The effects of windloading and stress corrosion are critical considerations in the design of building facades. Yet, these powerful forces are often discounted in the selection and specification of architectural louvers, grilles and sun controls which are typically exposed to the most severe loading conditions in the facade.

Windload Research
Positive pressures arise from wind striking the windward facade of a structure and increase proportionately to the height above grade. In addition, the boundary layer of air moving around a structure produces vortices that create negative pressures or suction on all sides of the building. Research demonstrates that maximum negative pressures exceed maximum positive pressures by as much as 50% and occur at all levels without correlation to height above grade.

Dynamic Loading
Maximum positive and negative loading events are of high intensity but short duration. Peak pressures are therefore deemed to be dynamic and have the capacity to impart continuous vibration of constantly varying intensity and amplitude.

Design Practice
Designers wisely detail louvers in reveals, airways and other "protected" locations to shield them from prevailing wind and storm conditions and to prevent moisture infiltration. Yet, it is precisely in these locations where louvers are routinely subjected to maximum negative pressures and loading conditions regardless of location above grade. Ironically, louvers incorporate some of the longest unsupported components in the facade.

Vibration And Failure
A sequence of phenomenon occur which inevitably result in the premature failure of louvers assembled with threaded fasteners. Vibration induced by intermittent and dynamic windloading causes wear and enlargement of the invasive formations produced in the base metal by threaded fasteners. Connections that resist initial disengagement are subjected to continued vibration which work hardens and embrittles the invasive formations. At the same time, the dissimilar dielectric properties of the base metal and threaded fastener produce galvanic corrosion in the threaded formations which progressively erode the strength of the connection until unavoidable failure occurs.

Stronger Than Stainless Steel Fasteners
Theoretical calculations prepared in accordance with American Welding Society (AWS) standards demonstrate that welded connections are 5 to 8 times stronger than stainless steel threaded fastener connections. Calculations are available upon request from Airolite or your local Airolite Sales Representative.

Corrosion Resistance
Louver, grille and sun control products constructed with mechanical fasteners are typically produced from pre-finished components that are sheared, sawed-to-length or fabricated after coating, leaving raw and unfinished edges and surfaces that invite adhesion failure and corrosion.

Advantages and Benefits
Airolite utilizes all-welded assembly to produce fully-fused blade and frame connections. Airolite all-welded louvers provide the strength and durability to assure advantages and benefits as follows:

• Greater resistance to vibration damage.
• Elimination of the potential for galvanic corrosion.

Independent laboratory tests demonstrate the significance of the Airolite all-welded advantage in comparative destructive testing of welded and non-welded louver assemblies. Test results include an outline of the experimental procedure, results and an analysis of service durability.

Contact your local Sales Representative for a detailed copy of the Airolite test results.