Earthquake capacity design considerations

摘要

Under moderate seismic acceleration levels a cooling tower structural design is governed by shell buckling control requirements and service loading including wind. However, when the earthquake acceleration level is increased, there arise issues which affect the functionality of the structure, particularly with respect to the column sizes. The capacity design method allows the sustaining of larger earthquake shocks with moderate damages and without catastrophic failures associated with casualties, thus leading to relatively high acceleration demands. The basic principle of controlled structural damage is often impossible to materialize, so the choice of the behaviour factor often evolves into an arbitrary choice of the lowest number that would yield a buildable and functional structure. It is proposed to re-examine the requirements for basic ground acceleration, either directly or indirectly, through the definition of a behaviour factor for cooling towers corresponding to a specific energy release mechanism.