ch 22
steel reinforcements in concrete elements that are permanently exposed to the earth, such as in footings, must have a minimum concrete cover of how many inches?
3 inches
the strength of concrete in a residential concrete slab-on-ground is generally
3000 psi
hooks in bars are produced by turning the bars through
90 degrees to 180 degrees
t/f - according to building codes, plain concrete is not permitted in new construction.
False
the term "flying form" refers to what?
a large formwork assembly for floor and roof slabs
the tendons used for prestressing a PT concrete slab-on-ground generally consist of...
a single 1/2in diameter, seven-wire strand
high-density overlay (HDO) on form plywood does what?
all of the above
in a typical sitecast reinforced-concrete structure, the cost of formwork and shores is...?
approximately equal to the combined cost of concrete and steel
a doubly reinforced beam is one in which reinforcing bars are provided where?
at the top and bottom of the beam
height adjustability in shores made of dimension lumber is provided through what...?
both A and B
the chairs used to support reinforcing steel bars are generally...
both A and C
t/f - a PT concrete slab-on-ground must have perimeter and intermediate ribs.
false
t/f - reshoring concrete structures is necessary where excessive deflection of floor slabs or foundation settlement is anticipated on removal of shores.
false
in site-cast concrete construction, shores are used where?
in elevated concrete slabs
stirrups are used in a concrete beam to do what?
increase the shear strength of the beam beyond that provided by concrete
aluminum is commonly used as form and shore material because why?
it's strength-to-weight ratio is high, which reduces the weight of forms and shores
in a PT concrete slab-on-ground, the tendons are stressed from the...
live ends
pocket formers in a PT concrete slab-on-ground are used at
live ends
stirrups are generally made of what type of bars?
no. 3 or no. 4 bars
an isolated concrete slab-on-ground is generally
none of the above
concrete shell roofs are not commonly used because why?
none of the above
hooks are used...
none of the above
the yield strength of prestressing steel is...
none of the above
formwork for a concrete wall generally consists of
plywood, form ties, walers, and stiffbacks fastened together with clamps
the most important reason for providing ties in a concrete column is to...
prevent the buckling of longitudinal column bars
form liners are used to do what?
produce textured concrete surfaces
a vapor retarder is required under what?
some interior concrete slabs-on-ground
scaffold-type shores are generally made from?
steel pipes
the term Tendons includes what...?
strands
the structural design of formwork design is the responsibility of who?
the general contractor
pretensioning is generally done where?
the precaster's plant
the most important reason for providing ties in a concrete wall is to...
ties are generally not provided in a concrete wall
t/f - a construction joint in a concrete slab-on-ground is required if the concrete in the slab cannot be placed in one continuous operation.
true
t/f - the primary purpose of steel reinforcement is to increase the tensile strength of concrete elements. however, steel reinforcement is also used to increase the shear strength and compressive strength of concrete elements.
true
t/f - the term prestressed concrete refers to both pretensioned and posttensioned concrete.
true
mechanical splicers are used...
where lap splicing of reinforcing bars will produce excessive congestion
