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- Experimental tests of partially encased beams at elevated and room temperaturePublication . Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.; Barreira, Luísa; Gonçalves, CarlosThis work presents the experimental tests developed on partially encased beams (PEB) at elevated temperature and room temperature. PEB were built with IPE100 steel profile. Two beam lengths were tested (2.5 and 4 m) at room, 400 and 600 ºC. Seven series were tested to compare the performance of PEB using two different stirrups shear conditions (welded -W and not welded to web - NW). The behaviour of IPE 100 PEB was also compared with IPE 100 bare steel beam at room temperature. Most of the beams attained the ultimate limit state by lateral torsional buckling (LTB), with exception for those tested at 600 ºC which collapsed by the formation of a plastic hinge (PH). The performance of each PEB was characterized based on some load events. The load value for plastic behaviour (FMpl), the load value for displacement equal to L/30 (FL/30) and the load value for the ultimate load (Fu). The bending strength of the PEB at room temperature is almost two times the bending resistance of bare steel beam. The reduction on bending resistance of PEB is not directly proportional to the increase of temperature. An increase of temperature from room to 400ºC and to 600ºC leads to a reduction of 37 % and 64% on FL/30, respectively. The ultimate load of PEB increased 85% in comparison with bare steel at room temperature. A decrease in the ultimate load of 24% and 22% was verified when temperature increased from room to 400 ºC and from 400 ºC to 600 ºC, respectively. The bending resistance of PEB without welded stirrups slightly decreased in comparison to PEB with welded stirrups.
- Thermomechanical behavior of circular steel archesPublication . Gomes, Margarida; Mesquita, L.M.R.Circular steel arches are structural members curved in the plane of the applied loads, where the radius of curvature is much higher than the cross-section depth. The main objective of this work is to evaluate the behaviour of circular arches at room and elevated temperatures, like those that can arise from fires. The in plane buckling of arches is analysed numerically, using ANSYS software, considering different domains, linear elastic analysis, nonlinear elastic analysis and nonlinear geometric and material analysis, where the structural capacity of arches are studied in function of the geometric imperfections and residual stresses. The results are compared with those obtained by the simplified methods of Eurocode 3 part 1.1 and 1.2. The circular steel arches considered comprise a parametric analysis for arches with different spans, radius of curvature and opening angle at different temperature values, and subjected to an uniform radial distributed load. The values of the critical compression loads and the collapse loads were obtained for the different arcs, supports and temperatures. For the different geometries, the results allows to define the instability failure modes, symmetric or antisymmetric. It is concluded that increasing the arch height to the span ratio produces a decrease of the elastic critical load and the collapse load of the arch. The collapse mode for shorter arches is due to the formation of a plastic hinge whereas in the long span arches the structure will became instable before plastification, producing in plane instability in its stronger plane.
- Fire behaviour of mortars with portland cement and residual diatomaceous earthPublication . Magalhães, Leandro; Zolin, Renan Calvo; Alves, Matheus Henrique; Barreira, Luísa; Ferreira, Débora; Luso, Eduarda; Mesquita, L.M.R.; Óscar, LimaThe high pollution levels produced by the manufacturing of conventional Portland cement have motivated several studies in an attempt to modernize this process with alternative binders and the conscious use of natural resources. The correct treatment of residues has become a matter of great concern. The project “BacchusTech” aims to reuse diatomaceous earth from wine filtrations, introducing them into the composition of cement mortars through the reduction of cement and sand, seeking to valorise this winemaking residue and contributing to a sustainable construction. Three compositions of Portland cement-based mortars introducing residual diatomaceous earth are studied and fire behaviour tests are performed to the obtained specimens of mortars. The characterisation of these elements regarding their reaction to fire is performed using the cone calorimeter equipment.
- Estudio analítico de la inestabilidad por pandeo lateral de vigas parcialmente embebidas expuestas a fuego ISO 834Publication . Ramos Gavilán, Ana Belén; Piloto, P.A.G.; Mesquita, L.M.R.En base a un modelo de elementos finitos (EF) capaz de simular el comportamiento de las vigas analizadas en el trabajo de Piloto et al. [1], este estudio aborda el análisis numérico de vigas parcialmente embebidas (VPE) generadas en base a un perfil IPE100, sometidas a flexión en tres puntos y expuestas a fuego normalizado ISO834 [2]. El resultado numérico del instante de inestabilidad por pandeo lateral (PL) y de fallo según la norma UNE-EN 1363-1:2015 [3], sirve de base para valorar el ajuste del resultado analítico de resistencia a flexión de VPE considerando inestabilidad por PL, obtenido a través de un procedimiento de cálculo que adapta la formulación de la norma UNE-EN 1993-1-2:2011 [4] a las VPE.
