CH 12 Light gauge steel
How do we estimate the depth of light gauge FLOOR JOIST
1/20 of the span, round up to the nearest 2-inch dimension.
How do we estimate the depth of rafters in a gable or hip roof?
1/24 its span, round up to the nearest 2-inch dimension
how is light gauge steel classified?
Depth x Width x Type x Thickness
In a non-combustible building what are walls sheathed with?
Gypsum sheathing panels.
Brass
Is formulated of copper and zinc plus small amounts of other metals. Resistant to corrosion
What does the International Residential Code for One-and Two-family Dwellings dictate?
The International Code Council has incorporated prescriptive requirements for steel framed residential construction. these requirements do not require employment of an engineer or architect, the builder can design and build as if it was wood he was using.
How to find the depth of light gauge steel roof trusses
Usually based on the desired roof pitch. A typical depth is 1/4 of the width of the building, which corresponds to a 6:12 pitch.
End clips are used for?
joining members that meet at right angles.
LG members can be these items for a Fire-resistant building
-Interior walls and partitions, suspended ceilings and fascias, parapets, and backup walls for many kinds of exterior cladding materials.
Copper
-slightly more dense than steel -when it oxidizes it forms a self-protecting coat -not amendable to heat treatment -ductile and easy to fabricate -highest thermal and electrical conductivity -may be casted, drawn, extruded, and hot or cold rolled -used in roofing, and flashing sheet, piping and tubing, and wiring for electricity and communications.
Advantages of steel framing
-versatile -flexible -requires simple tools -has internal cavities for utilities and thermal insulation -can be used in buildings requiring non -combustible material -lighter in weight than wood -straighter and more uniform than wood -unaffected by humidity may corrode -termite and decay proof
For an exterior cladding back up stud that is 3-5/8" in depth, what is the max height it can span
12 feet
how much width can a 6" or 8" stud wall support?
150 feet
for an exterior cladding back up stud that is 6" in depth what is the max height it can be span?
19 feet
How much do you add to the depth of a exterior cladding back up stud if brittle material is used such as brick
2 inches
How far apart are framing members spaced?
24 inches O.C
For an exterior cladding back up stud that is 8" in depth what is the max height it can span?
30 feet
how much width can a 3-5/8" or 4" stud support?
60 feet
Mixing LG steel studs with concrete creates
A thin but relatively stiff wall panel.
How do you find the load that a Load bearing stud can hold
Add up the total width of floor and roof slabs that contribute load to the stud wall.
What buildings can be entirely framed with LG?
Any building that can be framed with nominal 2-inch wood members.
What is the difference between Gypsum sheathing panels and Gypsum wall board?
Gypsum sheathing panels are made more resistant to moisture and weather with glass mat faces and specially formulated water-resistant gypsum cores.
what is most durable form of galvanizing?
Hot-dip galvanizing, in which the steel parts are submerged in a molten zinc bath to produce a thick coating, is the most durable form of galvanizing.
Chromium: does it corrode in air? how is it applied to other metals? what is its major function?
It does not corrode in air. it is often electroplated onto other metals for use in ornamental metalwork, bathroom etc. Major alloying ingredient in stainless steel
Describe how Light gauge reacts in cold environment
Light gauge steel framing must be detailed and insulated to minimize thermal bridging throughout the steel members.
nonstructural metal framing
Light gauge steel framing that is not load bearing
Titanium
Low density, about half the weight of steel, very strong, and one of the most corrosion resistant of all metals. replaced lead in paints and is used sometimes in sheet metal for construction.
Zinc
Low strength, relatively brittle, and moderately hard. used for roofing and flashing. alloys of zinc can be used to cast doorknobs and other small house fixtures.The most important job of zinc is to galvanize metals to prevent rusting.
what type of galvanizing is less durable?
Much less durable is the thin coating produced by ELECTROGALVANIZING.
Both non and load bearing walls can be made for
Residential and light commercial buildings.
Tin
Soft ductile, silvery metal that forms a self protecting oxide layer. steel cans have a tin coating in the interior. Tine was used as an alloy of 80% lead and 20% tin as a corrosion resistant coat but now zinc-tin alloy is used.
how is aluminum used as a coat
Steel sheet for architectural roofing is also frequently coated with zinc-aluminum alloy coating. The aluminum provides a superior protective oxide coating, and the zinc provides galvanic protection if the coating becomes damaged and the base steel exposed.
What other factors keep LG members from buckling twisting and failure under lateral wind and earthquake loads?
Subflooring, wall sheathing, roof sheathing, and interior finish materials.
Break down how LG load bearing walls are load bearing
The concrete panels provide shear resistance while the steel studs provide most of the resistance to gravity and wind loads acting perpendicular to the fact of the panel.
