Coastal Construction Manual - National Ready Mixed Concrete ...

3 IDENTIFYING HAZARDS
3.3 Coastal Hazards
This section addresses coastal hazards of high wind, earthquakes,
tsunamis, and other hazards and environmental effects. Coastal
flooding and erosion hazards are discussed separately, in Sections
3.4 and 3.5, respectively.
3.3.1 High Winds
High winds can originate from a number of events. Tropical
storms, hurricanes, typhoons, other coastal storms, and tornadoes
generate the most significant coastal wind hazards.
The most current design wind speeds are given by the national
load standard, ASCE 7-10, Minimum Design Loads for Buildings
and Other Structures (ASCE 2010). Figure 3-7, taken from ASCE
NOTE
Basic wind speeds given by
ASCE 7-10, shown in Figure 3-7
of this Manual, correspond to a
wind with a recurrence interval
of 700 years for Risk Category
II buildings.
The 2012 IRC contains a
simplified table based on
ASCE 7-10, which can be used
to obtain an effective basic
wind speed for sites where
topographic wind effects are a
concern.
7-10, shows the geographic distribution of design wind speeds for the continental United States and Alaska,
and lists design wind speeds for Hawaii, Puerto Rico, Guam, American Samoa, and the Virgin Islands. The
Hawaii State Building Code includes detailed design wind speed maps for all four counties in Hawaii. They
are available online at http://hawaii.gov/dags/bcc/comments/wind-maps-for-state-building-code.
High winds are capable of imposing large lateral (horizontal) and
uplift (vertical) forces on buildings. Residential buildings can
suffer extensive wind damage when they are improperly designed
and constructed and when wind speeds exceed design levels (see
Figures 3-8 and 3-9). The effects of high winds on a building
depend on many factors, including:
Wind speed (sustained and gusts) and duration of high winds
Height of building above ground
Exposure or shielding of the building (by topography,
vegetation, or other buildings) relative to wind direction
Strength of the structural frame, connections, and envelope
(walls and roof)
NOTE
It is generally beyond the
scope of most building designs
to account for a direct strike by
a tornado (the ASCE 7-10 wind
map in Figure 3-7 excludes
tornado effects). However,
use of wind-resistant design
techniques will reduce damage
caused by a tornado passing
nearby.
Section 3.3.1.3 discusses
tornado effects.
Shape of building and building components
Number, size, location, and strength of openings (e.g., windows, doors, vents)
Presence and strength of shutters or opening protection
Type, quantity, and velocity of wind-borne debris
Even when wind speeds do not exceed design levels, such as during Hurricane Ike, residential buildings can
suffer extensive wind damage when they are improperly designed and constructed. The beach house shown
in Figure 3-10 experienced damage to its roof structure. The apartment building in Figure 3-11 experienced
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