Listowel

Question 1

What was lacking in the NBCC prior to the arena collapses in 1959?

Answer 1

Little info recorded in Canada on snow loading on arch-shaped structures.

Question 2

NBCC 1953 to 1960 lacked…

Answer 2

provisions in selecting uniform and non-uniform snow loads on arch-structures

Question 3

1965 NBCC changes and issues

Answer 3

snow load distributions used in USSR.

Not directly applicable in Canada. Often experience one side completely clear.

Question 4

NBCC 1970 and 1975 changes

Answer 4

One-sided loading (1970 to 1975 the same)

Question 5

Issues discovered after 1975 Code

Answer 5

Only considered flat, long-span arches.

Steeper, shorter-span arch structures more common in Canada.

Question 6

1977 NBCC changes

Answer 6

Based on snow-load study in the Ottawa region:
- Provisions for uniform snow loads
- Slope reduction factors
- New distributions for nonuniform snow loads
- considering snow drift

Question 7

1980 NBCC changes

Answer 7

provided modifications to the distribution of snow loads on arch structures

Question 8

1985 NBCC changes

Answer 8

• increased the unit weight of snow by 1.9%
• simplifications to examine unbalanced loading on arches
• specified loading due to snow accumulation (formula)
• snow load factor due to tests in Canada
• wind exposure factor

Question 9

1990 NBCC changes

Answer 9

• increase unit weight of snow (2.4 to 3.0)
• Lowering wind exposure factor (0.75 to 0.5) for exposed roofs north of tree line
• Revised design snow loading formula (separating snow and rain loads)
  –> assumes snow would drift due to wind loads but not rain