To those with an untrained eye, a blast-resistant building may resemble a shipping container. But the differences between a shipping container and a blast-resistant building are paramount.
At RedGuard, we’ve been developing blast-resistant buildings since 2005, after a Texas City oil refinery accident killed 15 people and injured nearly 200 more. At the time, the company, then known as ABox4U, leased and sold shipping containers for use as storage boxes on refineries, construction, and other hazardous work sites.
The story goes that engineers investigating the Texas City accident observed that portable trailers that had been used as offices and break rooms for contractors, service technicians, and maintenance personnel, were decimated during the blast. On the other hand, steel shipping containers that stored tools and equipment appeared mostly unharmed. So, conversations behind the scenes started, and Jeff Lange, RedGuard’s founder, saw an industry need that he could fill.
Because of this history, many people will assume that a steel blast-resistant building is a shipping container. Let’s take a look at some of the similarities and, more importantly, the differences.
What goes into creating a shipping container?
Shipping containers are made to haul goods of all kinds across the lengths of oceans on container ships, and then they can be transferred by railcar or semi-truck once they arrive at the port. A shipping container is designed to be used for around 15 years, but some last for as many as 30 years. In recent years, many people have found some interesting alternative uses for these containers once their use shipping goods around the world ends. Recent examples include examples like homes, shopping centers, swimming pools, and even underground shelters.
Because their intended purpose starts in harsh environments, they have to be built ruggedly. Shipping containers have to get through many years of salty ocean spray, heavy rain, wind, hurricanes, and a lot of rough handling. For this reason, most are made with steel walls, welded to a steel frame. They have a closed top and doors that swing open on either end. For some of these same reasons, our designers decided to stick with steel components when designing our first blast-resistant buildings.
Because containers go from being stacked and stored on a yard, shipped on a container ship, transferred to a rail car, and then shipped on a semi-truck, all in the same journey, they have to conform to a set of industry standards. Shipping containers are made to conform to ISO standards so that they all have standard shapes, sizes and can be moved and hauled with the same equipment. Blast-resistant buildings also make use of these same standards, in order to ease transport and shipping.
It’s fair to point out that, yes there are a few similarities. But the differences are important.
How Do Blast-Resistant Buildings Differ?
You might say that shipping containers were the germ of an idea for blast-resistant buildings. They were the humble beginnings that sparked the idea, but things have changed since then. In some ways, drastically.
Designs for steel modular blast-resistant buildings vary depending on the manufacturer, so we can only tell you how RedGuard’s designs differ.
In designing a blast-resistant building, our engineers took a cue from the human body. They began with a steel frame with closely spaced vertical and horizontal stiffeners. “Closely spaced” being the key. The frame acts as a “rib cage” of sorts. The ribs of the human body, closely spaced in the same way, protect the body’s internal organs. The ribs compress to protect internal organs, the same way the steel frame of a blast-resistant building will. In the industry, this is called “dynamic load transfer,” or flex.
Talk about "flex" can be controversial in the blast-resistant building industry. And, we agree, too much flex could be bad. That's why RedGuard buildings are designed to minimally flex, allowing for much less deformation when compared to other steel blast-resistant buildings on the market. And, it's no theory. We've tested our design to demonstrate that it provides a safe environment for occupants.
Next, we use steel sheeting, either corrugated steel walls or flat plate, welded to the frame. That gives us a structure that is already quite strong. Then, engineered, steel, blast-resistant doors are added. And, possibly windows too, depending on how the building will be used. If you were modifying a shipping container, you would likely not use these blast-resistant doors and windows. The critical thing to remember about these items is that individually they have to be as strong as the structure itself, to protect the integrity of the building’s blast-resistant envelope.
The building design uses structural redundancy to ensure protection. Structural redundancy means that the failure of one element will not cause the failure of the whole structure. Every element of a blast-resistant module is carefully considered.
What about inside the blast resistant building?
Interior elements are also a significant consideration when it comes to blast resistance. Everything placed inside the building, like floor and ceiling tiles, electrical or plumbing components, furniture, wall coverings - everything - has to be considered. When a shipping container is customized for most purposes, these considerations wouldn’t be necessary.
During a blast event, fragmentation of interior components is dangerous. Perhaps one of the biggest dangers to occupants. If these elements were to become loose or dislodged, occupants of the building could be severely, possibly fatally, injured by flying debris. All internal elements are scrutinized to minimize the risk of impact. And, any added components, like cabinetry or furniture, must pass muster and must be used in ways that conform to safety.
Our early units — and to this day, many of our lease units — have interior walls made from oriented strand board (OSB), which minimizes the risk of fragmentation. Our latest fleet designs use Insulated Composite Panel that sits in an upper and lower track. The panels have a foam insulation core sandwiched between two pieces of aluminum that can be smooth or embossed. It minimizes the risk of creating any debris or shrapnel while providing additional insulation and a safe, bright, and easy-to-clean interior finish.
At one point, internal light fixtures presented a major challenge. Broken glass can be lethal in a blast, so we use tamper-proof fixtures, like those used in correctional facilities. These specialized fixtures have glass tubes, encased in a hard plastic shell, with another casing around the entire fixture. If a tube breaks during a blast event, the glass is safely contained behind two layers of protection.
Another internal element, the electrical conduits in RedGuard blast-resistant fleet buildings, are surface mounted. This allows personnel to see whether these components have been damaged after an explosion. We also included fire extinguishers, smoke detectors, and battery-powered emergency lights to help occupants instantly assess an emergency and escape to safety as quickly as possible. The insides of a blast-resistant building are engineered for safety, just as the exteriors are.
Other amenities that make a Blast-resistant Building specialized
As you can begin to understand, there are quite a few differences between a shipping container and a blast resistant building, both in the exterior design and on the inside.
Every time a new amenity or feature is added, careful consideration is taken in regard to the element’s effect on the building’s blast resistance. When you customize a regular shipping container, considerations of the sort don’t usually need to be taken. Most of the elements mentioned thus far are pieces that are considered standard, but it’s important to note the many options and features that can be added, based on needs and specifications. Just a few of the items up for consideration when creating blast resistant modular space:
- Gas detection units
- Pressurization with fresh air stacks
- Fireproof coatings
- Doors and windows
- Eternal aesthetics that allow you to change the look (like brick exteriors, for example.)
When you think of shipping containers, remember that while the humble beginnings of the blast-resistant buildings may have started there, today they are but distant cousins.