Steel Joists & Cold-Rolled Steel: A Comprehensive Guide PDF

HISTORY  Primarily introduced during the process of mass steel production back in mid-19th century.  Rapidly replaced timber construction as it became really popular in the 1940s and 1950s  Consequently, the American Iron and Steel Institute and other organizations establish standards for i...

HISTORY  Primarily introduced during the process of mass steel production back in mid-19th century.  Rapidly replaced timber construction as it became really popular in the 1940s and 1950s  Consequently, the American Iron and Steel Institute and other organizations establish standards for its design and use. WHAT IS LIGHT STEEL JOISTS?  It is also referred to as “light gauge steel” (LGS)  This is a structural component used for mainly framing, and supporting floors and roofs in buildings.  It is used throughout a structure as load-bearing exterior walls, exterior cladding, non- load-bearing facades, load- bearing floor joists and roof trusses.  Usually used in residential, commercial (warehouses, airplane hangars), and industrial buildings as an alternative to traditional wood or heavier steel joists. WHAT IS COLD-ROLLED STEEL?  A type of steel that has been processed at room temperature which improves its mechanical properties (strength, hardness) and surface finish. 1. COLD-ROLLED STEEL: Composition and Manufacturing  Manufactured through rolling or pressing steel into thin sections at room temperature.  Increases steel’s yield strength; ideal for lightweight, load-bearing structures.  Raw materials: carbon steel, alloyed with small amounts of manganese, sulfur, phosphorus.  COLD-ROLLED STEEL  Processed at room temperature after hot-rolling  Further rolling in cold reduction mills MANUFACTURING  Undergoes additional processes: annealing PROCESS (heating to soften the metal)  tempering - achieve mechanical properties  Smoother, polished finish due to rolling and SURFACE FINISH finishing processes.  Visually appealing. DIMENSIONAL  Tighter dimensional tolerances ACCURACY  Thinner and uniform thickness STRENGTH AND  Stronger and harder due to strain hardening from MECHANICAL rollilng. PROPERTIES  High tensile strength  Automotive components, appliances furniture, APPLICATIONS construction materials (light gauge steel joists) COST  Expensive due to additional processing HOT-ROLLED STEEL  Processed at high temperatures (above 1,700°F or MANUFACTURING 930°C). PROCESS  Rolled into desired shape whilst hot; cooled at room temperature. SURFACE FINISH  Rougher; due to cooling process and lack of  further finishing. DIMENSIONAL  Less precise dimensions ACCURACY  Warping or slight imperfections STRENGTH AND  Ductile and malleable MECHANICAL  Lower overall strength compared to cold-rolled PROPERTIES steel  Large structura components (I-beams, railroad APPLICATIONS tracks, sheet metal)  Used in heavy equipment and construction COST  Cheaper due to simpler processing ADVANTAGE: 1. Strength-to-weight ratio is higher than wood – it can withstand high wind loads (ideal for hurricane and seismic-prone areas) 2. Elastic – deforms under stress without breaking during natural disasters 3. Durable – Lifespan is longer when coated with protective measures against corrosion 4. Fire resistant - when used with fireproof coatings and fire-resistant barriers 5. Sustainable and recyclable – made of recycled steel; conducive to off-site manufacturing and prefabrication; less waste from offcuts; unused materials are recycled. 6. Consistency & Precision – uniform dimensions; precise and predictable performance. 7. Versatile 8. Pest resistance, mold, and mildew DISADVANTAGE: 9. High initial costs (compared to wood) 10. Need for special tools and expertise 11. Thermal conductivity – increase in costs if not properly insulated; it loses strength under extreme heat and may deform 12. Insulation and Acoustic – must be integrated with additional insulation into LGS structures same with acoustic. TYPES OF LIGHT GAUGE STEEL CONSTRUCTION SYSTEMS 1. LIGHT GAUGE STEEL FRAMING – instead of traditional framing, it uses steel studs. a) Steel Studs - produced in a C-shape with flanges and a lip to provide stiffness. 