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The Schoharie Creek Bridge was a
New York State Thruway {{Infobox road , state = NY , type = NYST , alternate_name = Governor Thomas E. Dewey Thruway , maint = NYSTA , map = {{maplink, frame=yes, plain=yes, frame-align=center, frame-width=290, type=line, stroke-width=2, type2=line, from2=New Yor ...
(
I-90 Interstate 90 (I-90) is an east–west transcontinental freeway and the longest Interstate Highway in the United States at . It begins in Seattle, Washington, and travels through the Pacific Northwest, Mountain West, Great Plains, Midwest, and ...
) bridge over the
Schoharie Creek Schoharie Creek is a river in New York that flows north from the foot of Indian Head Mountain in the Catskills through the Schoharie Valley to the Mohawk River. It is twice impounded north of Prattsville to create New York City's Schoharie ...
near
Fort Hunter Fort Hunter is a hamlet in the Town of Florida in Montgomery County, New York, United States, west of the capital at Albany, on the south bank of the Mohawk River and on the northeast bank of Schoharie Creek. The hamlet developed around a fort of ...
and the
Mohawk River The Mohawk River is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed October 3, 2011 river in the U.S. state of New York. It is the largest tributary of the Hudson River. The Mohawk f ...
in
New York State New York, officially the State of New York, is a state in the Northeastern United States. It is often called New York State to distinguish it from its largest city, New York City. With a total area of , New York is the 27th-largest U.S. stat ...
. On April 5, 1987 it collapsed due to
bridge scour Bridge scour is the removal of sediment such as sand and gravel from around bridge abutments or piers. Hydrodynamic scour, caused by fast flowing water, can carve out ''scour holes'', compromising the integrity of a structure. In the United States ...
at the
foundations Foundation may refer to: * Foundation (nonprofit), a type of charitable organization ** Foundation (United States law), a type of charitable organization in the U.S. ** Private foundation, a charitable organization that, while serving a good cause ...
after a record rainfall. The collapse killed ten people. The replacement bridge was completed and fully open to traffic on May 21, 1988. The failure of the Schoharie Creek Bridge motivated improvement in bridge design and inspection procedures within New York and beyond.


Bridge design and construction

The final design for the bridge was approved in January 1952 by the
New York State Department of Transportation The New York State Department of Transportation (NYSDOT) is the department of the New York state government responsible for the development and operation of highways, railroads, mass transit systems, ports, waterways and aviation facilities in ...
(previously the New York State Department of Public Works). The design described a crossing consisting of five simply supported spans with nominal lengths of , , , , and . The bridge was supported with
pier image:Brighton Pier, Brighton, East Sussex, England-2Oct2011 (1).jpg, Seaside pleasure pier in Brighton, England. The first seaside piers were built in England in the early 19th century. A pier is a raised structure that rises above a body of ...
frames along with
abutments An abutment is the substructure at the ends of a bridge span or dam supporting its superstructure. Single-span bridges have abutments at each end which provide vertical and lateral support for the span, as well as acting as retaining walls ...
at each end. The pier frames were constructed of two slightly tapered
columns A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member. ...
with tie beams. The columns were fixed in place within a lightly reinforced
plinth A pedestal (from French ''piédestal'', Italian ''piedistallo'' 'foot of a stall') or plinth is a support at the bottom of a statue, vase, column, or certain altars. Smaller pedestals, especially if round in shape, may be called socles. In c ...
positioned on a shallow, reinforced spread footing. The spread footing was to be protected with a dry layer of
riprap Riprap (in North American English), also known as rip rap, rip-rap, shot rock, rock armour (in British English) or rubble, is human-placed rock or other material used to protect shoreline structures against scour and water, wave, or ice erosion. ...
. The
superstructure A superstructure is an upward extension of an existing structure above a baseline. This term is applied to various kinds of physical structures such as buildings, bridges, or ships. Aboard ships and large boats On water craft, the superstruct ...
consisted of two longitudinal main girders with transverse floor beams. The skeleton of the bridge deck ( thick) was made up of steel stringers. Construction began on February 11, 1953 by B. Perini and Sons, Inc.


Service

The bridge was partially opened during the summer of 1954 before
construction Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and com ...
was completed. The Schoharie Creek Bridge (NY 1020940, New York State bridge identification number), began full service beginning in October 1954. In the spring and summer of 1955, the pier plinths began to show vertical cracks ranging from , as a result of high tensile stresses in the concrete plinth. Almost a year later, on October 16, 1955, the bridge was damaged by a
flood A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...
. In 1957, plinth reinforcement was added to each of the four piers.


Collapse

On the morning of April 5, 1987, during a high spring flood, the Schoharie Creek Bridge collapsed. A snowmelt combined with rainfall totaling produced an estimated 50-year flood on the creek. Pier three was the first to collapse, which caused the progressive collapse of spans three and four. Ninety minutes later pier two and span two collapsed. Two hours later pier one and span one shifted. A
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 ...
investigation suggested that pier two collapsed because the wreckage of pier three and the two spans may have partially blocked the river, redirecting and increasing the velocity of the flow of water to pier two. Six days later, upstream, a large section of the Mill Point Bridge collapsed. The bridge had been closed since the flood as a precaution, since inspection showed that its foundations had also been eroded.


