Aircraft/spacecraft hangars (also known as “hangars”) include buildings or structures designed to maintain, store, and protect aircraft (i.e. commercial aircraft, military aircraft, planes, helicopters, etc.) and/or spacecraft (i.e. launch vehicles, crewed vehicles, robotic probes, etc.)
Hangars are structurally distinct structures known for their enormous size, massive clear-span framing, colossal doors, enhanced fire suppression systems, and heavily reinforced foundations.
Famous aircraft/spacecraft hangars include: NASA’s Kennedy Space Center (KSC) Orbiter Processing Facility (OPF); The Cape Canaveral Space Force Station Hangar AE; and the Weeksville Dirigible Hangar near Elizabeth City, NC.
Aircraft hangars are generally classified based on functionality and with respect to National Fire Protection Association (NFPA )Standard on Aircraft Hangars, NFPA 409.
Key NFPA 409 Fire Protection Classifications include:
- Group I: Largest facilities; single fire area of 40,000 sq ft (3,716 sq m), or more
- Group II: Medium-sized facilities; single fire area between 12,001 and 40,000 sq ft.
- Group III: Smaller facilities; single fire area of 12,000 sq ft or less.
- Group IV: Specific membrane-covered, rigid steel frame structures.
Key Functional & Design Aircraft Hangar Classifications include:
- T-Hangars
- Box / Community Hangars
- Maintenance, Repair, and Overhaul (MRO) Hangars
- Corporate / Fixed Base Operator (FBO) Hangars
- Military Hangars
Similarly, spacecraft hangars are classified by their operational environment (terrestrial vs. extraterrestrial), functionality, and scale
Key Functional & Design Spacecraft Hangar Classifications include:
- Vertical Assembly / Integration Hangars: (i.e., the Vehicle Assembly Building).
- Horizontal Processing Hangars
- Mobile Service / Transport Hangars
Hangars include Reinforced Concrete structures (i.e. hardened hangars), Pre-Engineered Metal Buildings (PEMBs), and conventional steel buildings (CSBs). That said, due to their size and complexity – which includes large clear-span roofs, oversized doors, high wind exposure, fire-protection complexity, aircraft fuel hazards, corrosion exposure, crane/hoist loads, and operational impact risks – hangars have distinct design requirements.
Governing aircraft / spacecraft hangar design codes and standards include the International Building Code (IBC), the American Society of Civil Engineers (ASCE), “Minimum Design Loads and Associated Criteria for Buildings and Other Structures” (ASCE 7), the American Institute of Steel Construction (AISC) Steel Construction Manual, the American Concrete Institute (ACI) Building Code Requirements for Structural Concrete (ACI 318), the National Fire Protection Association (NFPA ) Standard on Aircraft Hangars, (NFPA 70). Similarly while aircraft hangars must also comply with Federal Aviation Administration (FAA) Advisory Circulars (AC 150/5300) and local airport authority minimum standards, spacecraft hangars must comply with the Unified Facilities Criteria (UFC) Standards UFC 4-211-01N / UFC 4-211-01 and other applicable codes.
For Construction-Defect Defense Litigators, ascertaining the causation, and thus liability of a construction defect, while avoiding technical blindsides and reigning in projected costs can be a daunting process. This is most notable for litigators seeking causation for construction and design standard-of-care violations, and those seeking causation for code violations and defective material quality.
For construction or design defects involving major components it is generally advisable to engage construction-defect experts early on in the case to determine causation, reduce risks, and limit costs.
Particularly, for construction or design defects involving structural components it is generally advisable to engage construction-defect and structural forensic engineering experts early on in the case to determine causation, reduce risks, and limit costs.
Below are the top 5 structural blind spots in Hangar Renovation for Construction-Defect Defense Litigators.
Steel Thermal Movement Restraint – Member / Connection Distress
Hangar structures are known for their impressive spans and ample space. That said, such design comes as a cost, as structural elements expand and contract significantly during fire and/or elevated temperatures.
During fire and/or elevated temperatures hangar structural members run the risk of thermal expansion-induced buckling, thermal-induced cracking, thermal-induced connection distress, thermal-induced joint failure and other issues due to sustained heat.
Key structural warning signs of thermal-induced buckling in steel members include:
- Excessive Out-of-Plane Bowing of Columns
- Excessive Out-of-Plane Curving of Beams
- Localized Flange Crippling in Beam members
- Localized Steel Web crippling
- Sagging Rafters
- Sheared-Off Bolts
- Elongated Bolt Holes
- Loosened Steel Fasteners
- Cracked Welds
Such issues are particularly pronounced after the introduction of retrofit elements – such as new rigid walls or equipment platforms – which can restrain thermal-movement in “original” floor and roof structural assemblies.
