Built to Endure

Specialized products and systems can help architects design buildings that can endure even the toughest disaster
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Sponsored by AMBICO Limited, Construction Specialties, Owens Corning®, and SAFTI FIRST Fire Rated Glazing Solutions
By Andrew A. Hunt

Learning Objectives:

  1. Define the different categories of hazards and the particular challenges they pose for buildings.
  2. Explain how the components of the building envelope contribute to a building’s durability and longevity, as well as its ability to withstand extreme events.
  3. Describe how assemblies and products are tested for fire resistance and what a product’s fire rating means.
  4. Discuss the difference between a resilient building and one that is designed to meet the building code’s hazard provisions.
  5. List examples of systems and products that can contribute to a building’s resilience.

Credits:

1.25 AIA LU/HSW
1 AIBD P-CE
0.1 IACET CEU*
AAA 1 Structured Learning Hour
AANB 1 Hour of Core Learning
AAPEI 1 Structured Learning Hour
SAA 1 Hour of Core Learning
MAA 1 Structured Learning Hour
NSAA 1 Hour of Core Learning
OAA 1 Learning Hour
NLAA 1 Hour of Core Learning
NWTAA 1 Structured Learning Hour
 
This course can be self-reported to the AIBC, as per their CE Guidelines.

Tornadoes. Hurricanes. Wildfires. Earthquakes. Almost every region in the country is vulnerable to at least one variety of natural hazard. And when one of these hazards manifests, we rely on our buildings to protect us.

Unfortunately, building designers must increasingly be aware of the risk of man-made disasters as well. These include foreign and domestic terrorist attacks as well as isolated acts of violence, such as mass shootings. These incidents are less predictable than natural disasters, although it’s fair to assume that high-occupancy buildings—schools, hospitals, and sports venues, for example—are likelier to be targets of a terrorist attack or mass shooting.

Zuckerberg San Francisco General Hospital, located on the San Andreas Fault Line

Photo courtesy of Construction Specialties

Located within the San Andreas Fault Line, the Zuckerberg San Francisco General Hospital was designed with a base-isolated foundation that allows it to move freely during an earthquake.

Hazards, whether natural or human-made, can exert extreme forces on buildings, from lateral and vertical movement, swift currents of water, and gusting wind, to extreme heat and high-velocity impacts. Within hazard-prone regions, the risk to individual buildings varies. For example, buildings on higher ground are less vulnerable to flooding than those in the floodplain, while buildings in flat, open areas are more exposed to wind than those in valleys or surrounded by other buildings or a lot of vegetation. Building age, construction, and configuration should also be considered. In general, buildings built to the standards of newer codes are better able to resist hazards than older buildings.

Some man-made disasters—bomb blasts and shootings, for example—impact buildings and their occupants differently than natural disasters such as hurricanes, and so require different approaches to reducing risk. Other hazards are more difficult to distinguish; for example, a wildfire or structure fire can be either man-made or “natural,” with similar results.

The Wild Card

Climate change is adding a layer of unpredictability to our understanding of natural hazards. Marked by record-breaking disasters, 2017 may be an indicator of the “new normal.” In quick succession, Hurricane Harvey inundated the Gulf Coast with rain, flooding Houston, our nation’s fourth most-populous city, followed by Hurricane Irma and Hurricane Maria, which destroyed Puerto Rico’s electricity grid and damaged more than 85 percent of the housing on the island of Dominica. In October, on the other side of the country, wildfires ripped through northern California, killing 42 people and destroying 5 percent of the housing stock in the town of Santa Rosa.

Regions unaccustomed to extreme cold, snow, and ice are experiencing severe winter storms, and regions known for cold winters are suffering heat waves. Coastal areas are enduring more frequent and intense tropical storms, and many parts of the country, not just the West, are witnessing more frequent and intense wildfires. Designers and building owners are tasked with the challenge of anticipating the hazards to which a building may be exposed over its lifetime, and the hazards faced in 30 years may be very different from the hazards faced today.

The Role of Buildings

We ask a lot of our buildings. Not only must they protect occupants during extreme events, they must withstand everyday stressors and forces, which include wind, rain, moisture, temperature fluctuations, and UV exposure. At the same time, code requirements (and our expectations) for energy performance have become more stringent. And of course, buildings must perform their programmatic functions and maintain their aesthetic integrity.

Building codes are one of the primary tools for ensuring buildings are designed and built so that they protect occupants from hazards. In fact, codes have often evolved in response to lessons learned from specific disasters. Tragic fires sparked requirements for fire-resistant construction, better access to exits, and fire sprinklers in certain categories of buildings, to name but a few examples. In other cases, jurisdictions that had no uniform code have adopted codes following major disasters. For example, the state of Florida had no uniform building code when Hurricane Andrew hit in 1992. Today, the Florida Building Code includes some of the country’s strictest provisions for mitigating the wind and coastal flooding hazards.

The lessons learned from natural disasters are encoded in the “hazard provisions” of model codes, which state and/or local jurisdictions can choose to adopt. However, it’s important to understand that the primary purpose of building codes is life safety—that is, to protect occupants long enough so that they can safely exit the building in the event of a disaster. Codes are not intended to explicitly protect the buildings themselves or ensure they may continue functioning after a disaster. More recently, performance-based codes and initiatives have been developed that include the goals of preserving the building and its functions along with occupant safety.

In general, current model building codes do not address specific man-made hazards, such as the threat of terrorist attacks or mass shootings. However, the Department of Defense (DoD) has published mandatory guidelines for mitigating the threat of terrorism for certain categories of DoD buildings under the Unified Facilities Criteria (UFC) 4-010-01: Antiterrorism Standards for Buildings, which can be used by the designers of other buildings as well.

