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: The Kelly Air Force Base hangar 375 (aka. “Big Texas”) in San Antonio, TX; NASA’s Kennedy Space Center (KSC) Multi-Payload Processing Facility (MPPF); NASA’s Marshall Space Flight Center (MSFC) Michoud Assembly Facility (MAF); and The Pearl Harbor Historic Hangars in Honolulu, HI.
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 Institire (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.
Hangar new builds and/or renovations (in existing buildings) can be tricky for General Contractors.
Below are the top 5 structural blind spots in Hangar Renovation for General Contractors.
For construction defects 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.
Preeminent Solutions is a WOSB-certified, DBE-certified, MWBE-certified, LDB-certified and soon-to-be 8(a)-certified and civil/structural engineering firm specializing in structural forensics and construction-defect expert witness work.
Contact us for your next aircraft and/or spacecraft hangar renovation project.
For construction defects 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.
Preeminent Solutions is a WOSB-certified, DBE-certified, MWBE-certified, LDB-certified and soon-to-be 8(a)-certified and civil/structural engineering firm specializing in structural forensics and construction-defect expert witness work.
Contact us for your next aircraft and/or spacecraft hangar construction-defect project.
Contraction Joint Distress – R/C Walls
Hangar walls, 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 reinforced concrete walls utilize joints, namely contraction joints (aka control joints) and isolation joints (aka expansion joints) to best withstand moisture-related loads and thermal-related loads without failure.
Contraction joints and isolation joints, divide the large hangar walls into smaller, individual segments.
Specifically, contraction joints (aka control joints) provide planes of weakness, thus limiting the location of cracks. As a consequence, the joints reduce the likelihood of moisture-induced and thermal-induced cracking.
Key structural warning signs of control joint failure in reinforced concrete walls include:
- Excessive Cracking
- Damaged Joint Sealant
- Rust Stains
- Exposed Reinforcement
- Concrete Subsurface Delamination
If your structure displays any of the above signs of control joint 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.
Fire-Damaged Steel Members
Hangars routinely host high-risk fuel and electrical operations – namely, aircraft fuel servicing, fuel transfer, electrical work, and battery work. Such operations significantly increase the risk of fire events and explosion events at each facility.
Unmitigated fire events and explosion events can significantly degrade concrete, steel, and aluminum members, as well as diminish coating and fireproofing efficacy.
Per AISC Design Guide 16 “Fire Resistance of Structural Steel Framing” a leading authority of the matter, fire damaged steel members are best categorized in the below categories:
- Category 1: Straight, or otherwise unaffected, steel members.
- Category 2: Noticeably deformed steel members.
- Category 3: Severely deformed steel members.
Structural steel exposed to temperatures of 1200 °F (roughly degrees 650 °C) or more can develop Category 2 and Category 3 deformations. Likewise, steel elements exposed to 1200 °F or more temperatures can develop a roughened and more visibly eroded surface than typical mill-rolled steel.
Other key structural warning signs of fire-induced material degradation in structural steel members include:
- Extreme Steel Member web deformation
- Extreme Steel Member flange crippling
- Excessive Column Member bowing.
- Cracked/Failed Welds
- Elongated or Sheared Bolt Holes
- Loose/Deformed Fasteners
Fire-damaged structural steel members provide a risk to life and a risk to property.
To reduce further risk, immediate post-fire damage assessment by qualified professional engineers is advised.
If your structure has experienced a recent fire event, or 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.
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.
Long-Span Cable Distress
Hangars house a variety of large-scale aircraft and/or spacecraft vehicles, ranging from hot air balloons to rockets. As a consequence, hangars must employ ample space, broad roofs, and large openings: conditions that are best supported by long-span members.
Long span members include structural elements—such as beams, trusses, or girders — designed to bridge large distances without requiring middle supports or columns.
Hangars typically employ long-span members, arches, cables, portal frames, rigid frames, and/or space frames to create unobstructed aircraft bays.
That said, due to the long spans, such systems are especially sensitive to key issues including:
- Corrosion
- Connection Issues
- Excessive Deflection
- Excessive Vibration Loads
- Excessive Roof Ponding Loads
- Roof Overload ( i.e. due to fire suppression systems or other additional weight.)
- Unexpected Suspended Loads (i.e. due to Crane Loading, etc.)
