Performance and Design Issues for High Strength Steel in Structures

Steel has been used in a very large number of structures for almost 150 years and the material has undergone major changes over that period. For many years the primary grades were carbon-manganese steel with low strength and high deformability. However, structural systems have evolved greatly, with taller buildings and longer span structures of all kinds. Along with new directions in architectural expression, engineering modeling and design techniques have been affected by computational equipment, and fabrication and erection changes have followed suit. As these advances have taken place, significant demands for higher performing materials have evolved, to the extent that ultra high strength steels with yield stress levels of 700 MPa and much higher are now being considered. The paper examines these developments, including very recent findings from a variety of sources, and looks to the practical uses of the high strengths. The discussion focuses on performance needs, steel products, fabrication options and realistic economies of scale. It is clear that high strength by itself is not a solution, and numerous options need to be evaluated before selecting systems and materials.