Post-Fire Ultimate Load

The ultimate load of the columns, P , is normally expressed as according to AISC [16]  

Analyzing the failure mechanism (delamination between webs and face sheet close to the support) and based on [17], it was concluded that ultimate failure was initiated by a shear failure at the web-face sheet junction. In fact, delamination initiated at a distance of 300 mm from the support, that is, at the location of maximum shear force within the fire-exposed region. The web-face sheet junction, furthermore, is the critical location in this critical cross section because  

1) the web shear stresses at the neutral axis position (where the maximum is) and the junction position are almost identical, 

3) the shear strength at the web-flange junction of pultruded shapes is much lower than in the web [18]. 

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Table 8.5 Reduction factors and comparison of predicted to experimental ultimate loads for post-fire specimens P-WCl and P-WC2 and reference specimen P-REF [14]. (With permission from ASCE.)...

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