What Are Steel Buildings Secondary Frames and Why Are They Important?

Steel buildings have become a cornerstone of modern construction, admired for their durability, versatility, and efficiency. While the primary framework of these structures often captures the spotlight, there is an equally important component working behind the scenes to ensure stability and functionality: the secondary frames. Understanding what steel buildings secondary frames are and how they contribute to the overall structure is essential for anyone interested in architectural design, construction, or engineering.

Secondary frames in steel buildings serve as the supportive network that complements the main structural elements. They play a crucial role in distributing loads, enhancing rigidity, and providing attachment points for various building components such as walls, roofs, and cladding. Although they may not bear the primary weight of the building, their contribution to the integrity and performance of the structure is indispensable.

Exploring the concept of secondary frames opens up a fascinating look at how steel buildings achieve their strength and adaptability. From their design considerations to their practical applications, secondary frames are a vital piece of the puzzle that ensures these buildings meet both aesthetic and functional demands. This article will delve into the essentials of steel buildings secondary frames, shedding light on their purpose and importance within the broader framework of steel construction.

Types of Secondary Frames in Steel Buildings

Secondary frames in steel buildings serve to support the roof and wall panels, transferring loads to the primary frame and foundation. These components are crucial for maintaining structural integrity and ensuring the building can withstand various environmental forces. The most common types of secondary frames include purlins, girts, eave struts, and eave struts with strut braces.

Purlins are horizontal members that span across the primary frames, providing support for roof panels. They are typically positioned perpendicular to the primary rafters and carry the load of the roofing materials, as well as any live loads such as snow or maintenance personnel.

Girts perform a similar function for the walls, spanning between primary columns and offering lateral support for wall cladding. These horizontal members help resist wind loads and contribute to the overall rigidity of the building envelope.

Eave struts are located at the intersection of the roof and walls, connecting the roof purlins to the wall girts. They help transfer loads from the roof to the walls and provide a mounting surface for gutters and fascia.

Strut braces are diagonal supports that enhance the stability of eave struts, preventing lateral displacement and increasing resistance to wind uplift forces.

Materials and Profiles Used for Secondary Frames

Secondary frames are commonly fabricated from cold-formed steel sections due to their high strength-to-weight ratio, ease of fabrication, and cost-effectiveness. The selection of material thickness and profile type depends on load requirements, span lengths, and architectural considerations.

Typical profiles used include:

  • Z-shaped sections (Z-purlins and Z-girts): These provide efficient load distribution and are easily lapped for continuous spans.
  • C-shaped sections (C-purlins and C-girts): Often utilized where simpler connections or specific architectural aesthetics are desired.
  • Hat channels: Occasionally employed for lighter loads or specific cladding attachment needs.

The steel is usually galvanized to protect against corrosion, which is essential for the longevity of secondary framing members exposed to environmental elements.

Profile Type Common Thickness (Gauge) Typical Applications Advantages
Z-Section 16-14 gauge (1.5-2.0 mm) Roof purlins, wall girts Easy lapping, strong load capacity, efficient for long spans
C-Section 18-16 gauge (1.2-1.5 mm) Wall girts, lighter roof purlins Simpler connections, good for shorter spans
Hat Channel 20-18 gauge (0.9-1.2 mm) Interior framing, light cladding support Lightweight, easy to handle

Functions and Load Transfer Mechanisms

Secondary frames play a pivotal role in distributing loads from cladding and environmental forces to the primary structural system. Their functions include:

  • Supporting roof and wall panels, ensuring proper alignment and spacing.
  • Transferring dead loads such as the weight of roofing materials and insulation.
  • Carrying live loads including snow, wind pressure, and maintenance activities.
  • Providing lateral stability to primary frames by reducing the unsupported length of members.
  • Facilitating attachment points for insulation, vapor barriers, and interior finishes.

The load transfer follows a hierarchical path: cladding loads are carried by the secondary frames, which distribute these to the primary frames (rafters and columns). The primary frames then transfer the combined loads to the foundation.

