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The simple model of Eurocode 3, for the fire resistance evaluation of stainless steel members, are based on the procedures used for carbon steel structural elements. However, due to the existing differences in the constitutive laws of these two materials, it is expected that it would not be possible to use, in both materials, the same formulae for the member stability calculation, as proposed in Eurocode 3. This paper aims at increasing the knowledge on the behaviour of stainless steel axially loaded columns at elevated temperatures. For this purpose, a geometrical and material non linear computer code has been used to determine the buckling load of these elements. The Eurocode formulae are evaluated and a new proposal, that ensures accurate and conservative results when compared with the numerical simulations, is presented. reduction factor for the flexural buckling in axis in case of fire χ min,fi minimum of the reduction factor χ i,fi NOTATIONS INTRODUCTIONThe use of stainless steel for structural purposes has been limited to projects with high architectural value, where the innovative character of the adopted solutions is intended to add value to the structure. The high initial cost of stainless steel, coupled with: (i) limited design rules, (ii) reduced number of available sections and (iii) lack of knowledge on the additional benefits of its use as a structural material, are some of the reasons that force designers to avoid its use. However, more accurate analyses point to a good performance of stainless steel when compared against conventional carbon steel in fire situation [1,2,3].The most important advantage of stainless steels is their corrosion resistance, however, their aesthetic appearance, ease of maintenance, durability and the low life-cycle costs are also valuable characteristics. Engineers often disregard these advantages of stainless steel due to its high initial cost. Nevertheless, greater importance is being given to total life costing because of high maintenance, shutdown, demolition and parts replacement costs. Experience has shown that the benefits of a long life with low maintenance and repair requirements more than compensates for the higher initial purchase cost of stainless steel.Part 1-4 of Eurocode 3 (EC3) "Supplementary rules for stainless steels" [4] gives design rules for stainless steel structural elements at room temperature, and only mentions the stainless steel structural elements fire resistance by referring to the fire part of the same Eurocode, EN 1993-1-2 [5]. Although carbon steel and stainless steel have different constitutive laws, EC3 states that the structural elements made of these two materials must be checked for their fire resistance with the same formulae. Thus, based on the formulae in Part 1-4 of EC3, Uppfeldt [6] presented a design model for stainless steel hollow columns in case of fire based on both experimental and numerical tests. Regarding the study of axially loaded carbon steel columns, Franssen in 1996 [7,8] proposed a procedure for the safety...

In building applications (e.g. industrial, offices and residential), the use of lightweight steel-framed structural elements is increasing given its advantages, such as exceptional strength-to-weight relation, great potential for recycling and reuse, humidity shape stability, easy prefabrication and rapid on-site erection. However, the high thermal conductivity of steel presents a drawback, which may lead to thermal bridges if not well designed and executed. Furthermore, given the high number of steel profiles and its reduced thickness, it is not an easy task to accurately predict its thermal performance in laboratory and even less in situ. In a previous article, the authors studied the importance of flaking heat loss in lightweight steel-framed walls. This article discusses several thermal bridges mitigation strategies to improve a lightweight steel-framed wall model, which increase its thermal performance and reduce the energy consumption. The implementation of those mitigation strategies leads to a reduction of 8.3% in the U-value, comparatively to the reference case. An optimization of the wall module insulation layers is also performed (e.g. making use of new insulation materials: aerogel and vacuum insulation panels), which combined with the mitigation approaches allows a decrease of 68% in the U-value, also relatively to the reference case. Some design rules for lightweight steel-framed elements are also presented.

The thermal performance of a modular lightweight steel framed wall was measured and calculated with three-dimensional finite element method model. The focus of this article is on the effect of flanking thermal losses. The calculated heat flux values varied from 222% (external surface) to + 50% (internal surface) when flanking loss was set to 0 as a reference case, thermal transmittance equal to 0.30 W/(m 2 ÁK). Other critical parameters were the existence of fixing 'L'-shaped steel elements and the perimeter thermal insulation (10 cm XPS).

The experimental characterization of the overall thermal transmittance of homogeneous, moderately-and non-homogeneous walls, windows, and construction elements with innovative materials is very important to predict their thermal performance. It is also important to evaluate if the standard calculation methods to estimate the U-value of new and existing walls can be applied to more complex configurations, since the correct estimation of this value is a critical requirement when performing building energy simulations or energy audit. This paper provides a survey on the main methods to measure the thermal transmittance and thermal behaviour of construction elements, considering laboratory conditions and in-situ non-destructive measurements. Five methods are described: the heat flow meter (HFM); the guarded hot plate (GHP); the hot box (HB), considering the guarded HB (GHB) and the calibrated HB (CHB); and the infrared thermography (IRT). Then, previous studies dedicated to the assessment of the thermal performance of different heavy-and light-weight walls are discussed. Particular attention is devoted to the measurement of the U-value of nonhomogeneous walls, including the effect of thermal bridging caused by steel framing or mortar joints, and the presence of PCMs or new insulation materials in the configuration of the walls. hot box; calibrated hot box; infrared thermography. Highlights: -Review on the main methods to measure the U-value of non-homogeneous walls. -Methods: heat flow meter, guarded hot plate, guarded and calibrated hot box, infrared thermography. -Standards framework and discussion of the main advantages and drawbacks of each method. -Description of methodologies and working principles of laboratory and in-situ measurements. -Measurement of the thermal transmittance of different heavy-and light-weight walls.

The sliding hinge joint (SHJ) is a type of supplemental energy dissipation system for column bases or beam-to-column connections of steel Moment Resisting Frames (MRFs). It is based on the application of symmetric/asymmetric friction dampers in joints to develop a dissipative mechanism alternative to the column/beam yielding. This typology was initially proposed in New Zealand and, more recently, is starting to be tested and applied also in Europe. While on the one hand this technology provides great benefits such as the damage avoidance, on the other hand, due to the high unloading stiffness of the dampers in tension or compression, its cyclic response is typically characterized by a limited self-centering capacity.To address this shortcoming, the objective of the work herein presented is to examine the possibility to add to these connections also a self-centering capacity proposing new layouts based on a combination of friction devices (providing energy dissipation capacity), pre-loaded threaded bars and disk springs (introducing in the joint restoring forces).In this paper, as a part of an ongoing wider experimental activity regarding the behaviour of self-centering connections, the attention is focused on the problem of achieving the selfcentering of the column bases of MRFs by studying a detail consisting in a column-splice equipped with friction dampers and threaded bars with Belleville disk springs, located above a traditional full-strength column base joint. The main benefits obtained with the proposed layout are that: i) the self-centering capability is obtained with elements (threaded bars and Belleville springs) which have a size comparable to the overall size of the column-splice cover plates; ii) all the re-centering elements are moved far from the concrete foundation avoiding any interaction with the footing. The work reports the main results of an experimental investigation and the analysis of a MRF equipped with the proposed column base joints.

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