Coastal Construction Manual - National Ready Mixed Concrete ...

INVESTIGATING REGULATORY REQUIREMENTS 5
In certain cases and most coastal areas, however, the IRC
requires structural elements to be “designed in accordance
with accepted engineering practice.” For example, engineered
design of structural elements which fall outside the scope
of requirements in the IRC such as building systems of
excessive weight, elements of excessive length or height, or
products not specifically addressed in the IRC is required.
IRC Section R322.3.6 requires that construction documents
be prepared and sealed by a registered design professional,
and include documentation that the design and methods
of construction to be used meet the applicable criteria of
the IRC.
Buildings in regions of high wind, seismic, snow, and flood
hazards as well as building elements outside of the range
of limitations in the IRC require design beyond the IRC
prescriptive provisions as follows:
Wind. Buildings located where the basic wind speed
equals or exceeds 110 miles per hour or where the IRC
indicates special design for wind is required (wind speed
triggers for the hurricane-prone region are based on
mapped wind speeds in the 2012 IRC).
Seismic. Buildings located in Seismic Design
Category E.
NOTE
The 2012 IRC replaces the previous
basic wind speed map, Figure
R301.2(4), with three new figures.
Figure R301.2(4)A presents a new
map of basic wind speeds based
on the ASCE 7-10 wind map data
but converted to allowable-stress
design (ASD) levels.
Figure R301.2(4)B provides
shaded regions that indicate
where wind speeds equal or
exceed the scope of the IRC and
use of recognized standards for
wind design is required.
Figure R301.2(4)C indicates
where the openings of buildings
must be protected from windborne
debris in accordance with
ASTM E1996.
Wind speed maps and triggers in the
2012 IRC are on an ASD basis, while
wind speed maps and triggers in
ASCE 7-10 are on a strength basis.
Snow. Buildings in regions with ground snow loads greater than 70 pounds per square foot.
Flood. Buildings and structures constructed in whole or in part in coastal high hazard areas (including
Zone V).
In addition to provisions of the IBC, applicable standards specifically recognized as accepted engineering
practice for wind design within the IRC are: American Forest and Paper Association (AF&PA), Wood Frame
Construction Manual for One- and Two-Family Dwellings (AF&PA 2012); ICC 600, Standard for Residential
Construction in High-Wind Regions (ICC 2008a); ASCE 7-10, Minimum Design Loads for Buildings and
Other Structures (ASCE 2010); and American Iron and Steel Institute (AISI), Standard for Cold-Formed
Steel Framing—Prescriptive Method For One- and Two-Family Dwellings with Supplement 2 (AISI 2007). For
flood, ASCE 24-05, Flood Resistant Design and Construction (ASCE 2005), is specifically recognized within
the IRC as an alternative to the flood design provisions of the IRC.
Engineered design requirements within both the IRC and IBC recognize ASCE 7 as the standard reference
for minimum design loads due to hazards such as wind, flood, and seismic. As a result, within this
Manual, provisions of ASCE 7 are used extensively for determination of minimum loads in accordance
with engineered design requirements of the codes. For many portions of the Pacific, Great Lakes, and New
England coasts, construction will generally fall within the prescriptive limits of the 2012 IRC and not require
engineered design.
COASTAL CONSTRUCTION MANUAL
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