The Art of Reading Buildings Quiz Chapters 2

Fire Service and Building Trade Knowledge

• Many firefighters have backgrounds in building trades such as carpentry, plumbing, and electrical work, either as volunteers or part-timers.
• A decline has been observed in new recruits having building trade backgrounds, necessitating additional training in building construction fundamentals.
• Core building concepts like loads and material strengths are essential for understanding potential building failures during fire suppression.

Understanding Loads in Building Structures

• A building must be able to withstand various loads, which are static and dynamic forces stemming from the structure and external factors.
• Major types of loads include:
  • Dead loads: The weight of the structure and any permanently attached components.
  • Live loads: Any transient or movable weights (e.g., furniture, people).
  • Additional classifications: concentrated loads, distributed loads, impact loads, repeated loads, static loads, suspended loads, and wind/snow loads.
• The term fire load refers to the potential heat energy from burning materials measured in British thermal units (BTUs).

Load Imposition and Interaction with Materials

• Loads can be imposed through three mechanisms:
  • Axial load: Applied through the center of a material.
  • Eccentric load: Applied off-center, inducing bending.
  • Torsion load: Causes twisting in the material.
• Imposed loads create stresses in materials termed as:
  • Compression: Material is flattened or crushed.
  • Tension: Material is stretched apart.
  • Shear: Material is torn or slides apart.

Material Characteristics and Their Role in Construction

• Material suitability for construction depends on various factors, including type, shape, orientation, mass, and surface properties.
• Surface-to-mass ratio is critical for firefighters; higher mass relative to surface area enhances heat resistance.
• As materials burn, loss of mass impacts structural integrity, with emphasis on how fire affects resistance to loads.

Evolution of Building Materials

• Traditional materials include wood, steel, concrete, and masonry, but innovative materials and composites are increasingly utilized.
• A shift from older, denser, and lower-pitch wood to lighter, faster-burning new-growth trees is evident.
• Modern lumber is generally lighter and less dense, causing faster and hotter burn rates than historical equivalents.

Engineered and Traditional Wood Products

• Engineered wood products may replace traditional hardwoods, leading to structural changes that impact fire resistance.
• Glued laminated timber (glulam) is used to create stronger beams from smaller pieces, maintaining strength under heat but presenting risks if adhesives fail during fire.
• Common sheathing materials include:
  • Plywood: Made of alternating layers of wood veneer, vulnerable to fire.
  • Particle board: Low resistance to fire, prone to breaking under pressure.
  • Decorative sheathing: Typically not load-bearing, contributing to rapid flame spread and toxicity when burnt.

Safety Implications for Firefighters

• Understanding building materials and their behaviour under heat is crucial for firefighting and rescue operations, as modern lightweight constructions can fail suddenly without prior warning signs.
• Traditional wood structures provided visual cues (e.g., sagging) for failure signs, which may not be present in contemporary lightweight materials.### Engineered Wood Products (EWP)
• Older roofs with conventional materials can sag before collapsing; newer lightweight wood trusses do not show such signs prior to failure.
• Traditional wood products include sawn lumber items like glue-laminated (glulam) timber and plywood sheathing.
• Plywood and similar products can emit flammable, toxic gases when exposed to heat or fire.
• Engineered wood utilizes weight-efficient materials made from wood chips, veneers, and recycled products, replacing sawn lumber and sheathing.
• EWP is sourced from new-growth forests or rapid-growth tree farms and can include non-wood fibers like hemp and wheat straw.
• The production process involves milling wood into finer forms, emulsifying in adhesives, and autoclaving to set the bindings.
• Common engineered wood types include Oriented Strand Board (OSB), Laminated Veneer Lumber (LVL), Laminated Strand Lumber (LSL), Cross-Laminated Timber (CLT), and Glued Laminated Timber (GLT).

Types of Engineered Wood

• OSB: Structural sheathing formed with wood shavings and urea-formaldehyde adhesive, aligned to achieve multidirectional strength; degrades rapidly with heat and direct flame.
• LVL: Made from thin wood veneers glued with phenolic resin, designed for structural beams and commonly used as replacement for solid lumber.
• LSL: Consists of flaked wood strands glued together; used similarly to LVL but may fail faster under fire conditions.
• CLT: Panels of timber boarded crosswise, used for structural columns and walls; offers better acoustics and reduced carbon footprint compared to traditional lumber.
• GLT: Comprised of multiple layers of dimensional timber for structural elements, it can be shaped to fit aesthetic design needs.