If your structure has experienced a recent fire event and/or displays any of the above signs of buckling, contact a qualified structural engineer
Similarly, consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding structural issues:
Link: https://psengrinc.com/learning/
Contact a qualified structural engineer if your structure displays any of the above signs of thermal-induced stress or other structural issues.
Roof Transition Distress
Hangar roofs cover considerable amounts of surface area.
For reference, the smallest NFPA 409 Single Fire Area, corresponding to Type V (000) Construction, consists of a surface area of 5,000 sq-ft (465 m2) or more.
Hangar roof transitions must withstand movement and moisture-related loads and thermal-related loads without failure.
Roof transitions include roof areas where different roof planes, different slopes, or different materials meet. Roof transitions also include areas where the roof meets the supporting wall.
Key structural warning signs of roof transition distress in long span steel roofs include:
- Twisted Roof Members
- Local Member Buckling
- Misaligned Connections
- Sheared-Off Bolts
- Elongated Bolt Holes
- Cracked Welds
- Sheared-Off Anchor Bolts
If your structure displays any of the above signs of roof transition distress, contact a qualified structural engineer
Similarly, consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding structural issues:
Link: https://psengrinc.com/learning/
Contact a qualified structural engineer if your structure displays any of the above signs of distress or other structural issues.
Hangar Door Corrosion
Hangars situated in coastal environments face particularly high risk for corrosion and further deterioration. Such risk is most pronounced in hangar doors.
The presence of high humidity levels (i.e. the presence of high concentrations of water vapor), sea salt aerosols (i.e. airborne chloride salt particles), and corrosive aircraft chemicals provide an ever-present corrosion risk for doors and their associated mechanical systems.
Such risks are exacerbated by extreme, hot temperatures which accelerate the oxidative process of corrosion.
Key signs of corrosion in steel hangar doors include:
- Paint Bubbling or Blistering:
- Flaking or Peeling Coatings
- Discoloration Around Fasteners
- Flaking or Peeling Coatings
- Thinning of Steel Sections
- Pinholes in Substrate
If your structure displays any of the above signs of structural degradation, contact a qualified structural engineer
Similarly, consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding structural issues:
Link: https://psengrinc.com/learning/
Contact a qualified structural engineer if your structure displays any of the above signs of structural degradation or other structural issues.
Foam Fire-Suppression Retrofit Impacts
Hangars encompass exceptionally massive building footprints and are typically comprised of 1 or more Hangar Fire Areas.
Per NFPA 409 guidelines, Hangar Fire Areas include areas within the hangar storage and servicing area, subject to loss by a single fire due to lack of internal subdivisions as specified within the code.
Such large hangar areas require large, distributed fire protection systems to protect life and property.
Per NFPA 409, hangars shall utilize one of the following fire protection strategies within storage and service areas:
- A Prescriptive Approach (i.e. the use the fire protection and life safety systems)
- A Fire-Risk-Based Approach
- A Performance-Based Design Approach
For existing hangars, designers and builders may utilize Foam Fire Suppression Systems in accordance with the NFPA prescriptive approach.
Foam Fire Suppression Systems include specialized fire protection systems that discharge a low-density mix of water, foam concentrate, and air to arrest fires and suppress vapor release to prevent reignition
Many aircraft hangars require specialized foam and/or fire-suppression systems due to fuel hazards.
Foam Fire Suppression Systems may include large pipe mains, foam systems, deluge piping, tanks, pumps, and suspended pipe networks. Retrofit updates can add additional tanks, piping, containment systems, and support platforms to existing hangars. Depending on the configuration, such additions to the Foam Fire Suppression System may impart significant loads unto the hangar roof system.
Key loads from Foam Fire Suppression Systems unto hangar roof structures include:
- Piping Weight (Dry Lines)
- Piping Weight with Water Loads (Wet Lines Only)
- Sway Bracing Loads (i.e. Loads Under Seismic, Wind, or Other lateral Loads)
- Thrust and Reaction Forces, namely at Pipe Bends, Tees, and End-of-Line Sections
Due to the abundance of long-span elements and limited redundancies, excessive loads from Foam Fire Suppression can negatively impact hangar roof structural elements.
