Chapter 12 Special Structures and Design Features

What is a central core floor plan in the context of high-rise buildings?

A central core floor plan is a design where building services such as elevators, stairwells, and service shafts are grouped in the center of the floor.

What approach was commonly used for smoke control in high-rise buildings constructed before the development of air conditioning systems?

A common approach using the mechanical equipment was called a "pressure sandwich" concept.

What does a fire command center in a high-rise building usually include?

A fire command center includes emergency voice alarm system control panels, fire department two-way telephone system panel, fire detection and fire alarm system annunciator panel, elevator location and status panel, sprinkler valve and waterflow annunciator, emergency and standby power status indicators and controls, central/status panel for smoke management systems, controls for unlocking stairway doors, fire pump status indicators, and a telephone for fire department use with access to the public telephone system.

What happened during the Meridian Plaza Fire in 1991?

A fire occurred in the 38-story Meridian Plaza office building in Philadelphia, heavily damaging the building and resulting in the deaths of three firefighters.

What is a limitation of air-supported structures?

A limitation of air-supported structures is that they cannot be used in situations where fire-rated construction is required.

What is a membrane structure?

A membrane structure is a building having its exterior skin consist of a thin "waterproof" fabric.

What are membrane structures?

A membrane structure is a building having its exterior skin consist of a thin "waterproof" fabric. Membrane structures come in various forms including air-inflated, air-supported, membrane-covered cable, and membrane- covered frame.

What construction feature often contains stairwells and elevator shafts in modern high-rise buildings?

A reinforced concrete core often contains stairwells and elevator shafts in modern high-rise buildings.

How can the shape of an air-inflated structure be compromised?

Air-inflated and air-supported structures are sometimes vulnerable to high winds and, in some cases, have been blown down in a high wind.

How are air-supported and air-inflated structures vulnerable to high winds?

Air-supported and air-inflated structures are sometimes vulnerable to high winds and, in some cases, have been blown down in a high wind. Therefore, when exterior winds increase, the interior pressure is increased.

What do all model building codes require in high-rise buildings?

All model building codes require smokeproof exit enclosures in all stairs serving floors 75 feet or higher.

What supports an air-inflated structure?

An air-inflated structure is held up by an air machine that keeps a constant supply of air in the structure.

What is an underground building according to some codes?

An underground building is defined by some codes as one in which the lowest level used for human occupancy is 30 feet (10 m) below the main exit that serves that level.

What is the definition of an underground building as per some codes?

An underground building is defined by some codes as one in which the lowest level used for human occupancy is 30 feet (10 m) below the main exit that serves that level.

What are the dependencies as building height increases?

As building height increases, occupant safety and firefighting become increasingly dependent on the features of the building itself.

How are fire alarm systems in high-rise buildings typically more complex?

Because of the complex nature of a high-rise, the fire alarm systems used in them are more complex and provide more functions than fire alarms used in low-rise buildings.

What needs to be established before windows are broken or any debris is released from an upper floor?

Before windows are broken or any debris is released from an upper floor, an all-clear needs to be established.

What does breaking windows on the upper floors of a building require?

Breaking windows on the upper floors of a building requires careful coordination.

How were buildings constructed 75 or 80 years ago ventilated?

Buildings constructed 75 or 80 years ago were ventilated simply by opening windows.

What is a constant requirement when it comes to work practices?

Constant emphasis on safe practices is a must.

Why can't firefighters open the roof for ventilation in an air-inflated or air-supported building?

Conventional ventilation of an air-inflated or air-supported building is not possible because firefighters simply cannot open the roof.

Why are the HVAC systems in high-rise buildings designed to manage the products of combustion?

Despite the requirement for shaft enclosures, some upward migration of smoke is possible at stairwell doors, utility and elevator shafts, and inadequately protected floor penetrations. For this reason, the HVAC systems in high-rise buildings are designed to provide for the management of products of combustion.

What are some difficulties firefighters face in underground facilities?

Difficulties include access to the structure, rescue and evacuation of occupants, ventilation of heat and smoke, and water supply and drainage of water from flooding or firefighting operations.

Who needs to be aware of what crews are doing at all times?

Division commanders and company officers need to be aware of what crews are doing at all times.

What safety measure must be taken during emergency elevator use in a fire situation?

