Fire exposed aluminium structures

Journal of Civil Engineering and Management, 2004

In the paper the attention is focused on the influence of high temperatures on the mechanical properties of the aluminium alloys selected by Eurocode 9 for structural uses. Therefore, based on the analysis of existing data taken from technical literature, the variation of the Youngs modulus, the conventional yielding strength, the ultimate strength, the hardening factor and the material ultimate strain are represented as a function of the temperature. A mechanical model, based on the well-known Ramberg-Osgood formulation, which appropriately takes into account the peculiarities of such materials at high temperatures, is provided. In particular, the combined influence of the hardening factor and temperature on the material stress-strain relationship is considered and analysed. Then, the proposed model has been introduced in a finite element program, devoted to the global analysis of structures under fire. .inally, the results obtained for a simple portal frame structure, designed with different aluminium alloys, are presented, showing the valuable effect of the material modelling on the structural behaviour of aluminium structures under fire.

This paper gives an overview of the structural behaviour and design of aluminium structures exposed to fire conditions. Two design approaches are elaborated: the "traditional" approach that is mainly based on conventions and the fire safety engineering approach that is more based on physics. For the traditional approach, equations for the aluminium member temperature are provided, mechanical properties are given and recently developed calculation models for flexural buckling, local buckling and heat affected zone rupture are presented. For the fire safety engineering approach the possibilities for evaluation of member temperature are provided, a constitutive model for aluminium alloys is given which can be implemented in finite element programmes and two design examples are presented to show the evaluation of the structural behaviour. The paper concludes that the fire safety engineering approach is preferred for the fire resistance evaluation in particular for structures made of materials sensitive to fire conditions, such as aluminium alloys. 1 email [email protected], telephone +31 15 2763464 86

Elektronički časopis građevinskog fakulteta Osijek

In this study, a performance analysis of a simple aluminum (EN AW-6061 T6) structure is presented under fire conditions. A simple structure was also analyzed in a steel (S235) building variant for comparison purposes. All loads were determined in accordance with Eurocode rules. Internal forces were calculated using the SCIA Engineer 19.1. Cross-section resistances and element stability checks were performed using EN1993-1-1 and EN1993-1-2 for steel and EN1999-1-1 and EN1999-1-2 for aluminum. The main conclusion of this study is that aluminum, although initially more expensive than steel, can offer rational solutions for structures in which the difference in structural performance in fire conditions between aluminum and steel is not sufficiently drastic to yield significantly higher costs for fire protection in aluminum. Furthermore, aluminum building variants offer less mass, easier transport, and resistance to corrosion. Hence, for structures with the aforementioned factors as the ...

Journal of Structural Fire Engineering, 2014

Fire is often the dominant design criterion for aluminium structures. Present design rules for aluminium constructions in fire neglect both the decrease in susceptibility to local buckling and the effects of creep, that are intrinsic to aluminium. They may therefore either overestimate or underestimate the temperature of failure, depending on the load and exposure period. As part of a larger research program aimed at remedying this situation, the present paper reports the results of an experimental study on 28 aluminium SHS members of alloy AA6060-T66 loaded in bending, with different cross-sections, temperatures, and rates of heating. The experimental set-up employs an electric heating tube or ‘sock’ on the inside of the specimen as well as heated supports and load application point, which give a high degree of control of temperature in time.

Fire Science and Technology, 2005

A series of fire resistance tests of aluminum alloy members was conducted. This study characterize temperature rise and collapse mechanism of the aluminum alloy members. Analytical expressions, based on lumped mass heat balance equation, have been developed to estimate the temperature rise of unprotected, protected aluminum members during fire. An evaluation method of critical temperature of aluminum alloy members was also proposed and compared to experimental data. The results of the calculations by these methods were found to be in a good agreement with the experimental results.

The use of aluminium as a construction material has been increasing since its first invention. At present, limited knowledge of the behaviour of aluminium beams in fire gives rise to excessively high insulation demands, decreasing its competitiveness. An explorative study is presented here that aims to assess the potential for improvement in the existing design standards for aluminium in fire conditions. At present, fire design for aluminium alloy beams is performed using the same system of cross-sectional slenderness classes as is employed at room temperature. Identical width-over-thickness ratio limits are used to define the boundaries between the classes. These limits are known (and demonstrated) to be conservative, but may in fact be over-conservative. Especially for tempered alloys, the geometric limits may be relaxed considerably, allowing cross-sections to be upgraded in class for fire design calculations.

Metallurgical and Materials Transactions A, 2008

An existing constitutive model for creep, developed by Dorn and Harmathy, is modified in order to be used for fire-exposed aluminum alloys. Two alloys, 5083-O/H111 and 6060-T66, are selected for the development of this constitutive model because of their different behavior at elevated temperature and their frequent application in structures for which fire design is relevant. The material parameters in the model are calibrated with the experimental results of creep tests, carried out with constant load and temperature in time. The model is validated with socalled transient state tests, with a constant load in time (stresses ranging from 20 to 150 N/mm 2 ) and with an increasing temperature (with heating rates ranging from 1.6°C/min to 11°C/min and critical temperatures ranging from 170°C to 380°C). These tests are considered as representative for fire-exposed, insulated aluminum members. The existing constitutive model of Dorn and Harmathy provides good agreement with the transient state tests carried out for the 5xxx series alloy, but appeared to be not suited for the 6xxx series alloy. This is attributed to the early development of tertiary creep in case of 6xxx series alloys. The existing model was modified to incorporate this first stage of tertiary creep, to arrive at a good agreement between the tests and the modified model for 6xxx series alloys.

Aluminium alloys are often used for temporary structures in the entertainment industry, such as temporary staging, towers or trusses for roof structures. For this kind of applications the structural elements are designed taking into account various aspects related to both the material properties and the temporary use, which are discussed in the first part of this paper. In the second part, the behavior of such structures exposed to fire is considered. A truss beam is analyzed considering the following scenario: during the construction phase, the truss elements are lifted using appropriate rigging equipments (chains, hooks, slings, etc.); usually the slings are made of polyester and, after lifting, are left on the truss. This material is very inflammable, so the possibility that the slings goes up in flames is considered; the behavior of the structure exposed to elevated temperature is analyzed and the structural safety is assessed.

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2017

The positive attributes of aluminium as a modern building material in construction practice have been used as background for a more intense application of this material type throughout the 21st century. Favourable properties of aluminium include most of the aspects of sustainability within the period of exploitation of the structure. One of the major problems with the application of aluminium in construction industry is the inherent fire resistance which needs further research if aluminium is to be more widely applied in construction practice. This paper describes research activities of an ongoing research project examining the mechanical and creep properties of aluminium alloy EN6082AW T6 exposed to fire. The research presented here is part of a joint research programme (the Croatian Science Foundation project No. UIP-2014-09-5711) conducted by the Universities of Split and Sheffield, whose aim is to explore the influence of creep on the behaviour of steel and aluminium columns in ...