Lesson 3: Behavior of Prestressed Concrete Beams Flashcards
3 types of vibration
- low-intensity vibration
- moderate-intensity vibration
- high-intensity vibration
this type of vibration is typically not harmful to humans or structures
low-intensity vibration
this type of vibration can cause discomfort and fatigue in humans
moderate-intensity vibration
this type of vibration can cause serious injuries to humans
high-intensity vibration
4 methods to lessen vibration
- isolating the source of vibration
- absorbing vibration
- dampening vibration
- designing structures to resist vibration
according to this criterion, a material will fail in shear when the shear stress reaches a critical value
Mohr-Coulomb failure criterion
it is the ability of a material to resist sudden forces without breaking or deforming
impact resistance
4 factors that affect impact resistance
- type of material
- thickness of the material
- presence of reinforcement
- shape of the material
it is the ability of a material to resist forces that tend to cause two parts of the material to slide past each other
shear resistance
4 factors that affect shear resistance
- type of material
- thickness of the material
- presence of reinforcement
- angle of the forces
3 advantages of using unbonded steel sections
- reduce the weight of the structure
- allow for thermal expansion and contraction
- allow for the use of different materials
3 disadvantages of using unbonded steel sections
- reduced strength and durability
- increased risk of corrosion
- increased maintenance requirements
3 types of cracks
- hairline cracks
- wide cracks
- delamination
cracks are small, narrow cracks that are typically less than 0.1 mm wide
hairline cracks
cracks are more than 0.1 mm wide
wide cracks
this crack is the separation of the concrete from the reinforcement
delamination
4 factors that affect the bond between steel and concrete
- surface profile of the steel reinforcement
- thickness of the concrete cover
- quality of the concrete
- construction practices
4 common causes of cracks
- loading
- shrinkage
- corrosion of reinforcement
- defects in the concrete
concrete is strong in _____ but weak in _____
compression; tension
concrete shrinks as it _____
dries
the steel reinforcement in concrete can corrode if it is exposed to _____ and _____
moisture; oxygen
5 ways to prevent cracking
- using high-quality concrete
- properly curing the concrete
- protecting the concrete from moisture and oxygen
- using corrosion-resistant reinforcement
- minimizing defects in the concrete
3 techniques to improve durability of reinforced concrete beams
- using high-quality concrete
- using corrosion-resistant reinforcement
- protecting the concrete from the environment.
3 techniques to control the deformation of reinforced concrete beams
- using high-strength concrete
- using closely spaced reinforcement
- using stirrups
3 techniques to control the deflection of reinforced concrete beams
- using a deeper beam
- using a smaller load
- using prestressing
3 things to consider regarding the deformation of reinforced concrete beam
- durability
- crack control
- deflection control
3 methods of analyzing deformation
- elastic theory of bending
- plastic theory of bending
- finite element method
this method of analyzing deformation assumes that the concrete and steel in the beam behave elastically
elastic theory of bending
this method of analyzing deformation assumes that the concrete in the beam behaves plastically after it reaches its yield strength
plastic theory of bending
this method of analyzing deformation is a more sophisticated method that can account for the non-linear behavior of concrete and steel
finite element method
four criteria to determine whether a prestressed concrete beam is superior to an ordinary concrete beam
- load-carrying capacity
- deflection resistance
- crack control
- durability
true or false:
prestressed concrete beams have a higher load-carrying capacity than ordinary concrete beams
true
true or false:
prestressed concrete beams have a better deflection resistance than ordinary concrete beams
true
true or false:
prestressed concrete beams are less likely to crack than ordinary concrete beams
true
true or false:
prestressed concrete beams are durable and can withstand a variety of environmental conditions
true