Increased Resistance, Easier
Evacuation
WTC Investigation Leads to Building and Fire Code Changes
Future buildings, especially tall structures,
should be increasingly resistant to fire, more easily evacuated in
emergencies, and safer overall thanks to 23 major and far-reaching
building and fire code changes approved recently by the
International Code Council (ICC) based on recommendations from the
US Commerce Department’s National Institute of Standards and
Technology (NIST).
The recommendations were part of NIST’s
investigation of the collapses of
New York City’s World Trade Center (WTC)
towers. The changes, adopted at the ICC hearings held in September
in Minneapolis,
MN, will be incorporated into the
2009 edition of the ICC’s I-Codes.
The following are the model building and fire
code changes:
• An additional (third) exit stairway for
buildings more than 420 feet high;
• An increase of 50 percent in the width of
exit stairways in new sprinklered buildings;
• Permitting the use of elevators for
occupant evacuation in fires and other emergencies for all
buildings, and as an alternative to the required additional exit
stairway for buildings more than 420 feet high. Passenger elevators
must meet specific criteria to be used for evacuation purposes;
• Hardening of exit stairway and passage way
enclosures, and elevator shaft enclosures, in building — all
buildings more than 420 feet high, for buildings 75-420 feet high
where failure of the enclosure would substantially jeopardize human
life, and in essential facilities such as hospitals;
• Separating exit stairway enclosures by a
distance not less than 30 feet or not less than one-fourth of the
maximum building diagonal, whichever is less. For example, a
building with a 50-foot by 50-foot floor plan would have a diagonal
of about 70 feet. One-fourth of 70 is 17.5 feet, which would be the
minimum distance required between exits (since it is less than 30
feet);
• A minimum of one fire service access elevator
for buildings more than 120 feet high;
• Fire service access elevator lobby sizes
that are a minimum of 150 square feet in area with sides at least 8
feet long;
• Keeping fire service access elevator
lobbies free of storage;
.
• Greater reliability of sprinklers with a minimum of two water
supply risers for each sprinkler zone in buildings more than 420
feet high. Each riser is required to supply sprinklers on alternate
floors and will be placed in remotely located stair enclosures;
.
• Providing minimum structural integrity for framed and bearing wall
structures;
.
• A one-hour increase in the fire-resistance
rating of
structural components and assemblies in buildings more than 420 feet
high;
- Explicit adoption of the ‘structural frame’ approach to fire
resistance ratings that requires all members of the primary
structural frame to have the higher fire resistance rating
commonly required for columns. The primary structural frame
includes the columns; other structural members including the
girders, beams, trusses and spandrels having direct connections
to the columns; and bracing members designed to carry gravity
loads;
- Broadening the definition of the primary structural frame to
include bracing members essential to vertical stability (such as
floor systems or cross bracing) whether or not they carry
gravity loads;
- Increasing bond strength for fireproofing to nearly
three times greater than currently required for buildings
75-420 feet high and seven times greater for buildings more
than 420 feet high.
- Field installation requirements for fireproofing to
ensure that:
- Installation complies with the manufacturer’s instructions;
- The substrates (surfaces being fireproofed)are clean and
free of any condition that prevents adhesion;
- Testing is conducted to demonstrate that required adhesion
is maintained for primed, painted or encapsulated steel
surfaces; and
- The finished condition of the installed fireproofing, upon
complete drying or curing, does not exhibit cracks, voids,
spalls, delamination or any exposure of the substrate.
Special field inspections of fireproofing to
ensure that its as-installed thickness, density and bond strength
meet specified requirements and that a bonding agent is applied when
the bond strength is less than required due to the effect of a
primed, painted or encapsulated steel surface. The inspections are
to be performed after the rough installation of mechanical,
electrical, plumbing, sprinkler and ceiling systems.
Luminous markings delineating the
exit path (including vertical exit enclosures and passageways) in
buildings more than 75 feet high to facilitate rapid egress and full
building evacuation. Broadening the use of luminous markings to
identify obstacles, exit doors, exit signs and floor numbers in the
exit path in buildings more than 75 feet high.
Luminous exit path markings in
existing buildings more than 75 feet high with the exception of
open, unenclosed stairs in historic buildings. Increasing the area
of the Fire Command Center (the area from which all fire department
operations are directed and usually housing the control panel for
alarms, sprinklers, etc.) from 96 square feet to 200 square feet
with at least one side 10 feet long in buildings more than 75 feet
high.
Approved radio coverage for all
buildings for emergency responders within the building based upon
the existing coverage level of public safety communications systems
at the exterior of the building. Approved coverage includes specific
requirements for signal strength, system design, installation and
maintenance.
Installing an emergency responder
radio communications system to provide the required level of radio
coverage throughout a building. Typical hardwired communications
systems would be replaced.
The following are nine model
building and fire code change proposals consistent with the NIST WTC
investigation recommendations that were not approved for the 2009
edition of the I-Codes but will be considered for resubmission at a
later date after being amended:
1. Requiring buildings more than
420 feet high to be designed to survive a building contents fire to
burnout without more than local failure of the structural frame.
2. Requiring structures not to
suffer a collapse disproportionate to a local initiating failure
caused by an accident or incident.
3. Requiring a risk assessment
and acceptable mitigation of risks for buildings more than 420 feet
high with an occupant load greater than 5,000; for buildings with an
occupant load greater than 10,000; and for buildings determined to
be at higher than normal risk.
4. Requiring use of a new
standard for conducting wind tunnel testing.
5. Requiring installation of
stairway communication and monitoring system at every fifth floor of
each exit stairway.
Also requiring, in buildings more
than 75 feet high, a video surveillance system in each exit
stairway, elevator lobby, elevator hoist way and elevator machine
room to enhance situational awareness of emergency responders.
6. Requiring fire safety and
evacuation plans for all occupancies and buildings where required by
the International Fire Code (the International Building Code is more
widely adopted across the country than the IFC; this would ensure
all situations are covered).
7. Requiring detailed schematic
building plans, including an approved Building Information Card, to
be located in fire command centers to show the type of construction,
stairway access and pressurization, fuel oil tank and hazardous
materials locations, standpipe availability and locations, in
addition to typical floor plan and details of the building core,
means of egress, elevator locations, fire protection systems,
firefighting equipment and fire department access.
8. Limiting the length of
horizontal transfer corridors used to connect a stairwell to 50 feet
or less in buildings more than 75 feet high.
9. Allowing the option to design
buildings more than 420 feet high using the ICC Performance Code,
instead of the highrise provisions of the International Building
Code. This change would allow the performance-based NIST WTC
recommendations to be considered in a holistic manner.
FSM
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