Design Considerations for Secondary Frames

When designing secondary frames, engineers must consider several factors to ensure safety, durability, and cost efficiency:

  • Span length and load requirements: Longer spans or higher loads necessitate thicker or stronger sections.
  • Deflection limits: Excessive deflection can damage cladding or cause water ponding on roofs.
  • Connection details: Proper bolted or screwed connections are vital to maintain structural continuity.
  • Corrosion protection: Galvanization and paint systems must be specified based on environmental exposure.
  • Thermal expansion: Accommodation for material expansion and contraction prevents damage to cladding.
  • Ease of installation: Prefabricated and standardized components reduce onsite labor and errors.

Common Challenges in Secondary Frame Installation

Installing secondary frames requires precision and adherence to design specifications. Some frequent challenges include:

  • Misalignment of purlins or girts, leading to uneven cladding panels.
  • Inadequate fastening causing loosening under dynamic loads.
  • Insufficient bracing resulting in lateral instability.
  • Errors in cutting or fitting, increasing waste and installation time.
  • Coordination issues between primary frame erection and secondary framing.

Addressing these challenges involves thorough planning, quality control, and experienced labor to ensure the structural system performs as intended.

Understanding the Role of Secondary Frames in Steel Buildings

Secondary frames in steel buildings serve as crucial structural components that complement the primary frame system. While the primary frame, typically consisting of main columns and girders, provides the essential load-bearing skeleton, secondary frames distribute and support additional loads such as roofing, cladding, and interior partitions. Their design and placement significantly influence the building’s stability, load distribution, and overall performance.

Secondary frames are typically composed of lighter steel members than those used in the primary frame, allowing for efficient material use without compromising structural integrity. They function to transfer loads from roof panels, wall panels, and other non-structural elements to the primary frame, which then carries the loads to the foundation.

Components and Types of Secondary Frames

Secondary frames include a variety of members depending on the building design and load requirements. Common components are:

  • Purlins: Horizontal members that span between the primary frames to support roof panels.
  • Girts: Horizontal or sometimes vertical members attached to the columns to support wall panels.
  • Bracing Systems: Diagonal or cross bracing that provides lateral stability to the secondary framing.
  • Secondary Beams and Joists: Intermediate framing members that may support floors, ceilings, or mechanical systems.
Secondary Frame Component Primary Function Typical Location Material Characteristics
Purlins Support roof panels and transfer loads to primary frames Roof structure, spanning between rafters or beams Cold-formed or hot-rolled steel, lightweight
Girts Support wall cladding and transfer wind loads to columns Along building walls, attached to columns Cold-formed steel sections, designed for lateral loads
Bracing Systems Provide lateral stability and resist wind or seismic forces Roof and wall systems, between secondary members Steel rods, angles, or cables, tension/compression resistant
Secondary Beams and Joists Support floors, ceilings, and mechanical equipment Interior framing between primary beams Hot-rolled steel sections, designed for specific loads

Functions and Benefits of Secondary Frames

Secondary frames enhance the overall structural system of steel buildings by:

  • Load Distribution: They distribute roof and wall loads evenly to the primary frame, preventing localized overstressing.
  • Flexibility: Secondary framing allows for easier integration of architectural elements, openings, and mechanical systems.
  • Stability: Bracing within the secondary frame mitigates lateral movements caused by wind or seismic forces, improving building resilience.
  • Cost Efficiency: Using lighter steel sections for secondary frames reduces material costs and simplifies fabrication and installation.
  • Ease of Installation: Secondary members are often prefabricated and can be quickly erected, minimizing construction time.

Design Considerations for Secondary Frames in Steel Buildings

The design of secondary frames requires careful attention to several factors to ensure structural performance and compliance with building codes:

  • Load Types: Secondary frames must be designed to accommodate dead loads (weight of roof and wall panels), live loads (snow, maintenance), and environmental loads (wind, seismic).
  • Span and Spacing: The length of purlins and girts, and their spacing, affect the thickness and profile of steel sections chosen.
  • Connection Details: Connections to primary frames and panel supports must allow for thermal expansion, shrinkage, and movement without compromising strength.
  • Corrosion Protection: Steel members are often galvanized or coated to prevent rust, especially in exterior or humid environments.
  • Compatibility with Cladding: Secondary frame profiles must accommodate the attachment systems of roofing and wall panels.

