Lesson 3: Behavior of Prestressed Concrete Beams

Question 1

3 types of vibration

Answer 1

• low-intensity vibration
• moderate-intensity vibration
• high-intensity vibration

Question 2

this type of vibration is typically not harmful to humans or structures

Answer 2

low-intensity vibration

Question 3

this type of vibration can cause discomfort and fatigue in humans

Answer 3

moderate-intensity vibration

Question 4

this type of vibration can cause serious injuries to humans

Answer 4

high-intensity vibration

Question 5

4 methods to lessen vibration

Answer 5

• isolating the source of vibration
• absorbing vibration
• dampening vibration
• designing structures to resist vibration

Question 6

according to this criterion, a material will fail in shear when the shear stress reaches a critical value

Answer 6

Mohr-Coulomb failure criterion

Question 7

it is the ability of a material to resist sudden forces without breaking or deforming

Answer 7

impact resistance

Question 8

4 factors that affect impact resistance

Answer 8

• type of material
• thickness of the material
• presence of reinforcement
• shape of the material

Question 9

it is the ability of a material to resist forces that tend to cause two parts of the material to slide past each other

Answer 9

shear resistance

Question 10

4 factors that affect shear resistance

Answer 10

• type of material
• thickness of the material
• presence of reinforcement
• angle of the forces

Question 11

3 advantages of using unbonded steel sections

Answer 11

• reduce the weight of the structure
• allow for thermal expansion and contraction
• allow for the use of different materials

Question 12

3 disadvantages of using unbonded steel sections

Answer 12

• reduced strength and durability
• increased risk of corrosion
• increased maintenance requirements

Question 13

3 types of cracks

Answer 13

• hairline cracks
• wide cracks
• delamination

Question 14

cracks are small, narrow cracks that are typically less than 0.1 mm wide

Answer 14

hairline cracks

Question 15

cracks are more than 0.1 mm wide

Answer 15

wide cracks

Question 16

this crack is the separation of the concrete from the reinforcement

Answer 16

delamination

Question 17

4 factors that affect the bond between steel and concrete

Answer 17

• surface profile of the steel reinforcement
• thickness of the concrete cover
• quality of the concrete
• construction practices

Question 18

4 common causes of cracks

Answer 18

• loading
• shrinkage
• corrosion of reinforcement
• defects in the concrete

Question 19

concrete is strong in _____ but weak in _____

Answer 19

compression; tension

Question 20

concrete shrinks as it _____

Answer 20

dries

Question 21

the steel reinforcement in concrete can corrode if it is exposed to _____ and _____

Answer 21

moisture; oxygen

Question 22

5 ways to prevent cracking

Answer 22

• using high-quality concrete
• properly curing the concrete
• protecting the concrete from moisture and oxygen
• using corrosion-resistant reinforcement
• minimizing defects in the concrete

Question 23

3 techniques to improve durability of reinforced concrete beams

Answer 23

• using high-quality concrete
• using corrosion-resistant reinforcement
• protecting the concrete from the environment.

Question 24

3 techniques to control the deformation of reinforced concrete beams

Answer 24

• using high-strength concrete
• using closely spaced reinforcement
• using stirrups

Question 25

3 techniques to control the deflection of reinforced concrete beams

Answer 25

* using a deeper beam * using a smaller load * using prestressing

Question 26

3 things to consider regarding the deformation of reinforced concrete beam

Answer 26

* durability * crack control * deflection control

Question 27

3 methods of analyzing deformation

Answer 27

* elastic theory of bending * plastic theory of bending * finite element method

Question 28

this method of analyzing deformation assumes that the concrete and steel in the beam behave elastically

Answer 28

elastic theory of bending

Question 29

this method of analyzing deformation assumes that the concrete in the beam behaves plastically after it reaches its yield strength

Answer 29

plastic theory of bending

Question 30

this method of analyzing deformation is a more sophisticated method that can account for the non-linear behavior of concrete and steel

Answer 30

finite element method

Question 31

four criteria to determine whether a prestressed concrete beam is superior to an ordinary concrete beam

Answer 31

* load-carrying capacity * deflection resistance * crack control * durability

Question 32

true or false: prestressed concrete beams have a higher load-carrying capacity than ordinary concrete beams

Answer 32

true

Question 33

true or false: prestressed concrete beams have a better deflection resistance than ordinary concrete beams

Answer 33

true

Question 34

true or false: prestressed concrete beams are less likely to crack than ordinary concrete beams

Answer 34

true

Question 35

true or false: prestressed concrete beams are durable and can withstand a variety of environmental conditions

Answer 35

true