Chapter 8 - Slender Columns

Question 1

What’s the equation for the radius of gyration?

Answer 1

i = (I/A)^0.5

Where:
I = second moment of area.
A = area of section.

Question 2

What are the β0 values for the following unbraced end conditions: fixed-fixed, fixed-pinned, pinned-pinned, cantilever?

Answer 2

Fixed-fixed = 0.5
FIxed-pinned = 0.7
Pinned-pinned = 1.0
Cantilever = 2.0

Question 3

What is the difference between a braced member and an bracing member?

Answer 3

Braced member is a structural member which is assumed not to contribute to the lateral stability of a structure.

Whereas bracing members do contribute to the lateral stability of a structure.

Question 4

How are pcr and fcd related?

Answer 4

If pcr > fcd, the column will crush before it buckles.

If pcr < fcd, the column will buckle before it crushes.

Question 5

What is the minimum value for ki and why?

Answer 5

Minimum ki value = 0.1

Because you can never have a truly ridgid connection.

Question 6

What is the word and letter equation for k?

Answer 6

k = column stiffness/sum of beam stiffnesses

k = (EcmIcol/Lcol)/Sum(2Ecm*Ibeam/Lbeam)

Question 7

What an assumption you make about the columns above and below the one you are analysing?

Answer 7

The stiffnesses of the columns above and below are ignored from analysis.

Question 8

How do you know if a section order analysis is required or not?

Answer 8

If λlim > λ, second order analysis is not required.

If λlim < λ, second order analysis is required.

Question 9

What is the difference between a second order and first order analysis?

Answer 9

Second order analysis take into account structural deformations whereas first order doesn’t. First order does take into account geometric imperfections though.