FIRE PERFORMANCE OF STRUCTURAL STEEL TUBULAR COLUMNS WITH AND WITHOUT INFILLS

Abstract

The fire design of structures facilitates the safety, serviceability, and durability of structures from the fire. Steel structures are vulnerable to fire due to high temperature-associated deterioration of strength and stiffness properties. Efforts have been made to enhance structural steel performance in fire by applying fire protection paints and boards. Despite such efforts, the fire safety measures do not offer steel structures a great deal of resistance against fire. Toward this end, the researchers have introduced a new kind of structural steel offering greater endurance against fire than conventional structural steel. Generally, this new type of structural steel is called fire-resistant steel. An extensive literature review identified several research gaps showing lack of studies regarding the performance of fire-resistant steels at material and structural levels in the fire and thus showing the deficiencies of using conventional structural steel over fire-resistant steel in fire. Therefore, the present study attempts to study various aspects of conventional structural steel and fire-resistant steel in fire. The identified research gaps are discussed in four components in the upcoming paragraphs. The first component of the thesis is to investigate the elevated-temperature behavior of novel structural steels (conventional structural steel and fire-resistant steel) at the material and structural levels. The steady-state tensile tests were performed on the steel coupons using a strain rate of 0.005mm/mm/min at room and elevated temperatures. Different responses, such as displacement, load, and temperature, were noted during the execution of the tensile test, which was to be processed to produce an engineering stress-strain curve. The engineering stress-strain curve is an elementary characteristic of a material from which various mechanical properties were computed. This was followed by a numerical study using the finite element method-based computer program ABAQUS to examine the structural performance of structural steel members at elevated temperatures. Based on the findings of this study, the performance of conventional structural steel and fire-resistant steel at the material and structural levels was determined.