Key structural warning signs of hangar roof overload due to Foam Fire Suppression loading include:
- Sagging or Bowing in Roof Trusses
- Sagging of Rafter Beams
- Sagging Roof Decks at Perimeter
- Loose or Buckling Cross-Bracing
- Cracked Welds
- Sheared Connection Bolts
- Torn or Elongated Gusset Plates
Likewise, depending on the configuration, Foam Fire Suppression Systems can impart significant loads unto the hangar vertical elements (i.e. the columns, and portal frames).
Key structural warning signs of hangar column overload due to Foam Fire Suppression loading include:
- Slippage or Shear deformation in Bolted Rafter-to-Column
- Out-of-Plumb Columns (Extreme Cases)
- Column Base Plate Uplift or Deformation
- Column Pedestal Cracking (Extreme Cases)
- Cracked Welds
- Sheared Connection Bolts
- Torn or Elongated Gusset Plates
The above issues are especially relevant in the retrofit of older structures.
Consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding roof overloading issues:
Link: https://psengrinc.com/learning/
Contact a qualified mechanical engineer and/or fire suppression specialist if your structure displays any issues with the fire suppression system.
Contact a qualified structural engineer if your structure displays any of the above signs of structural overloading or other structural issues.
Fire Protection Systems, Water Loads
Hangars encompass exceptionally massive building footprints and are typically comprised of 1 or more Hangar Fire Areas.
Per NFPA 409 guidelines, Hangar Fire Areas include areas within the hangar storage and servicing area, subject to loss by a single fire due to lack of internal subdivisions as specified within the code.
Such large hangar areas require large, distributed fire protection systems to protect life and property.
Per NFPA 409, hangars shall utilize one of the following fire protection strategies within storage and service areas:
- A Prescriptive Approach (i.e. the use the fire protection and life safety systems)
- A Fire-Risk-Based Approach
- A Performance-Based Design Approach
Often designers and builders utilize a prescriptive approach in the design of new hangars and/or retrofit of existing hangars.
Hangar Fire Protection Systems may include large pipe mains, foam systems, deluge piping, tanks, pumps, and suspended pipe networks. Depending on the configuration, such Fire Protection Systems can impart significant loads unto the hangar roof system.
Key loads from Fire Protection Systems unto hangar vertical and lateral structures include:
- Piping Weight (Dry Lines)
- Piping Weight with Water Loads (Wet Lines Only)
- Sway Bracing Loads (i.e. Loads Under Seismic, Wind, or Other lateral Loads)
- Thrust and Reaction Forces, namely at Pipe Bends, Tees, and End-of-Line Sections
Due to the abundance of long-span elements and limited redundancies, excess loads from fire suppression systems can negatively impact hangar structural elements, namely the roof.
Key structural warning signs of hangar roof overload due to Fire Protection System loading include:
- Sagging or Bowing in Roof Trusses
- Sagging of Rafter Beams
- Sagging Roof Decks at Perimeter
- Loose or Buckling Cross-Bracing
- Cracked Welds
- Sheared Connection Bolts
- Torn or Elongated Gusset Plates
Likewise, depending on the configuration, Fire Protection Systems can impart significant loads unto the hangar column system.
Key structural warning signs of hangar column overload due to fire suppression equipment loading include:
- Slippage or Shear deformation in Bolted Rafter-to-Column
- Out-of-Plumb Columns (Extreme Cases)
- Column Base Plate Uplift or Deformation
- Column Pedestal Cracking (Extreme Cases)
- Cracked Welds
- Sheared Connection Bolts
- Torn or Elongated Gusset Plates
The above issues are especially relevant in the retrofit of older structures.
Consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding roof overloading issues:
Link: https://psengrinc.com/learning/
Contact a qualified mechanical engineer and/or fire suppression specialist if your structure displays any issues with the fire suppression system.
Contact a qualified structural engineer if your structure displays any of the above signs of structural overloading or other structural issues.
Preeminent Solutions is a DBE-certified, MWBE-certified, LDB-certified and soon to be 8(a)-certified and WOSB-certified, civil/structural engineering firm.
We have over 30 years’ experience in civil/structural design, forensics, and expert work
We’re Licensed in CA, FL, TX, NJ, NY, DC, MD, VA, TN, MS, GA, NC, SC, LA, & more.
Reach out if your team is in need of structural engineering support.
Preeminent Solutions, Inc.
Forensic Structural Engineers & Consultants
📞 (321) 244-8699 | (407) 901-0133
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