Bridge Failures
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FAILURE BRIDGE FAILURES Part 1
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Failed Structures Part 1 - Bridge Failures
Transcript of Bridge Failures
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Bridge Failures
Part 1
Introduction
Tay Bridge
Ashtabula Bridge
Hackensack River Bridge
Tacoma Narrows Bridge
Menai Straits Bridge
Silver Bridge
Cypress Street Viaduct
San Francisco Oakland Bay Bridge
MacArthur Maze
Mianus River Bridge
Bridges revised after failure of Mianus River Bridge
Schoharie Creek Bridge
Quebec Bridge
King Bridge
Murrow Floating Bridge
Glossary
Reference
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statistics regarding Failures are oFten inaccurate...
...since many Failures are concealed
and not reported.
Introduction This book will give you an insight into a variety of bridge failures both nationally and internationally. Bridges fail for many different reasons, some causes covered in this book included: construction failures, design failures, maintenance failures and unpredictable failures (hurricanes, explosions and vehicle impacts) also know as the ‘Act of God’.
The history of iron bridge failures during the 19th century is a fascinating story and one that continues to impress engineers today with their professional responsibilities. A frightening number of railroad bridges collapsed between 1875 and 1900 which was around the time when railroads were expanding. The Railway Gazette in 1895 published a discouraging summary of iron bridge failures resulting from railway traffic, listing 502 cases in the period 1878 through 1895, noting that the first 251 occurred in 10 years, whereas the second 251 occurred in only 8 years. In the years 1888 to 1891 there were 162 such accidents.
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The economics of the expansion and railroads equipment technology demanded bridges to support heavier and heavier loads, and the bridges had to be constructed in irregular, unusual environments. These bridges were subjected to large gravity loads, to dynamic vibrations, and to the changing positions of the train.
Petroski (1985) has noted that the railroads brought together the machines of the mechanical engineer and the stationary structures of the civil engineer, and the demands of each provided stimulus for the evolution of the others. The trial and error experience of the railroad bridge builders provided much of the foundation for modern fracture mechanics and other material science knowledge.
Complete collapse of bridge structures is not common now, but there are still difficulties. Most bridge failures in this country have been due to design methods that were not sophisticated enough to account for subtle conditions and secondary loads, such as wind induced excitations and thermal effects. There have also been a number of failures caused by detail deficiencies: joints, bearings, supporting corbels, poorly welded connections and so on. Other failures were caused by impact loading from collisions. Finally, a few catastrophic collapses have been due to inadequate maintenance.
4Tay Bridge Scotland, England
Construction Started Bridge Opened Collapsed Date Deaths Caused Engineer Reason for Failure Type of FailureSpan of Bridge
1871Sept 26th 1877Dec 28th, 187995Sir Thomas BouchViolent Wind StormEngineering1.5 km (1 mile)
Completed in 1877, the bridge was 1.5 km long. It was comprised of 85 iron latice-truss spans supported 27 m above an inlet of the North Sea on the east coast of Scotland, known as the Firth of Tay.
The bridge was one of two proposed by Sir Thomas Bouch, engineer for the North British Railway Company. The Tay Bridge, and another over the Firth of Forth, were inspired by fierce competition between rival railroad companies and the desire to eliminate slow ferry crossing over the large estuaries. Both bridges were nearly the same overall length, but the Firth of Tay was more shallow, permitting the economical construction of multiple spans.
Construction began in 1871. The 6 year project was difficult and there were several accidents, causing the deaths of 20 workers. At the time of the opening of the Tay Bridge, on September 26, 1877, Thomas Bouch had completed the design for the companion Firth of Forth Bridge. For the deeper estuary, he proposed a dramatic and daring suspension bridge.
Most of the spans of the Tay Bridge were deck trusses, with trains travelling above the deep trusses. However, to provide clearance for the shipping channel, the 13 center spans were raised above the railway level so that trains ran inside them, a through truss arrangement or lattice tunnel.
