Analysis of a Half-Scale Composite Floor System Test under Column Loss Scenarios

This paper describes modeling and analysis of a half-scale steel gravity frame system with composite concrete slab on steel deck that was constructed and tested at the University of Illinois under corner, edge, and interior column removal scenarios. For each scenario, distributed floor loading was incrementally increased until the floor system could not sustain additional load. The experimental results showed that the ultimate capacity of the floor system ranged from 44 % to 62 % of the applicable gravity load combination (1.2D + 0.5L), indicating a potential vulnerability to collapse. Analyses of the floor system used a component-based modeling approach for the shear connections, with load-displacement curves for each bolt row calibrated against experimental data from half-scale connections. Girders, beams, and columns were modeled with beam elements, and alternating strips of shell elements were used to represent the ribbed profile of the concrete slab on steel deck. The model accounted for partial continuity of the steel deck, as influenced by the actual placement of shear studs and spot welds. Blind pre-test predictions are compared with experimental data for the four column removal scenarios. The modeling approach was refined after each of the first two tests, and two factors were identified as having a significant influence on the response of the system: the post-ultimate softening modulus of concrete in tension and the out-of-plane (torsional and transverse shear) behavior of the shear connections.