If you’re looking for the answer to, “What are blast-resistant modular buildings?” then this article is exactly what you need. Over the course of this article, we’ll discuss the costs involved in the construction of a blast-resistant building project as well as its important design aspects.
Blast-resistant modular buildings are structures that have been specially designed to resist significant explosions and to protect property and personnel in hazardous working environments like ones encountered in petrochemical facilities, oil and gas refineries and chemical processing plants. Blast-resistant modular buildings are also known as blast-resistant units, blast-resistant modules, or simply as BRMs or BRBs.
Typically used in oil and gas facilities, military buildings and high-security federally-owned buildings, BRMs are constructed with thick walls of special steel that can withstand extremely high blast pressures. Moving to the inside of the structure, the same assurance is also provided with the non-structural components of BRMs such as the electrics, plumbing, the light fixtures and the cabinetry.
Now that we’ve given you the basics on BRMs, let’s move on to their architectural design aspect.
Architectural Aspect of BRM Design
When it comes to the architectural aspect of BRMs, the primary aim is to minimize the damage to the structure and its occupants in the event of an explosion. The priority is to prevent complete structural failure of the whole building or large parts of it. Another major requirement is to minimize the impact of blast waves and projectiles that may be transmitted into the structure through openings. The main architectural challenge with blast-resistant buildings is to come up with a solution that satisfies all major requirements, such as the construction budget, aesthetics, firefighting regulations and accessibility variations.
Planning & Layout
The planning stage of a BRM is critical as a lot can be done in terms of limiting potentials hazards and the damage and injury risk associated with them. Some important considerations include the levels of danger in the area of construction, analyzing the need of blast protection for non-structural and structural members, and strategic placement of shelter areas within the project.
In buildings where there’s a risk of external threats, the goal should be to maximize the standoff distance between the potential threats and building as much as possible. If your project is in a congested commercial area or city center, chances are that there isn’t much scope in terms of positioning the building. However, it’s important to secure standoff areas wherever possible. This can also be achieved by placing obstructions such as trees and bollards in strategic locations around the building.
Internal Layout & Structural Form
A crucial parameter, structural form has a significant bearing on the blast loads of the structure. Structural forms that involve domes and arches are more likely to reduce the effects of a blast compared to those that have a cubicle form. Another factor that greatly influences the blast load magnitude experienced by the building is its plan-shape. If the building has a complex shape, it’ll cause the blast waves to reflect multiple times, potentially increasing the impact of the explosion. Another point worth noting is that single-story structures, if applicable, offer better blast-resistance compared to multistory ones.
Also, fully or partially embed structures have superior levels of blast resistance. These buildings utilize the shock absorbing properties of the soil to their advantage. The soil can provide protection in the event of a nuclear explosion as well.
When it comes to the building’s internal layout, the aim while undertaking this parameter should be isolating the assets of the greatest value from the potential threat. This means that the layout should be arranged in such a way that there’s maximum distance between the most valuable assets and the highest potential threat. Some effective internal layout strategies used in the construction of BRMs include:
- Walls of reinforced concrete for the protecting foyer areas.
- Double-dooring and eccentric arrangement of corridor doors to limit the blast pressure from being transmitted into the building’s interior.
- Controlled building entrance that’s separated from the other parts of the structure
- Installing fire-resistant structural members
Installations
Interior installations such as water, gas, and steam lines, electrical and plumbing connections, water storage systems and elevators should be planned to be resistant to the affects of explosion. It’s critical to prioritize installation connections and their use should be avoided in areas that have a high risk of deformation. The installation of electrical and gas lines should also be avoided in areas that are likely to receive high damage. These include external walls, roof slabs, ceilings and lobbies. Installation feeding points and main control units should be placed in areas where they’re shielded from direct or high exposure to the blast waves. Furthermore, it’s important to provide a secondary installation system located away from the main system that can be used as a reserve in the event of an explosion.
Cladding & Glazing
Glass from shattered building windows can cause a large number of casualties in the event of an explosion. Therefore, it’s critical to opt for a safer glazing solution. Laminated glass is a viable option as it doesn’t break into large dangerous shards when it shatters. Another effective solution is applying a transparent anti-shatter film to the glazing’s interior surface.
When it comes to the building’s cladding, numerous design aspects should be considered to maximize the protection for the building’s inhabitants and minimizing damage to the structure itself. Minimal amount of glazing should be used in the facade. This reduces glazing induced internal damage and limits the amount of blast waves that enter the building. Furthermore, it’s vital to ensure that the connections between the cladding and the structure are strong, secure and accessible. This will allow a quick and effective inspection for movements or failures after the structure has been subjected to an explosion.
Having discussed the architectural aspect of BRM design, let’s take a look at the factors that influence the costs of a BRM project.
Costs of a BRM Project
As there’s such a wide array of options and variables when it comes to the construction of a BRM structure, there’s no single answer to how much it costs. They ultimately depend on the size and the amenities that are required for the structure.
However, before you start entertaining bids from BRM manufacturers, here are some key points to address:
- How long do you plan to use the building
- The location of the building in terms of proximity to threats and hazards
- The size and type of the building
- If gas detection and pressurization features are required
- The specifications of the required interior components (communications, electrical connections, fixtures)
- State-specific building regulations and requirements
- The base of the building
How Long Do You Plan to Use the Building?
The first factor to consider is how long you intend to use the building. This will determine whether you should lease the building or purchase it, which probably has the biggest impact on your project’s cost.
