Fire induced progressive collapse of steel building structures: The role of interior gravity columns

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Fire induced progressive collapse of steel building structures: The role of interior gravity columns

Anil Agarwal a,⇑, Amit H. Varma b

a Bentley Systems, Inc., 515 Mullica Hill Rd., A209, Glasboro, NJ 08028, United States

b School of Civil Eng., Purdue Univ., West Lafayette, IN 47907, United States

 

a b s t r a c t

This paper presents a qualitative assessment of the importance of gravity columns on the stability behavior

of a typical mid-rise (10 story) steel building subjected to corner compartment fires. Two ten-story

steel buildings with composite floor systems were designed following the design practices in the US.

One of these buildings had perimeter moment resisting frames (MRFs) to resist lateral loads while the

other building had an interior core of RC shear walls. Effects of gravity loads and fire conditions were simulated

using the finite element method and numerical analysis techniques.

The results from the numerical investigations indicated that gravity columns govern the overall stability

of building structures under fire conditions. Gravity columns have the highest utilization ratio, and

they are most likely to reach their critical temperatures first. If gravity column failure occurs, the

load shed or dropped by the failed column has to be redistributed to the neighboring columns to maintain

overall structural stability. This axial load redistribution can occur through the development of alternate

load paths including catenary action. Simulation results indicate that the presence of steel

reinforcement in the concrete slabs (in addition to the minimum shrinkage reinforcement) facilitates uniform

redistribution of the axial load dropped by the failed gravity column to the neighboring columns.

The additional steel reinforcement improves the flexural and tensile strengths of the composite floor system,

which enhances its ability to develop alternate load paths including catenary action in the slab, and

thus maintain structural stability after gravity column failure.

 

a r t i c l e i n f o

Article history:

Available online 13 October 2013

Keywords:

Fire analysis

Fire safety

Progressive collapse

Fire induced collapse

Steel building design

 

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