- Transport and Erection During Construction
Key signs of structural overload in structural cables include:
- Birdcaging of Cables
- Neckaging (i.e. thinning) of Cables
- Excessive Elongation of Cables
- Slackening Segments
- Sheared-Off or Stretched Bolts
- Ovalization or Scoring of Connection Pins
- Excessive Bending or Bowing of Socket Plates
- Excessive Bowing or Shifting of Anchor Plates
Due to the relatively limited degree of redundancy in long-span systems, smaller issues should be addressed immediately to avoid magnification into larger issues, particularly with connection issues between long-span arch members and the supporting frame members.
Key signs of structural overload in supporting frame members include:
- Excessive Movement under Lateral Loads
- Out-of-Plumb Columns
- Bowing Columns
- Local Web Crippling near Concentrated Lateral Loads
- Local Flange Buckling
- Twisted Girts
- Corroded Base Plates
- Severe Cracking or spalling Near Concrete Plinths/Grout Pads.
- Cracked Welds
Note: Structural overloading is a serious risk to life and public safety. As a consequence, it must be addressed as soon as possible. Contact a qualified structural engineer immediately if your structure displays any of the above signs of overloading.
Consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding structural overloading issues:
Link: https://psengrinc.com/learning/
Contact a qualified structural engineer if your structure displays any of the above signs of overloading.
Wind-Load Resistance
Often hangar new-builds and/or pre-existing structures are situated in areas with high wind-risk, due to Hurricanes, Tropical cyclones, and/or other windstorms.
In high wind-risk regions, hangars must maintain structural integrity while protecting aircraft and spacecraft from environmental conditions.
Per the 2024 International Building Code (IBC) Code, the governing code on the matter at time of this publication, in high wind-risk regions, structures shall be designed to withstand the minimum wind loads in accordance with ASCE 7.
Key exceptions include:
- Designs using theTelecommunications Industry Association (TIA), “Maintenance and Condition Assessment of Telecommunication Towers”, TIA-222 for antenna-supporting structures and antennas
- Wind tunnel tests in accordance with ASCE 49, “Wind Tunnel Testing for Buildings and Other Structures”
- Temporary structures in compliance with IBC Section 3013
- Designs using theNational Association of Architectural Metal Manufacturers (NAAMM) “Guide Specifications For Design of Metal Flagpoles,” NAAMM FP 1001
Key signs of high wind-risk susceptibility (i.e. poor wind-risk resistance) in buildings include:
- Missing or Under-designed Hurricane Strap Connections
- Long and/or Unbraced Overhang Eaves
- Loose and/or Degraded Roof Decking
- Loose and/or Degraded Exterior Wall Panels
- Corroded / Deteriorated Connection Fasteners
- Corroded / Deteriorated Anchorage to Foundation
- Unreinforced or Under-reinforced Masonry Walls
- Excessively Large Shear Wall Openings
- Poor Floor Slab / Roof Continuity
- Discontinuous Vertical and Lateral Load Paths
- Preexisting Failed Connection Joints at Corners
- Sagging Roof Lines
- Bowing and/or Leaning Columns and Walls (particularly at corners of structure.)
- Severe Diagonal Cracking in Reinforced Concrete Elements
- Severe Horizontal Cracking in Vertical Masonry Elements
Wind loads include major forces that impact the Lateral Force Resisting System (LFRS) , and thus the overall stability, of a structure.
It is imperative for public safety that structures are able to withstand design wind load demands, particularly in high wind-risk areas.
Key signs of wind damage in buildings include:
- Membrane peeling or unzipping along perimeter flashing and eaves.
- Twisting of Roof Purlins due to Unbalanced Wind Loads
- Buckling of Long-Span Open-web Steel Joists
- Excessive Deflection/Ponding on Roof
- Warping of Wall Panels
- Out-of-Square Roll-up Door Frames
- Out-of-plumb Columns or Portal Frames
- Deformed Anchor Bolt and Base plate Connections for Column Supports
- Fractured Welds
- Fracture Surface Corrosion due to Impact and Removal of Protective Coating
- Beam Connection Corrosion and Deterioration
Such issues are especially relevant in the retrofit of older structures.
Consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding structural wind damage:
Link: https://psengrinc.com/learning/
Contact a qualified structural engineer if your structure displays any of the above signs of wind damage.
Preeminent Solutions is a DBE-certified, MWBE-certified, LDB-certified and soon to be 8(a)-certified and WOSB-certified, civil/structural engineering firm.
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