On Sunday evening, December 28th, 1879, 2 years after the completion of the bridge, a severe gale struck the Firth of Tay. At about 7pm, with the violent windstorm still building, a mail train with 6 coaches containing 75 crew and passengers stopped at the south end of the bridge. The night watchman at the southern approached to the bridge gave a harrowing account of the events that transpired subsequently.
The watchman discussed the weather conditions with the engine driver, but the driver decided to risk the crossing. The train never reached the north end of the bridge.
the collapse oF the tay Bridge is one oF the most puBlished engineering disasters oF all time
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Tay Bridge, Scotland
dundee
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Firth oF tay
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scotlandnew–on–tay
Firth oF tay
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Fig 1 Left: Tay Bridge after the collapse
Fig 2Right: Old Tay Bridge next to the rehabilitated bridge
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12Ashtabula BridgeOhio, USA
Construction Started Bridge Opened Collapsed date Deaths Caused Engineer Reason for Failure Type of Failure Span of Bridge
18631865Dec 29th 187692William HoweSnow StormFatigue/Brittle Fracture21m
On December 29th, 1876, during a winter snowstorm, an iron railroad bridge collapsed st Ashtabula, Ohio, after 11 years of service. A train pulled by 2 locomotives was crossing the bridge, heading west. The first locomotive was almost across when the bridge began to fail. That locomotive barely made it safely to the west abutment, but the second locomotive and 11 cars fell 20 meters into Ashtabula Creek. The fall and the fires caused by the coal stoves in the cars caused over 80 deaths.
The most probable cause of the failure was fatigue and brittle fracture at a flaw in an iron
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casting. The Ashtabula Bridge was built between 1863 and 1865, using prestressing methods developed for timber Howe trusses. At the time, structural analysis was more an art than a science. Determining the capacity of slender compressive members was an unresolved issue. Standard design and material specifications did not exist. The concept of fatigue was not commonly understood.
For material scientists, the failure illustrated the unreliability of iron castings, 10 years later, specifications explicitly forbade the use of cast iron in any part of a bridge structure.
16Hackensack River Bascule Bridge
New Jersey, USAConstruction Started Bridge Opened Collapsed date Deaths Caused Engineer Reason for Failure Type of Failure Span of Bridge
19111927Dec 15th 1928-222ftMoving StructureDesign Deficiencies-
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On December 15th, 1928, the eastern leaf of a double leaf bascule bridge in Hackensack, New Jersey, fell while it was being lowered into place. The bridge was less than 2 years old. Design deficiencies, principally the failure to account properly for dynamic effects in the moving structure, were blamed for the failure.
The bridge was adequately designed for static loads, but it was actually an operating piece of machinery. The collapse was caused by dynamic distortions and oscillations involving friction and inertia. Large oscillatory motions and cyclic stress reversals, while the bridge was in motion, produced excessive stresses in the counterweight tower and progressive fracture. Failure to consider the bridge as a machine was directly responsible for the collapse.
20Tacoma Narrow Bridge
Washington, USAConstruction Started Bridge Opened Length/Span of Bridge Collapsed date Deaths Caused Engineer Reason for Failure Type of Failure
193819400.9 km (0.5 mi)Nov 7th 19400Leo MoisseiffWind-InducedUnpredictable
Tac
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One of the most spectacular failures in the history of engineering occurred on November 7th, 1940, when Tacoma Narrows Bridge over Puget Sound in Washington State collapsed due to wind-induced excitations. The 853 meter main span suspension bridge failed dramatically 4 months after completion in a wind of only 68 km/h (42 mi/h).
Built between 1938 and 1940, the Tacoma Narrows Bridge was opened to traffic on July 1st, 1940. At the time of construction, the 853 meter main span was the 3rd longest suspension bridges in existence. The span of the Golden Gate Bridge in San Francisco was 1280 meters and the George Washington Bridge span in New York was 1070 meters. The slender Tacoma Narrows Bridge presents a dramatic, graceful silhouette suspended from it’s 2 128 meter high towers. It was designed without stiffening trusses, for aesthetic reasons.
