Strolling through the warm breeze down MacArthur Causeway, while contemplating the deep blue waves of the Atlantic Ocean, you will find yourself mesmerized by The Crown of Miami. Royal Caribbean’s Cruise Terminal has earned its majestic name as it resembles the shape of a giant crown made of glass. To accomplish the vision of a crystalline facade, the design required the installation of a window system called a Curtain Wall. This architectural gem wrapped in glass is able to safely sustain itself in the middle of hurricane city with the help of structural calculations performed by Eastern Engineering Group 🌴.
Before learning about the engineering behind window systems, I didn’t understand how this terminal was able to maintain its structural integrity considering the location it was built on. I mean, think about it. A cruise terminal covered in glass? IN FLORIDA? Am I the only one who thinks this is a hazard? I certainly did not know what I was getting myself into when I decided to “dive” a little deeper. Not only are window structures designed to take on different types of pressures, but they also go through rigorous testing to make sure they can truly endure these forces.
This being said, get ready to explore a small fraction of the endless ocean of windows, as we unravel the engineering behind the Curtain Wall that hangs royally at The Crown of Miami. 👑
Let’s Talk About Wind(ows)
A window is defined as an opening that allows the passage of light and sometimes air. However, this explanation falls short considering windows play an important role in the concealment of a structure. For structural engineers, windows are more than just an aesthetic accessory for an establishment. To some extent, windows become the “protective armor” of a structure. Structural Calculations will determine the specific structural design that will allow this window system to be functional and safe.
For our Cruise Terminal example, functionality would include the passage of light and preventing heat and water from coming into the facility. Safety would mean the windows are able to receive strong wind pressures and the impact of an object, without compromising the stability of the structure.
Even though there are multiple factors to consider, wind and what wind may be able to transport was the aspect that concerned me the most. Yes, we can address the elephant in the room. Hurricanes terrify me 🙄. Therefore, to build up my understanding behind the engineering of window structures, it was also important for me to learn a little bit more about wind.
The Power of Wind
Wind Load is the total force an object receives considering the wind speed and direction the wind blows. There are two types of wind loads a building will receive. Uplift Load vertical pressures of wind that can cause lifting effects. And Lateral Loads involving horizontal pressure, that can cause a building to move off its foundation. Lateral loads could cause vertical elements to crack.
During a hurricane, wind presses against the glass and the load is extreme. The amount of pressure our terminal could potentially receive, was what dictated the conditions for the structural calculations. This being said, lateral loads will be our concern for this window system. Depending on the direction of the wind, this one can produce either positive or negative pressures. Positive pressures when it pushes, negative pressures when it “pulls”.
When wind is exerting a positive pressure onto the face of a structure, the pressures that build up on all the opposing sides create a suctioning effect. Therefore, why we say negative pressures are “pulling”. In other words, when roofs flew off during Hurricane Andrew back in 1992, it wasn’t because wind was pushing them up, but it was suctioning the roofs off instead. How is this even possible? With an increase in velocity, a decrease in pressure occurs and the results is a vacuum effect. Apparently, I did not assist any of my physics classes when this concept was explained 🙄. However, this principle explains why anytime a car rushes past yours in the highway, you feel like it pulls your car towards it.
Don’t Go Breaking My Window
When it comes to structural calculations, enclosed facilities are calculated to remain enclosed. Enclosed meaning closed off on all sides. Even though the outside facade, meaning walls and windows, might have been calculated to endure strong wind pressures, the inside was certainly not. If the glass receives an impact that causes it to give away and break out, it creates an imbalance of pressure inside and outside the structure. This imbalance can compromise the structure and harm the occupants.
After 1992 The Florida Building Code changed drastically. Currently, it enforces very strict laws that demand the windows of a structure not only to remain attached to the building in case of a hurricane, but to remain enclosed as well.
How do they regulate this? Window structures must pass several tests in order to receive the approval of the building department before installation. Additionally, shutters and impact windows are the two ways of safely protecting windows against impact. Since Royal Caribbean’s cruise terminal is saturated with windows, shutters are not an efficient way to protect this structure. Consequently, impact glass panels were the wise choice for our curtain wall.
The Regal Curtain Wall
A Curtain Wall is usually an aluminum-framed wall formed by glass panels that is anchored to the outside of a structure. In other words, the windows are hanging from the structure, rather than fitted into the structure. This system can carry its own weight, while transferring the load of wind and gravity to the structure.
The Curtain Wall design that was selected came from Florida Approval FL #28879-1. An NOA (Notice of Acceptance) or Florida Approval is a pre-approved document for a pre-designed and pre-engineered product. Learn more about NOAs on our blog article Structural Design and Structural Analysis.
This document was designed to ensure certain structures, like our curtain wall, have been tested and approved to be installed because their structural calculations were proven to be accurate, hence safe. (Phew 😅) This window structure was tested to specifically endure large and small missile impacts, cyclic wind pressures, among others.
In the Crown of Miami’s curtain wall design, double glazed insulating panels were decided upon for use. Now, by double glazed I do not mean extra portions of superb, sugary goodness typically found atop donuts 😋. When it comes to glass, the term glazed refers to the act of being fitted with panes of glass. A pane is the actual piece of glass that makes up a window. Double glazed simply denotes the presence of two glass panes. In the middle of these panes, there is usually air or a non-reactive gas. This substance serves to decrease the effect of heat, which makes them energy efficient. In essence, not only are these windows safe, but they are also environmentally friendly 😍.
Artistic Structural Calculations
As we see millions of windows every day, they have become ordinary and we tend to miss their elaborate structures. Furthermore, I did not expect window systems to require so many calculations and tests in order to be effective. Although this article has briefly touched on some of the aspects to consider when performing structural calculations for windows. Let me emphasize on the fact that there is still a deep ocean to unravel before we can entirely explain their structure.
Throughout the experience of writing this article, I was mind-blown by the engineering process for window structures. Understanding the behavior of wind and the ways it can affect a structure, allows engineers to determine what designs work best. This is one of the many reasons we believe structural engineering is the point where art and engineering meet. Combining scientific knowledge with design, is an art of its own.
Windows to the Soul
Structures that display a window facade have become increasingly popular. Not only because they are aesthetically pleasing, but windows are also our gate to the outside world. As we become more environmentally conscious, we have learned to appreciate the outside world and we realize how important it is for our mental sanity. William Shakespeare once said, “your eyes are the windows to your soul”. I believe windows give structures a soul. This terminal was certainly capable to match the majestic image the brand can portray. The feeling of bliss you get when walking into an establishment that is full of natural lighting is certainly indescribable. And this is the experience Royal Caribbean was definitely able to safely accomplish for their guests.
**Thank you Alphacladding for making us a part of your team and allowing us to do the structural calculations for the window system of this project.**