Fire Service Considerations

• Engineered wood presents advantages like increased strength and efficient material use but poses fire risks due to flammability and toxic gas emissions.
• Adhesives in engineered wood, such as urea-formaldehyde, phenolic, and melamine-formaldehyde, release harmful gases when heated.

Steel as a Building Material

• Steel is vital for large commercial structures due to its high strength, versatility, and ability to be fabricated into various shapes and sizes.
• Manufactured from iron ore and carbon, the processes include casting, hot-rolling, and cold-rolling.
• Steel loses significant strength at elevated temperatures, with a notable reduction at 800°F and 1,100°F which can lead to structural failure due to elongation and buckling.

Cast Iron Characteristics

• Known for good compressive strength but is brittle; susceptible to cracking under load, especially in high-temperature environments.
• Cast iron resists slow heating but can fracture due to sudden temperature changes or impact from firefighting efforts.

Aluminum and Titanium

• Aluminum: Soft metal with a great strength-to-weight ratio, used primarily for trims and special applications; fails quickly in fires.
• Titanium: Lightweight and corrosion-resistant with excellent heat resistance, rarely used in construction due to high costs but may become more prevalent in innovative designs.

Concrete Properties

• Concrete is a composite material comprising Portland cement, sand, gravel, and water, known for its excellent compressive strength but poor tensile strength.
• Curing leads to a solid mass, with the final strength being dependent on the water-to-cement ratio.
• Common forms include reinforced concrete (with steel rebar) and precast slabs.
• Concrete acts as a heat sink and tends to crack or spall when moisture content expands during heating.### Concrete and Spalling
• Spalling weakens concrete by reducing its critical mass, crucial for structural integrity.
• Exposed steel rebar can conduct heat from a fire, leading to further spalling and potential failure.
• Concrete retains heat after a fire, posing risks to firefighters during overhaul.

Masonry Materials and Construction

• Masonry includes materials like brick, tile, concrete block (CMU), and stone, known for their brittleness.
• CMU, commonly used for walls, offers compressive strength, suitable for load-bearing and veneer structures.
• Mortar, made from sand, cement or lime, and water, binds masonry units but has minimal tensile or shear strength.

Structural Responses

• Masonry walls strengthen under axial loads but have a maximum weight limit before failure occurs.
• Despite excellent fire resistance, walls may collapse post-fire without roof support due to lack of compressive forces.
• Mortar's susceptibility to spalling, aging, and washout can compromise wall stability during fires.

Composite Materials

• Composites combine various materials, including plastics and metals, designed for strength with minimal mass, challenging for firefighting.
• Plastics, derived from petroleum, are prevalent in construction for their versatility, but they melt readily and emit hazardous gases when burning.

Carbon-Fiber Reinforced Polymer (CFRP)

• CFRPs consist of carbon fibers bound by polymers, providing high strength and resistance to heat and corrosion.
• CFRPs maintain heat resistance initially but can deteriorate under fire, releasing harmful carbon particles.

Evolving Building Technologies

• Advances in material science are leading to increased use of composites, raising concerns for fireground operations.
• Staying informed about new technologies in building materials is essential for firefighters to modify their operational tactics.

General Building Concepts

• Concrete combines sand, aggregate, water, and Portland cement, prized for its compressive strength but weak in tension and shear.
• Reinforcement with steel enhances concrete's performance in tensile applications; forms include monolithic, pre-tensioned, and precast.
• Technological advancements continuously influence building construction materials and methods.

Key Questions for Review

• Understand the types of loads and their effects on materials.
• Differentiate between compression, tension, and shear forces.
• Recognize factors influencing suitable materials in construction.
• Distinguish between brittle and ductile materials.

Test your knowledge on the essential aspects of building construction relevant to the fire service. This quiz covers the understanding of loads, the number of skilled tradespeople, and the significance of construction knowledge for new recruits. Assess your grasp of key terms and concepts crucial for effective firefighting.