Failure occurred shortly before noon on November 7th 1940, when almost the entire suspension span was torn loose. The collapse was initiated at midspan when the stiffening girders buckled. The suspender cables failed and flew high into the air above the main cables, while larger sections of the deck fell progressively towards the towers. The 335 meter side spans remained intact, bending the towers backwards 4 meters under their pull.
No lives were lost in the collapse, there were only a few people on the bridge. Among these was F. B. Farquharson of the University of Washington, who had been conducting experiments on a model of the bridge. At the time of the collapse, he was on the main span taking motion pictures of the abnormal twisting motions.
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one oF the most
spectacular
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3rd lo
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est suspen
sion
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28Menai Straits Bridge
Anglesey, WalesConstruction Started Bridge Opened Collapsed date Deaths Caused Engineer Reason for Failure Type of FailureSpan of Bridge
1819182518260Thomas TelfordHurricaneUnpredictable0.4 km (0.2 mi)
Like Menai Straits, many lightweight suspension bridges have experienced failures. In 1826, 1 year after completion, Thomas Telford’s Menai Straits Bridge in eastern England was partially destroyed in a hurricane. The deck of the 170 meter long span had undergone vertical undulations before breaking. The Menai Straits Bridge was repaired and strengthened, but wind deformations continued to be large and unacceptable.
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Menai Straits Bridge, Wales
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34Silver BridgePoint Pleasant,
West Virginia, USA
Construction Started Bridge Opened Collapsed date Deaths Caused Engineer Reason for Failure Type of Failure Span of Bridge
-1929Dec 196744 (2 unfound)-Overloading, age, otherFracture of Eyebar0.5 km
The most tragic highway bridge collapse ever to occur in the United States was the December 1967 failure of the 40 year old suspension bridge over the Ohio River between Point Pleasure, West Virginia and Gallipolis, Ohio. Called the ‘Silver Bridge’ because of its silver paint, the bridge was not suspended from the wire cables that support modern suspension bridges, but from 2 chains made up of 15 meter long ‘eyebar’ links. The Silver Bridge was the first eyebar suspension bridge in the country in which the eyebars performed double duty as the top chords of the stiffening trusses in both the main and anchor spans. In addition, this bridge was the first to use high-strength, heat-treated carbon steel bars.
The Silver Bridge was 2 traffic lanes wide and had a total length of about 530 meters, including a main suspension span of 213 meters and 2 approach anchor spans of 116 meters each. Completed in 1929, the original bridge occurred Friday, December 15th, 1967, when the bridge was fully loaded with Christmas shopping traffic. All 3 of the spans and the 2 towers collapsed into the river. Of the 64 persons in the 31 vehicles that fell
with the bridge, 44 died and 2 were never found. There were 18 survivors, 9 of which were injured.
Early in the investigation, authorities focused on several potential contributing factors: overloading, age, fatigue and corrosion. The unique design of the bridge was also studied, as was the record of inspections performed by West Virginia’s highway department.
The final report was issued in April 1971 by the National Transportation Safety Board, 3 years after the failure. The reported concluded that the collapse was initiated by an eyebar failure. The eyebar fractured through development of a critical-size flaw, as a result of the combined effects of stress corrosion and corrosion fatigue.
the most tragic highway Bridge collapse that ever occurred in the united states
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Fig 6: Part of the side span of the collapsed Silver Bridge
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silver Bridge was
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42Cypress Street Viaduct
Oakland, California, USAConstruction Started Bridge Opened Collapsed date Deaths Caused Engineer Reason for Failure Type of Failure Span of Bridge
19561957October 17th 198963Frederickson & WatsonEarthquakeEngineering1.6 miles
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On October 17, 1989, the portion of the structure from 16th Street north all the way to the MacArthur Maze collapsed during the Loma Prieta earthquake, due to ground saturation and structural flaws.
