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Industrial sites include a wide variety of buildings that fall into two main categories: conventional construction (steel-framed, masonry, precast concrete, etc.) and modular construction (trailers, shipping containers, and Blast Resistant Modular steel).
Buildings at modern facilities and new buildings for aging facilities should be designed with facility siting and personnel protection in mind. Buildings using conventional construction are specifically configured for their purpose and can be designed to resist the loads associated with most potential hazards, although not all construction materials are suitable for all hazards. If designed, tested, built, and installed correctly, reinforced concrete construction certainly provides the greatest inherent capacity against blast, fragment thermal, and toxic hazards.
Design beyond blast for a truly hazard resistant building
In the United States, facility siting is a requirement of the OSHA PSM standards and is intended to provide safety to onsite occupants from hazards that include explosion, thermal, and toxic events. The American Petroleum Institute Recommended Practices (API RP) 752 and 753 provide guidance for the siting of permanent and temporary buildings, respectively. While these guidance documents provide a good starting point for the location of personnel on-site, there is a heavy bias towards protecting against vapor cloud explosion events.
As a result, the design of buildings at industrial facilities has typically focused on the structural response of building components to blast loads and not on the vulnerability to building occupants associated with a full range of hazards such as fragment, thermal, and gas ingress (flammable and toxic) in addition to blast. Therefore, a disconnect exists between “hazard resistant buildings” and the actual protection afforded to occupants, which can result in unknowingly placing personnel in buildings that afford inadequate protection.
Benefits of modular construction
Modular construction has many benefits for industrial applications - most notably the time and flexibility offered. With modular construction, a building can be designed, fabricated, and assembled in a fraction of the time of a site-built structure with the flexibility to adapt the modular layout with floorplans to meet the site’s needs.
TIME – With the modular building and/or building sections designed and fabricated off-site, and delivered ready to assemble, building finalization is simply a matter of selecting floor layout and any optional items. Having the structural modular sections fabricated off-site also removes approximately 60 to 70% of the building construction activities on-site. This reduction of on-site activities decreases the overall construction schedule by at least 30 to 40% when compared to traditional site-built construction. Other benefits from minimizing on-site construction activities include fewer disruptions to site operations, improved overall site safety, and greatly reduces the risk of construction weather delays.
FLEXIBILITY – The modular construction can often be configured to make the best use of available space, which allows for a flexible floorplan that fits the site’s needs. Office spaces, meeting rooms, locker rooms, break rooms, bathrooms, and conference rooms are just a few options for modular fit-out.
Benefits of concrete construction
In addition to having inherent weather protection against sun, wind, rain, and storm debris, reinforced concrete construction has inherent thermal and blast protection that is not present in fabricated metal panel buildings. To determine the degree of protection reinforced concrete provides beyond traditional metal construction, a full-scale testing program was undertaken to compare concrete panels to corrugated metal panels.
Reinforced concrete buildings provide thermal resistance that metal buildings cannot without installing thermally resistant materials that, unfortunately, produce smoke and toxic off-gas when exposed to fire events. This thermal protection extends beyond hazardous events to climate control, requiring less energy to heat and cool depending on the local climate.
In addition, reinforced concrete construction can be designed to provide minimum deflection at design basis blast loads, while metal panel construction is designed to deflect inches on the reflected surfaces. While both construction types may be designed to meet ASCE blast design criteria, metal building construction may experience internal debris vulnerability not experienced incorrectly designed reinforced concrete construction at design basis loads. In some cases, metal buildings use clearance zones around the interior walls to limit debris hazards, but this “clear zone” wastes useable space and often gets encroached on by occupants over time and defeats the attempt at debris impact mitigation.
BakerRisk designs the best hazard resistant building
BakerRisk® has been a leading designer of blast-resistant buildings since the 1980s, working with major operating companies to provide blast protection for building occupants long before the BP Texas City incident created a demand that resulted in the popularity of blast resistant metal buildings (BRMs).
FORTRESS Protective Buildings, LLC (FORTRESS) understands that truly protecting people goes beyond blast protection to encompass building occupant vulnerability from a range of hazards. With this focus, FORTRESS offers a precast concrete modular building system designed by BakerRisk and manufactured by Tindall to protect workers from hazards that may be present at industrial facilities handling flammable, toxic, explosive, or other energetic materials.
The name FORTRESS is derived from the acronym Fragment Overpressure Radiation Toxic Resistant Emergency Safety Shelter, accurately designating FORTRESS as a multi-hazard resistant building. BakerRisk has designed FORTRESS to be a Safe Haven, providing a high degree of protection from fragment, blast, thermal, gas ingress, and extreme weather. However, unlike other buildings that claim hazard protection, FORTRESS has been full scale proof-tested at or beyond the design specifications for fragment, blast, thermal, and toxic hazards to ensure minimum vulnerability to occupants. Validation testing results and videos are provided to customers as part of the technical package.
How is FORTRESS different?
FORTRESS is designed and engineered to provide an easy to construct building that is not only designed to remain structurally sound after a hazardous event but also provide proven protection for building occupants. FORTRESS uses modular concrete construction, which provides a high degree of protection from potential hazards while simplifying construction, reducing the necessary time-on-site, and allowing for a variety of configurations to fit a range of floor plans and functions.
FORTRESS is designed to ensure that occupants of the building are not subjected to life-threatening hazards associated with most buildings at design loads, which include:
- Significant structural deflections, approaching incipient failure or structural collapse
- Generation of internal debris, both from damaged structural components and from non-structural items commonly found in buildings (items attached or near to walls or roofs such as light fixtures, cabinets, ducts, or wall finishing)
- Significant heat rise that would be hazardous to occupants or would heat interior items producing smoke or toxic fumes
- Uncontrolled leakage of toxic or flammable gases from the building’s exterior
FORTRESS, unlike other industrial “resistant” buildings, has been subjected to a full-scale testing program to confirm occupants of the building are exposed to negligible vulnerability for design basis events. In summary, FORTRESS is designed and tested to:
- Blast: 8 psi overpressure at >> 200 ms (long duration)
- Negligible occupant vulnerability
- Reusable and occupiable after safety checks/minor repairs following design-basis load
- Fragmentation: 13 lb projectile at 171 ft/s (116 mph) velocity
- Very minor local spalling observed
- Thermal: 1-hour direct impingement for ¼-inch saturated propane jet fire
- Local spalling observed on the building exterior, but internal air temperature < 139 ºF and negligible smoke/toxic off-gassing
- Toxic: < 0.1 ACH infiltration for main building and < 0.03 ACH infiltration for interior Shelter-In-Place (SIP) room (if selected)
- SIP Control Box, designed and engineered to provide system specification
- Extreme Weather: Resistant to high wind and debris from hurricane and tornado natural hazards
FORTRESS’s promise of quality
FORTRESS has partnered with Tindall, an industry leader in precast concrete manufacturing, to fabricate the structural modular sections. Tindall has been PCI (Precast/Prestressed Concrete Institute) certified for over 50 years. Through a stringent quality assurance program with inspection and testing protocols, the PCI certification ensures that the FORTRESS modules are fabricated to our high design specifications. Once the modular sections have been delivered to the site, they are assembled and sealed to create a controlled environment for a quality interior fit-out.
For more information, contact us at www.fortressprotectivebuildings.com/contact/ or call your FORTRESS team at (281) 822-3100. To see a full range of full-scale testing videos and footage on the construction of FORTRESS Nameplate #1, visit the FORTRESS website today!