Because fire is a deadly threat common to all buildings, it requires special attention. A good portion of the International Building Code (IBC) is dedicated to ensuring occupants are protected in the event of fire. Code provisions focus on building design and construction, with the goal of containing a fire (i.e., preventing it from spreading) while ensuring safe egress for occupants in every building type, from single-family homes to high-rise office buildings. This is the purpose of fire ratings for assemblies and doors—to ensure they can contain a fire for a certain period of time. For example, a 1-hour fire-rated door should be able to withstand a fire for at least 1 hour before failing. We will explore this concept further in a later section.

Now, let’s take a look at the common categories of natural and man-made hazards and typical mitigation strategies for each.

Building of fire- and hurricane-rated curtain walls

Photo courtesy of SAFTI FIRST Fire Rated Glazing Solutions

Ensuring buildings can withstand the challenges of an increasingly hostile environment includes protection from wind, rain, and wild fire. Improved building design technologies can include fire- and hurricane-rated curtain walls, as shown here, to provide additional protection from high-velocity wind events.

Designing For Specific Hazards

When we talk about hazard mitigation, we’re referring to strategies that minimize risk. Each hazard type poses specific challenges to buildings and requires specific mitigation strategies, though these sometimes overlap. Here is a brief overview of the major categories of hazards:

Water Inundation

This occurs any time water penetrates the building envelope, typically during a flood. Flooding occurs on the coast, along rivers, creeks, and other waterways, and in urban environments when stormwater systems are overwhelmed. Mitigation strategies include avoiding sites in the floodplain, elevating structures or critical equipment, dry floodproofing (preventing water from entering a building or portion thereof), and wet floodproofing, which allows water to enter the building but requires materials and finishes that can withstand prolonged contact with water.

Wind

High winds often are associated with storms such as hurricanes, tornadoes, and typhoons, but they can occur independently as well. Typical mitigation strategies include addressing weak points in the buildings so that they can resist the lateral and uplift forces; protecting windows and openings from potential impacts from wind-borne debris and/or specifying impact-resistant glazing and framing systems; strengthening the connections between structural components; and ensuring adequate connecting to the foundation. Safe rooms are also a form of mitigation.

Earth Movement

Though primarily associated with earthquakes, earth movement encompasses a variety of hazards, including landslides, tsunamis, and seiches (mini-tsunamis on inland lakes). Mitigation depends on the level of protection desired but usually involves strengthening the building structure and the connections between structural components, bracing nonstructural components so they do not break loose during an event, and designing expansion joints that allow a building to withstand both lateral and vertical movement.

Fire

Fire is a unique hazard in that it can potentially occur in any building. Fires can start in any type of structure in any location; they can be human-made or “natural.” Much of the building code requirements were developed to protect occupants from fire hazard, and mitigation strategies consider the building’s design, construction, materials, and more. Structures located in the wildland-urban interface (WUI) represent a special problem. Mitigation strategies in the WUI are more effective when adjacent properties implement them as well. Such strategies include creating a defensible space around the building; specifying noncombustible (or ignition-resistant) materials; protecting eaves and overhangs; and incorporating fire-suppression systems (interior or exterior sprinklers), alarms, and firestop walls.

Terrorist Attacks

Some of the weapons commonly used by terrorists include explosive devices, guns, and chemical or biological weapons. Explosions exert tremendous forces on a building, from the initial shock wave to the negative pressures that follow it. The impacts to buildings include structural damage, fire, and injuries caused by flying debris and high-velocity glass fragments. Mitigation strategies include prevention of the attack (through intelligence and early warning systems); delaying the attack with the creation of buffer zones; strengthening the building’s structural integrity; and addressing vulnerabilities in the building envelope, including windows and doors.

Secondary Hazards

It’s also important to understand that exposure to one hazard can leave a building more vulnerable to another hazard. For example, buildings at or near the bottom of a slope that recently experienced a fire may be exposed to flooding and mudslides should the fire be followed by heavy rains. Earthquakes often destroy gas and water lines, leaving buildings vulnerable to fires.

 

[ Page 1 of 4 ]      
Originally published in Architectural Record

Notice

Academies
Built to Endure
Buyer's Guide
Blast-Resistant Arched Transom Frame and Door Assembly
The Davis Barracks at West Point Military Academy required an ornate arched transom frame design that incorporated recessed paneled doors and transom panels. The entire assembly had to comply with Unified Facility Criteria (UFC) 4-010-01 standard for minimum antiterrorism door and frame assemblies. AMBICO’s ability to perform blast analysis for unique designs proved essential in the blast performance certification of this assembly.
AMBICO Limited
www.ambico.com
SSR/SSRW Seismic Floor Cover
CS’ SSR/SSRW seismic expansion joint cover is designed to handle everyday thermal movement as well as multidirectional movement that occurs during an earthquake. This virtually invisible floor cover accepts a variety of floor finishes to provide a seamless transition over expansion joints.
Construction Specialties
www.c-sgroup.com/ejc
Thermafiber® SAFB Formaldehyde-Free
Thermafiber® SAFB (Sound Attenuation Fire Blankets) Formaldehyde-Free mineral wool insulation is a solution for architects, specifiers, and contractors interested in achieving green building standards and using products that exclude red-list* materials like formaldehyde.
Owens Corning®
www.owenscorning.com
Clear, 2-Hour Fire Resistive Butt-Glazed Walls
SuperLite II-XLM 120 with GPX Architectural Series perimeter framing is the only clear, 2-hour fire resistive butt-glazed wall without vertical mullions or black spacers for truly transparent design. It meets ASTM E-119/UL 263 with hose stream and CPSC Category II, and it’s listed by UL and Intertek for interior and exterior applications.
SAFTI FIRST Fire Rated Glazing Solutions
www.safti.com/product/superlite-ii-xlm-120/