When it was in use, the upper tier was used by southbound traffic, and the lower tier was used by northbound traffic. Some sections of the Cypress Street Viaduct were largely supported by two columns on either side, but some sections were only supported beneath by a single supporting column. The design was unable to survive the earthquake because the upper portions of the exterior columns were not tied by reinforcing to the lower columns, and the columns were not sufficiently ringed to prevent bursting.
At the time of its design, such structures were not analysed as a whole, and it appears that large structure motion contributed to the collapse. It was built on filled land, which is highly susceptible to soil liquefaction during an earthquake and exhibits larger ground motion.
After the earth stopped moving, local residents and workers began crawling into and climbing upon the shattered structure with the goal of rescuing those left alive. Many were saved; some only by amputation of trapped limbs. The collapse of the upper tier onto the lower tier resulted in 42 fatalities, two-thirds of the total quake death toll of 63.
The viaduct was torn down, Cypress Street was renamed (now known as Mandela Parkway, in honor of Nelson Mandela) with a landscaped median planted where the viaduct once stood. Before reconstruction occurred, the viaduct ended at the 8th Street exit on the southern end, with the two roadways going over 7th Street, while the southbound exit off the MacArthur Maze onto Cypress Street at 32nd Street remained open to local traffic on the northern end.
The Cypress Viaduct was demolished soon after the earthquake, but a replacement freeway was not substantially completed until July 1997, due to lawsuits by environmentalists and local residents.
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Fig 7
46San Francisco Oakland Bay Bridge
California, USAConstruction Started Bridge Opened Collapsed date Deaths Caused Engineer Reason for Failure Type of Failure Span of Bridge
July 8th 1933November 12th 1936October 27, 20090-Eyebar CrackEngineering8.4 mi
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The San Francisco, Oakland Bay Bridge, known locally as the Bay Bridge, is a pair of bridges spanning San Francisco Bay of California, USA. As part of the Interstate 80 and the direct road route between San Francisco and Oakland, it carries approximately 270,000 vehicles a day on its two decks. It has one of the longest spans in the world.
On October 27, 2009, during the evening commute, the steel crossbeam and two steel tie rods repaired over Labor Day weekend snapped off the Bay Bridge’s eastern span and fell to the upper deck. The cause may have been due to metal-on-metal vibration from bridge traffic and wind gusts of up to 55 miles per hour causing
failure of one rod which broke off, which then led to the metal section crashing down. Three vehicles were either struck by or hit the fallen debris, though there were no injuries.
On November 1, Caltrans announced that the bridge would probably stay closed at least through the morning commute of Monday, November 2, after repairs performed during the weekend failed a stress test on Sunday. The pieces which broke off on October 27 were a saddle, crossbars, and two tension rods.
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OaklandSan Francisco
California
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California
54MacArthur MazeOakland, California, USA
Construction Started Bridge Opened Collapsed date Deaths Caused Engineer Reason for Failure Type of Failure Span of Bridge
1933-April 27, 2007--Vehicle CrashEngineering500m (approx)
The Maze started as part of the construction of the Bay Bridge in the 1930’s. It was technically named the “Distribution Structure”, but owing to it’s size and complexity, was given the name “Maze” by the media and public.
During the October 17, 1989, Loma Prieta earthquake, which measured 7.1, the double-decked Cypress Street Viaduct on 1-880 between 1-80 and the 14th Street exit collapsed, crushing cars and killing 42 people. Traffic on the MacArthur Maze headed towards 1-880 was re-routed to 1-980, and ramps at both ends of the viaduct leading to the former Cypress Structure were signed for local traffic access to Cypress Street.
