Portal Frame versus X-Bracing

But I say to you, Love your enemies and pray for those who persecute you, so that you may be sons of your Father who is in heaven; for he makes his sun rise on the evil and on the good, and sends rain on the just and on the unjust.
Jesus Christ 

Understanding X-Cable Bracing

Your steel building requires bracing to increase its ability to withstand lateral loads.  In other words, you won’t want it to collapse when strong forces are applied, thus, this additional bracing is factored into the design phase.

X-Cable Bracing is the standard bracing applied to, at minimum, 1 of a typically equally spaced bays.  

EXAMPLE:  40 x 60 x 14 building would require 1 X-Cable Bracing to be designed into each end wall and each sidewall.

Bay spacing can range from 10 to 30’ on the Sidewalls.

Bay spacing can range from 5 to 28’ on the Endwall (Gable Ends)

Typical design for 40’ wide Endwall would be 2@20’ with 1 Bay X-Cable Braced, see image 1:

Typical design for 60’ long Sidewall would be 2@30, with 1 Bay X-Cable Braced, see image 2:

When Portal Frame or Non-Expandable Endwall Frame is Required

However, let’s say you want to put 2 large framed openings in ONLY the Endwall, using both Bay 1 and Bay 2.  In this case, you would require a Non-Expandable Endwall end frame in order to secure the lack of X-Cable Bracing.  

Keep in mind, your overhead doors generally require 2 feet clearance per side and overhead when X-Bracing is utilized in at least 1 Bay.

Portal framing takes up more space interiorly, requiring 3-4’ clearance on sides and overhead.  Take this into consideration when choosing building heights and door sizes.

If you wanted to put 2 large framed openings in ONLY the Sidewall spaced at 2 Bays of 30’ each.  A Portal Frame would be used in lieu of X-Cable Bracing in Bay 1, as shown above.

Getting Creative with Bay Spacings

Depending on the size opening you require, you may still be able to stagger the Bay widths and use X-Cable Bracing in one of the Bays still, see image with 2 Bays of 25’ and one Bay at 10’.

If you wanted to put 3 large framed openings in ONLY the Sidewall, 3 Bays of 20’ each, using up ALL 3 Bays, then Portal Frame would be necessary.

In summary, there are options for your design.  Portal Framing costs more since the steel is beefed up to support your openings.  However, your design choices would be worth it if you want large overhead doors along the entire length or width of your building.  Again, keep in the mind the general clearances required (noted above) for installed overhead doors.