Structural Robustness and Optimization of Steel Frames for Fire Exposure

May 28, 2015
Publication: Structures Congress Proceedings
Author(s): Kevin LaMalva Allan Jowsey Yujie Wang

For standard fire resistance design, the architect usually serves as the responsible party for satisfying code requirements for structural fire protection. As such, the architect typically selects qualified fire resistance assemblies from available listings, and the structural engineer may not have any influence in this regard. However, this long-standing paradigm is now starting to be challenged by engineers, contractors and approving authorities alike. In North America, the structural fire resistance of a steel frame is typically provided by the application of a passive fire protection material that has been qualified and listed based upon standard fire testing. Structural engineers are not conventionally trained in fire resistance design and may not be aware of the qualification process. Moreover, structural engineers may not be aware of the value that they could offer architects as it pertains to optimization of a fire resistance design. This paper explores the benefit of structural engineering participation in the fire resistance design process. It highlights associated design responsibilities and illustrates key considerations, benefits and limitations pertinent to fire resistance design. The American Institute of Steel Construction (AISC) provides a standardized methodology to assess robustness of structures in fire, including a load combination associated with an accidental loading scenario. A worked example within this paper illustrates the application of these methods within the context of the optimization of a fire resistance design. Fundamentally, the worked example considers a steel framed building, evaluates the load-bearing capacity of each member individually and evaluates performance in comparison to the failure criteria typically adopted within fire tests. Additionally, discussion is provided with respect to the viability of passive fire protection material and importantly, how the structural analysis can inform the steelwork specification to ensure an economic and up-front value-engineered optimized solution with advantageous impacts on construction sequencing.