At 3.42am on the morning of Sunday, April 29, 2007, a tank truck carrying 8,600 gallons (32,500 liters) of unleaded petrol overturned on the connector from Interstate 80 west, from Berkeley, to Interstate 880 south. The intense heat from the subsequent fuel spill and fire weakened the steel structure of the roadway above, which served as the connecting ramp from Interstate 80 east, from San Francisci, to Interstate 580 east, to Oakland, collapsing approximately 168 feet (50m) of it onto the lower connector. The truck driver involved suffered second degree burns on his hands but was nonetheless able to walk 1.5 miles to a gas station, where he found a taxi and was givena ride to Oakland Kaiser Medical Centre. No other vehicles or persons were reported to be involved in the accident.
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The California Highway Patrol (CHP) initially reported that they suspect that the tanker had been speeding and bounced off a guard rail leading to the overturn.
The collapse of this bridge cut off the return route from San Francsico for many East Bay commuters. To help ease the expected traffic snarl, Caltrans set up temporary detours within the days following the incident, Bay Area Rapid Transit (BART) added additional capacity to lines serving areas that had been impacted by the accident, and on Monday April 30, all public transportation in the Bay Area was free, with the estimated cost of $2.5 million. Initial cost projections for rebuilding the 580 connector alone reached $10 million. However, due to the urgency to reopen such a vital highway link the project was expedited, and most demolition work and debris removal was completed by the Tuesday following the accident.
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60Mianus River Bridge
Connecticut, USAConstruction Started Bridge Opened Collapsed date Deaths Caused Engineer Reason for Failure Type of Failure Span of Bridge
19551958June 28th 19833-CorrosionMaintenance500m
The sudden collapse of a 30 meters long 3-lane section of the Connecticut Turnpike killed 3 people and injured 3 others on June 28th, 1983, The collapse occurred at 1.28am, causing 4 vehicles to plunge 20 meters onto the tidal flats and bank of the Mianus River. The adjacent 3-lane section remained intact. Timing of the incident was very fortunate, there could have been many more deaths if the accident occurred later in the day. This section of the Turnpike normally carries 100,000 vehicles per day.
5 days after the accident, drivers found a fragment from the hanger connection, a missing section of a pin that was fractured. The rest of the broken 180mm pin was still connected to the cantilevered end of the bridge. They were used to pass through
hangers and through the face of the steel girders.There was a heavy concentration of rust found behind the cap plate and the 350mm diameter washers. The corrosion would not have been directly visible to inspectors, but it was substantial enough to exert sufficient pressure to deform the cap plate visibly.
The significant amount of corrosion found in the hanger connection region caused investigators to look for a source of water responsible for it. They found that 10 years prior to the collapse, roadway drains had been paved over. This permitted water, deicing salts and other residue to flow through the joint between the cantilevered and suspended spans, dropping directly onto the hanger assembly.
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Fig 8
Failure of the Mianus River Bridge stimulated concerns for inspection and maintenance. In an emergency program, the Connecticut Department of Transportation repaired hundreds of bridges at a cost of $1.2 billion, with a budget 5 times greater than that available before the Mianus River Bridge failure. Cracks in hangers were discovered and repaired on the Yankee Doodle Bridge over the Norwalk River in Connecticut in 1984, a more redundant multiple-girder bridge. In Boston, 2 broken hangers were found in the Harvard Bridge over the Charles River as a result of the intense inspection activity immediately following the Mianus River Bridge collapse.
In particular, the Mianus River incident pointed out the vulnerability of pin-connected hung spans for bridges that lack redundancy. There are many bridges throughout the country that were built using similar pin-hanger connections. Such bridges were quickly identified and prioritised for retrofit projects to reduce their failure potential. Bridges having multiple girders are not as critical, since loss of one pin connection will not bring about a total collapse. In the case of the Mianus River Bridge, calculations easily established that the failure of only one pin or hanger was sufficient to bring down the entire section that collapsed.