2. STEEL PANEL SYSTEMS – prefabricated panels. a) Flat panels – cladding, curtain walls; structural: walls, floors, roofs (steel frames filled with insulation and structural sheathing). 3. MODULAR CONSTRUCTION - production of entire sections of a building (modules); later assembled on-site. a) Modules – light gauge steel framing and steel panel systems; both COMPOSITE SYSTEMS - use steel in combination with other materials. 1. Steel-concrete composite - concrete slab is poured onto steel decking for tensile reinforcement for the concrete and formwork. 2. Light Gauge steel framing with exterior insulation and finish systems (EIFS) - provides thermal insulation and weatherproofing; steel is responsible for structural integrity; energy efficient. 3. Acoustic Insulation A. Light steel wall (external) wall supporting brickwork without sheating board B. Light steel wall (external) wall supporting brickwork with sheating board.  LIGHT STEEL JOISTS TYPES TYPES 1. C-Joists (Cold-Formed Steel Joists or C-shaped Joists)  "C" cross-section  Used in floor and wall framing; ideal for non-load-bearing and load-bearing walls, and as rafters and trusses. 2. I- Joists  I-shaped profile  Same to traditional steel but lighter  Used in floor and roof systems where longer spans are required  Long span capabilities, lightweight 3. Box Joists  Rectangular or box shape  Used in specialized applications; higher load capacity is needed  Higher strength; greater resistance to buckling. 4. Hat Channels (Furring 5. Z-Joists Channels)  Hat-like cross-section  Z-shaped cross-section  for non-structural  Used in roofs and walls, often in purposes, like supporting horizontal applications. drywall, ceilings, or  Ideal for creating horizontal lightweight cladding spanning members, resistant to systems. lateral forces.  Ideal for secondary framing. 6. Track and Stud System  Track: U-shape & Studs have C- shape  Wall framing and curtain wall systems  Ideal for partition walls 7. Open Web Steel Joists (Bar Joists)  Truss-like design with open webbing  Used for longer-span roof and floor applications  Allowing passage of mechanical systems (ductwork, plumbing, electrical). 8. Hat Joists  Hat resembles cross-section  Used for roofing and cladding systems;  Additional support and spacing  Lightweight cladding systems; reduces the amount of structural framing required KEY STANDARDS AND CERTIFICATIONS:  AISI S100: This North American specification outlines the design requirements for cold-formed steel structures and is often referenced by the International Building Code (IBC).  ASTM A653/A653M: This standard defines the zinc or zinc-iron alloy coating applied to light gauge steel to prevent corrosion, ensuring durability.  ASTM C645: This specification focuses on non-structural steel framing members, detailing the requirements for light gauge steel used in non-load-bearing walls.  LEED (Leadership in Energy and Environmental Design) promotes the use of materials like light gauge steel due to its recyclable properties, contributing to more sustainable, energy-efficient buildings. FOREIGN BUILDINGS THAT INCORPORATES LIGHT STEEL JOISTS 1. The Leadenhall Building (UK)- commercial skyscraper uses steel framing, light steel joists. a) “cheesegrater” - slanted profile; preserving slightlines b) preserve sightlines of St. Paul's Cathedral. London has strict planning regulations called protected views. 2. The New York Times Building (USA) - uses light steel framing for its iconic facade. 3. Pompidou Centre (France) - designed by Renzo Piano and Richard Rogers 4. The Louvre Pyramid (France) - incorporates a steel framework with joists to support the glass panels. 5. Mactan-Cebu International Airport (Terminal 2), Lapu-Lapu City - incorporates steel joists to support the sweeping arches of the timber roof. 6. Eastgate center: Commercial Building, Harare, Zimbabwe  Exemplifies light gauge steel construction in a mixed-usecommercial complex.  Designed for sustainability, it features offices, shops, and a cinema, drawing inspiration from termite mounds.  Light gauge steel allows flexible internal structures, while a brick facade enhances local aesthetics and thermal efficiency.