Generic nonlinear modelling of a steel beam in a frame sub-assembly at elevated temperatures

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

“…2c) e tot ¼ ðy À y n Þj; ð1Þ in which y n is the location of the neutral fibre of the steel section below the local reference level, which is assumed to be coincident with the top fibre of the steel cross-section. For the analysis herein, the appropriate membrane strain is taken from the Green-Lagrange strain tensor as [32,33] …”

Thermoelastic lateral-torsional buckling of fixed slender beams under linear temperature gradient

“…2). The need for defining an effective centroid in thermoelastic analysis was recognized by Bradford et al [3,4]. The longitudinal normal strain zz and stress s zz due to pure uniform compression can be expressed as [8] zz ¼ w 0 and s zz ¼ EðyÞw 0 ,…”

“…However, because the elastic modulus under a linear temperature gradient field is a function of the coordinates of the material point, the beam cannot be considered as homogeneous in resisting thermoelastic action and an axial force that acts at the geometric centroidal axis will produce additional bending moments in the beam. To avoid the complexity of these additional bending moments in the analysis, an effective centroidal axis needs to be determined such that when an axial compressive force acts in the direction of the effective centroidal axis, it produces pure axial compression [4]. In many ways this concept is identical to that of transformed areas in section composed of more than one material, but formulating this under thermal loading is complicated.…”

Elastic behaviour of panel zone in steel moment resisting frames at elevated temperatures

“…In corner and exterior joints, there is usually a significant moment imbalance that produces high shear stresses in the panel zone [2]. This phenomenon can be much more significant at elevated temperatures, since large axial forces are induced in the beams in a compartment fire which are partly or fully restrained against thermal expansion by the cooler columns and other portions of the frame [3][4][5][6]. The resulting deformations of the panel zone produced by these forces can have a significant effect on the structural response of the frame in both the elastic and inelastic ranges of frame behaviour [7,8]; the actions generated in this way are generally outside those considered in the usual paradigm of joint design.…”