Base Shear Estimated from Floor Accelerations and Column Shears

This paper compares base shear computed from floor accelerations (inertial base shear) and column shears (structural base shear) for several single-degree-of-freedom (SDF) systems and two mid-rise, multi-story buildings due to a suite of 30 earthquake ground motions. The presented results show that the inertial base shear is close to structural base shear in short-period (<1 sec) SDF systems but may significantly exceed the structural base shear for individual ground motions in longer period (> 1 sec) SDF systems. Furthermore, the inertial base shear exceeds the structural base shear in the median by 10% to 20% and may exceed the structural base shear by as much as 70% for individual ground motions in multi-story buildings. Therefore, it is concluded that the inertial base shear should be used with caution to estimate the structural base shear in buildings with long fundamental vibration period whose motions are recorded during individual earthquake ground shaking.