LEC 1.2

Question 1

Steel bars strengthen concrete and resist tensile stress

Answer 1

Principle of RC

Question 2

The reinforcement of reinforced concrete is _______________.

Answer 2

steel bars

Question 3

In prestressed concrete, __________ introduces compressive stress in concrete

Answer 3

tendon

Question 4

A ________ in prestressed concrete is a high-strength steel wire, strand, or bar that is used to compress concrete. ______ are embedded in concrete to improve its performance and structural capacity.

Answer 4

tendon, Tendons

Question 5

In reinforced concrete, the _______ of steel is the minimum specified yield stress

Answer 5

grade

Question 6

Whar grade is the most widely used in reinforcing bars

Answer 6

Grade 420(60)

Question 7

What grades are widely used in the Philippines

Answer 7

Grade 230(33), 280(40), and 420(60)

Question 8

Grades _________ and ___________ exhibit well- defined yield point and elastic-plastic strain behavior.

Answer 8

280, 420

Question 9

ACI allows Grade ____________ for longitudnial reinforcement in structural members other than those of “special seismic systems” and Grade __________ for confinement reinforcement in earhquake - resistant members and spirals in columns

Answer 9

550(80), 690 (100)

Question 10

_________________________ in the form of groups of wires forming strands or as individual wires are used for prestressing concrete.

Answer 10

Wire reinforcement

Question 11

The most prevalent strand is the ____________ either stress relieved (normal relaxation) or low relaxation conforming to ASTM A416M.

Answer 11

7-wire strand

Question 12

________________________ is now regarded as the standard type. These strands have a center wire enclosed by six helically wound outside wires.

Answer 12

Low - relaxation reinforcement

Question 13

usual nominal diameters for 7 - wire strand are ________, _______ and ______ in.

Answer 13

1/4, 3/8, 1/2

Question 14

The minimum tensile strength for strands of Grade ___________ and that of Grade ___________ in prestressed concrete.

Answer 14

1725, 1860

Question 15

T/F

The wires in prestressed concrete has a well defined yield point.

Answer 15

F

Question 16

A value of __________________ is often used for 7 - wire strands conforming to ASTM A416M

Answer 16

186,000 MPa

Question 17

Nonprestressed concrete has a f’c of

Answer 17

21 - 35 MPa

Question 18

Prestressed concrete has a f’c of ______________ MPa

Answer 18

35-56

Question 19

Columns of tall buildings has a f’c of

Answer 19

42-97 MPa