Fujita Tornado Intensity Scale: A Reassessment From Structural Engineering Perspective.
Fujita Tornado Intensity Scale: A Reassessment From
Structural Engineering Perspective.
Phan, L. T.; Simiu, E.
Design for Wind and Wind Hazard Mitigation, 2nd
U.S./Japan Workshop. Technical Memorandum of PWRI 3680.
Proceedings. May 24-26, 1999, Tsukuba Science City,
Japan, 123-130pp AND Wind Wind and Seismic Effects.
U.S./Japan Natural Resources Development Program (UJNR).
Joint Meeting, 31st. Technical Memorandum of PWRI 3653.
Proceedings. May 11-14, 1999, Tsukuba, Japan, 71-78 pp,
wind effects; building construction; weather effects;
meteorology; standards; structural engineering; wind
engineering; damage; tornadoes
On May 27, 1997 the town of Jarrell in central Texas,
and on May 30, 1998 the town of Spencer in South Dakota
were hit by two violent tornadoes. We evaluated the
structural damage caused by the Jarrell tornado and
concluded that the worst damage can be explained by wind
speeds corresponding to an F3 rating on the Fujita
tornado intensity scale (wind speeds of 71 m/s to 92
m/s). An F4 (93 m/s to 116 m/s) rating, or the F5 (117
m/s to 142 m/s) rating officially issued by the National
Weather Service (NWS), need not be assumed to explain
that damage. We also present assessments of damage in
the Spencer tornado, and suggest there is an
inconsistency between the NWS ratings of the Jarrell and
Spencer tornadoes. We ascribe the NWS ratings to the
failure of the Fujita scale to account explicitly for
the dependence of wind speeds causing specified types of
damage upon two structural engineering factors: (1) the
basic design wind speed at the geographical location of
interest, and (2) quality of construction, defined as
degree of conformity to applicable standards
requirements. We address the need for a stronger
involvement of the structural engineering profession in
nationwide efforts to develop an improved tornado
classification scale and a more realistic tornado