Author(s)

I. U. Amobi & H. C. Uzoegbo

Abstract

As industries are upgrading rapidly from a lower steel grade to higher ones it has become necessary to study the effect of changing from lower steel grades to higher grades. This paper reports on fatigue life and behaviour, economic implications and material composition of these higher strength steels (HSS) as compared to the conventional grades. Three grades are commercially available in South Africa: 300W, 350W and 460W. These different steel grades (conventional and HSS) with the same moment capacities were subjected to constant dynamic stresses and the fatigue crack growth of the overloading and unloading were monitored and compared with each other. The influences of the overloading and unloading made standard grades perform better under repeated loading than the HSS, since HSS have been proved to have poor ductility, resulting in a lower number of cycles to failure. An 85% increase in material cost was generated as HSS replaces the conventional lower steel grades. A reduction in the number of cycles to failure in HSS was over 500%. Keywords: steel grade, HSS, fatigue, low-cycle fatigue, high-cycle fatigue, load capacity, cycles to failure. 1 Introduction There is a trend towards increasing the strength grade of the general purpose steel for construction in most countries. This trend was prompted by increased loading on structures, larger spans and architectural designs that require smaller sections. Australia and other countries around the world have in recent years changed from lower steel grades to higher ones. In 2005, South Africa changed

Keywords

steel grade, HSS, fatigue, low-cycle fatigue, high-cycle fatigue, load capacity, cycles to failure.