Structural glass exterior systems provide striking architectural statement

Scott Welch
November 4, 2008
COMMERCIAL : HARDWARE

From the breakthrough designs of the Apple Store's all-glass cube entrances to the soaring skyscrapers of Dubai, structural glass exteriors have become an increasingly popular choice for architectural design, especially in office buildings, retail storefronts and hospitality applications.

The desire for modern, open aesthetic initially drove the use of structural glass exteriors. Today, green build initiatives and Leadership in Energy and Environmental Design requirements that reward daylighting complement that vision. Higher real estate values for buildings with more windows and increased office productivity from exposure to natural light add to the appeal.

In the past decade, glass has evolved in commercial applications from a purely decorative material to a structural element. It is the only common material to find entirely new functionality. Structural glass systems for exteriors offer architects contemporary design options for all-glass facades and overhead safety relevant glazing. Regardless of the final application, most architects seek to minimize framing and hardware to maximize the openness and transparency of glass. They can achieve their goal in many ways with different structures behind the wall or systems to attach and support the glass panels.

Glass fin systems are a common application, consisting of perpendicular glass pieces that support facades and resist lateral loads. The fins transfer high support forces into the building’s substructure and provide a connection point for structural glass fittings to hold and position the exterior glass panels. Another option is a frame-supported glass system that maximizes transparency through the application of frameless glazing. Other options include cable or tension rod supports.

Generally, structural glass systems feature spider fittings or single-point fixings to connect the glass to the structure. The legs of the spider connection are outfitted with glass connectors that transfer loads and support the weight of the glass. Drilled holes in the glass allow bolts to create a mechanical connection between the glass and the fitting. Fixation points can vary from one to several depending on panel sizes to absorb the loads.

Clamping brackets are another option. In a clamped system, glass panels are secured through the glazing joints rather than bolting through the glass. This eliminates the need to drill or machine the glass before installation. Although brackets tend to cover more glass surface area than bolted connections, hardware manufacturers are getting creative with the shape and look of the clamps, making them architecturally and aesthetically complementary to the glass. Clamping systems also can be used with tension rods or cable-type structures.

Of course, safe load capacity is limited with glass compared to other structural materials. Although glass has a high yield stress, it is susceptible to brittle failure and has a tendency to shatter upon localized impact. Working with a specialized structural glass design expert can help overcome the limitations of working with a product that has enormous aesthetic upside.

As the adoption of glass continues to accelerate in commercial settings, architects will demand increased freedom and aesthetics from the hardware. Hardware manufacturers will answer their demands with technology that allows glass to balance its unique structural function and aesthetic benefits.

The author is manager of marketing and sales operations, Dorma Glas, Dorma Group North America, Millersville, Md., 410/923-0890, ext. 209, swelch@dorma-usa.com.