Earthquake Design Formula Considering Local Soil Conditions

A new earthquake code formula is proposed, based on the principles of the response spectrum technique considering the local soil conditions. Six different groups of soil are defined from the viewpoint of their predominant periods. After the natural period and fraction of critical damping are estimated, for a structure, the seismic forces may be evaluated by means of these idealized spectrum curves more realistically than would be possible from an existing building code formula. The soil structure period relations and the possibility of resonance which are usually overlooked in the provisions of the earthquake codes, are duly taken into account. The formula is also intended to evaluate the seismic forces of structures other than ordinary buildings, such as bridges, dams, towers, elevated tanks, chimneys, etc. For the purpose of emphasizing the need for a new approach, the earthquake response of a hypothetical 10-story reinforced concrete building under two different subsoil conditions is included.