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This paper presented the results of numerical analyses on the fire resistance of composite columns with partially encased steel columns (PEC). This investigation used 2D and 3D finite element models and assessed for the design method of composite elements under compression according to the Annex G of Eurocode 4. New proposals were presented to determine the buckling resistance of PEC under standard fire. The 2D and 3D numerical models were based on American and European steel profiles. The 2D thermal model was used to improve the design method of the current version of the Eurocode 4, enhancing the balance summation model, which is currently used to determine the plastic resistance to axial compression and the effective flexural stiffness of the four components of the cross-section. The 3D thermomechanical model used the temperature field for each fire rating time (30, 60, 90, and 120 min) and applied the incremental load step solution method, based on the Newton–Raphson, to determine the buckling load of partially encased columns with 3 and 5 m, considering different supporting conditions. These results present a safer buckling curve when compared to curve "c". [ABSTRACT FROM AUTHOR]

Light Timer Frame Walls are made of solid timber elements and are usually fire protected by other materials. This investigation determines the residual load bearing capacity of Light Timber Frame Walls for fire rating periods of 30, 60, 90 and 120 min. The timber frame is made with 3 studs and 2 tracks, using two different fire protection levels (one and two gypsum layers). The computational model includes the thermal analysis under standard fire, including all types of materials and a sequential mechanical analysis with incremental load applied for each fire rating periods, applied just for the load bearing material. Nonlinear solution methods are used with small tolerance values for solution convergence, to determine the correct temperature and displacement fields. The thermal and the mechanical properties are considered temperature dependent. The mechanical analysis considers large displacement behaviour, and the charring effect of wood is included by the reduction of the stiffness and strength of the timber. The results show that the load bearing capacity decreases with the fire exposure time. A new proposal is presented between the load bearing capacity and the fire rating and finally the char layer is compared with the current and future version of Eurocode 5, part 1.2. [ABSTRACT FROM AUTHOR]

A computational model is presented to evaluate the thermal effects on composite slabs with still deck, originated by standard fire exposure. Composite slabs with profiled steel deck are widely used in buildings which require fire resistance. Computational simulations are of great importance in this field and consist of an alternative to experimental fire tests that are expensive, time-consuming and require semi-specialized technical equipment. However, computational simulations must be reliable and realistic. The resulting transient and non-linear thermal problem is solved by the Finite Element Method in ANSYS and Matlab. The finite element models are three-dimensional, full scale, and multi-domain. Additionally, the models also include an air gap between the steel deck and the concrete part of the slab, in order to simulate the thermal effects induced by the debonding between the steel deck and the concrete, verified in previous experimental investigations. The results of the numerical simulations are validated against the results of experimental fire tests. The fire resistance of the composite slabs determined computationally is also compared with simplified calculation methods available in standards. [ABSTRACT FROM AUTHOR]