- Fire protection durability of intumescent coatings after accelerated agingPublication . Thabet, R.; Benarous, Abdallah; Mesquita, L.M.R.Intumescent coating is a reactive chemical material, which is used as the main fire protection material to steel structures. When intumescent coating is exposed to fire, the chemical components in the intumescent coating react to cause the coating to swell forming a lightweight flame-retardant char to protect the steel substrate from excessive rise in temperature. However, exposure to long-term environmental conditions can cause the intumescent coating to lose some of the reactive materials, thus reducing the effectiveness of the intumescent coating over time. Because fire safety requirement is throughout the entire life of a building structure, which may last many tens of years, it is important to understand the long-term protection performance of intumescent coating under exposure to environmental conditions, [1].
- Thermal conductivity of calcium silicate boards at high temperatures: an experimental approachPublication . Oliveira, Thiago; Alves, Thiago Antonini; Mesquita, L.M.R.Thermal conductivity analysis of insulation materials is of great importance for determining the critical temperature of structures. The magnitude of this thermal property has a significant influence on the analysis of temperature distribution and heat flow which depends essentially on the thermal properties of the protection material. The most common method for obtaining the required fire resistance is through passive fire protection materials, such as the calcium silicate boards. By using this material, it is possible to slow down the temperature increase on the structural elements surface during a fire situation. Knowing accurate information about the effects of high temperatures on thermal conductivity is certainly an important prerequisite for running a high-performance design involving safety in buildings. Therefore, an investigation of two different calcium silicate boards has been performed to demonstrate how the thermal conductivity is highly affected when exposed to high temperatures. A set of experimental tests is presented. They were conducted in different techniques such as: the transient plane source (TPS) and the guarded hot plate.
- Numerical analysis of lateral torsional buckling of steel i-beams with and without web-openings under firePublication . Benyettou, Sabrina; Kada, Abdelhak; Lamri, B.; Mesquita, L.M.R.Steel structures are being widely used in construction industry owing to their excellent structural flexibility and to their high ductility to withstand lateral forces. However, for the case of solid and cellular steel beams, high temperature effect may result in different fire response for each case due to a great reduction of yield stress and Young’s modulus. Moreover, when the beams are not restrained, lateral torsional bending phenomenon which are bound to take place is made worse in the case of fire. The aim of this study is to analyse the behaviour of steel beams with and without web openings when taking into account the effect of geometry and material imperfections. The results from the finite element models produced lateral and vertical displacements as well as the buckling moments.
- Axial buckling load of partially encased columns under fire – new formulaePublication . Piloto, P.A.G.; Mesquita, L.M.R.; Ramos Gavilán, Ana Belén; Almeida, DavidFire resistance of partially encased columns (HEB and IPE) depends on the temperature evolution during fire exposure. This paper aims to assess de effect of the balanced summation model into the design of the axial buckling load of partially encased columns under fire, according to EN 1994-1-2. New formulae will be proposed to evaluate the fire resistance, based on new simple formulas to determine the flange temperature, the residual height and temperature of the web, the residual cross section and temperature of concrete, the reduced stiffness and strength of reinforcement. ANSYS was used to validate new and safe formulae, based on the analysis of the cross section totally engulfed in fire.
- Inelastic behaviour of partially encased sections: numerical comparisonPublication . Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.; Meda, AlbertoPartially encased sections are made of composite steel and concrete casted between flanges. They present an attractive solution in comparison with bare steel or reinforced concrete counterparts. This paper intends to validate experimental results for bending and axial loading members at room temperature, (Elghazouli et al, 2008). The experiments were conducted at the Imperial College in London and aimed to provide essential data for validating future analytical and design studies. This numerical comparison is based on three dimensional finite element modelling, simulating bond contact and failure of concrete. The numerical results agree well with experimental results.
- Comportamento de vigas em aço protegidas com tinta intumescentePublication . Mesquita, L.M.R.; Piloto, P.A.G.; Vaz, M.A.P.; Vila Real, Paulo M.M.; Ramos, F.Uma viga sem constrangimentos laterais submetida a um carregamento mecânico e sujeita a um aumento de temperatura, por exemplo proveniente de um incêndio, pode atingir o colapso pelo fenómeno de instabilidade por encurvadura lateral torsional, originado pela diminuição da capacidade resistente. Este trabalho apresenta o procedimento experimental e os ensaios realizados para a determinação da resistência ao fogo de vigas de aço IPE100 protegidas com tinta intumescente. São analisadas diferentes espessuras de protecção ao fogo, verificando-se experimentalmente, como seria de esperar, um aumento da temperatura crítica e do tempo de resistência ao fogo com o aumento da espessura do intumescente. Com base nos resultados experimentais é apresentada a evolução da condutividade térmica da tinta intumescente com a temperatura. Finalmente compara-se a espessura de tinta intumescente obtida à custa da condutividade térmica avaliada experimentalmente com a espessura proposta pelo fabricante.