Asif Mohammed

Bio: Asif Mohammed is an academic researcher from Brunel University London. The author has contributed to research in topics: Buckling. The author has an hindex of 1, co-authored 1 publications receiving 14 citations.

Numerical modelling and fire design of stainless steel hollow section columns

Abstract: In this paper, the elevated temperature buckling performance and design of cold-formed square, rectangular and circular hollow section columns made of stainless steel is studied through a numerical modelling investigation. The finite element analysis software Abaqus was employed to perform the simulations, where the validity of the models was established by replicating the results of flexural buckling tests at both elevated and room temperatures from literature test programmes. In total, twelve square (SHS) and rectangular (RHS) hollow section columns tested at elevated temperature and eleven circular (CHS) hollow section columns tested at room temperature were simulated. Following this, a comprehensive numerical parametric investigation was performed to systematically assess the effect of variation of the governing parameters including the grade of stainless steel (austenitic, duplex and ferritic) and the elevated temperature member slenderness ( λ ‾ θ = 0.1–2.0) for all considered cross-section shapes with the addition of the aspect ratio of the cross-section (h/b = 1.0 and 1.5) and the column axis of buckling (major and minor) for the SHS and RHS. The applicability and accuracy of the design methods recommended in EN 1993-1-2 and the Design Manual for Stainless Steel Structures were carefully assessed on the basis of the numerical flexural buckling performance results. New buckling formulations for the fire design of cold-formed stainless steel SHS/RHS and CHS columns were proposed, and their suitability was confirmed by means of reliability analysis.

Local buckling of stainless steel plates in fire

Abstract: The local buckling behaviour and design of stainless steel plates in fire are investigated in this paper. Finite element models of stainless steel plates able to mimic their response in fire are created and validated against experimental results from the literature. Parametric studies are then performed and the results are utilised to assess the current design provisions set out in the European structural steel fire design code EN 1993-1-2; shortcomings in the prediction of the local buckling response of stainless steel plates in fire are revealed. A new effective width based design approach able to reflect the variation in strength and stiffness of stainless steel at different temperature levels in the determination of the local plate slenderness and thereby the ultimate resistances of stainless steel plates in fire is put forward. The proposed approach is shown to provide significantly higher levels of accuracy and reliability relative to the current provisions in EN 1993-1-2 for a wide range of plate slendernesses, elevated temperature levels, stainless steel grades and loading conditions. The design rules proposed for the local buckling assessment of stainless steel plates at elevated temperatures in this paper are due to be incorporated into the upcoming version of the European steel fire design standard EN 1993-1-2.

Flexural buckling behaviour and residual strengths of stainless steel CHS columns after exposure to fire

Abstract: The flexural buckling behaviour and residual strengths of stainless steel circular hollow section (CHS) columns after exposure to fire were studied, based on a thorough experimental and numerical modelling programme, and reported in this paper. The experimental programme was performed on three series of specimens, and each series contained five geometrically identical specimens, with one unheated and the other four heated to different levels of elevated temperatures (namely 300 °C, 600 °C, 800 °C and 1000 °C). The detailed heating, soaking and cooling processes, material testing and pin-ended column tests were described, with the derived key experimental results fully presented. The testing programme was supplemented by a numerical modelling programme, including a validation study where finite element models were developed and validated against the test results, and a parametric study where the validated finite element models were employed to derive further numerical results over an extended range of cross-section dimensions and member lengths. Due to the absence of existing design codes for stainless steel structures after exposure to fire, the codified design provisions for stainless steel CHS columns at ambient temperature, as established in the Europe, America and Australia/New Zealand, were assessed for their applicability to stainless steel CHS columns after exposure to fire, based on the obtained test and numerical data. The assessment results generally revealed that the design buckling curve, as adopted in the European code, and the tangent modulus method, as employed in the American specification, lead to unsafe and scattered design flexural buckling strengths for stainless steel CHS columns after exposure to fire, while the explicit approach, as used in the Australian/New Zealand standard, yields a high level of accuracy and consistency in predicting the post-fire flexural buckling strengths of stainless steel CHS columns.

Fire testing of austenitic stainless steel I-section beam–columns

Abstract: With the increasing use of stainless steel elements in construction, the need for comprehensive rules to enable their efficient structural design is clear. To date, the fire behaviour of stainless steel I-section beam–columns has been the subject of relatively little research. In particular, there is an absence of experimental data. To address this gap in knowledge, full-scale anisothermal fire tests on six grade 1.4301 austenitic stainless steel I-section beam–columns have been carried out; the test procedure and results are reported herein. The test specimens were subjected to eccentric axial compression with two eccentricity values so as to achieve different combinations of axial compression and uniform minor axis bending. Complementary initial local and global geometric imperfection measurements, room temperature tensile coupon tests and room temperature beam–column tests were also carried out. Based on the obtained experimental results, together with additional numerical results from a previous study, the existing design rules in the European structural steel fire design standard EN 1993-1-2 and the new design method of Kucukler et al. (2021) for stainless steel beam–columns in fire, which will be incorporated into the next version of EN 1993-1-2, are assessed.