Choosing the Right Structural System for an Aircraft Hangar: Portal Frame, Long-Span Truss, or Bolted Sphere Structure?

 Aircraft hangars are among the most demanding types of large-span buildings. Unlike ordinary industrial warehouses, they must provide sufficient clear space for aircraft parking, maintenance, inspection, and movement.

One of the most important decisions during the planning stage is choosing the right structural system.

Should you use a rigid portal frame, a long-span steel truss, or a bolted sphere structure?

There is no universal answer. Each system has different structural characteristics, construction requirements, and economic considerations. Understanding these differences can help project owners and engineering teams make better decisions before moving into detailed design.

1. Why Structural Selection Matters in Aircraft Hangar Projects

An aircraft hangar is not simply a large building with a roof. Its structural system must work together with several important functional requirements.

These include:

• Large unobstructed interior spaces for aircraft operations.

• Wide hangar door openings with sufficient clearance.

• Roof structures capable of supporting environmental and operational loads.

• Adequate internal height for different aircraft types.

• Space for lighting, ventilation, fire protection, and maintenance equipment.

• Structural coordination with cranes, platforms, and other mechanical systems where required.

A structural solution that works well for a small maintenance hangar may not be the most economical option for a wide-body aircraft maintenance facility.

That is why structural selection should start with the actual operational requirements rather than simply choosing the cheapest construction method.

2. Rigid Portal Frame: A Practical Choice for Conventional Hangars

Rigid portal frames are widely used in industrial buildings and smaller aircraft hangars.

They generally consist of steel columns and rafters connected through moment-resisting joints, creating a stable structural frame.

Where does this system work best?

Portal frames are often suitable for:

• Small and medium-sized aircraft hangars.

• General aviation facilities.

• Maintenance workshops.

• Buildings with moderate clear-span requirements.

Advantages

• Relatively straightforward structural configuration.

• Established fabrication and construction methods.

• Convenient integration with conventional industrial building systems.

• Economical for suitable building spans and loading conditions.

Potential limitations

As the required span increases, the bending moments and member sizes may increase considerably.

Large hangar door openings also create additional structural coordination challenges. The columns and supporting members around the entrance must be designed to accommodate the opening arrangement and associated loads.

For very large aircraft facilities, conventional portal framing may become less efficient than other structural alternatives.

3. Long-Span Steel Truss: An Effective Solution for Wider Openings

Steel trusses are frequently considered when a hangar requires a wider unobstructed interior space.

A truss uses interconnected members arranged in triangular configurations to transfer loads through axial forces.

This structural principle can provide an efficient way to cover large distances without relying on intermediate columns.

Where does this system work best?

• Large aircraft hangars.

• Aircraft maintenance facilities.

• Aviation assembly buildings.

• Hangars requiring substantial clear internal space.

Advantages

• Suitable for relatively large structural spans.

• Efficient load transfer through truss members.

• Flexible structural configurations.

• Can accommodate different roof geometries and architectural requirements.

Potential limitations

Trusses can require considerable fabrication and connection work.

Their structural depth, transportation dimensions, lifting requirements, and erection sequence must also be considered.

For exceptionally large roofs, the number of components and connection details can increase construction complexity.

The final design should therefore consider not only structural efficiency but also fabrication, transportation, and installation conditions.

4. Bolted Sphere Structure: An Alternative for Large-Span Hangars

Bolted sphere structures use spherical joints to connect steel members into a three-dimensional structural system.

Unlike conventional two-dimensional framing, this system distributes loads through an interconnected spatial arrangement of members.

It can be particularly interesting for hangars with large roof areas and demanding column-free space requirements.

Where can it be considered?

• Large aircraft maintenance hangars.

• Wide-span airport facilities.

• Aviation exhibition and assembly buildings.

• Hangars with complex roof configurations.

Key advantages

Three-dimensional load distribution

The interconnected structural arrangement allows loads to be transferred through multiple members and structural directions.

Large-span adaptability

The system can be engineered for substantial roof spans while minimizing the need for internal supporting columns.

Modular fabrication

Members and connection components can be manufactured in a controlled factory environment and transported to the construction site for assembly.

Flexible roof configurations

The structural system can accommodate different roof shapes and architectural arrangements, subject to engineering requirements.

Important considerations

A bolted sphere structure is not automatically the best solution for every hangar.

Its suitability depends on span, roof geometry, loading conditions, structural depth, connection design, and construction methodology.

The engineering team must also carefully coordinate the roof structure with the hangar door system, particularly where large clear openings are required.

5. Comparing the Three Structural Systems

Each structural system has its own advantages. The following comparison provides a preliminary reference for project planning.

Evaluation	Portal Frame	Steel Truss	Bolted Sphere Structure
Typical application	Small–medium hangars	Medium–large hangars	Large-span facilities
Structural arrangement	2D rigid frames	2D triangulated frames	3D interconnected system
Large-span adaptability	Depends on design	Good	Good
Internal column reduction	Depends on span	Good	Good
Fabrication	Relatively straightforward	More member connections	Modular components
Roof geometry	Relatively simple	Flexible	Flexible
Design complexity	Relatively low	Moderate–high	Moderate–high

It is important to remember that this is a general comparison rather than a universal ranking. Actual structural performance and project cost depend on engineering calculations and project-specific conditions.

6. Don't Forget the Hangar Door

One factor that is sometimes overlooked during structural selection is the hangar door.

Unlike ordinary industrial warehouse doors, aircraft hangar doors can occupy a substantial portion of the front elevation.

Common configurations include:

• Sliding hangar doors.

• Bi-fold doors.

• Vertical-lift doors.

• Fabric folding doors.

The selected door system affects the structural arrangement around the entrance, available headroom, support requirements, and installation sequence.

For large hangars, the roof structure, entrance framing, door tracks, and supporting foundations should be coordinated during the early design stage.

A structurally efficient roof is not enough if the entrance cannot accommodate the aircraft it is intended to serve.

7. Which Structural System Should You Choose?

The right choice depends on the size and operational requirements of the facility.

Here is a practical way to approach the decision:

Choose a portal frame when:

The project involves a relatively conventional hangar with moderate spans, straightforward geometry, and familiar construction requirements.

Consider a long-span steel truss when:

The building requires a wider unobstructed interior and the project benefits from a conventional triangulated structural arrangement.

Consider a bolted sphere structure when:

The project involves a substantial roof span, requires a three-dimensional structural arrangement, or benefits from modular prefabrication and flexible roof geometry.

For large aviation projects, comparing at least two feasible structural alternatives during the preliminary design stage is often worthwhile.

Final Thoughts

Choosing an aircraft hangar structural system is not simply a comparison of steel quantities or construction prices.

It involves balancing structural performance, aircraft clearance, hangar door requirements, fabrication capabilities, transportation, installation, and long-term operational needs.

At LF-BJMB®, we believe that large-span structural solutions should be selected according to the actual requirements of each project.

As a specialist in bolted sphere structural systems, LF-BJMB® focuses on engineering, manufacturing, and installation solutions for large-span buildings.

For aircraft hangar projects, the most suitable structural system should always be determined through project-specific engineering evaluation.

LF-BJMB® | Large-Span Steel Structure Solutions. Beyond Span. Value Across the Project Lifecycle.