Ultimate Strength of Uniaxially Compressed Mild Steel Plate at Elevated Temperatures

Abstract

Mild steel plates used in buildings and offshore platforms are prone to fire accidents. These plates being ductile are designed effectively for buckling and ultimate strength characteristics under static loads. These characteristics get drastically affected due to reduction in stiffness of the stress strain characteristics of mild steel with increase in temperatures. This paper presents a numerical study conducted on clamped plates at elevated constant temperature for the assessment of reduced buckling and ultimate strengths. Coupled Nonlinear static thermal analysis on clamped plates was performed using standard FE software ANSYS®. Both geometric and material nonlinearities are considered in the analysis. The study comprises of plates with varying aspect ratio (1 to 4) and breadth to thickness (28 to 128) at constant elevated temperatures of 0 °C, 200 °C, 400 °C, 600 °C and 800 °C. Nondimensional plate slenderness ratios based on AISC and Eurocode at elevated temperature was evaluated. Several charts showing normalised buckling stress vs temperature and normalised ultimate strength vs temperature for varied nondimensional plate slenderness ratio and plate aspect ratios are drawn. The buckling and ultimate strengths from this study are found to be underestimated in comparison to Eurocode and AISC calculations. The reduction in buckling and ultimate strength was found to be significant beyond 400 °C. It is observed that for all plate aspect ratios, the effect of plate breadth to thickness ratio is important for temperatures below 500°C and at 800°C ultimate strength of plate is only about 10% of that of at normal temperature.