## 5 Conclusions  
In the present paper, the thermo-structural behavior of LWC in composite slabs with profile steel decking subjected to fire and a constant load were studied. Extensive experimental tests and numerical analysis were performed and, based on the respective experimental and numerical results, the following conclusions can be drawn:  
Experimental results:  
1. The measured temperatures on the steel decking profile are lower than the ISO 834 curve. This phenomenon is due to free water vaporization, and the debonding effect that introduces an air gap between the concrete and the steel decking profile. 2. Concrete contains water that vaporizes at temperatures above 100 \({}^{\circ}\)C. In this work, the measured temperatures on the concrete show a non-constant increase and a plateau at 100 \({}^{\circ}\)C. This is caused by the vaporization process of the free water, which is an endothermic reaction and consumes energy, slowing down the heating up of the concrete. 3. The thermal properties (thermal conductivity, specific heat) of concrete, the moisture content and the porosity affect the increase in temperature in the slab. Furthermore, the complex heat transfer phenomenon due to the vaporization in LWC slabs causes a greater distortion. This effect is mainly due to the porosity of the material, which is directly related to its moisture content. 4. The higher moisture content of LWC composite slabs causes the measured temperature in LWC composite slabs to be lower than NC. Therefore, LWC composite slabs have lower heat transfer under fire conditions than NC. 5. The insulation criteria of the composite slab and the influence of the trapezoidal shape is studied on the non-exposed surface. The temperature variation between the thinner and thicker part is lower than 15 \({}^{\circ}\)C. Therefore, based on the temperature measured, the insulation and integrity criteria are met for all the samples. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Time (s)** & **LWC-1** & **LWC-2** & **LWC-3** & **NC** \\ \hline
100 & 4.20 & 11.76 & 3.39 & 62.48 \\
300 & 24.91 & 29.89 & 27.89 & 52.78 \\
500 & 12.04 & 12.60 & 14.44 & 33.02 \\
700 & 4.10 & 3.20 & 3.63 & 12.74 \\
900 &  
6. The experimental results show that there is debonding between the steel decking and the concrete slab. This phenomenon introduces a gap between both materials; thus, the heat transfer in the composite slab is influenced and the pressure in the internal concrete pores is reduced. Spalling is not observed in any of the tests carried out. It can be concluded that the steel decking prevents direct fire exposure to the concrete core and acts as a barrier to the expansive effect of spalling on this type of structural element. 7. In general, the vertical deflection under fire conditions has three stages. The first stage is caused by the thermal expansion and reduction of the mechanical properties of steel. The second stage involves the load transfer to the concrete. Finally, the slab collapses. 8. Although the deflection measured in all the slabs is very similar, the load-bearing capacity (R30) is reached only for LWC-3 and NC. It is observed that the structural behavior of the lighter slabs does not accomplish the minimum load-bearing capacity of 30 min. To achieve the load-bearing capacity, two possible solutions can be used. First, composite slabs should be reinforced to ensure the minimum value of R30 is reached. Second, active fire protection elements can be used on the trapezoidal steel decking so that the temperature increase in the steel decking is slowed down and its mechanical properties are maintained for longer. A combination of the two solutions is also possible. Numerical simulation:
1. ANSYS Workbench Mechanical can link a thermal analysis to a structural analysis, sharing Engineering Data, Geometry and Model directly. When directly linked, bodies in the structural model cannot be suppressed independently of the thermal analysis. When the same mesh is used, temperature mapping is usually simple.