The effect of torsional oscillations on earthquake stresses

A comparison is made between the maximum stresses induced by earthquake-excited vibrations of an unsymmetrical structure and those induced in a symmetrical structure. These stresses are compared with the commonly used equivalent static method of analysis, and it is shown that the static method underestimates significantly the magnitude of the maximum stresses. Although the maximum stresses are quite sensitive to changes in the relative rigidity of the walls, an energy analysis of the vibration problem shows that the relative rigidities are not crucially important in determining the ultimate strength of the building.