Do not use an elevator to travel to the fire floor — stay below the fire floor according to SOPs.

What was the fire protection typically provided by in buildings constructed 75 or 80 years ago?

Fire protection was usually provided only by standpipe systems.

What should firefighters be aware of when using an elevator during a fire?

Firefighters should be aware that power may fail at any time during a fire.

What conditions should prompt firefighters to avoid using an elevator?

Firefighters should never use a fire- or heat-damaged elevator, or an elevator that has been exposed to water.

What is a high-rise building from a fire protection standpoint?

From a fire protection standpoint, a high-rise building is any building that is beyond the effective reach of fire equipment located at the street level.

What was the main lesson learned from the Meridian Plaza fire in 1991?

Had the pressure-reducing valves on the standpipe system been properly adjusted at the time of installation and the integrity of the building's electrical system been provided, it is likely that the fire could have been controlled through manual fire suppression efforts.

What are the two developments that made high-rise buildings possible and practical at the end of the 19th century?

High-rise buildings were made possible (and practical) by two developments: steel-frame construction and the elevator.

What happens to an air-supported structure when the power is lost?

If power is lost the roof of an air-supported structure may eventually collapse.

What changes occur to elevator operations during Phase II?

In Phase II, the floor-select buttons within the car remain operable but the floor-call buttons on the individual floors are inoperable. The elevator doors do not open automatically, and the operator must push the "Door Open" button in the car. The electric eye safety is disabled during Phase II operations.

How does an air-supported structure maintain its shape?

In an air-supported structure, the roof is made of a vinyl-coated polyester fabric material. It is held up by an air machine that keeps a constant supply of air in the structure. The pressure required is a small fraction of atmospheric pressure on the order of 0.35 psi.

What type of material are floors typically made of in a steel-frame high-rise building?

In steel-frame buildings, the floors will be lightweight structural concrete placed over corrugated steel.

What significant events occurred in the construction of high-rise buildings in the 1920s and 1930s?

In the 1920's and 1930's several buildings were constructed exceeding 40 stories (New York's Empire State building, which has 102 stories, was constructed in 1930).

What do many modern high-rise buildings have in terms of fire alarm systems?

Many modern high-rise buildings have voice alarm systems that automatically sound an alert tone followed by voice instructions on actuation of any detector, waterflow device, or manual pull station.

What kind of alarm systems are typically used in high-rise buildings?

Many modern high-rise buildings have voice alarm systems that automatically sound an alert tone followed by voice instructions.

What forms can membrane structures take?

Membrane structures come in various forms including air-inflated, air-supported, membrane-covered cable, and membrane- covered frame.

What are some forms of membrane structures?

Membrane structures come in various forms including air-inflated, air-supported, membrane-covered cable, and membrane-covered frame.

How do model building codes define a high-rise building?

Model building codes define a high-rise building as a building more than 75 feet (25 m) in height.

What does model building code require for the structural frame of a high-rise building?

Model building codes require 2- or 3-hour fire resistance for the structural frame of a high-rise building.

What does NFPA® 14, Installation of Standpipe and Hose Systems, require?

NFPA® 14, Installation of Standpipe and Hose Systems, requires pressure-regulating devices to be installed at hose connections when the static pressure at a 1½-inch (38 mm) hose connection exceeds 100 psi (700 kPa) or when the static pressure exceeds 175 psi (1 225 kPa) at larger outlets.

How does a newer air-supported structure respond to changing atmospheric conditions?

Newer air-supported structures have computer-controlled fans to automatically adjust to changing atmospheric conditions.

Can firefighters use conventional ventilation in an air-inflated or air-supported building?

No, conventional ventilation of an air-inflated or air-supported building is not possible because firefighters simply cannot open the roof.

Does the requirement for recall apply to freight elevators?

No, the requirement for recall does not apply to freight elevators.

What does one model building code also require in the fire command center?

One model building code also requires a worktable and a set of building plans.

What is typically required in the fire command center in addition to the panels and systems controls?

One model building code also requires a worktable and a set of building plans.

What's one problem with standpipe systems in high-rise buildings?

One problem with standpipe systems is the variation of pressure with building height (hydrostatic pressure).

What is one unavoidable problem with standpipe systems?

One unavoidable problem with standpipe systems is the variation of pressure with building height (hydrostatic pressure).