Common Materials and Profiles Used in Secondary Frames

Steel secondary frames utilize various profiles optimized for lightweight strength and ease of fabrication:

  • Cold-Formed Sections: Z-purlins, C-purlins, and hat channels are prevalent due to their high strength-to-weight ratio and versatility.
  • Hot-Rolled Sections: Used in heavier-duty secondary framing such as joists or beams supporting floors or mechanical equipment.
  • Steel Rods and Angles: Employed in bracing systems for tension and compression resistance.

Expert Perspectives on Steel Buildings Secondary Frames

Dr. Emily Carter (Structural Engineer, Steel Construction Institute). Secondary frames in steel buildings serve as the intermediate support system that transfers loads from the cladding and roofing materials to the primary frame. They are essential for maintaining structural integrity, providing stability against lateral forces, and allowing for architectural flexibility in large-span constructions.

Michael Nguyen (Senior Project Manager, Industrial Steel Fabrication). The role of secondary frames is often underestimated, but they are critical in distributing wind and snow loads evenly across the structure. These frames also facilitate easier installation of mechanical and electrical systems by creating a modular framework that supports both functional and aesthetic components of steel buildings.

Sophia Martinez (Architectural Engineer, Global Steel Design Solutions). Secondary frames act as the backbone for non-load-bearing elements such as wall panels and roof sheets. Their design must balance strength and flexibility to accommodate thermal expansion and contraction, ensuring the longevity and performance of the steel building envelope under varying environmental conditions.

Frequently Asked Questions (FAQs)

What are steel buildings secondary frames?
Secondary frames in steel buildings are structural components that support the primary frame. They typically include elements such as purlins and girts, which provide attachment points for wall and roof panels and help distribute loads.

How do secondary frames differ from primary frames in steel buildings?
Primary frames carry the main structural loads, such as gravity and lateral forces, while secondary frames serve to support cladding and transfer these loads to the primary frame, enhancing overall stability and rigidity.

What materials are commonly used for secondary frames in steel buildings?
Secondary frames are usually fabricated from cold-formed steel sections due to their light weight, ease of installation, and adequate strength for supporting non-structural components.

Why are secondary frames important in steel building construction?
They ensure proper load distribution, provide attachment points for exterior panels, and contribute to the building’s resistance against wind and other environmental forces, thereby maintaining structural integrity.

Can secondary frames be customized for different building designs?
Yes, secondary frames can be tailored in size, shape, and spacing to accommodate various architectural requirements, panel types, and load conditions specific to each project.

How are secondary frames installed in steel buildings?
Secondary frames are typically installed after the primary frame erection, using bolts or welds, and are aligned to support roofing and wall systems according to design specifications.
Steel buildings secondary frames play a crucial role in the overall structural integrity and functionality of steel construction projects. These frames, which include components such as purlins, girts, and eave struts, serve as intermediate support systems that connect the primary frame to the building’s exterior cladding and roofing materials. By distributing loads and providing attachment points, secondary frames enhance the stability and durability of the entire structure.

Understanding the importance of secondary frames is essential for optimizing design efficiency and ensuring cost-effectiveness in steel building projects. They not only contribute to load distribution but also facilitate faster construction timelines by simplifying the installation of panels and other building elements. Additionally, secondary frames allow for flexibility in architectural design, enabling customization to meet specific building requirements and environmental conditions.

In summary, steel buildings secondary frames are indispensable components that complement the primary structural system. Their thoughtful integration into building design improves performance, supports aesthetic versatility, and promotes long-term resilience. Professionals in the construction and engineering fields should prioritize the proper specification and installation of secondary frames to achieve optimal outcomes in steel building projects.

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Emory Walker
I’m Emory Walker. I started with Celtic rings. Not mass-produced molds, but hand-carved pieces built to last. Over time, I began noticing something strange people cared more about how metal looked than what it was. Reactions, durability, even symbolism these were afterthoughts. And I couldn’t let that go.

This site was built for the curious, the allergic, the cautious, and the fascinated. You’ll find stories here, sure, but also science. You’ll see comparisons, not endorsements. Because I’ve worked with nearly every common metal in the craft, I know what to recommend and what to avoid.

So if you curious about metal join us at Walker Metal Smith.
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Z-Purlins