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Constructions Ch. 11
Steel
69
Architecture
Undergraduate 1
04/10/2012

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Cards

Term
bessemer process
Definition
steelmaking process,air blown into vessel of molten iron to burn out impurities
Term
steel
Definition

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

Term
cast iron
Definition
3-4% carbon, more impurities than steel
Term
ferrous
Definition
iron-based material
Term
iron ore
Definition
oxides of iron
Term
basic oxygen process
Definition
-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

Term
beam blanks
or 
blooms
Definition
very thick approximations of the desired final steel shape
Term
weathering steel
Definition

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

Term
angles
Definition

L-shaped steel pieces, versatile

-short beams, connection between girders and columns, diagonal braces 

Term
gusset plates
Definition
flat plates used at the joints of the truss
Term
cast steel
Definition
pouring molten steel directly into a mold and allowing to cool to achieve desired shape
Term

hollow structural sections

HSS

Definition

sheet or plate metal cold-formed into hollow shapes that are then welded along the longitudinal seam

-"structural tubing"

Term

open-web steel joist

OWSJ

Definition
-mass-produced truss (made from hot and cold rolled shapes)used in closely spaced arrays to support floor and roof decks
Term
joist girders
Definition
prefabricated steel trusses designed to carry heavy loads, particularly bays of steel joists
Term
rivet
Definition

steel fastener consisting of a cylindrical building and    a formed head

-replaced today by high strength bolts and welding

Term
bearing type connection
Definition

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

Term

slip-critical connection

(friction type)

Definition
bolts are preloaded to an extent that friction between the adjoining faces of the steel members (faying surfaces) resists movement between the members
Term
faying surfaces
Definition
adjoining faces of the steel members
Term
bolts in bearing type conditions are stressed primarily in _____, while those in slip critical conditions are stressed in ______
Definition

shear

 

tension

Term
column splices and beam to column connections in tall buildings must be designed as __________ connections
Definition
slip critical
Term
galling
Definition

tearing of the surfaces of joined stell members by a bolt head or nut

-can be prevented by using washers

Term
turn-of-nut method
Definition

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)

Term

load indicator washer

also known as

direct tension indicator(DTI)

Definition
placed under head of bolt or nut, flattens in proportion to the tension of the bolt
Term
tension control bolts
Definition
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
Term

lockpin and collar fastener

(swedge bolt)

Definition
boltlike steel pin with annular rings that relies on a steel collar in lieu of a conventional nut to hold the pin
Term
backup/backing bars
Definition
small strips of steel welded beneath a groove prior to beginning the actual weld to prevent molten metal from dripping out of the groove
Term
demand-critical welds
Definition
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
Term
shear connection
Definition

joins web of the beam to the column, transmitting vertical (shear) forces from beam to column

- does NOT transmit bending forces(bending moment)

Term
moment connection
Definition
capable of transmitting bending forces between a beam and column
Term
stiffener plates
Definition
used if column flanges are insufficiently strong to accept force from beam flanges
Term
braced frame
Definition
uses stable diagonal triangle configurations (diagonal bracing) /\
Term
eccentric bracing
Definition
diagonal braces connect to beam with some distance between them/-\
-more resilient than conventional
shear bracing
Term
shear walls
Definition
stiff walls made of steel or concrete that serve the same purpose as diagonal bracing, no moment bracing needed
Term
moment resisting frames
Definition
no diagonal bracing or shear walls; moment connections
Term
rigid core
Definition
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
Term
rigid perimeter
Definition
shear walls, diagonal bracing, moment connections, interior assembled with shear w/ diaphragm
Term
camber
Definition
curved slightly in an upward direction
Term
baseplates
Definition
distribute concentrated loads of steel columns across a larger area of the concrete
Term
leveling plates
Definition
placed on bed of grout atop concrete
Term
plumbed up
Definition
first tier of framing is straightened and squared with cables before tightening
Term
drift pins
Definition
temporary pins used to hold pieces together until a few bolts can be inserted
Term
metal decking
Definition
thin sheet of metal that had been corrugated to increase its stiffness
Term
roof decking
Definition
single corrugated sheets where concentrated loads are not expected to be great
Term
cellular decking
Definition
two sheets welded together, one corrugated one flat; no structural assistance needed. place for wiring
Term
puddle welded
Definition
method of joining decking to joists and beams and girders by melting through decking to supporting member below
Term
composite metal decking
Definition
works with concrete floor to make stiff lightweight deck
Term
shear studs
Definition
welded every few inches to the top of each beam for floor beams
Term
subperlins
Definition
steel pieces used to support insulating boards acting as formwork for roof slabs
Term
girts
Definition
horizontal z shapes or channels span between the outside columns of the building when used sheet metal as siding
Term
slab fireproofing
Definition
surrounding beam with box made of plaster, gypsum, mineral fiber, etc.
Term
intumescent mastics and paints
Definition
thin coatings that allow steel structural elements to remain exposed in view in low risk situations; expand when heated to form thick protective char
Term
castellated beam
Definition
flame cutting web of flange in zigzag path, then reassembling point to point to make hexagon shape
Term
plate girders
Definition
 weld steel exactly where it needs to be
Term
rigid steel frames
Definition
produced by welding together steel wide flange sections
Term
steel trusses
Definition
triangulated arrangements of steel members that are generally deeper and lighter than improved beams and can span longer distances
Term
space truss(frame)
Definition
truss made three dimensional; carries load by bending along both axes( like two way slab)
Term
arches
Definition
produced by bending standard wide flanges into cylindrical roof vaults or circular domes
Term
anticlastic curvature
Definition
saddle shaped created by cable stays; means of restraining cable net in roof
Term
composite column
Definition
combine strength of structural steel shapes and site cast concrete(ex. steel pipe filled w/ concrete)
Term
what is the difference between iron and steel? what is the difference between wrought iron and cast iron?
Definition

.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)

Term
by weight, what is the major raw material used in the making of cast iron?
Definition
carbon
Term
how are steel structural shapes produced? how are the weights and thicknesses of a shape changed?
Definition

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

Term
how does the work of the fabricatior differ from that of the erector?
Definition

the fabricator delivers the steel components ready to be assembled

 

the erector receives the components and assembled at the building site

Term
explain the designation W21x68
Definition

a W21x68 is a wide flange steel section

21=depth

68=lbs./linear foot

Term
how can you tell a shear connection from a moment connection? what is the role of each?
Definition

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

Term
why might a beam be coped?
Definition

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

Term
what is the advantage of composite construction?
Definition

stiff, lightweight and economical

steel beam or deck and the concrete floor acts as a single structural unit, allowing for lighter steel member

Term
list 3 different structural systems in steel that might be suitable for the roof of an athletic house:
Definition

1. truss

2. dome

3. space truss

Term
explain the advantages and disadvantages of a steel building structure with respect to fire. how can the disadvantages be overcome?
Definition

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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