What is the procedure for LG construction?
The ground floor (foundation) is framed with steel joists then mastic adhesive is applied to the upper edges of the joists, then wood panels are attached to those joists. Next steel studs are laid out on completed floor and assembled and attached to form the wall frames, they are then plumbed up and attached to the floor joist.
what is Light gauge's steel thermal conductivity level relative to other materials?
The thermal conductivity of light gauge steel framing members is much higher than that of wood, and any other primary structural material as well.
where are light gauge steel members cut to size?
They are cut on the construction site with power saws of hand shears. for large projects members may be delivered precut to the site.
what is a way for small parts to be galvanized?
Threaded steel fasteners and other small parts may be mechanically galvanized, in which zinc is fused to the steel at room temperature in a tumbler that contains zinc dust, impact media and other materials. mechanical galvanizing produces uniform thickness.
What are LG steel members more prone to than wood apart from thermal conductivity?
Twisting and buckling, so we must
What are Track sections
Used for the top and bottom plates, they are slightly oversized so that the stud or joist members can nest into them.
How are LG members joined together
Usually joined by Self-drilling screws, which drill their own holes and form helical threads in the holes as they are installed, these screws are plated in cadmium or zinc. Welding is often used to assemble panels of light gauge steel framing.
Type 316 stainless steel
With higher nickel content and the addition of small amounts of molybdenum, is more corrosion resistant than type 304 . It is also used in marine environments.
what changes must be made if a building is to be fully non-combustible?
Wood structural panels for sub flooring must be replaced with corrugated steel decking with concrete topping or precast concrete.
A web stiffener is used for
aid in transmitting wall loads vertically through the joist, it is a two piece assembly.
What 2 things can we do to counter buckling and twisting of LG members?
brace LG studs at 4 ft intervals with steel straps screwed to the faces of the studs or with 1-1/2inch channels that pass through the LG studs prepunched holes and welded or screwed to an angle clip at each stud.
How are LG members made load bearing?
by casting cement into a framework of steel studs.
C-sections
for wall, floor, and roof framing. also called joist sections or studs. the web of these members may be punched at every 2 ft to run wiring and plumbing.
Magnesium
is a strong, remarkably lightweight metal that is much used in aircraft but remains too costly for general use in buildings. found in tools and an alloying element that increases strength and corrosion resistance of aluminum.
Type 410 stainless steel
is less corrosion resistant than 300 series however its crystalline structure allows it to be heat treated and made stronger
Bronze
is made of 10 percent tin and 90 percent copper, found in statues, bells, etc. resistant to corrosion
cold formed metal framing
light gauge steel members used in structural applications and exterior wall cladding systems.
How is a concrete-to-steel bond made?
may be created by stud anchors, sheet metal shear strips, welded wire reinforcing, or expanded metal that is welded or screwed to the studs.
Aluminum
nonferrous metal most often used in construction, lighter than steel and has moderate to high strength. Can be hardened by cold working and heating can also be cast, forged, drawn, and stamped. -self protecting from corrosion.
LG members that are load bearing can be made either ____ or ____
off site or on site
what type of connection methods can be used with steel frames?
screws and welding
How do you insulate LG steel members
spray a continuous layer of insulation rigid foam, semirigid mineral fiber, or other insulation. Must be placed on one side of member (exterior side)
Type 304
stainless steal, is the type most commonly specified and provides adequate corrosion resistance for most applications.
annealing
steel is brought to a very high temperature and then cooled very slowly. It will become softer, easier to work with, and less brittle.
Galvanizing: what metal is used, how it reacts if scratched
the application of zinc to prevent steel from rusting. The zinc itself creates a gray oxide coating, and even if the zinc is scratched the zinc interact electrochemically with the exposed steel to continue to protect the steel this is called galvanic protection.
How do we estimate the depth of rafters in a shed roof
the horizontal distance between supports. Estimate the rafter at 1/24 its span, round up to the nearest 2-inch dimension.
What happens in cold environment if LG steel is not insulated?
the thermal performance of the wall or roof is greatly reduced -energy losses increase substantially -moisture condensation within the framing cavity or on interior building surfaces -growth of mold and mildew and discoloration.
ASTM standard A1003
this is the light gauge steel used in manufacturing and is metallic coated with zinc or aluminum zinc alloy to protect against corrosion.
Foundation clips are used for?
to attach the ground-floor platform to anchor bolts embedded in the foundation.
Joist hangers are used for?
to connect joists to headers and trimmers around openings.
LG members are labeled nonstructural metal framing when...??
when they frame interior partitions and other nonloadbearing applications.
What happens if you apply to much insulate to the interior of a LG structure
you expose the metal components to lower temperatures, increasing the risk of condensation within the framing cavity.