Figure from:Behaviour of reinforced concrete structures in fire

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Fig. 11 - Comparison of predicted central deflections for different fire compartment positions. — Figure 11 - Comparison of predicted central deflections for different fire compartment positions.

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Fig. 2 - Concrete structure layout for whole ground floor heated by the ISO 384 fire. Therefore, at the fire limit state, the total desi partial safety factor of 0.5 i example. The characteristi s applied c strength of co 45MPa and 460MPa, respectively. required for the building. Therefore to the imposed load. This loading is used th It is also assumed that two hours’ fire the nominal covers of beams, Slabs and col requ ired fire resistance are 30mm, 25mm and 25mm respectively '*. According 23 each floor slab is nom inally 250 mm thick and designed as a flat slab. The di gn load on the structure is 10.75 kN/m? when the roughout the ncrete and reinforcing steel are assumed to be resistance is umns for the to Eurocode mensions of

the cross-sections of beams and columns are 500mm x 350mm and 350mm x 350mm respectively. Fig. 3 shows the cross-section details of beams and columns.

Fig. 5 - Predicted deflections at key positions of the concrete floor.

Fig. 6 - Predicted vertical deflections at the tops of three ground floor columns, A1, B2 and C3.

Fig. 7 - Deflection profiles at 150min, with cracking patterns of bottom layer of floor slab. RE hE ee UY Uy Fig. 7 shows the deflection profile of the structure modelled at 150min. A vector plot f the distribution of principal membrane tractions (forces per unit width of slab) at the Gauss oints of the slab elements at 150min is shown in Fig. 8. In this plot, the lengths of the vectors re proportional to their magnitudes; thin vector lines denote tension and thick lines denote ompression. The figure shows repeated patterns clearly indicating tension fields in the tral region of each floor panel, together with the peripheral compression ‘rings’ which are sile membrane action. It is obvious that the area in tension is rather aller than the compression region. This is because the deflections are relatively small, less /30, so tensile membrane action is not very significant. ome) =) o Pp ro) oS iq>) a. n x. (=) jo) i oe 5 nNna020 iq>) 8 = = S ©