Primary vs secondary framing in PEB is the concern of all the builders, cause the PEBs known as metal building systems, are a popular construction choice due to their ease of assembly, cost-effectiveness, and durability.
As most of these types of buildings are constructed from pre-fabricated steel components -it becomes essential to choose from primary or secondary framing to make the construction faster as compared to traditional methods.
Let us dive into the details of these structures –
Pre-engineered building structures are essentially built with two main skeletal systems: designated as primary & secondary frames.
It is important to understand the difference between these two types of structural skeletal systems to make informed and important decisions during the construction process.
Primary vs Secondary Framing in PEB Structures: 5 Key Differences
Difference 1: Function
When taken into consideration the primary frame is known to act as the backbone of a PEB structure.
The main function of this type of frame is to carry the weight of the building, including the roof and the wall panels, including any additional loads which can be natural or artificial ranging from snow or different types of equipment.
The structure of these primary members works together to efficiently transfer the load down to the foundation, which ensures the stability of the building constructed.
Let us take human anatomy to showcase as an example to draw comparisons – imagine the primary frame as the skeleton of a human body, that holds everything upright and provides a strong base for the smooth movement of the entire structure so that the sturdiness of the building does not ruin the framing due to rigidity.
Now let’s take a look at secondary frames, in contrast, these types of frames are known to play a supporting role.
The main function of these frames is to provide rigidity and support for cladding, which are the materials that cover the roof and walls of the PEBs.
The installed cladding panels do not have a supporting structure itself, hence they won’t be able to maintain their shape or withstand external forces on their own.
Here is where the importance of secondary framing comes into play, they ensure the cladding remains stretched and provides a smooth surface for insulation and other finishing materials.
In addition, the secondary frames play a secondary role in transferring wind loads to the existing primary frame.
It is designed in a way that it can distribute these lateral forces across multiple points, the secondary frame helps to maintain the overall stability of the entire PEB structure during an occasion of high windy conditions.
Difference 2: Material and Design
The materials and designs of the primary and secondary frames reflect their respective purposes.
Primary frames, the workhorses of the PEB construction, are commonly made of high-strength, hot-rolled steel sections.
These include familiar designs such as I-beams and columns, which were chosen for their high load-bearing capability.
The hot-rolling technique produces denser and stronger steel than cold-formed choices, making it perfect for supporting the entire building’s weight.
In contrast, secondary frames make use of cold-formed steel parts such as C-purlins and Z-purlins. These lighter-weight choices are ideal for their primary purpose of supporting cladding.
The cold-forming method produces complicated structures with high strength-to-weight ratios, making them ideal for this application.
Furthermore, the uniform shapes of these components enable speedy construction and easy integration with the core frame.
Primary frames can be custom-designed to meet a building’s exact load needs, whereas secondary frames are normally available in standard sizes.
This approach enables efficient manufacture and simplifies the construction procedure for the majority of PEB applications.
However, certain projects may necessitate the use of unique secondary frame parts to accommodate certain architectural features or cladding materials.
Difference 3: Size and Weight
The size and weight of the primary and secondary frames are another key distinction.
Primary frame members, designed to carry substantial loads, are significantly larger and heavier compared to their secondary counterparts.
Imagine the thick leg bones in a human body compared to the thinner ribs. This size difference allows the primary frame to handle the heavier weight of the entire structure.
Secondary frames, on the other hand, are designed for efficiency in supporting cladding.
They are much lighter and have smaller profiles compared to primary members. This allows for easier handling and faster assembly during construction.
While lighter, these cold-formed sections are still strong enough to provide the necessary support for the building’s cladding materials.
Considerations for Choosing Primary Frame Size and Weight
Selecting the appropriate size and weight for primary frames involves careful consideration of several factors, including the building’s size and intended use, along with local building codes and potential snow or wind loads.
Difference 4: Complexity of Fabrication and Erection
The fabrication and erection processes also differ significantly between primary and secondary frames.
Due to their larger size and the need for precise connections to handle heavy loads, primary frames often involve more complex fabrication processes.
This might include techniques like welding, drilling, and intricate cutting to ensure a strong and stable structure.
Additionally, erecting primary frames requires specialized equipment due to their weight and size.
In contrast, the fabrication and erection of secondary frames are generally simpler and faster.
Their standardized design and lighter weight allow for efficient mass production and easier handling on-site.
Typically, these frames are connected using bolts or screws, streamlining the erection process and reducing reliance on specialized equipment.
Difference 5: Cost
Cost is another key factor to consider. The primary frame, due to its use of more material (thicker steel sections) and complex fabrication processes (welding, intricate cutting), typically commands a higher price point compared to the secondary frame.
Secondary frames, on the other hand, benefit from their lighter weight and simpler design, resulting in lower material and fabrication costs.
Additionally, the faster erection process associated with secondary frames translates to reduced labor costs.
While both frames are generally cost-effective compared to traditional construction methods, understanding this cost difference can be helpful when making budgetary decisions for your PEB project.
Conclusion
Finally, primary and secondary frames serve unique but equally crucial roles in PEB architectures.
Primary frames, made of strong hot-rolled steel, serve as the building’s backbone, supporting the full weight and transferring loads to the foundation.
Secondary frames, constructed of lighter cold-formed steel pieces, offer support and rigidity to the cladding. These frames vary in function, material, size, production difficulty, and cost.
Understanding these key differences is critical for the successful design and construction of PEB structures.
Engineers can choose the proper frame types and sizes based on building size, function, and local codes.
For complex PEB projects, engaging a qualified structural engineer can help assure a safe, efficient, and cost-effective design that satisfies all of your needs.
