Civil Engineering Association

ROTATION CAPACITY AND OVERSTRENGTH OF STEEL MEMBERS FOR SEISMIC DESIGN

Earthquake is generally considered the most destructive and frightening of all
forces of nature. It consists in sudden slippages or movements in a portion of the earth’s crust accompanied by a series of vibrations. After shocks with similar or minor intensity can follow the main quake. Earthquakes can occur at any time of the day, of the week, of the month and of the year. Every day small ground motions are registered in some parts of the world, but they have generally small intensities and do not cause great damages, while every year two or three strong earthquakes fill the mass media with dramatic accounts of human losses. Geologists have identified regions where earthquakes are likely to occur. With the increasing population of the world and urban migration trends, higher death tolls and greater property losses are more likely in many areas prone to earthquakes. At least 70 million people face significant risk of death or injury from earthquakes because they live in the 39 states that are seismically active. Deaths and injuries derived form earthquakes, vary according to a lot of factors, one of the most important is safety of structure in which people live. Often the real tragedy is that human losses are due not tothe earthquakes themselves but to the failure of the constructions. Actually, seismic design has brought a lot of progress into the engineering practice. The current work has the purpose to furnish a small contribute to the difficult topic of the structural behaviour under seismic actions. The attention is focused on Steel Moment Resisting Frames and in particular on the Member behaviour. Starting form the assumption that in modern design practice it is generally accepted that steel is an excellent material for seismic-resistant structures because of its strength, ductility and capability to withstanding substantial inelastic deformations, an experimental campaign on steel beams has been made. The principal scope of the work has been the revision of the
classification criteria of steel members actually adopted by seismic codes and the introduction of a new criterion which takes into account the principal factors that influence the structural response.