How does thermal expansion influence PEB framing design?

• A. Metals expand/contract with temperature; design includes expansion joints or slip connections to accommodate movement.
• B. Temperature has no effect on steel.
• C. Expansion joints are optional.
• D. Movement is ignored.

Answer: (A)

Thermal expansion causes metals to lengthen when heated and shorten when cooled, so PEB framing must accommodate that movement. In long-span frames exposed to temperature changes, the steel will grow and contract, and without a plan to absorb this movement the connections, joints, and attached envelope components can experience excessive stresses, misalignment, and damage. To prevent this, designers include expansion joints or slip connections that allow relative movement between sections or between the frame and the rest of the building, maintaining structural integrity and keeping doors, windows, and cladding functioning properly through temperature cycles.

Statements that temperature has no effect, that expansion joints are optional, or that movement can be ignored don’t reflect how steel behaves with heat or how the building envelope must remain functional across temperature changes.