Fire performance of innovative steel-concrete composite columns using high strength steels
KeywordFire resistance; Steel-concrete composite sections; Concrete-filled steel tubular columns; Concrete-filled double steel columns; Embedded steel profiles; High strength steel
Rights© 2016 Elsevier. Reproduced in accordance with the publisher's self-archiving policy. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
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AbstractThis paper presents the results of a numerical investigation on strategies for enhancing the fire behaviour of concrete-filled steel tubular (CFST) columns by using inner steel profiles such as circular hollow sections (CHS), HEB profiles or embedded steel core profiles. A three-dimensional finite element model is developed for that purpose, which is capable for representing the various types of sections studied and the nonlinear behaviour of the materials at elevated temperatures. High strength steel is considered in the numerical model, as a possible way to lengthen the fire endurance. The numerical model is validated against experimental results available in the literature for various types of steel-concrete composite sections using inner steel profiles, obtaining satisfactory results. Based on the developed numerical model, parametric studies are conducted for investigating the influence of the cross-sectional geometry and the steel grade of the inner profiles on the fire performance of these composite columns, for eventually providing some practical recommendations.
CitationEspinos A, Romero ML and Lam D (2016) Fire performance of innovative steel-concrete composite columns using high strength steels. Thin Walled Structures. 106:113-128.
Link to publisher’s versionhttps://doi.org/10.1016/j.tws.2016.04.014
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Design and processing of low alloy high carbon steels by powder metallurgy. P/M processing and liquid phase sintering of newly designed low-alloy high carbon steels based on Fe-0.85Mo-C-Si-Mn with high toughness and strength.Wronski, Andrew S.; Abosbaia, Alhadi A.S. (University of BradfordSchool of Engineering, Design and Technology, 2011-03-31)The work presented has the ultimate aim to increase dynamic mechanical properties by improvements in density and optimisation of microstructure of ultra high carbon PM steels by careful selection of processes, i.e. mixing, binding, alloying, heating profile and intelligent heat treatment. ThermoCalc modelling was employed to predict liquid phase amounts for two different powder grades, Astaloy 85Mo or Astaloy CrL with additive elements such as (0.4-0.6wt%)Si, (1.2-1.4wt%)C and (1-1.5wt%)Mn, in the sintering temperature range 1285-1300ºC and such powder mixes were pressed and liquid phase sintered. In high-C steels carbide networks form at the prior particle boundaries, leading to brittleness, unless the steel is heat-treated. To assist the breaking up of these continuous carbide networks, 0.4-0.6% silicon, in the form of silicon carbide, was added. The water gas shift reaction (C + H2O = CO + H2, start from ~500ºC) and Boudouard reaction (from ~500ºC complete ~930ºC) form CO gas in the early part of sintering and can lead to large porosity, which lowers mechanical properties. With the use of careful powder drying, low dew point atmospheres and optimisation of heating profiles, densities in excess of 7.70g/cm3 were attained. The brittle microstructure, containing carbide networks and free of cracks, is transformed by intelligent heat treatment to a tougher one of ferrite plus sub-micron spheroidised carbides. This gives the potential for production of components, which are both tough and suitable for sizing to improve dimensional tolerance. Yield strengths up to 410 MPa, fracture strengths up to 950 MPa and strains of up to 16 % were attained. Forging experiments were subsequently carried out for spheroidised specimens of Fe-0.85Mo+06Si+1.4C, for different strain rates of 10-3, 10-2, 10-1 and 1sec-1 and heated in argon to 700¿C, density ~7.8g/cm3 and 769 MPa yield strength were obtained.
An experimental study of relative structural fire behaviour and robustness of different types of steel joint in restrained steel framesWang, Y.C.; Dai, Xianghe; Bailey, C.G. (2011-07)This paper describes the experimental results of ten fire tests on medium-scale restrained steel sub-frames to investigate the relative behaviour and robustness of different types of steel joint in steel framed structures in fire. The ten fire tests were designed to investigate the effects of two column sizes (simulating two different levels of axial restraint to the connected beam) and five different types of joint, including fin plate, web cleat, flush endplate, flexible endplate and extended endplate connections. Each test frame, in the form of “rugby goalpost” consisting of one beam and two columns, was connected through two identical beam to column joints. All the steelwork was unprotected except for the top flange of the beam which was protected to simulate the effect of a concrete slab in reducing the beam top flange temperature. The column ends were restrained to examine the effects of axial restraint on the beam and the joints. This paper presents the observations of structural fire behaviour, including joint failure modes and beam limiting temperatures, the development of deflections at beam middle span and axial forces in the joints at elevated temperatures. The main conclusions are: (1) failure (fracture) was observed only in joints when the beam was in catenary action and a variety of joint failure modes were observed which provides valuable data in understanding joint behaviour; (2) the medium-scale steel beams were able to undergo very large deflections View the MathML source without failure; (3) the specimens with stronger connections such as extended endplate reached higher than their limiting temperatures, defined as the beam bottom flange temperature at middle span at which the axial load in the beam returned to zero. But the difference in beam limiting temperatures using different types of joint is small, less than 50 °C; also the column size had little effect (less than 30 °C) on the beam limiting temperature; (4) the beams connected to the larger column experienced less deflections, but higher axial force due to the higher axial restraint to the beam, which led to fracture of the joint components in these tests; in contrast, the lighter columns visibly deformed and formed plastic hinges at the joints, but there was little evidence of connection fracture in the test frames using the light columns; (5) the web cleat connection appears to have the best performance.