Two other considerations for high-rise fire
safety include exterior wall assemblies and
performance-based fire resistance. Exterior
wall assemblies that include combustible materials
are another fire protection issue that is being
discussed in the media and fire safety community.
These exterior wall assemblies are popular as they
provide the opportunity to make a building iconic
and aesthetically pleasing. Additionally, these
assemblies improve energy efficiency and reduce
water and air infiltration.

Even with these benefits, they have their
shortcomings. In recent years, significant damage
has resulted from rapid and extensive fire spread
over the length of the building's facade either
externally or internally through the insulation
cavity. The investigations into the cause of these
fires have revealed that wall assemblies that contain
combustible materials were a contributing factor to
the rapid fire spread in these incidents.

For example, media reports and social media videos
of tall building fires in the United Arab Emirates
(UAE) as recently as March 2016 at the Ajman One
Tower and on New Year's Eve (2015) at the Address
Downtown Dubai Hotel have shown the world how
fire can quickly spread up multiple levels of a high-
rise building that has exterior wall assemblies
containing combustible materials.

Examples of exterior wall assemblies that contain
combustible materials include exterior insulation
finish systems (EIFS), metal composite material
(MCM) claddings, high-pressure laminates, foam
plastic in cavity walls, and water-resistive barriers
(WRB). In regards to fire safety, the combustibility of
the assembly's components impacts its fire hazard.
For example, the foam insulation that is part of EIFS
and MCM assemblies is combustible and
propagates rapid flame spread when exposed to fire.




Common fire spread scenarios include fire spread
up a wall, either via the outside surface or through
concealed spaces within the wall. Additionally, in
the fire events cited earlier, fire spread into the
interior floor areas was controlled by the sprinklers
that were installed in the interior of the building.
However, the sprinklers could not control the fire
from spreading up the building's exterior.

Currently, there are several test standards that
evaluate exterior, non-load-bearing wall assemblies
that include combustible components. In the
United States, the most prevalent test method is
outlined in NFPA 285, Standard Fire Test Method
for Evaluation of Fire Propagation Characteristics of
Exterior Non-Load-Bearing Wall Assemblies
Containing Combustible Components. Other
standards are available in Canada (CAN/ULC S-
134), United Kingdom (BS 8414) and internationally
(ISO 13785).

Moving forward, complying with one of the
applicable test standards is an important step in
reducing the risk that an exterior fire will spread up
multiple levels in a tall building. At the same time,
passing a test procedure does not preclude
designers and engineers from taking other steps to
ensure that adequate life safety is provided
throughout a tall building.

Performance-Based Fire Resistance

The consequences of partial or global collapse of tall
buildings due to a severe fire pose a significant risk
to occupants and the fire service. Tall buildings
often have unique design features whose role in the
structure and fire response are not easily
understood using traditional fire protection
methods. These unique factors may warrant a need
to adopt an advanced structural fire
engineering analysis to demonstrate that the
building's performance objectives are met.
Performance - based design of structural fire
resistance entails three steps: (1) determination of
the thermal boundary conditions to a structure
resulting from a fire; (2) calculation of the thermal
response of the structure to the fire exposure, and
(3) determination of the structural response of the
structure. Guidance on performing this type of
analysis can be found in the SFPE Engineering
Standard on Calculating Fire Exposures to
Structures, and SFPE Engineering Standard on
Calculation Methods to Predict the Thermal
Performance of Structural and Fire Resistive
Assemblies.

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