Fatigue Failure - PowerPoint

							Fatigue Failure

  Case Studies
Tacoma Bridge

 Tacoma Narrows
   Washington
Tacoma Bridge
       • Built 1940
       • Failed 7th November
         1940
Tacoma Bridge
       • Designed to withstand
         winds of 120 mph.

       • Failed during a 42
         mph wind
Tacoma Bridge
       • Failure due to
         resonance
       • The natural frequency
         of the material
         occurred at wind
         speeds of 42 mph
Tacoma Bridge
       • A cable supported
         bridge is subject to
         wind induced drag
         (static), vibration and
         buffeting .
Tacoma Bridge
       • For modest span
         bridges, drag generally
         controls the strength
         required to resist wind
         forces.
Tacoma Bridge
       • Vibration becomes
         critical when the wind
         reaches a critical
         velocity that triggers a
         self-exited unstable
         condition.
Tacoma Bridge
       • Buffeting influences
         fatigue influences
         fatigue of the bridge
         materials
Silver bridge

  Ohio River
Silver Bridge
       • Built 1928
       • Eye-bar suspension
         bridge
       • Total length 2,345 feet
Silver bridge
       • The Silver Bridge
         was the first eye-
         bar suspension
         bridge of its type to
         be constructed in
         the United States.
Silver bridge
       • The bridge's eye-
         bars were linked
         together in pairs
         like a chain.
Silver bridge
       • A huge 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.
Silver Bridge
       • The bridge collapsed
         on 15th December
         1967.
Silver bridge
       • The cause of failure
         was attributed to a
         cleavage fracture in
         the lower limb of
         eye-bar 330 at joint
         C13N of the north
         eye-bar suspension
         chain in the Ohio
         side span
Silver bridge
       • The fracture was
         caused from a
         minute crack
         formed during the
         casting of the steel
         eye-bar
Silver bridge
        Over the years,
        stress corrosion and
        corrosion fatigue
        allowed the crack to
        grow, causing the
        failure of the entire
        structure.
Hyatt Regency hotel

     Kansas City
Hyatt Regency Hotel
          • Built in Kansas City,
            Missouri in 1978
          • A state of the art
            facility, this hotel
            boasted a 40 story
            hotel tower and
            conference facilities.
          • These two components
            were connected by an
            open concept atrium.
Hyatt Regency Hotel
          • Within this atrium,
            three suspended
            walkways connected
            the hotel and
            conference facilities
            on the second, third
            and fourth levels.
Hyatt Regency Hotel
          • Project began in 1976
          • Gillum-Colaco
            International Inc.
            (G.C.E. Inc.) were the
            consulting structural
            engineering firm.
Hyatt Regency Hotel
          • The proposed design
            for the walkway’s
Hyatt Regency Hotel
          • In the winter of 1978
            Havens Steel
            Company entered the
            contract to fabricate
            and erect the atrium
            steel for the project
            under the standards of
            the American Institute
            of Steel Construction
            for steel fabricators.
The proposed structure of these
  walkways was as follows:
                • Wide flange beams were
                  to be used on either side of
                  the walkway which was
                  hung from a box beam
                • A clip angle was welded
                  to the top of the box beam
                  which connected to the
                  flange beams with bolts
The proposed structure of these
  walkways was as follows:
                • One end of the
                  walkway was welded
                  to a fixed plate while
                  the other end was
                  supported by a sliding
                  bearing
The proposed structure of these
  walkways was as follows:
                • Each box beam of the
                  walkway was supported
                  by a washer and nut which
                  was threaded onto the
                  supporting rod Since the
                  bolt connection to the
                  wide flange had virtually
                  no moment, it was
                  modelled as a hinge.
Hyatt Regency Hotel
          • The fixed end of the
            walkway was also
            modelled as a hinge
            while the bearing end
            was modelled as a
            roller.
Hyatt Regency Hotel
          • Due to disputes
            between the G.C.E.
            and Havens, design
            changes from a single
            to a double hanger rod
            box beam connection
            were implemented.
Hyatt regency hotel
          • Havens did not want
            to have to thread the
            entire rod in order to
            install the washer and
            nut.
This revised design consisted of
         the following:
                • One end of each
                  support rod was
                  attached to the
                  atrium's roof cross
                  beams
This revised design consisted of
         the following:
                • The bottom end went
                  through the box beam
                  where a washer and
                  nut were threaded on
This revised design consisted of
         the following:
                • The second rod was
                  attached to the box
                  beam 4" from the first
                  rod - additional rods
                  suspended down to
                  support the second
                  level in a similar
                  manner
Failure
    • The design's failure
      was due to the
      addition of another rod
      in the actual design
      the load on the nut
      connecting the fourth
      floor segment was
      increased.
Failure
    • The original load for
      each hanger rod was to
      be 90 kN, but with the
      design alteration the
      load was increased to
      181 kN for the fourth
      floor box beam
Failure
    • Since the box beams
      were longitudinally
      welded, as proposed in
      the original design,
      they could not hold the
      weight of the two
      walkways
Failure
    • During the collapse,
      the box beam split and
      the support rod pulled
      through the box beam
      resulting in the fourth
      and second level
      walkways falling to
      the ground level.
Example of material failure.
Catastrophic storage tank failure
• October 2005 Antwerp.
• Tank D2; an atmospheric storage tank with a
  floating roof and ‘cone-up base, containing
  37,000m³ of crude oil failed.
• The tank was 54.5m dia. and 17m high
Section through base of tank
Tank contents
        • 40,000m³ = @251600
          bbl
        • July 07: Brent crude $75
          per bbl.
        • @ $18 million
        • 40,000m³ - assuming a
          density of 1,000 kg/m³ =
          168 kN/m²
        • = 0.168 N/ mm²
                Design details


• The base was designed as a cone-up base
• The purpose to allow the run off of any trapped
  moisture.
• Due to the poor ground conditions on which the
  tank was founded it is assumed a crease was formed
  in the tank base during the initial hydrostatic test.
                      Cont..


• On unloading the steel returned to its original shape
  and the crease went undetected.
• Originally constructed in 1971, the terminal
  changed ownership in 1990, again the damage went
  undetected.
• The crease formed what was effectively a gutter,
  trapping water.
                 Tank base

• The steel in the
  region of the crease
  began to corrode
  resulting in the base
  eventually splitting.
• Rupture in base
  @200mm wide and
  35m in length
                    Cont..
• The force of the escaping oil resulted in the
  sand base fluidising and the tank partially
  overturning.
• Upon inspection the remaining tanks were
  found to have identical defects.