Bridges revised after failure of the Mianus River Bridge
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The Silver Bridge (see pg31) collapse had earlier indicated the desirability for redundancy. Of course, the Mianus River Bridge was designed in 1955, with construction complete in 1958. This was a decade prior to the collapse of the Silver Bridge, so the lessons of the collapse were not available to the Mianus Bridge designers. However the lessons of nonredundancy are now part of standard bridge design procedure. Concerns for structural integrity attempt to eliminate the potential for catastrophic collapse due to failure of a simple member of connector. Creative details are being applied to retrofit existing bridges that are deficient in this respect. Retrofits to increase redundancy include adding beams and placing slings under existing pin hanger connections.
66Schoharie Creek Bridge
New York, USAConstruction Started Bridge Opened Collapsed date Deaths Caused Engineer Reason for Failure Type of Failure Span of Bridge
-1956April 5th 198710-ErosionMaintenance165m
On April 5th, 1987 a bridge on Interstate 90 in New York State collapsed into the storm swollen Schoharie Creek. 3 vehicles and a tractor trailer fell 24 meters into the creek, along with 90 meters of the 165 meter long bridge. 10 lives were lost in the failure.
The Schoharie Creek Bridge was 35 meters wide and carried 4 lanes of traffic, made of built up riveted plate girders supported by reinforced concrete piers on spread footings. The bridge was 31 years old at the time of its collapse. It was originally built in 1956 and rehabilitated in 1981.
The cause of the collapse of the Schoharie Creek bridge was scour of the footings at the base of the supporting piers. The Failure initiated with collapse of a single concrete pier into the fast moving creek. Because of the simply supported condition, 2 spans fell simultaneously with the pier, along with a car and truck occupying the spans. 3 more cars drove off the bridge into the raging creek, and within 90 minutes, a second pier and span collapsed.
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Fig 9
ConsTrucTioNFailures During
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ConsTrucTioNFailures During
72Quebec BridgeCanada
Construction StartedBridge Opened Collapsed date Deaths Caused Engineer Reason for Failure Type of Failure Span of Bridge
1902-Aug 1907 / Sept 191685Theodore CooperFell when being liftedDesign Deficiency2.5 km (1.5 mi)
The great Quebec Bridge over the St. Lawrence River was started in 1902, but it was 3 years before any steel of the main span was erected. The cantilever bridge, with a clear center span of 550 meters and 150 meters anchor spans, went far beyond any precendent for such structures. Modeled on the Firth of Forth Bridge, the main span of the Quebec Bridge was 30 meters longer, and the structure was much more economical, appearing even fragile in comparison with the massive Forth Bridge.
The bridge is very well known for 2 tragic failures associated with its construction. The first was a collapse of the main structure in August 1907, and the second was a fall of the center span as it was being lifted into place in September 1916. Together, these accidents killed 85 construction workers.
At the time of the first collapse, the south anchor and cantilever arms were complete and about one third of the suspended 206 meter truss span had been cantilevered out from the balanced arms.
At 5.15pm on August 29th, 1907, the entire structure suddenly collapsed. The subsequent investigation uncovered numerous design deficiencies. The Quebec Bridge was designed by Theodore Cooper, James Eads’ chief engineer at St. Louis, Missouri. The bridge was designed to be the world’s longest span bridge. However, at the time of construction, the aging design engineer stayed in New York, leaving construction supervision to others. Had he been closer to the site, his orders to halt construction may have been received in time to prevent the catastrophe.
The Royal Commission of Inquiry blamed the collapse on failure of the lower chords in the anchor arm near the main pier.
Right: The suspended span of the Quebec Bridge being lifted into position just before it fell.
the Bridge was designed to Be the world’s longest span Bridge
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Fig 10
76King Bridge Melbourne, Australia
Construction Started Bridge Opened Collapsed date Deaths Caused Engineer Reason for Failure Type of Failure Span of Bridge
1959196110th July 1962-Utah AustraliaBrittle fractureMaintenance49m
450 miles southwest of Sydney lies Melbourne, capital of the rival state of Victoria. Its River Yarra presents no serious barrier to communications. Even in the centre of the city the river is no more than 300 feet wide. The length of Melbourne’s longest bridge is determined not by the crossing but by the problem of grade separation. The proposal to build this bridge, now know as King’s Bridge, was referred to the Country Roads Board for investigation and report.
