Design Loads of Steel Buildings
Before the design process of steel buildings begins, customers are advised to visit the local code authorities and get hold of the proper building codes and loadings for the particular locations of the structures. It must be emphasized that this is the responsibility of the customers and not the suppliers of steel buildings.
Here are the descriptions of the design loads for steel buildings:
- Dead Load – The building’s dead load refers to the weight of the structure itself including the primary and secondary framing, purlins, trim, roof, trim, screws, eave struts and bolts.
- Collateral Load – These are additional dead loads that hung from the steel building such as sprinkler systems, drop ceilings, HVAC ducts, lighting, etc.
- Roof Live Load – Roof live loads are very much different from “snow” loads because they are produced (1) by people and movable objects during the life of the building and (2) on occasions such as during maintenance by workers, equipment and materials.
- Ground Snow Load – This is not the same as the roof snow load. This value should represent the snow load that has a 50-year mean recurrence interval. The value of this should be greater than the roof snow load.
- Roof Snow Load – The roof snow load is naturally lower than the ground snow load since it is but natural that most of the snow will fall on the ground.
- Snow Exposure Factor – The characteristic of the site where the steel building is located greatly affects the amount of snow falling on the roof. Aside from roof snow load, authorities have defined another loading, snow exposure load. For example, there would a greater amount of snow falling on the roofs of steel buildings located in wooded areas than those in flat, open areas.
The snow exposure factor is determined based on the type of terrain and roof exposure condition that are representative of the anticipated conditions during the life of the steel buildings.
The terrain categories are:
1) Exposure A – Large city centers where more than half of the buildings have a height of 70 feet and above.
2) Exposure B – Urban and suburban areas, wooded areas or other terrain with a large number of closely spaced obstructions. If the building site does not meet the two other categories, this category shall be assumed.
3) Exposure C – Open terrain with scattered obstructions, including rolling terrains or other irregularities. Regions with flat open areas, grasslands and shorelines in hurricane-prone areas, are included in this category.
4) Exposure D – Flat, unobstructed areas exposed to wind flowing over open water.
The types of roof condition are:
1) Partially Exposed
2) Fully Enclosed
3) Sheltered
(to be continued)
