Point Pleasant Bridge Disaster
4A6 (1) Group 19
Daire McCormack
Natasha Brady
Peadar Barrett
Background and Purpose of Project
The Silver Bridge was constructed in 1928 and spanned the Ohio River between Point
Pleasant, West Virginia and Kanauga, Ohio. The bridge obtained its name as it was the first
painted aluminium bridge in the world. This was a busy commuting route and upon the
completion the bridge was described as ‘the railway to the south’. The bridge spanned
approximately 680m and consisted of two lanes measuring 6.7m and one footpath 1.5m in
width. Following the bridges completion in 1928 it underwent significant renovations in 1951
due to structural degradation and a change in ownership.
The bridge was constructed by the American Bridge Company and the West Virginia Ohio
Bridge Corporation and was not purchased by the state of West Virginia until 1941 for
$1,040,000. This purchasing fee also included a $70,000 contract for bridge repairs and
inspection. An inspection of the bridge carried out in 1951 was followed with a substantial list
of required repairs, including restoring the disintegrated concrete of the piers and waterproofing
the roadway of the anchorages, however several of these concerns were not addressed due to a
The bridge was inspected regularly, in accordance with the standards set out by
the American Society of Civil Engineers, in July 1955, November 1961 and April 1967.
lack of funding.
Structural Design
Silver Bridge was constructed with some unique and previously untested methods of
construction such as high tension eye-bar chains, a unique anchorage system, and
rocker towers. The bridge's eye-bars were linked together in pairs like a chain while a
large pin passed through the eye and linked each piece to the next. Each chain link
consisted of a pair of 2" x 12" bars and was connected by an 11" pin. The failure of one
of these bars would lead to massive amounts of stress being transferred to the
remaining bar.
The rocker towers allowed movement of the bridge due to live loads, vibrations and
expansion and contraction due to temperature changes. This movement was done by
placing a curved fitting next to a flat one at the bottom of the piers. The rocker was then
fitted with dowel rods to keep the structure from shifting horizontally.
An unusual anchorage was designed consisting of a reinforced concrete trough 60.96m
long and 10.36m wide filled with soil and reinforced concrete. The huge trough was
supported on 406 0.4m octagonal reinforced concrete piles in which the cable pull is
resisted by the weight of the anchorage and by sharing the halves of the piles. These
untested construction methods coupled with increased loading and inadequate funding
lead to the collapse of silver bridge and the causes of this collapse are discussed in detail
in the next section.
Collapse
At approximately 5pm, on December 15th 1967, The Silver Bridge collapsed into the Ohio
River below, taking a mere minute for the superstructure to fall completely into the river,
leaving only the piers behind. At the time of collapse, rush-hour traffic was crossing the
bridge, a total of 37 vehicles, of which 31 fell with the buckling bridge. Claiming 46 lives and
injuring 9, and destroying a major transportation route, which had connected West Virginia
and Ohio for 39 years previously.
Wreckage Analysis
An investigation, led by John Bennet, found that the collapse of the bridge was due to a defect in a
single link, eyebar 330 at joint C13N of the north eye-bar suspension chain in the Ohio side span. The
cause of failure is attributed to a cleavage fracture in the lower limb of the eyebar. The Bridge was
constructed of heat treated carbon steel, which is prone to cracking. The cleavage fracture was
caused by a minute crack in casting. When a crack in the eyebar reached critical depth of about 1/8
inch deep, it caused an unsupportable load to shift onto the other side of the eye, causing it to break
due to ductile overload. Unable to support the weight of the entire bridge, the north side chain also
snapped.
“A chain is only as strong as its weakest link”
Over the years two concepts known as Stress Corrosion Cracking and Corrosion Fatigue, allowed the
minute crack formed during casting to grow, rendering the collapse of The Silver Bridge inevitable.
Stress corrosion cracking is the unexpected failure of normally ductile metals subjected to a tensile
stress in a corrosive environment, especially at elevated temperature in the case of metals.
Corrosion fatigue is fatigue in a corrosive environment. It is the mechanical degradation of a material
under the joint action of corrosion and cyclic loading. When the bridge was designed in 1927, stress
corrosion cracking and corrosion fatigue were unknown, and the flaw could not have been detected,
even today, unless the bridge was completely disassembled and assessed.
Added to this, at the time of deign, the design loads were based on Model-T traffic. In 1928, the
average weight of a vehicle was no more than 680kg, which had tripled by 1967, far exceeding any
projected life span that could have been expected for the bridge. The bridge was simply not
designed to carry such heavy loads, coupled with old age, and lack of knowledge all contributed to
the collapse of The Point Pleasant Bridge.
Aftermath
In the aftermath of the Point Pleasant Bridge collapse, some very important developments occurred.
There were two other bridges built in a similar manner to the Point Pleasant Bridge that closed
immediately, one upstream of the Point Pleasant Bridge at St. Mary’s West Virginia and a longer
bridge at Florianopolis in Brazil. The bridge at St. Mary’s was destroyed with a controlled explosion in
1971 but the bridge at Florianopolis still stands today though it remains closed to traffic. The longer
bridge at Florianopolis is still most likely structurally sound as it was built to a higher factor of safety
than the Point Pleasant Bridge.
The collapse of the Point Pleasant Bridge highlighted the need to inspect older bridges to assess
their structural integrity. In the United States legislature was passed to ensure that older bridges
were regularly inspected and the National Bridge Inspection Standards (NBIS) was founded. These
standards required periodic inspection of all bridges in the USA.
Recommendations Made:
In the official highway accident report on the incident a number of recommendations were made by
the Highway Safety Board.
These were:
1. Identify Bridge building materials susceptible to slow flaw growth by any of the
suspected mechanisms.
2. Determine critical flaw size under various stress levels in bridge building materials.
3. Develop inspection equipment capable of detecting critical or near critical flaws in
standing bridge structures.
4. Devise analytical procedures to identify critical locations in bridge structures which
require detailed inspection.
5. Develop standards which incorporate appropriate safeguards in the design and
fabrication of future bridges to ensure protection against failure of material such as
occurred in the Point Pleasant Bridge.
6. Develop standards for the qualification of materials for future bridge structures
using the information disclosed in this investigation.
7. Devise techniques for repair, protection, or salvage of bridges damaged by internal
flaws.
8. Expand the knowledge of loading history and life expectancy of bridges.
References

NTSB Report Number: HAR-71-01
Collapse of U.S. Highway Bridge, Point Pleasant, West Virginia, December 15,
1967.
Found at http://www.ntsb.gov/publictn/1971/HAR7101.htm

www.wikipedia.org/silver_bridge_(bridge)

www.corrosion–doctors.org/Bridges/Silver-Bridge.htm

www.wvculture.org

http://Ref-raff.wikispaces.com