"Exposure to fire: The faceplate that is exposed to fire loses strength and stiffness; however, similar to Reinforced Concrete (RC) construction, the bulk of the concrete and the opposite faceplate maintain good strength and stiffness. As such, Steel-Plate Composite (SC) structures have better fire resistance than pure steel structures. Fire resistance of SC walls is potentially lower than RC structures; however, the fire resistance is enhanced if a suitable protection coating is applied to the faceplate(s) or fire-resistant steel is used. The member strength and stiffness during fire-exposure is also improved by embedding another steel plate within the concrete, that is, between the faceplates. ANSI/AISC N690 does not currently cover SC walls with embedded steel plates." - Design Guide 32 §1.2.1(d)

Fire protection requirements can vary by jurisdiction and will need to be addressed by jurisdiction.  There may be opportunity in the near future to utilize the use of performance-based methods to design fire protection through the use of Appendix E of the next edition of ASCE/SEI 7.

Rainier Square: Rainier Square: Rainier Square Tower has petitioned and succeeded in allowing the walls to only require fire protection on the outer, occupant side of the core walls.  The project originally detailed the walls to receive spray-applied cementitious fire protection on both sides of the wall. The removal of the fire protection from the inside of the core is expected to save approximately one million dollars from the job, not including schedule savings.

Fire protection and fire separation rating research were completed in early 2020. The research uses a combination of performance-based fire engineering and test specimen validation.  A bare, 12” thick wall (no fire protection) can provide a 2-hr separation assuming an axial load ratio (demand/capacity) less than or equal to 15% and slenderness of the wall less than or equal to 20. Axial load, wall thickness, and wall slenderness play into the fire design. With the completion of this study, the fire-resistive system is also scalable using the published fire design method."