If you require buildings just for the duration of a turnaround but won’t be needing the space after it’s done, leasing a BRM is a viable option. Some manufacturers offer modular buildings for specific uses and in standard sizes.
If there’s a scope for flexibility in your specifications, make sure that you let the manufacturer know. This will ensure that all cost saving efforts are accommodated. For instance, if there’s a scope for flexibility with a building, chances are that you can use an existing building from your fleet. This will be significantly more cost-effective than modifying a standardized building.
What are the Hazard Levels in the Area of Construction?
Another critical factor to consider is the location where the building will be placed. This is important as the proximity of the building from potential threats determine the PSI levels it’ll be exposed to in the event of an explosion. Also, the duration of exposure, usually measured in milliseconds, is an equally important factor. BRMs come with various “response levels”, which is a measure of a BRM’s resistance to PSI levels and duration of exposure. To ensure safety in dangerous work environments, BRMs in dangerous areas should have low to moderate response ratings.
Talking about the response levels of BRMs, buildings that have a low to moderate BRM can actually provide better protection to their inhabitants. Although it appears counter-intuitive, response ratings are assigned to buildings on the basis of how much it would cost to repair the building after it has been subjected to an explosion, instead of the level of protection it provides.
Response levels were established by the ASCE (American Society of Civil Engineers). Here is how each level is defined:
- Low Response: The total repair costs are low to moderate. The building can be reused after it has been subjected to a blast; however, repairs need to be performed to restore the building’s structural integrity.
- Medium Response: The building is likely to suffer component damage on a wide scale, making it unsuitable to be occupied until repairs are performed after an explosion. The total repair costs are high.
- High Response: It’s highly likely that the building has lost structural integrity and there’s a high risk of it collapsing due to weather conditions such as strong wind, rain and snow. The building is essentially written off as repair costs would be equal to the building’s replacement costs.
The costs of low and medium response buildings are significantly higher as their construction requires additional raw materials such as reinforced concrete and steel. Furthermore, they have more structural support, thicker walls and additional connect point welds.
In some cases, C1D1 or C1D2 electrical classifications are required by buildings that are located in close proximity to the explosion hazard. However, structures classified as “General Purpose” can be placed in the area of hazard, but not in close proximity to the hazard.
The bottom line is that buildings that are placed closer to the explosion hazard require a design that can withstand high blast pressures and a C1D2 electrical classification. On the other hand, buildings that are at a considerable distance from the explosion hazard, but still within the blast zone, can have a “General Purpose” electrical classification and a regular design.
The Type & Size of the BRM
Contrary to popular belief, not all BRMs are the same. In fact, a blast-resistant building can be designed to have the appearance and functions of almost any kind of building. As we’ve already discussed, the cost of a BRM is ultimately driven by its specifications with regards to amenities, and the actual size of the project, which will obviously determine the amount of raw material that’ll be required for its construction.
Additional factors to consider include the impact the width and height of the structure have on transportation costs. If you require a large amount of space, you can opt either opt for a single building, multiple buildings or a building that’s comprised of multiple sections, where a larger area is created by placing several components together.
Requirements in Terms of Interior Finish & Internal Components
While the exterior is obviously important in BRMs, internal components also play a huge role in how effective a BRM project is. One of the most prominent sources of casualties in explosions is projectiles. Therefore, it’s vitally important to ensure that the internal components of the building are designed and installed in such a way that they don’t turn into projectiles in the event of an explosion.
This means that all internal components such as plumbing fixtures gas, electrical and water connections, furniture, cabinetry, etc need to be taken into account. This will naturally have an impact on the total costs of the project.
Another factor that has a bearing on the total costs of the project is the electrical finish. In some BRM projects, surface mounted electrical are utilized, so that all the wiring and connections are visible on the walls and ceilings. While this does have an impact on the interior’s aesthetic appeal, it’s a more cost-effective method and provides superior accessibility.
Does the Project Require Pressurization & Gas Detection Features?
If the BRM is to be placed in an area where hazardous elements are present in the atmosphere, it’s likely that the building will require the use of gas detection and pressurization. These are yet other factors that will drive up the costs of the project.
Adding gas detection and pressurization capabilities means that changes need to be made to other elements of the building as well. For instance, you have to consider how the openings of the building are sealed in order to prevent toxins from entering.
The same goes for adding pressurization. A wide array of additional components such as fresh air stacks will need to be incorporated into the design. All this will add complexity to the project, which in turn, will drive up the costs of the project.
Are There Any State-Specific Building Regulations You Need to Consider?
Depending on the location where the project is being placed, the authority that has jurisdiction over that area may have their unique set of regulations and requirements. These can be state-level or federal-level regulations.
These regulations need to be considered at the initial stage of the planning process to ensure that the project remains compliant during all stages of its construction and usage and the costs of compliance can be taken into account and planned for.
Examples of AHJ requirements include the installation of fire alarms and sprinklers, specific type of electrical finish or utility connections and special equipment for controlling and regulating emissions.
So What Are the Final Costs of a BRM?
As you might have gleaned from the points mentioned above, all the different elements of a BRM are interconnected. This means that the final costs depend upon a wide array of factors, which makes it impossible to state an accurate cost estimate.
However, the two most important factors to be considered are the project’s proximity to the blast hazards and whether you want a temporary or permanent building. Once you have these two factors in order, you can start to look at individual specifications and how complex the project needs to be.
