Marr (1996) compiled the information on ice storms from Storm Data in a database. Storm
Data's predecessors, Monthly Weather Review (19211949), The Report of the Chief of the Weather
Bureau (19291935), U.S. Meteorological Yearbook (19361949), and Climatological Data, National
Summary (19501959) also included storm information. Tattelman and Gringorten's table of extreme
ice loads (Fig. 6) are given as maximum ice thicknesses, rather than the equivalent uniform thick-
ness, in each of seven regions of the country for return periods ranging from 50 to 300 years.
All this information was
reviewed by the Ice Load Task Committee for ASCE 7 when it was formed in 1993 to develop a
standard for ice loads for ice-sensitive structures, which include overhead lines and communi-
cation towers. In the 1995 revision of ASCE 7 the committee chose to include the ice-load map
from ASCE 74. For the 1998 revision of the standard we developed a new ice-load map for
freezing rain. The draft of ASCE 7-98 is currently in the committee balloting process. After revi-
sions are made in response to the balloting the draft will go out for public ballot and will finally
be published at the end of this year. The data, models, and extreme value analysis that were used
in developing the map in the draft of ASCE 7-98 are described
briefly in Sections 4 and 7.
Figure 6. Maximum ice thicknesses (cm) for return periods from 2 to 100 years at
representative points (AVG) and at the most severe location (MAX) in each of seven
regions of the United States. (From Tattelman and Gringorten 1973.)
6
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