Chapter 22
Steel reinforcement in concrete elements that are permanently exposed to the earth, such as in footings, must have a minimum concrete cover of
3 in.
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 or 180 degrees
Height adjustability in shores made of dimension umber is provided through
A. lapped members clamped together with specially made clamps. B. a screw-based metal assembly C. (A) OR (B)
A PT concrete slab-on-groud must have perimeter and intermediate ribs.
False
According to building codes, plain concrete (concrete without steel reinforcement) is no permitted in a new construction
False
Reshoring concrete structures is necessary where excessive deflection of floor slabs or foundation settlement is anticipated on removal of shores.
False
High-density overlay (HDO) on form plywood
Improves the strippability of forms allows easier cleaning of forms Increases reusability of forms ALL OF THE ABOVE
Stirrups are generally made of
No. 3 or No. 4 bars
The chairs used to support reinforcing steel bars are generally
Plastic chairs Steel chairs with plastic-coated feet. BOTH
Which of the following statements is true?
Pretensioning is generally done at the precaster's plant and yields a precast, prestressed concrete member
Which of the following statements is true?
The term tendons includes strands
The most important reason for providing ties in a concrete wall is to
Ties are generally not provided in a concrete wall
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
The term PRESTRESSSED CONCRETE refers to both pretensioned and posttensioned concrete
True
The term flying form refers to
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 1/2-in.-diameter, seven-wire strand
In a typical sitecast reinforced-concrete structure, the cost of formwork and shores is
approximately equal to the combined cost of concrete and steel.
The structural design of formwork design is the responsibility of the
general contractor
In site-cast concrete construction, shores are used
in elevated concrete slabs
Aluminum is commonly used as form ad shore material because
its strength-to-weight ratio is high, which reduces the weight of forms and shores.
Pocket formers in a PT concrete slab-on-ground are used at
live ends
In a PT concrete slab-on-ground, the tendons are stressed from the
live ends.
An isolated concrete slab-on-ground is generally
none of the above
Concrete shell roofs are not commonly used because
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
produce textured concrete surfaces
A doubly reinforced beam is one in which
reinforcing bars are provided at the top and bottom of the beam
Scaffold-type shores are generally made from
steel pipes
Stirrups are used in a concrete beam
to increase the shear strength of the beam beyond that provided by concrete
A vapor retarder is required under
under some interior concrete slabs-on-ground
Mechanical couplers are used
where the lap-splice length of reinforcing bars is excessive
A construction joint in a concrete slab-on-ground is required if the concrete in the slab cannot be paced in one continuous operation
True