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) Space Systems Processing Facility (SSPF); NASA’s Marshall Space Flight Center (MSFC) Michoud Assembly Facility (MAF); and The Chicago O’Hare International Airport American Airlines’ Hangar 2.
Aircraft hangars are generally classified based on functionality and with respect to National Fire Proetction 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.
For Construction-Defect Plaintiff 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.
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 Plaintiff Litigators.
Steel Thermal Movement Restraint – Member Material Deterioration
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 material degradation in steel members include:
- Blistering/Peeling Paint
- Excessive Post-Fire Discoloration from heat
- Micro-fissures in Steel Segments
- Necking (i.e. Localized Thinning) of Steel Members
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, or is showing any of the above signs of material 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 material degradation or other structural issues.
Column Base corrosion
Hangar column bases face a high risk for corrosion and further deterioration. Column bases are routinely exposed to salts, fuel, chemicals, water, and slab moisture and more
Corrosion at column base plates, and correspondingly column anchor rods, reduce uplift and lateral capacity limited strength in wind-prone areas.
Such risks are exacerbated by extreme, hot temperatures which accelerate the oxidative process of corrosion.
Key signs of column base plate corrosion in hangars include:
- Reddish-Brown Discoloration
- Paint Blistering or Bubbling:
- Flaking and Scaling Steel:
- Surface Pitting
- Pack Rust Expansion
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.
Expansion Joint Distress – R/C Slabs
Hangar foundation slabs, 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.
Foundation slabs 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 slabs into smaller, individual segments.
Specifically, expansion joints (aka isolation joints) provide complete, full-depth separation between individual sections of slab. As a consequence, the joints reduce the likelihood of moisture-induced and thermal-induced cracking.
Typically, expansion joints are covered and filled, particularly for fire-related structures.
Key structural warning signs of expansion joint failure in reinforced concrete slabs include:
- Uneven Slab Transitions
- Concrete Cracking
- Concrete Delamination
- Concrete Spalling
- Excessive Cracking
- Concrete Efflorescence
- Water Infiltration and Leaks
- Damaged Sealant
- Damaged Filler
If your structure displays any of the above signs of expansion 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.
Demolition-Induced Instability
Hangar renovation-related demolition can uncover a host of underlying issues in existing structures.
Excessive demolition without appropriate temporary shoring, can destabilize sections of existing structures.
Note: Structural instability is a threat to life and must be address immediately.
Key signs of structural instability due to demolition include:
- Rapidly Expanding Cracks
- Diagonal Cracks in Concrete Beams
- Diagonal Cracks in Concrete Walls
- Stair-step cracking in Masonry Walls
- Widening vertical tension cracks in load-bearing elements
- Severe Horizontal Cracking and Bulging in Masonry Walls Cracks Radiating from Corners of Windows and Doors
- Crushed or Spalling Concrete around Compressed Zones
Key signs of roof or slab discontinuity due to demolition include:
- Sagging Rooflines near Cut Zones
- Dipping Roof Ridges near Cut Zones
- Rafter Separation from Supporting Walls
- Truss Separation from Supporting Walls
- Buckled Metal Deck Panels
- Sheared Fasteners
- Torn Flashing at Transition Joints
- Severe Diagonal Concrete Cracking in Slabs
- Spalling or Chipping of Concrete
- Rusting steel reinforcement
- Concrete Slab Efflorescence on the Slab Underside
- Rust Stains bleeding through Concrete Pores
Consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding structural performance:
Link: https://psengrinc.com/learning/
Contact a qualified structural engineer if your structure displays any of the above signs of structural instability.
Slab Cracking and Subgrade Issues
Hangar foundation slabs span relatively large areas and must withstand high and concentrated loads repeatedly without failure.
While in operation, hangar foundation slabs may show signs of cracking.
Key causes of hangar foundation slab cracking may include:
- Concrete Slab Shrinkage,
- Concrete curling (i.e. the Upward/Downward Bending of the Corners of Slab.)
- Aircraft / Spacecraft Vehicle Loads
- Structural Settlement
- Thermal Effects.
Some cracking may be serviceability-related, while other cracks indicate insufficient capacity or subgrade problems.
Key signs of subgrade problems in concrete foundation slabs include:
- Diagonal/Shear Cracking at Slab Corners
- Sloping Floors
- Uneven Transitions
- Rocking or Hollow Slabs
- Visible slab sinking
- Severe Concrete Cracking
- Concrete Spalling
- Concrete Delamination
- Pooling Water
Consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding foundation issues:
Link:
https://psengrinc.com/learning/
Contact a qualified structural engineer if your structure displays any of the above signs of slab or foundation capacity 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.
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Reach out if your team is in need of structural engineering support.
Preeminent Solutions, Inc.
Forensic Structural Engineers & Consultants
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