Design Loads:

Load for which awning and canopies may need to be designed can be categorized as follows:

Dead Load
This is the self-weight of the awning or canopy frame, fabric and hardware. This load must always be included with other design loads since it is always acting on the structure. For instance, if one were designing an awning for 20 psf snow load, and the structure itself weighed 2 psf, then the design for snow should actually account for 22 psf total load.

Wind Load
This load, as well as snow load, are usually the most critical loads on awnings and canopies.

Important aspects of wind load are:

A. Speed or Velocity
Basic wind pressure is a function of its speed. Basic wind pressure (psf) can be computed as the product of 0.00256 times the square of the wind speed (mph). It can be readily observed then, for example, that the wind forces on an awning are four times greater if the wind speed is doubled, and the forces are nine times greater if the wind speed is tripled. Design wind speeds are generally shown on maps published in the building code. Local codes may require higher design wind speeds.

B. Exposure
This is a general category for the amount of protection from the wind that is afforded by the surrounding environment. Structures located in wooded areas, for instance, do not have to be designed for as much wind force as a structure located in an open area.

C. Gusts
These are short-term excursions of velocity above the steady design velocity, which must be accounted for in the design.

D. Drag, Lift
Drag is the wind-induced pressure toward the fabric surface, and lift is the pressure away from the fabric surface. Wind forces on an awning system act in different directions (toward or away from the fabric surface depending on a variety of factors). When designing an awning frame, all these factors must be taken into account.

E. Return Period
This term is used to describe the time interval which is the basis for establishing the required design wind speed. For most applications the return period is 50 years. This simply means that the required design wind speed is that which has a 0.02 statistical probability of occurring once in 50 years. Loss and safety experts have determined that it is an acceptable level of risk and have based code design requirements on it.