week5:Building ConstructionTypes 2018

Building Construction Classifications

Overview of Building Types

Construction types are categorized into five main classifications based on their material properties and fire resistance:

  • Type 1 – Fire Resistive Construction: This type features structural components made from non-combustible or limited combustible materials. Typical fire-resistive ratings range from three to four hours.

  • Type 2 – Non-combustible Construction: Similar to Type 1 but may involve some combustible materials used in non-structural elements.

  • Type 3 – Ordinary Construction: Combines non-combustible walls with combustible elements like wooden roofs and interiors.

  • Type 4 – Heavy Timber Construction: This type involves substantial timber framing, providing some fire resistance due to the thickness of the wood.

  • Type 5 – Wood Frame Construction: Predominantly uses wood materials for both structural and non-structural components, thus having the least fire resistance.

Fire Resistive Construction

Fire resistive construction is pivotal for buildings that must withstand significant fire durations without failure:

  • Structural Elements: Composed entirely of non-combustible materials including columns, beams, walls, and roofs.

  • Implementation: Commonly found in high-rises, arenas, and assembly-type occupancies, which require high safety standards.

  • Fire Ratings: Typically, these constructions have a fire-resistive rating of three to four hours, providing ample time for evacuation in the event of a fire.

Non-Combustible Construction

This type focuses on maximizing the fire resistance of steel and other materials:

  • Steel Characteristics: Steel members can experience substantial elongation at fire temperatures, particularly above 1000°F, which may lead to structural issues if not properly restrained.

  • Failure Temperatures: Steel tends to lose structural integrity above 1300°F, leading to potential building collapse, particularly when tied to other structural elements.

  • Thermal Conductivity: Due to being good thermal conductors, steel can transmit heat rapidly, posing risks as heat spreads through walls to combustible materials in the vicinity.

  • Protection Measures: Non-combustible buildings with sprinkler systems effectively delay collapse until fire mitigation is achieved; however, they do not qualify as fire-resistive constructions by definition.

Ordinary Construction

Ordinary construction types are particularly noted for their vulnerabilities:

  • Characteristics: These buildings commonly feature a mix of non-combustible walls with wooden roof structures. Older structures often consist of unreinforced masonry.

  • Fire Spread Risks: This type is susceptible to fire and smoke spreading rapidly through concealed spaces, necessitating fire stops to impede such movement.

  • Void Spaces Risks: The presence of void spaces enhances fire hazards as they lack effective fire separation.

  • Construction Material Weaknesses: Newer methods using lightweight parallel chord truss systems have been noted for their rapid failure under heat, adding to the risk during firefighting efforts.

Heavy Timber Construction

Heavy timber, while offering some advantages, presents its own challenges:

  • Material Composition: Exterior walls are made of masonry, with solid wood utilized for interior structural members.

  • Fire Behavior: Fires in heavy timber constructions can endure for extended periods, which can pose risks for firefighters due to prolonged exposure and instability post-fire.

Wood Characteristics and Types of Wood Constructions
Characteristics of Wood

Wood's ignition and combustion processes are primarily driven by pyrolysis, which involves thermal breakdown leading to combustion reactions:

  • Factors Influencing Ignition: Wood's ignition depends on the temperature rise sufficient for pyrolysis, moisture content (wet wood is harder to ignite), and thickness (thin pieces ignite faster than thick logs).

  • Benefits of Wood: Advantages include lightweight, ease of construction, adaptability to various designs, availability, and a wide variety of products tailored for construction.

  • Negative Aspects: Wood lacks high fire resistance and is less capable of withstanding severe weather conditions, such as heavy winds from tornadoes or hurricanes.

Types of Wood Frame Buildings

  • Log Cabin: Characterized by wood interiors and high fire load due to plywood contributions.

  • Post and Frame: Early form of high-rise buildings, framed rather than wall-bearing.

  • Balloon Frame: Noted for interconnected voids, which can lead to rapid fire spread due to insufficient fire stopping between floors.

  • Platform Frame: Offers a well-defined sequence of construction that allows for fire compartmentalization by erecting floor platforms sequentially.

  • Plank and Beam construction: Similar sequence as platform frames, promoting efficiency in construction.

Fire Protection Measures

Utilizing passive fire protection systems is critical in mitigating fire risks in various construction types:

  • Fire Stopping and Draft Stopping: These limit the movement of flames and hot gases, helping to contain fires within specific areas. Fire stops typically address vertical movements, while draft stops limit horizontal movements.

  • Material Installation: Proper installation of fire-resistant materials subsumes using mineral fiber insulation, fire-rated partitions, and fire-rated doors to prevent the spread of fire and smoke throughout buildings.

These detailed understandings of construction types, their characteristics, and fire safety measures will be crucial while preparing for topics on building construction classifications in your upcoming exam.