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| steelmaking process,air blown into vessel of molten iron to burn out impurities |
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any range of alloys of iron that contain less than three-tenths of 1% carbon, plus traces of beneficial elements such as manganese and silicon
-detrimental impurities: phosphorus, sulfur, oxygen, nitrogen |
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| 3-4% carbon, more impurities than steel |
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| -hollow, water-cooled lance is lowered into a container of molten iron and recycled steel scrap
-stream of pure oxygen blown at high pressure from lance into the metal to burn off impurities
-flux of lime and fluorspar added |
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| very thick approximations of the desired final steel shape |
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used where steel without any protective finish will remain exposed to exterior conditions in the completed construction
-developes oxide coating that protects it
-highway and bridge construction |
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L-shaped steel pieces, versatile
-short beams, connection between girders and columns, diagonal braces |
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| flat plates used at the joints of the truss |
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| pouring molten steel directly into a mold and allowing to cool to achieve desired shape |
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hollow structural sections
HSS |
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sheet or plate metal cold-formed into hollow shapes that are then welded along the longitudinal seam
-"structural tubing" |
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open-web steel joist
OWSJ |
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| -mass-produced truss (made from hot and cold rolled shapes)used in closely spaced arrays to support floor and roof decks |
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| prefabricated steel trusses designed to carry heavy loads, particularly bays of steel joists |
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steel fastener consisting of a cylindrical building and a formed head
-replaced today by high strength bolts and welding |
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installed to a snug-tight condition
-movement between the jointed members is resisted by the bolts themselves as the sides of the bolt holes in the connected members bear against the bodies of the bolts |
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slip-critical connection
(friction type) |
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| bolts are preloaded to an extent that friction between the adjoining faces of the steel members (faying surfaces) resists movement between the members |
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| adjoining faces of the steel members |
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| bolts in bearing type conditions are stressed primarily in _____, while those in slip critical conditions are stressed in ______ |
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| column splices and beam to column connections in tall buildings must be designed as __________ connections |
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tearing of the surfaces of joined stell members by a bolt head or nut
-can be prevented by using washers |
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method to judge if slip-critical connection is tight enough
-bolt tightened snugly, then turned a specified fraction of the turn (determined by bolt length) |
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load indicator washer
also known as
direct tension indicator(DTI) |
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| placed under head of bolt or nut, flattens in proportion to the tension of the bolt |
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| bolts with protruding splined ends that are gripped by shear wrench, spinning them the opposite way of the nut. the splines then twist and fall off when the required tension is reached |
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lockpin and collar fastener
(swedge bolt) |
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| boltlike steel pin with annular rings that relies on a steel collar in lieu of a conventional nut to hold the pin |
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| small strips of steel welded beneath a groove prior to beginning the actual weld to prevent molten metal from dripping out of the groove |
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| welds in structural connections that may be subjected to very high stresses during a seismic event and that are critical to maintaining the stability of the building structure |
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joins web of the beam to the column, transmitting vertical (shear) forces from beam to column
- does NOT transmit bending forces(bending moment) |
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| capable of transmitting bending forces between a beam and column |
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| used if column flanges are insufficiently strong to accept force from beam flanges |
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| uses stable diagonal triangle configurations (diagonal bracing) /\ |
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diagonal braces connect to beam with some distance between them/-\
-more resilient than conventional
shear bracing |
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| stiff walls made of steel or concrete that serve the same purpose as diagonal bracing, no moment bracing needed |
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| no diagonal bracing or shear walls; moment connections |
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| core is structured as stiff tower w/ diagonal bracing, shear walls or moments, rest of building made from shear connections and diaphragm action of floors |
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| shear walls, diagonal bracing, moment connections, interior assembled with shear w/ diaphragm |
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| curved slightly in an upward direction |
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| distribute concentrated loads of steel columns across a larger area of the concrete |
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| placed on bed of grout atop concrete |
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| first tier of framing is straightened and squared with cables before tightening |
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| temporary pins used to hold pieces together until a few bolts can be inserted |
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| thin sheet of metal that had been corrugated to increase its stiffness |
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| single corrugated sheets where concentrated loads are not expected to be great |
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| two sheets welded together, one corrugated one flat; no structural assistance needed. place for wiring |
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| method of joining decking to joists and beams and girders by melting through decking to supporting member below |
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| works with concrete floor to make stiff lightweight deck |
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| welded every few inches to the top of each beam for floor beams |
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| steel pieces used to support insulating boards acting as formwork for roof slabs |
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| horizontal z shapes or channels span between the outside columns of the building when used sheet metal as siding |
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| surrounding beam with box made of plaster, gypsum, mineral fiber, etc. |
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| intumescent mastics and paints |
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| thin coatings that allow steel structural elements to remain exposed in view in low risk situations; expand when heated to form thick protective char |
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| flame cutting web of flange in zigzag path, then reassembling point to point to make hexagon shape |
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| weld steel exactly where it needs to be |
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| produced by welding together steel wide flange sections |
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| triangulated arrangements of steel members that are generally deeper and lighter than improved beams and can span longer distances |
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| truss made three dimensional; carries load by bending along both axes( like two way slab) |
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| produced by bending standard wide flanges into cylindrical roof vaults or circular domes |
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| saddle shaped created by cable stays; means of restraining cable net in roof |
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| combine strength of structural steel shapes and site cast concrete(ex. steel pipe filled w/ concrete) |
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| what is the difference between iron and steel? what is the difference between wrought iron and cast iron? |
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.iron and steel: iron is element, steel is alloy comprised of iron and carbon. steel is stronger, better tension/compression
.wrought iron and cast iron: wrought iron is pounded into desired shape; cast iron is poured into mold (faster) |
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| by weight, what is the major raw material used in the making of cast iron? |
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| how are steel structural shapes produced? how are the weights and thicknesses of a shape changed? |
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beam blank is passed through succession of rollers which squeeze material to desired shape and size
they are then cut into shapes by a hot saw, then cut at desired lengths |
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| how does the work of the fabricatior differ from that of the erector? |
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the fabricator delivers the steel components ready to be assembled
the erector receives the components and assembled at the building site |
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| explain the designation W21x68 |
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a W21x68 is a wide flange steel section
21=depth
68=lbs./linear foot |
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| how can you tell a shear connection from a moment connection? what is the role of each? |
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shear: capable of transmitting vertical forces from a beam to column, no value in transmitting bending forces
--web only
moment: beam flanges are attached to adjoining member with welds or bolts. one member cannot rotate without rotating the adjacent member. transfers bending forces
--web and flanges |
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| why might a beam be coped? |
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a coped beam is one whose top flanges are cut away so that the tops of the beam the the girder are all level with one another
increase bending moments at the ends of the beam |
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| what is the advantage of composite construction? |
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stiff, lightweight and economical
steel beam or deck and the concrete floor acts as a single structural unit, allowing for lighter steel member |
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| list 3 different structural systems in steel that might be suitable for the roof of an athletic house: |
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1. truss
2. dome
3. space truss |
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| explain the advantages and disadvantages of a steel building structure with respect to fire. how can the disadvantages be overcome? |
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a:normal building fire cannot melt structural steel, too resistant.
d: steel beams soften when heated, building fire weakedn the steel enough to cause structural failure
o: exposed steel framing limited to five stories.
taller buildings, steel encased in masonry, concrete, or plaster |
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