In the building enclosure industry, a structural glass wall is mostly transparent and can be designed with minimal structural elements, except for the glass. A more modern alternative to curtainwalls, structural glass walls eliminate continuous glass supports, greatly decreasing the visual sightlines within the system. When considering a structural glass wall system, it is crucial to identify the type of support system: dead loaded, tensile or suspended, and how the system will interact with and impact the building structure
Structural glass walls that are dead loaded typically have the least impact on the building structure. In this case, the load of the system is transferred to the base of the system, which is supported by a structural concrete footing or slab. Similar to a dead-loaded, high span curtainwall, the structure at the top connections of this design will need to accommodate mostly wind load anchor connection reactions. These systems are often more economical than alternative support systems but aren’t without limitations.
With tensile support systems, the structure that supports the glass facade is created by an engineered assembly of cables or rods, brackets and fittings. The tensioned cables or rods distribute the load of the façade system to the building structure that surrounds the glazed opening. The structure that surrounds the glazed opening will need to be designed to accept the forces created by the tension structure. Using cables or rods as the support structure for the glass decreases the amount of solid structure elements visible within the system.
Suspended systems, such as a structural glass fin wall, use vertical, tempered glass mullions as the system support and hang from the building structure above. By hanging the system from above, these systems can span vertically without the concerns for any progressive collapse if a lower glass lite is broken.
What to Consider
As designers continue to push the envelope of what is possible with structural glass wall systems, the question is not “can it be done?” but rather, “can the project afford it?” By creating a budget, the specific priorities for the project can start to be identified. This will allow the building designers to set the design intent and engage with the appropriate system designers and consultants.
Harmonizing the project budget and design intent is a key objective in early feasibility analyses. Performing a high-level feasibility study of the design concept should also be considered. There are many factors that determine the price of a structural glass wall system: glass module sizes, glass types, support type, number of points of support and required thermal capabilities of the glazed element, among others.
These system components must be designed to meet project performance requirements, such as blast or ballistic considerations, seismic criteria, acoustics and general load and deflection criteria. This study can often identify major issues and even show that this addition is impossible to build onto this type of structure.
A study like this can also determine the availability of materials based on manufacturers’ capabilities and availability. Structural glass wall systems are inherently custom systems that utilize unique and custom components and accessories. The more custom or unique a particular component, the number of suppliers that can fabricate those components shrinks, which could impact project budget and product lead times.
Accounting for system component lead times is paramount in establishing a sound project schedule. If only one manufacturer can make a certain glass or component and that manufacturer’s availability does not align with the schedule needs of the project, this can be a limiting factor and should be taken into consideration. Logistics and transportation can also impact the feasibility of a structural glass wall project.
Who Should be Involved
When designing and developing the structural wall system, there are a number of parties that should be involved throughout the process. A collaborative process is key and should include relevant stakeholders, such as the engineer of record, design architect and architect of record, construction manager and owner representation. Engaging with specialized consultants, designers, installers and manufacturers can help ensure quality and accuracy of information used in this process.
A ‘design-assist’ approach for the execution of this scope of work will yield the best results: scheduled meetings over a set period of time where the concerns of the different members of the team are addressed and resolved so as not to impact the overall project’s design, procurement, manufacturing/fabrication and installation of this element of the building. This approach will also yield the most complete information for the team’s understanding based upon the entire team’s involvement and participation. This type of consistent communication among all of these parties is essential in choosing the correct glass wall structure and ensuring that this element of the facade will be both properly designed and properly installed.
The installation of a structural glass wall system is not a production orientated process. It is all about precision. Installers are handling very large, heavy pieces of glass with precise engineered connections that will have small tolerances. In some structural designs, holes in massive pieces of glass will need to align with holes in other massive pieces of glass.
Safety needs to be top of mind during this process. Everyone working on the project should be aware of the safety hazards, means and methods and a secondary fail-safe should be developed. A safety plan should be created involving all the other contractors, and safe areas need to be dedicated around the area in case a piece of glass falls. Pedestrian traffic should also be kept in mind. Street permits may have to be obtained and utilized, which could alter the contractor’s plans.
When a structural glass wall system is chosen to be used in a project, it is crucial to choose the proper support system, whether it is dead loaded, tensile or suspended. It is also important to determine if this type of wall system is feasible and fits into the project’s budget and timeline. Ensuring that all parties (contractors, structural engineers, building owners and subcontractors) are involved in the process every step of the way will help the structural glass wall system be installed in a timely manner and keep everyone safe.