Module 7

Question 1

Historical Performance Objectives of design

Answer 1

• life safety in rare earthquake

- serviceability

Question 2

serviceability

Answer 2

building remains functional after frequent events

Question 3

Modern Performance Parameters

Answer 3

• annual probability of collapse
• expected annual monetary loss (EAL)
• downtime

Question 4

downtime

Answer 4

time building will likely remain unoperation following a certain intensity event

Question 5

ELF

Answer 5

Equivalent Lateral Force Method
1. estimate Tn
2. read off spectral accn demand
3, Identify mu or Ry and calculate design base shear force
4. Distribute base shear as a set of equivalent lateral forces and identify design actions on structural members

Question 6

Variation of ELF

Answer 6

first develop an inelastic spectrum for the target ductility level using R - mu - T relationship

Question 7

Limitations of ELF

Answer 7

• period of vibration is required at start (can be affected by strength and section sizes)
• ductility is set/assumed to be purely a function of structural typology (not checked)

Question 8

Uncertainties affecting dynamic response in EQ

Answer 8

• seismic intensity
• uncertainty in period
• uncertainty in damping

Question 9

Impact of Foundation Flexibility

Answer 9

• system stiffness reduces … natural period increases
• causes decrease in Sa but increase in Sd
• may not be conservative to neglect effects of foundation flexibility
• can also change system ductility capacity

Question 10

non structural elements can be

Answer 10

• acceleration sensitive (sprinklers, chimneys)

- drift sensitive ( windows)

Question 11

Three possible retrofit strategies

Answer 11

1. increasing strength and stiffness
2. improving connection details - increase displacement capacity
3. adding damping

Question 12

increasing strength and stiffness

Answer 12

adding new structural elements

• reduces Tn
• increases Sa (bad for accn sensitive non-structural elements)
• decreases Sd (helps reduce both structural and non-structural drift damage)

Question 13

improving connection details

Answer 13

• means that hopefully disp capacity > disp demand
• does not change period or seismic demands
• check that drift-sensitive non-structural elements can resist new increased structural capacity

Question 14

adding damping

Answer 14

• not as common bc EXPENSIVE
• energy dissipation
• reduce Sd and Sa for elastic system by a factor n

Question 15

n

Answer 15

n = sqrt ( 0.10 / (0.05 + damping) )