridge collapsed in 1983, killing three motorists. The replacement span is officially named the Michael L. Morano Bridge, after a state senator Michael L. Morano who represented Greenwich.

Collapse

The bridge had a 100-foot (30.5 m) section of its deck of its northbound

span Span may refer to: Science, technology and engineering * Span (unit), the width of a human hand * Span (engineering), a section between two intermediate supports * Wingspan, the distance between the wingtips of a bird or aircraft * Sorbitan ester ...

collapse on June 28, 1983. Three people were killed and three more were seriously injured when two cars and two tractor-trailers fell with the bridge into the Mianus River 70 feet (21.3 m) below. Casualties from the collapse were few because the disaster occurred at 1:30 a.m., when traffic was low on the often-crowded highway.

Causes

The collapse was caused by the failure of two pin and hanger assemblies that held the deck in place on the outer side of the bridge, according to an investigation by the

National Transportation Safety Board The National Transportation Safety Board (NTSB) is an independent U.S. government investigative agency responsible for civil transportation accident investigation. In this role, the NTSB investigates and reports on aviation accidents and incid ...

Rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH ...

formed within the bearing of the pin, exerting a force on the hanger which was beyond design limits for the retaining clamps. It forced the hanger on the inside part of the

expansion joint An expansion joint, or movement joint, is an assembly designed to hold parts together while safely absorbing temperature-induced expansion and contraction of building materials, and vibration, or to allow movement due to ground settlement or seis ...

at the southeast corner off the end of the pin that was holding it, and the load was shifted to outside hanger. The extra load on the remaining hanger started a

fatigue crack In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striations on some parts of ...

at a sharp corner on the pin. When it failed catastrophically, the deck was supported at just three corners. When two heavy trucks and a car entered the section, the remaining expansion joint failed, and the deck crashed into the river below. The ensuing investigation cited corrosion from water buildup due to inadequate drainage as a cause. During road mending some 10 years before, the highway drains had been deliberately blocked and the crew failed to unblock them when the road work was completed. Rainwater leaked down through the pin bearings, causing them to rust. The outer bearings were fracture-critical and non-redundant, a design flaw of this particular type of structure. The bearings were difficult to inspect close-up, although traces of rust could be seen near the affected bearings. The incident was also blamed on inadequate inspection resources in the state of

Connecticut Connecticut () is the southernmost state in the New England region of the Northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, New York to the west, and Long Island Sound to the south. Its cap ...

. At the time of the disaster, the state had just 12 engineers, working in pairs, assigned to inspect 3,425 bridges. The collapse came despite the nationwide inspection procedures brought about by the collapse of the

Silver Bridge The Silver Bridge was an eyebar-chain suspension bridge built in 1928 and named for the color of its aluminum paint. The bridge carried U.S. Route 35 over the Ohio River, connecting Point Pleasant, West Virginia, and Gallipolis, Ohio. On Dece ...

in West Virginia in December 1967.

Reaction

The interstate was not fully reopened for six months, and then only with a temporary truss. In total, final repairs cost over $20 million. During the rebuilding, traffic was diverted onto US-1 and local streets in Greenwich, causing the worst traffic problems the town had ever seen. The Mianus River Bridge was completely reconstructed in the late 1980s. Work included replacing all of the structural steel, rebuilding and expanding the bridge deck to accommodate a wider roadway, and repairing the bridge piers to extend their service life. The replacement span was completed in 1992. It eliminated the pin-and-hanger assemblies that caused the collapse of the original bridge. Governor William O'Neill afterward proposed a $5.5 billion transportation spending package to pay for rehabilitation and replacement of bridges and other transportation projects in Connecticut. In 1992, the bridge was officially named the Michael L. Morano Bridge, after a state senator who represented nearby Greenwich.

References

External links

NTSB report on the collapseA history of the Connecticut Turnpike (I-95)
at NYC Roads.com * - Archival news footage of the disaster via YouTube
28 June 1983
on Connecticut History website {{Greenwich, Connecticut Bridge disasters in the United States Bridge disasters caused by maintenance error Buildings and structures in Greenwich, Connecticut Bridges completed in 1958 1958 establishments in Connecticut Disasters in Connecticut Transportation disasters in Connecticut 1983 disasters in the United States Bridges in Fairfield County, Connecticut Road bridges in Connecticut Interstate 95 Bridges on the Interstate Highway System Former toll bridges in Connecticut Girder bridges in the United States

Collapse

Causes

Reaction

See also

References

External links