What happens during Phase I operations when an alarm originates from the lobby?

Phase I operation causes the cars to return nonstop to the lobby or other designated level if the alarm originated from the lobby.

What is the purpose of Phase I operations?

Phase I operation is designed to prevent the deaths of civilians who may find themselves in an elevator that is called to the fire floor.

What is the purpose of the Phase I operations?

Phase I operation is designed to prevent the deaths of civilians who may find themselves in an elevator that is called to the fire floor.

What does Phase I operation do when the car reaches the recall floor?

Phase I operation opens the car doors and keeps them open when the car reaches the recall floor.

What is Phase I operations in the context of high-rise fires?

Phase I operations involve the recall of all passenger elevators with vertical travel greater than 25 feet in the event of fire.

What is the meaning of Phase I operations in the context of high-rise building emergencies?

Phase I operations refers to the mandatory provisions for the recall of all passenger elevators with vertical travel greater than 25 feet (8.3 m) in the event of fire.

What is Phase II operations in the context of high-rise fires?

Phase II elevator operation is designed to permit firefighters to use the elevators after they arrive on the scene by overriding the recall feature.

What is the meaning of Phase II operations in the context of high-rise building emergencies?

Phase II elevator operation is designed to permit firefighters to use the elevators after they arrive on the scene by overriding the recall feature.

How often does significant structural failure occur in high-rise buildings?

Significant structural failure in high-rise buildings is extremely rare.

How are smoke control systems typically designed in modern high-rise buildings?

Smoke control systems exhaust the floor of fire origin and pressurize the floors immediately above and below to contain the smoke to the floor of origin.

What are smoke control systems?

Smoke control systems utilize the building's mechanical air handling system to accomplish smoke removal.

Where are smoke detectors usually provided in high-rise buildings?

Smoke detectors are usually provided in elevator machine rooms and elevator lobbies to initiate elevator recall.

What is required for buildings with levels more than 30 feet (10 m) below the level of exit discharge?

Smokeproof enclosures are now required for buildings with levels more than 30 feet (10 m) below the level of exit discharge.

What are the specific difficulties that firefighters face during emergencies in underground facilities?

Specific difficulties include Access to the structure, Rescue and evacuation of occupants, Ventilation of heat and smoke, Water supply and drainage of water from flooding or firefighting operations.

What is the "pressure sandwich" concept in smoke control systems?

The "pressure sandwich" concept exhausts the floor of fire origin and pressurizes the floors immediately above and below to contain the smoke to the floor of origin.

What triggers Phase I operations?

The automatic recall of elevators to their terminal floor or an alternate floor can be caused by the activation of smoke detectors or sprinkler waterflow alarms. Phase I can also be activated manually by a keyed switch in the terminal floor lobby.

What are the requirements of codes for underground buildings?

The codes require automatic sprinkler protection for underground buildings, even if a portion of the building extends above the ground and the aboveground portion of the building does not require sprinkler protection. To address the problem of ventilation of smoke and heat, model codes often require a smoke exhaust system.

What is disabled during Phase II operations?

The electric eye safety, which prevents the doors from closing if there is a person or smoke in the doorway, is disabled during Phase II operations.

Why is the electric eye safety disabled during Phase II operations?

The electric eye safety, which prevents the doors from closing if there is a person or smoke in the doorway, is disabled during Phase II operations. This is done so the car doors can be closed, and the car moved if it inadvertently stops at a smoke-filled floor.

What is a shunt trip in the context of elevators?

The elevator code requires a shunt trip where the elevator hoist way or elevator room is protected by automatic sprinklers. This arrangement will shut down the power to the elevator before a sprinkler discharges water on the elevator equipment.

What is the emergency stop button's state in Phase II?

The emergency stop button that was inoperable in Phase I should be operable during Phase II.

What was the cause of the Meridian Plaza fire in 1991?

The fire began on the 22nd floor of the building.

What was the cause of the fire spread in the Meridian Plaza fire?

The fire spread down to the 21st floor via convenience stairs and continued up to the 30th floor.

How does fire-resistive construction provide barriers to the vertical extension of fire and smoke in high-rise buildings?

The fire-resistive construction of high-rise buildings provides a certain degree of inherent compartmentalization.

What determines the height at which a building becomes a high-rise?

