Abstract This paper presents a review of recent studies of the behaviour of steel–concrete composite structures in fire, including an assessment of research investigations and their implications on fire‐resistant design of composite structures. The paper focuses on the three main parts of composite structure: floor systems, columns and joints. The section on composite floor systems includes bending behaviour of conventional composite floor/beam system with composite slabs on top of a solid steel I‐beam; tensile membrane action in this system; slim‐floor construction; composite cellular beam; composite truss and composite beam with precast concrete slabs. The section on composite columns includes studies of concrete‐filled tubular (CFT) column; design of composite columns and performance of CFT columns within structures. The section on joints covers both steel and composite joints, including experiments on joints in fire; finite element simulation; the component method; behaviour of different joint components at elevated temperatures and implications of joint behaviour on steel and composite structural behaviour in fire. Within each section, wherever appropriate, the effects of whole structural behaviour are discussed. Furthermore, potential future research studies are identified to help understand the subject and develop improved performance‐based practical fire resistant design calculation methods.
Abstract This paper presents the results of an experimental study to investigate the failure modes of intumescent coatings and their effects on temperatures attained in steel sections and load carrying capacities of steel columns. Primer and intumescent coatings were applied to unloaded steel plates, unloaded I‐shaped short sections and axially loaded I‐shaped long columns. For the axially loaded columns, three different surface treatments were considered. The failure modes of intumescent coatings include distributed fine cracking, discrete wide and deep cracking, and detachment. Distributed fine cracks appeared on the unloaded plate specimens. Discrete crack was the main failure mode on the unloaded steel sections. For the loaded long columns, the intumescent coating failure modes included both discrete crack and detachment. Intumescent coating failure affected the average temperatures attained, with average temperatures of the plate specimens, unloaded steel sections and loaded steel columns being 411°C, 472°C and 543°C respectively after 30 minutes of standard fire exposure. Different surface treatment does not seem to have much effect on fire resistance of the carbon steel columns, the two columns reaching fire resistance times of 38 and 39.5 minutes respectively.
Au-Ag composite nanoparticles were synthesized by simultaneously reduction of HAuCl_4 and AgNO_3(using) NaHB_4 as reducing agent.The morphology and size of the particles were measured by the transmission electron microscopy(TEM).UV-vis absorption spectra results show that Au-Ag composite nanoparticles prepared by the one step co-reduction method have only one plasmon absorption band.The maximum absorption peak of Au-Ag composite nanoparticles between the absorption peaks of pure gold and pure silver nanoparticles and shift towards longer wavelength with increasing the molar ratio of Au and Ag ions in the reaction solution.The numerical analysis results based on the Mie scattering theory quantitatively account for the observed optical absorption properties dependence on the composition of Au-Ag composite nanoparticles.
Purpose – Three test platforms for long-term continuous loading are adopted to test the actuator prototypes of the 500-meter aperture spherical radio telescope (FAST). However, the wire ropes that are the key components of these platforms often break during testing. The purpose of this paper is to present an effective dimension design method for these wire ropes. This method is based on fatigue reliability theory. Design/methodology/approach – Three types of stresses are introduced into the total stress model of the wire rope according to the complicated stress conditions. The fatigue strength of the ropes is also discussed in this paper. Then, the total stress model and the results of fatigue strength analysis are applied to set the optimization function for these wire ropes. Subsequently, this optimization function is used to calculate the reliability of previously developed wire ropes in relation to the actuator test platform. Findings – The wire rope is unreliable, which is a finding that corresponds to those of previous tests. Upon drawing the optimal curve from the optimization function (whose optimal objective is the wire diameter), a wire rope is optimized for the FAST actuator test platforms. Finally, this optimized rope is used on the new actuator test platform. No fracture phenomenon has been detected in tests conducted over the past six months. Originality/value – The fatigue reliability theory-based optimization function for wire ropes can be adopted for the universal dimension design of other wire ropes.
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