## 4 Results and Observations
### Unprotected Slim Floor Specimens  
During the fire tests, WFRC 66162 and WFRC 67756, data recordings were conducted in terms of temperatures and vertical deformations. The recorded data has been reported in form of MS excel files and is available on the website, steelconstructin.info [28]. Though thermal data was recorded at various locations, comparisons are made only for two selected locations for each slim floor specimen to avoid any repetitions. These locations represent the middle part of the test assembly which is almost free from any influences resulting from the presence of boundaries such as the furnace walls. Further, the structural response of both slim floor beams was analysed via mid-span deflection in comparison to that recorded during the tests. Thermal results from FEM are presented for selected thermocouple positions at sections A-A' and section B-B' for test WFRC 66162 in Figure 6. The thermal gradient across the section after 120 min of heating is significant at both locations as seen in Figure 6a,b. Figure 5: Slim floor protected with an intunescent coating. Thermal predictions obtained using SAFIR and ABAQUS are presented in comparison to the recorded test data, Figure 6c,d. It is seen that the thermal predictions are in good agreement for 3D analysis irrespective of the position of the thermocouples across the section. On the other hand, these predictions slightly differ for thermocouples locations 3, 4 and 5 located on the web for 2D FEM performed using SAFIR as shown in Figure 5. This is due to the limitations of 2D modelling where the boundary conditions along the span cannot be modelled due to limitations of the approach. During the tests, heat also transfers toward section A-A' from the thin exposed sides of the concrete ribs due to the steel docking shape. This heat is in addition to the heat coming from the exposed bottom parts of the flange. The heat transfer from the ribs of the concrete cannot be modelled using the 2D FEM approach as result lower temperatures are predicted on the web. Hence, the predicted temperatures using 2D FEM for this part are lesser than those recorded during the test. On the other hand, thermal predictions result from 2D and 3D FEM for section B-B' are in good agreement with the recorded test data for section B-B' as boundary conditions were modelled with accuracy for both modelling methods (Figure 6d). In this case, the temperature provided by the 2D model are generally greater than those obtained applying the 3D model, as no longitudinal heat flux is considered in the 2D model. The thermal analysis method used is further assessed by analysing the predictions obtained on the thermal behaviour for WFRC 67756 with respect to the recorded test data. Like the previous case, data comparisons have been made for section A-A' and section B-B' and are presented in Figure 6. The 3D FEM results are in very good agreement with the test data for both locations. The obtained FE results from 2D modelling are in good agreement for section B-B' while in the case of thermocouples located on the steel web, the results differ slightly from the test data for section A-A', Figure 7c,d. It should be kept in mind that the thermal results estimated from 2D and 3D modelling are in good agreement with the test data, however, 3D modelling yields better results in comparison to 2D modelling. This indicates that the FEM approach in 2D and 3D adopted for thermal analysis of slim floors can be used for the fire design and verification of these systems with  
Figure 6: Thermal comparisons for WFRC 66162: (**a**) Thermal contours at section AA’ after 120 min, (**b**) Thermal contours at section BB’ after 120 min, (**c**) Test vs. FEM at section AA’ (**d**) Test vs. FEM at section BB’. high confidence to predict their thermal behaviour in fire, with the great benefit of reducing the computational burden. The structural response of ASBs in fire was estimated through their mid-span deflection. Figure 8 shows the predicted and measured mid-span deflection for tests WFRC 66162 and WFRC 67756.