Casualties

At the time of the collapse, one car and one
tractor A tractor is an engineering vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds, for the purposes of hauling a trailer or machinery such as that used in agriculture, mining or construction. Most common ...
-
semitrailer A semi-trailer is a trailer without a front axle. In the United States, the term is also used to refer to the combination of a truck and a semi-trailer; a tractor-trailer. A large proportion of a semi-trailer's weight is supported by a tracto ...
were on the bridge. Before the road could be blocked off, three more cars drove into the gap. During the following three weeks, nine bodies were recovered from the river. The body of the 10th victim was recovered from the Mohawk River in July 1989.


Failure analysis

Eyewitnesses observed that the third pier from the west abutment (pier three) failed first. Photos taken the day of the event show that the nose of pier three had fallen relative to its tail, which seemed to remain in position. The single concrete column at the nose of pier three lost support, causing that column to buckle and the two spans supported by pier three to fall into the swollen creek. A short while later, eyewitnesses watched as the second pier from the west abutment failed. An on-site news team recorded this event on video tape. The video showed a sudden and catastrophic drop at the tail-end of the second pier. This caused the span immediately west of pier two to also fall into the creek. Because of the high profile of this catastrophe and loss of life, 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 ...
started investigations in the immediate aftermath of the failure. The
New York State Thruway Authority The New York State Thruway Authority (NYSTA) is a public benefit corporation in New York State, United States. The NYSTA was formed in 1950 with the responsibility of constructing, maintaining, and operating the New York State Thruway, a syste ...
hired a consortium made up of staff from Wiss, Janney, Elstner Associates, Inc., and Mueser Rutledge Consulting Engineers to lead the investigation on their behalf. Divers began removing steel from the river bed after the water levels receded. Construction of a cofferdam around portions of the site allowed de-watering. Investigations showed significant local erosion of the stream bed that occurred before the failure and likely additional scour due to the obstructive nature of the bridge decks that fell into the creek after the failure. The nose of pier three laid in a large asymmetrical horseshoe-shaped scour hole. The observed failure of the downstream (tail) end of pier two added confusion to the causative analysis. To study the causes of the failure, the investigating engineering team commissioned a physical model study at the hydraulics laboratory at Colorado State University. A physical hydraulic model of the regional flow field constructed at a non-distorted scale of 1:50 using clear water and sand bed allowed observation of the failure progression. The Schoharie Creek makes an approximate 120-degree bend to the left looking downstream towards the bridge site. Measurements of the flow field approaching the bridge model showed that the maximum velocity coincided with the location of pier three, the pier with significant submergence closest to the outside of the bend. The model study clearly showed that once the flat face of the pier three
spread footing A shallow foundation is a type of building Foundation (engineering), foundation that transfers structural load to the earth very near to the surface, rather than to a subsurface layer or a range of depths, as does a deep foundation. Customarily, a ...
was exposed to the flow, it generated a large
horseshoe vortex The horseshoe vortex model is a simplified representation of the vortex system present in the flow of air around a wing. This vortex system is modelled by the ''bound vortex'' (bound to the wing) and two '' trailing vortices'', therefore having ...
that accentuated local scour around the pier nose.
Secondary flow In fluid dynamics, flow can be decomposed into primary plus secondary flow, a relatively weaker flow pattern superimposed on the stronger primary flow pattern. The primary flow is often chosen to be an exact solution to simplified or approximated ...
naturally occurs when a river flows around a bend. Higher velocity flow, which has higher momentum, resists the curvature of the river bend and moves towards the outside bank. Since this flow exists near the water surface, it causes flow near the bed to move towards the inside of the bend. As a result, the flow near the bed of the river channel at the bridge opening had an angle relative to the alignment of pier 3. This led to a component of velocity near the stream bed moving from pier 3 towards pier 2. A second physical hydraulic model constructed at a scale of 1:15 with the appropriate
angle of attack In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
relative to the axis of pier 3 allowed detailed phenomenological study of the scour process. The investigations concluded that the bridge collapsed due to extensive
scour Scour may refer to: Hydrodynamic processes * Hydrodynamic scour, the removal of sediment such as sand and silt from around an object * Bridge scour, erosion of soil around at the base of a bridge pier or abutments via the flow of air, ice, or ...
under pier three. Results from the physical hydraulic model studies showed that once the flat nose of the spread footing became exposed to the flow, an intense
horseshoe vortex The horseshoe vortex model is a simplified representation of the vortex system present in the flow of air around a wing. This vortex system is modelled by the ''bound vortex'' (bound to the wing) and two '' trailing vortices'', therefore having ...
exhumed bed material from the nose of that pier. Once the scour depth at the nose of the pier exceeded the depth of the spread footing, undermining began. Because of the angle of attack created by the secondary flow, scour preferentially affected the right-hand portion of the pier as eroded bed material swept downstream. With each successive increment of undermining, which progressed from the nose of the pier towards the tail, the upper portion of the plinth experienced increasing tension. Evidence from post-event analysis of the dewatered site suggested that undermining of the pier three spread footing was extensive, well in excess of 50 percent of its length, when the plinth suddenly failed. This allowed the nose of pier three to drop into the scour hole. The simple-span bridge design had no ability to resist the resulting lateral load on the unsupported column, leading to sudden, catastrophic and progressive collapse of both spans supported by pier 3. The original design of the bridge specified abandonment in place of steel sheet piling installed during construction to stabilize the construction site at piers 2 and 3. This would have protected those piers from scour, but was not done. The foundation of the pier was bearing on erodible soil, consisting of layers of gravel, sand and silt, inter-bedded with folded and tilted till. This allowed high velocity flood waters to penetrate the bearing stratum. The area left around the footing was not filled with riprap stone, but instead was back-filled with erodible soil and topped off with dry riprap. Riprap protection, inspection, and maintenance were determined to have been inadequate. The investigations showed that the scouring process under the piers began shortly after the bridge was built. At the time of the collapse, the upstream end of pier 3 fell into a scour hole approximately deep. Investigators estimated that about of the pier was undermined. Another factor that contributed to the failure was the weight of the riprap used in the construction. The design specification called for riprap with 50 percent of the stones heavier than , and the remainder between . Investigators found that heavier riprap weights of should have been specified. Other considerations as to the cause of the collapse included design of the superstructure, quality of materials and construction, and inspection and maintenance. Investigations found that these factors did not contribute to the collapse. Twelve hours before the Schoharie Creek Bridge collapsed due to heavy rainfall, the rush of water through the Blenheim-Gilboa Pumped Storage Power Project upstream hit a historic high. To cope with the overload, the dam released water into the Schoharie Creek according to the rate at which it was entering the reservoir from upstream, adding to the load in the creek.