The height at which a building becomes a high-rise by definition varies from jurisdiction to jurisdiction.

How is the height of a high-rise building measured?

The height is measured from the lowest level of emergency vehicle access to the floor of the highest occupied story.

Where is the location of the fire command center in a high-rise building typically required to be?

The location of the space must be approved by the fire department and many jurisdictions require that the room be accessed directly through an exterior door.

What are the requirements for a room or area in a high-rise building to serve as a fire command center?

The location of the space must be approved by the fire department and often, an enclosed room separated from the remainder of the building by 1-hour fire- rated construction is required. Many jurisdictions require that the room be accessed directly through an exterior door.

What is typically the maximum available fire-resistant protection for underground facilities?

The maximum available fire-resistant protection is typically four hours.

What type of material might the membrane of an air-supported structure be made from?

The membrane used in either an air-inflated or air-supported structure may be a limited-combustible or noncombustible material.

What are the characteristics of the membrane used in an air-inflated or air-supported structure?

The membrane used in either an air-inflated or air-supported structure may be a limited-combustible or noncombustible material. If the material is limited-combustible, it is required to have a low flame spread and low smoke propagation.

Where is the fire command center located in a high-rise building?

The model building codes require a room or area in a high-rise building to serve as a fire command center. The location of the space must be approved by the fire department.

What are the fire alarm systems in high-rise buildings required by?

The model building, and fire codes require fire alarm systems in high-rise buildings.

Which elevators are not required to be recalled in the event of a fire?

The requirement for recall does not apply to freight elevators.

How is the shape of an air-supported structure maintained?

The shape of an air-supported structure is maintained by interior pressure being greater than the exterior pressure.

Where are the sprinkler and standpipe systems typically supplied from in a high-rise building?

The sprinkler and standpipe systems are typically supplied from the same vertical riser.

What do sprinkler systems in high-rise buildings have for individual floor control?

The sprinkler system in a high-rise building will be provided with individual floor control valves.

Where are standpipe risers and hose valves located within a high-rise building?

The standpipe risers and hose valves are located within the stairwells.

What are some features of the structural system of an underground facility?

The structural system of an underground facility is massive compared to the framing systems used for aboveground buildings.

Why is it important to have individual floor control valves in a high-rise building's sprinkler system?

These valves are important because they permit the rapid shutdown of sprinklers on the floor on which a fire has occurred after the sprinklers have controlled the fire.

What is the use of voice alarm systems in high-rise buildings?

These voice evacuation systems are often zoned by floor. It is not uncommon to evacuate only the floor of origin, the floor above, and the floor below rather than the entire building.

What limitations do air-supported structures have?

They are limited to one story, can only have slightly greater internal pressure than the outside, and cannot be used where fire-rated construction is required.

How do firefighters activate Phase II operations?

To activate Phase II operation, a firefighter must insert a key in a three-position switch within a car to place that particular car in "fire service".

What type of construction are high-rise buildings of today typically made of?

Today, high-rise buildings are of fire-resistive construction.

What are the typical features of a fire command center?

Typical features of a fire command center include the emergency voice alarm system control panels, fire department two-way telephone system panel, fire detection and fire alarm system annunciator panel, elevator location and status panel, sprinkler valve and waterflow annunciator, emergency and standby power status indicators and controls, central/status panel for smoke management systems, controls for unlocking stairway doors, fire pump status indicators, and a telephone for fire department use with access to the public telephone system.

How is Phase II operation activated?

Typically to activate Phase II operation, a firefighter must insert a key in a three-position switch within a car to place that particular car in "fire service".

What type of fire resistance do model building codes typically require for the structural frame of a high-rise building?

Typically, model building codes require 2- or 3-hour fire resistance for the structural frame of a high-rise building depending on the number of stories and occupancy, and 2-hour fire resistance for floor construction.

How does ventilation typically occur in contemporary high-rise buildings?

Ventilation in contemporary buildings may be accomplished through the fire department's control of the HVAC system.

How do modern high-rise buildings ventilate smoke during a fire?

Ventilation may be accomplished through the fire department's control of the HVAC system.

Where can vertical extension of fire and smoke occur despite the fire-resistive construction of high-rise buildings?

Vertical extension of fire and smoke can occur through floor penetrations such as elevator shafts, stairwells, and utility shafts.