About Awnings & Specifications
An awning is an architectural projection that provides weather protection, identity or decoration to the building it is being attached. When considering an awning it is important to recognize the purpose of your project, the style and size of an awning project along with other key considerations. Purpose
- The purpose would satisfy any one or all of the following functional objectives: Energy savings; weather protection (Sun, rain, snow, sleet, hail, and wind), identification, or aestheticsStyle, Configuration, Color
- Most awnings
and canopies consist of fabric stretched over and secured to a fixed metal frame that is secured by laces, screws or staples. These frames may be welded, bolted or otherwise connected. Other awnings and canopies that consist of individual fabric panels can be attached using the staple in method. Still other awnings and canopies consist of rollers and lateral arms that can be retracted manually or automatically. It should be noted, however, that the possible combinations of awning styles
, configurations and colors are limitless.Size and Fit
- The size of an awning is determined by its length, width and projection from the building to which it is attached. Other aspects of size include clear height (underneath), rise (pitch) of roof and post or rafter spacing. The fit of an awning is determined by the interfacing of its frame
with other connecting structures (most often a building, but frequently the ground or a concrete slab on the ground). In the case of a building, it is important to coordinate the appropriate parts of the awning frame with structural members in the building so that loads are transmitted properly.Strength
- After stable configuration has been established for an awning frame
, members should be chosen for strength consistent with the amount and type of stress imposed on them. The most common types of stress are tension, compression, bending and shear.Frames fixed vs. Movable
- Frame systems are recommended by the manufacturer, according to personal preference and regional norms. A fixed awning frame cannot be deployed from a stowed position and vice a versa. A movable awning can be stowed against the building to which it is attached. The standard lateral arm and drop arm awnings are examples of movable awnings.* Copyright Awning Division of Industrial Fabrics Association International. 1 All about Fabric Awnings - A guide for city officials, architects and design professionals by: Professional Awning Manufacturers Association a division of IFAI
Awning and Canopy Loads
- Self-weight of the awning or canopy frame, fabric & hardware. Load must always be included with other design loads since it is always acting on the structureWind Load
- This load, as well as snow load, is usually the most critical load on awnings and canopies.
- Speed or velocity - Design wind speeds are generally shown on maps published in the building code. Local codes may require higher design wind speeds.
- Exposure – The amount of protection from wind that is afforded by the surrounding environment.
- Gusts- These are short- term excursions of velocity.
- 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.
- Return period- 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 1 in 50 years. Loss/safety expertsdetermined it is acceptable.
- Required design snow loads are established by maps published in the building code. As in the case for wind, sometimes local requirements are more stringent. On the other hand, in many localities there is no requirement for snow load.
- Ground snow- Beginning point for snow design, the pressure of the designed snow load occurring at ground level.
- Exposure- The amount of protection from the wind that is afforded by the surrounding environment.
- Flat roof snow load- Occurring at the actual roof level, results from factoring ground snow load by coefficient accounting for exposure & height. Many timesflat roof snow load can be as little as 0.6 or 0.7 times the ground snow load.
- Drifting- Building codes require that drifting snow be accounted for in the design of roofs.
- These are loads that are associated with the forces related to human occupants, furniture, equipments, etc. Since these loads are movable, the live load stipulation is an allowance for the most sever anticipated condition or case.Ponding
- This is a potential load on an awning or canopy and must be addressed in one of several ways.
- Design for ponding must be taken structurally
- Keeping the fabric properly supported and taut will avoid the problem
- Remove snow before it melts and ponds water