Experimental and analytical studies of steel joint components at elevated temperatures

Abstract

This paper reports on experimental furnace testing and development of simple analytical models intended to initiate the development of a Component Method for modelling of steel beam-to-column connections in fire conditions. The basic theme of the Component Method is to consider any joint as an assembly of individual simple components. Each of these components is simply a non-linear spring, possessing its own level of strength and stiffness in tension, compression or shear, and these will degrade as its temperature rises.The main objective of this study was to investigate experimentally and analytically the behaviour of tension and compression zones of end-plate connections at elevated temperatures. A series of experiments has been carried out, and these are described in the paper. Simplified analytical models of the component behaviour have been developed, and these have been validated against the tests and against detailed finite element simulations. The simplified models have been shown to be very reliable for this very common type of joint, although similar equations will need to be developed for other configurations. The component models developed have been shown to produce moment-rotation curves which correlate well with the results of previous furnace tests on complete connection behaviour in fire. The principles of the Component Method can be used directly in either simplified or finite element modelling, without attempting to predict of the overall joint behaviour in fire. This will enable semi-rigid behaviour to be taken into account in the analytical fire engineering design of steel-framed buildings, for which it is inadequate simply to consider the degradation of the ambient-temperature moment-rotation characteristics of a joint without taking account of the high axial forces which also occur.

A review of progressive collapse research and regulations

“…This intermediate approach drastically reduces computational time compared to three-dimensional finite-element analysis and allows the impact of variations of structural configurations to be investigated quickly. Very good results have been obtained for progressive collapse analysis (Izzuddin et al, 2008) as well as analysis of structures under elevated temperature conditions, where the effect on material properties can be included (Bayo et al, 2006;Burgess et al, 2005;Spyrou et al, 2000).…”

Experimental and analytical investigation of the ‘tension zone’ components within a steel joint at elevated temperatures

“…A specially designed experimental arrangement was constructed, including a furnace and an image acquisition and processing system [22,23]. Developments in video camera and digital image processing technology now permit real-time displacement measurements to be taken from a video image.…”

Non-discretisation formulation for the non-linear analysis of semi-rigid steel frames at elevated temperatures

“…This was based on the formulation of El-Zanaty and Murray [3] at ambient temperatures, which was modified for the deterioration of the material strength with increasing temperature using a set of non-linear stress-strain temperature relationships based on a Ramberg-Osgood formulation in which thermal creep effects were included implicitly. Subsequent studies undertaken by Burgess, Plank and co-workers [4][5][6] have significantly refined and extended this approach. Including the joints is important, in order to establish that joint robustness [5,7] will not deteriorate in such a way as to lead to partial or progressive structural collapse.…”

“…Subsequent studies undertaken by Burgess, Plank and co-workers [4][5][6] have significantly refined and extended this approach. Including the joints is important, in order to establish that joint robustness [5,7] will not deteriorate in such a way as to lead to partial or progressive structural collapse. A methodology for a numerical technique for studying the large-displacement inelastic behaviour of building frames subjected to a localised fire, which can consider the simultaneous effects of axial force, bending moments and thermal expansion, was proposed by Liew et al [8].…”