Chapter 22

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Steel reinforcement in concrete elements that are permanently exposed to the earth such as in footings must have a minimum concrete cover of

3 inches

the strength of concrete is a residential concrete slab on ground is generally

3000 psi

Hooks in bars are produced by turning the bars through

90 or 180 degrees

Stirrups are generally made of

No 3 or No 4 bars

the term flying form refers to

a large formwork asembly for floor and roof slabs

the tendons used for prestressing PT concrete slab on ground generally consists of

a single 1/2 inch diameter seven wired 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

A PT concrete slab on ground must have perimeter and intermediate ribs

false

According to building codes, plain concrete (concrete without steel reinforcement) is not permitted in new construction.

false

Restoring concrete structures is necessary where excessive deflection of floor slabs or foundation settlement is anticipated on removal of shores

false

The structural design of formwork design is the responsibility of the

general contractor

High density overlay HDO on form plywood

improves the stripability of forms, allows easier cleaning of forms and increases usability of forms

In a site cast concrete construction shores are used

in elevated concrete slabs

Aluminum is commonly used as form and shore material because

its strength to weight ratio is high which reduces the weight of forms and shores

Height adjustability in shores made of dimension lumber is provided through

lapped members clamped together with spcially made clamps or a screw based metal assembly

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

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

The chairs are used to support reinforcing steel bars are generally

plastic chairs and steel chairs with plastic coated feet

Formwork for a concrete wall generally consists of

plywood form ties walers and stiffbacks fastened together with clamps

Which of the following statements is true

pretensioning is generally done at the precasters plant and yields a precast prestressed concrete member

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 of

steel pipes

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

Stirrups are used in a concrete beam

to increase the shear strength of the beam beyond that provided by concrete

A construction joint in a concrete slab on ground is required if the concrete in the slab cannot be palced in one continuous operation

true

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 comprehensive strength of concrete elements.

true

The term prestressed concrete refers to both pretensioned and posttensioned concrete

true

A capor retarder is required under

under some interior concrete slabs on ground

Mechanical couplers are used

where lap splicing of bars will produce excessive congestion


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