The Board invited tenders to design and build on the basis of an outline drawing, prepared by its engineers, which showed grades, clearances and other limited conditions within which the contractor was required to work. The specification laid down general requirements for design, such as loading and permissible stresses for various types of materials and standards which would have to be met for workmanship and properties of materials. Tenders for structures of reinforced concrete, prestressed concrete, mild steel, high-tensile steel, or light alloy would be considered.
The high-level bridge and its associated elevated roadway were opened to traffic on the 12th April 1961. Shortly after 11am on the 10th July 1962, a low loader and trailer, of unladen weight 17 tons, and carrying a load of about 28 tons, drove onto the bridge from the South Melbourne side. Its total weight of 45 tons was well below the specified maximum and considerably below the designed strength, but when it reached close to the southern end of the western half of the bridge, that span sank. Complete collapse was prevented only because the concrete deck had come to rest on vertical concrete walls, which had been built to enclose the space underneath. Four parallel girders, all approximately 100 feet in length, had collapsed, and subsequently examination revealed that all four had fractured approximately 16 feet from the southern end and three of them had fractures at a simliar position 16 feet from their northern ends. Every fracture had started at the toe of a transverse fillet weld at the end of a flange cover plate. The lower flange in each case was completely fractured and the crack extended up the web, in some instances through the upper flange. All evidence pointed to brittle fracture of the parent metal.
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Fig 11
80Murrow Floating Bridge
Seattle, WashingtonConstruction Started Bridge Opened Collapsed date Deaths Caused Engineer Reason for Failure Type of Failure Span of Bridge
-1940Dec 1958 / Jan 1960--FractureEngineering2 km
Each bridge, like each building, is a unique site specific project. Lessons learned from the performance of one type of structure may not be directly applicable to dissimilar structures. However, there is nearly always some value in studying cases where problems were encountered.
While under construction, the precast sectional floating bridge across Washington State’s Hood Canal experienced a set of mishaps between December 1958 and January 1960. The highway bridge, 1972 meters long, consisted of 23 concrete pontoons supporting an elevated roadway structure. Individual pontoons were 15 meters wide and 110 meters long. Pontoons were joined together with a steel transition hinged span at each shore to adjust for a 5.5 meter tidal range. Except for the 2 center pontoons, which could be retracted to provide a ship passageway, each unit was anchored with 2 550 tonne concrete blocks.
The pontoons with their sections of roadway were fabricated at a casting yard 35 miles from the bridge site. In December 1958, two pontoons sank in the channel leading from the precasting
yard. One unit containing a completed deck section became completely submerged. The other pontoon had only the columns constructed and sank on a 22 degree slope, with the columns projecting above water. The sunken pontoons, each representing an investment of $500,000 were salvaged by building walls from the steel panel forms attached to the sides into a floating cofferdam on the totally submerged unit by winch lifting from barges for the other unit. The sunken pontoons had to be salvaged or removed since they blocked the entrance to the dock where the fabrication yard was located. The cost of salvage was about 75% of the amounts already spent on the 2 units.
Cause of the sinking was discovered a year later when a third pontoon started to sink. It was found that wood blocks plugging holes at one end of the pontoon had worked loose and allowed water to flow into the internal compartments. The holes were near the water line and were used to hold anchor lines that strung the pontoons together into the floating bridge.
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In December 1959, two pontoons collided and the end wall of one was punctured by the projecting shear keys of the other. Repairs were necessary before the pontoons could be joined together. A storm the following month caught the bridge while the grout in the joints was not fully hardened, and deformations of the prestressed concrete bottom slabs and ordinary reinforced concrete top slabs became cracks. Strengthening of the design was then agreed upon, chiefly by adding 24 post-tensioned cables through the pontoons and by replacing the portland cement with a fast-setting epoxy in the joint fillers. The completed Hood Canal Bridge performed without significant problems until the winter of 1979, when half of the bridge was lost in a severe wind and rain storm.
