Estimation of Maximum Roof Displacement Demands in Regular Multistory Buildings

For approximate estimation of the maximum inelastic roof displacement demand for existing multistory buildings, the current displacement coefficient method uses the maximum linear elastic displacement of the first-mode single-degree-of-freedom (SDOF) system corresponding to the buildings. The statistics of the SDOF system estimate of the roof displacement on the following topics are presented by three SAC steel buildings subjected to 72 earthquake ground motions recorded on firm sites. (a) How uncertain is the first-mode SDOF system estimation of the roof displacement? (b) What are the main sources of uncertainty in the estimation of the roof displacement? (c) How can the uncertainty be reduced? It is shown from the study that the maximum inelastic roof displacement demand of multistory buildings can be more accurately and more directly estimated by the maximum inelastic displacement of the first-mode elastoplastic SDOF system. This is especially true for low-rise buildings.