CHAPTER 13 Copyright © 2007 Thomson Delmar Learning 13.1 Building Construction

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning 13.2 Objectives (1 of 2) Describe the relationship between loads, imposition of loads, and forces. List and define four structural elements. Identify the effects of fire on five common building materials. List and define the five general types of building construction. List and define hazards associated with alternative building construction types

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning 13.3 Objectives (2 of 2) List five building collapse hazards associated with fire suppression operations. List five indicators of collapse or structural failure that might be found during fire suppression operations.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning 13.4 Introduction Collapse of burning buildings has killed and injured many firefighters engaged in aggressive fireground operations. Firefighters must understand building construction from the perspective of assembly methods, materials used, and how buildings react to heat and fire. Understanding building construction requires a long-term commitment to study and research.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning 13.5 Building Construction Loads and Forces There are two basics types of loads: live and dead. –Further description includes impact loads and distributed loads. Fire load is a fire service term. Loads can be imposed axial, eccentric, or tensional. Loads create a force within the material. –Forces include compression, tension, and shear. –Gravity is primary collapse force.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning 13.6 Structural Elements (1 of 2) Beams, columns, and walls. –Beams distribute loads perpendicular to the load. –Beams consist of a top chord, bottom chord, and web. –Top chords are usually under compression. –Bottom chords are typically under tensile force. –A truss is a beam formed by geometric triangles.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning 13.7 Structural Elements (2 of 2) Columns are elements under compression. Walls are a form of column. –They may be load bearing or not. Connection points transfer the load from columns and beams. Connection points are usually the weak link in fire conditions.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning 13.8 Fire Effects on Building Materials Construction materials are chosen based on many factors. –Cost –Quality –Suitability Fire resilience may be considered. Advanced technology may change materials found in construction.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning 13.9 Fire Effects on Building Materials—Wood Wood is the most common material used. –Adds to fire load. –May lead to increased instability during fire. The mass of the wood affects its strength when exposed to fire.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Fire Effects on Building Materials—Steel Excellent shear, tensile, and compression strength. When heated, expands and becomes more pliable. Structural steel loses 50% of strength at 1100° Fahrenheit. Steel will buckle when unable to expand. Important to keep cool under fire conditions.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Fire Effects on Building Materials—Concrete It is a mixture of Portland cement, sand, water, and gravel. Steel can be added for strength. Moisture may cause “spalling” when heated.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Fire Effects on Building Materials—Masonry Term used for block, brick, and tile materials May be load bearing or veneer Excellent fire resistance except for mortar which may fail quickly under fire conditions

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Fire Effects on Building Materials—Composites Composites challenge firefighters in determining fire resilience. Lightweight wooden I beams made from wood chips and glue will fail quickly in a fire. Plastics are used to reinforce other materials. Oriented strand board (OSB) and polystyrene are strong, but fail quickly when heated.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Types of Building Construction There are five broad categories. Renovations may have multiple types of construction. Fire ratings are designed to give occupants more time to escape.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Type I: Fire-Resistive Construction It is designed to stop spread of fire from one area to another. Steel and concrete used for structural members. There is a three- to four- hour fire resistive requirement. Fire may spread through broken windows, elevator shafts, and utility runs.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Type II: Noncombustible Construction Steel is the primary material used. It may have combustible contents causing fire spread. Suburban strip malls are typically Type II construction.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Type III: Ordinary Construction Masonry walls with wood roofs and floors May have many void spaces for fire spread Sagging floors of older buildings reinforced with steel rods Floor beams, typically “gravity” fit, may fail quickly when floors sag

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Type IV: Heavy Timber Construction Thick masonry walls with large dimension lumber for floors and roofs. Few void spaces, but many open spaces. Floors will collapse when sagging leaving walls unsupported.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Type V: Frame Construction The wood frame is most common. It may be “balloon frame” or “platform.” Newer lightweight buildings are like a “horizontal balloon frame”. It is protected from fire by covering with gypsum board. Brick veneers may be frame construction.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Other Construction Types Newer methods may not fit into the five general areas.. Lightweight steel frame looks like wood frame. Insulated concrete forms use expanded polystyrene blocks to make forms that are poured, very flammable when gypsum board fails. Manufactured buildings are low mass causing rapid fire spread.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Construction Type to Occupancy Use Anticipated use determines occupancy classification. Common classifications –Residential –Commercial –Business –Industrial –Hazardous –Educational Classification will help firefighters understand specific fire problems. Buildings constructed under one type may have been converted to different use.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Collapse Hazards at Structure Fires Firefighters need to preplan buildings in their jurisdictions. Understanding the signs of stress or failure is critical. Identifying potential collapse zones is critical.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Collapse Hazards at Structure Fires—Trusses Truss roof collapses have killed and injured many firefighters. Trusses are beams that use triangles of lumber to replace mass. Failure of a single part will cause entire truss to fail. Failure of a single truss may lead to multiple truss failures. Gusset plates used to join wood components absorb heat faster than the wood. Steel trusses have a high surface to mass ratio. An open web steel truss is called a bar joist.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Parallel Chord Truss

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Open Web Steel Joists

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Wood Trusses

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Collapse Hazards at Structure Fires—Void Spaces Trusses create large void spaces that allow fire travel. Fire in void spaces may go undetected causing rapid fire spread. Void spaces may penetrate multiple buildings that share walls.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Truss Construction Void Spaces

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Collapse Hazards at Structure Fires—Roof Structures There are multiple types of roof shapes. May hide heavy HVAC and utility equipment on roof. Roof style may allow for large volumes of fire. Mansard roofs have many concealed spaces. Dormers may be ornamental or actual living space.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Collapse Hazards at Structure Fires—Stairs Stairs are critical avenues for firefighters to make rescues and reach the fire. Older buildings use durable, high mass stairs. New buildings use lighter weight stairs built off site with low mass materials. Engineered wood and plastics are used and may cause failure before other structural members.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Collapse Hazards at Structure Fires—Signs Waiting for visual indicators is dangerous; rely on construction knowledge and preplanning. Factors and visual indicators that may assist in predicting a collapse: Age of building Cracks Presence of tie rods Open spans Sagging floors Smoke from cracks Bulging walls

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Collapse Hazards at Structure Fires—Buildings Under Construction Unsafe during construction, remodeling, and restoration. Must meet fire and life safety codes only when complete and occupancy permit issued. Protective features may be missing, incomplete, or out of service. Stacked construction material may overload structural elements.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Collapse Hazards at Structure Fires—Preparing for Collapse After initial search activities, risk vs. benefit must be considered for property. Defensive (exterior) firefighting activities are still dangerous if in a collapse zone.

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Parapet Wall Collapse

CHAPTER 13 Copyright © 2007 Thomson Delmar Learning Summary Firefighters must know and understand building construction. Understand the different materials used and tactics for firefighting. Understand the possibility of multiple types of construction due to renovation. Understand construction methods and identify the weakness that may cause collapse. Firefighters need to work toward safe fireground operations.