In one of the most interesting and costly recent bridge construction accidents, the landmark Murrow Floating Bridge over Lake Washington, sank during a rehabilitant project, on November 25th 1990. This bridge opened to traffic in 1940. It was the world’s first floating concrete highway bridge.
world’s First Floating concrete highway Bridge
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Glossary
AbutmENt - the outermost end supports on a bridge, which carry the load from the deck
Arch bridgE - a curved structure that converts the downward force of its own weight, and of any weight pressing down on top of it, into an outward force along its sides and base
AquEduct - a bridge or channel for conveying water, usually over long distances
bASculE - a type of bridge with a pivoting section that is raised and lowered using counterweights.
brittlE - characteristic of a material that fails without warning; brittle materials do not stretch or shorten before failing
bucklE - to bend under compression
cANtilEvEr - a long projecting beam or girder fixed at only one end, used chiefly in bridge construction.
corbElS - a projection jutting out from a wall to support a structure.
EStuAry - the tidal mouth of a large river, where the tide meets the stream.
EyEbAr - a tension member, used especially in bridge and roof trusses, having the form of a metal bar enlarged at each end to include an eye.
flANgE - a projecting flat rim, collar, or rib on an object, serving to strengthen or attach or (on a wheel) to maintain position on a rail
girdEr - a large iron or steel beam or compound structure used for building bridges and the framework of large buildings.
locomotivE - a powered rail vehicle used for pulling trains.
oScillAtE - move or swing back and forth at a regular speed.
PoNtooN - A floating structure serving as a dock.
rAftErS - one of several internal beams extending from the eaves to the peak of a roof and constituting its framework.
rEhAbilitAtE - Restore to former privileges or reputation after a period of critical or official disfavor/failure.
SPAN - The extent or measure of space between two points or extremities.
StrutS - a rod or bar forming part of a framework and designed to resist compression.
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torSioN - an action that twists a material
truSS - a framework, typically consisting of rafters, posts, and struts.
viAduct - a long bridge like structure, typically a series of arches, carrying a road or railroad across a valley or other low ground.
Reference
bookS
Construction Failure
A span of Bridges, an illustrated history
Design and Construction Failures, lessons from forensic investigations
Failed Bridges: Case Studies, Causes and Consequences
WEbSitES
http://www.freewebs.com/silverbridgeaccident/thebridgecollapse.htmhttp://bit.ly/mhT4V9
http://failuremag.com/index.php/feature/article/the_tay_bridge_disaster/
http://cpsbethanyr.pbworks.com/w/page/7960034/My%20Disaster%20Topic%20on%20the%20Tay%20Bridge%20disasterhttp://bit.ly/awjaX0
http://en.wikipedia.org/wiki/Cypress_Street_Viaducthttp://bit.ly/ysr2I4
http://www.engineering.com/Library/ArticlesPage/tabid/85/articleType/ArticleView/articleId/73/Cypress-Street-Viaducts.aspxhttp://bit.ly/wpYXrz
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imAgES
Fig 1http://cpsbethanyr.pbworks.com/w/page/7960034/My%20Disaster%20Topic%20on%20the%20Tay%20Bridge%20disaster
Fig 2http://resources.jorum.ac.uk/xmlui/bitstream/handle/123456789/1039/Items/TAY_1_section14.html
Fig 3Tacoma Narrow BridgeConstruction Failure, pg 140
Fig 4http://www.enm.bris.ac.uk/anm/tacoma/tacoma.html
Fig 5http://www.enm.bris.ac.uk/anm/tacoma/tacoma.html
Fig 6http://www.freewebs.com/silverbridgeaccident/thebridgecollapse.htm
Fig 7Construction Failure, pg 37
Fig 8Construction Failure, pg 146
Fig 9http://laser.umkc.edu/~chen/research%20projects.html
Fig 10Construction Failure Pg
Fig 11Construction Failure, pg 98
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