Loads, and what the steel detailer should know
Some may argue that and understanding of loads and how they affect a steel structure is the realm of the engineer and designer, which is absolutely true - but it's an advantage to any structural steel detailer to have at least a basic understanding of what it takes for a building to remain upright and comfortable for it's inhabitants against the onslaught of forces acing against it.
Loads acting on steel structures may be divided in 3 main groups:
- Dead or Static Loads
- Live Loads, and
- Environmental Loads
Dead or Static Loads are loads imposed by Gravity - these would include the self-weight of the structure including all items that are permanently connected to, and forming part of the structure, including, walls, roofs, exterior finishes, also permanent mechanical equipment including, plumbing and electrical services, air conditioning, elevators, etc. In fact, anything that will be in place during the expected lifespan of the building.
Occupancy Loads: are also vertical loads imposed by Gravity, but unlike static loads, are transient in nature, that is to say, inanimate objects that are not connected to, or forming part of the structure, which may be moved around and relocated according to the requirements of the occupants. Examples of such loads include, furniture, moveable partitions, office equipment, etc.
Occupancy Loads are sometimes referred to as Superimposed Loads under the heading of Gravity Loads, or they may be considered to be Live Loads.
Live loads are dynamic in nature and may be generated from within or outside of the structure. Those from within are produced by the use and occupancy of the building and may be induced by human activity, vehicles in motion, or operational machinery and equipment.
Occupancy Loads may be considered to be Superimposed Loads.
Those from outside of the structure may be generated by vehicle traffic when in close proximity to a road or railway. Ice, snow and rain may also be classified as live loads.
Environmental Loads include Wind and Seismic Loads