Loads on Buildings Flashcards
what are dead loads? How are most dead loads calculated?
vertical loads due to weight of the building and any permanent equipment
From a published lists of building material weights found in standard reference sources
What are live loads? How are live loads established?
loads imposed on the building’s particular use and occupancy, and are generally considered moveable or temporary like people, furniture, and moveable equipment.
Wind, earthquake, and snow loads are NOT considered live loads
By the building code for different occupancies
What is a concentrated load? What is the unit of area over which concrete load is assumed to be located?
Code requires floors be designed to support concentrated loads IF the specified load on an otherwise unloaded floor would produce stresses greater than those caused by the uniform load
Concentrated load is assumed to located on any space 2.5 sf
Does the IBC allow for the live load to be reduced?
In most cases, yes! It may NOT be reduced for:
- any public assembly occupancy with a live load < 100 psf
- For any member supporting one floor of a public parking garage
- If the live load > 100 psf
What is the IBC method to calculate live load reduction for members supporting > 150 sf?
R = r(A-150) where r = rate of reduction = 0.08 A = tributary area R must be < 40% for horizontal members or < 60% for vertical members
What are the 4 variables that affect wind loading on a building?
- velocity
- height of the wind above the ground
- building’s surroundings
- size, shape, and surface texture of the building
What are 3 forces on a building due to wind:
- Positive pressure on the windward side
- Negative pressure / suction on leeward side and roof
- Greater pressure at building corners and projections (overhangs, parapets)
What is building drift? Rule of thumb for the maximum allowable building drift?
the distance a building moves from side to side in the wind
Building
should be designed so max drift < 1/500 of building’s height
What is a dynamic load? Examples?
How is it treated by iBC?
when a load is applied suddenly or changes rapidly
(Ex cars in a parking garages, elevators traveling, helicopter roof landing pad)
often treated by IBC as a static load value multiplied by an impact factor
What is a resonant load?
a unique type of dynamic load. A rhythmic application of a force to a structure with the same fundamental period as the structure itself.
Often small compared to other loads, but slowly build and amplify over time
What is the fundamental period of a building?
the time it takes the structure to complete one full oscillation
What is the coefficient of expansion?
Coefficient of expansion = the amount of the change in a material when heated/cooled, measured in inch per degree Fahrenheit
What is a temperature induced load? Example?
What is the solution for resisting this type of load?
Temperature-induced load = if a material is restrained so it cannot move and is subjected to a temperature change, a laid is introduced on the material in addition to any other applied loads
Ie a glass breaking when a metal frame contracts or masonry walls cracking when expansion joints are not provided
Solution is simple = material or assembly must be allowed to expand and contract for the expected distance
For a retaining wall resisting soil loads, what is the relationship between sliding and lateral forces?
The retaining wall must be designed to resist sliding by at least 1.5 x lateral force
A retaining wall must resist overturning by at least __ the overturning moment.
1.5 times