See also

*
List of bridge disasters This is a list of bridge failures. Before 1800 1800–1899 1900–1949 1950–1999 2000–present Bridge disasters in fiction *Harry Potter and the Half-Blood Prince (2005 novel): the fictional Brockdale Bridge, by the Death Eaters ( ...
*
Bridge scour Bridge scour is the removal of sediment such as sand and gravel from around bridge abutments or piers. Hydrodynamic scour, caused by fast flowing water, can carve out ''scour holes'', compromising the integrity of a structure. In the United States ...


References


Further reading

*Boorstin, Robert O. (1987). "Bridge Collapses on the Thruway, Trapping Vehicles," ''The New York Times,'' April 6, 1987; Volume CXXXVI, No. 47,101. *Huber, Frank. (1991). “Update: Bridge Scour.” ''Civil Engineering,'' ASCE, Vol. 61, No. 9, pp 62–63, September 1991. *Levy, Matthys and Salvadori, Mario (1992). ''Why Buildings Fall Down.'' New York: W.W. Norton and Company. *National Transportation Safety Board (NTSB). (1988). “Collapse of New York Thruway (I-90) Bridge over the Schoharie Creek, near Amsterdam, New York, April 5, 1987.” Highway Accident Report: NTSB/HAR-88/02, Washington, D.C. * Springer Netherlands. "The collapse of the Schoharie Creek Bridge: a case study in concrete fracture mechanics", ''International Journal of Fracture,'' Volume 51, Number September 1, 1991. *Palmer, R., and Turkiyyah, G. (1999). “CAESAR: An Expert System for Evaluation of Scour and Stream Stability.” National Cooperative Highway Research Program (NCHRP) Report 426, Washington D. C. *Shepherd, Robin and Frost, J. David (1995). ''Failures in Civil Engineering: Structural, Foundation and Geoenvironmental Case Studies.'' American Society of Civil Engineers, New York, New York. *Thornton, C. H., Tomasetti, R. L., and Joseph, L. M. (1988). “Lessons From Schoharie Creek,” ''Civil Engineering,'' Vol. 58, No.5, pp. 46–49, May 1988. *Thornton-Tomasetti, P. C. (1987) “Overview Report Investigation of the New York State Thruway Schoharie Creek Bridge Collapse.” Prepared for: New York State Disaster Preparedness Commission, December 1987. *Wiss, Janney, Elstner Associates, Inc., and Mueser Rutledge Consulting Engineers (1987) “Collapse of Thruway Bridge at Schoharie Creek,” ''Final Report,'' Prepared for: New York State Thruway Authority, November 1987. *Johnson, Diane M. ''The Schoharie.''BookBaby, 2017. A novel. *Swenson DV, Ingraffea AR. The Collapse of the Schoharie Creek Bridge: A Case Study in Concrete Fracture Mechanics. Int. J. Fracture, 51, 73-92, 1991.


External links


NTSB report synopsisSenate reportMueser Rutledge Consulting Engineers report synopsis
{{New York State Thruway Authority Bridge disasters in the United States Bridge disasters caused by construction error Bridge disasters caused by engineering error Montgomery County, New York Disasters in New York (state) Transportation disasters in New York (state) 1987 in New York (state) 1987 disasters in the United States Bridge disasters caused by scour damage Construction accidents in the United States