Generalized Method for Estimating Drift in High-Rise Structures

An approximate method for estimating the drift of multi-bent structures is presented. Structures that are singly or doubly symmetrical in plan and comprising any combination of shear walls, coupled walls, rigid frames and braced frames, can be considered. Results for structures that are uniform with height compare closely with results from stiffness matrix computer analyses. The method is developed from coupled-wall deflection theory which is expressed in terms of two non-dimensional structural parameters. The parameters involve three structural properties: the individual bending stiffness of the walls, the overall bending stiffness related to axial deformations of the walls and racking stiffness caused by reverse bending of the beams. Similar properties are calculated for rigid frames, braced frames and shear walls and then combined to determine values of the two parameters for the total structure. These values are then substituted into a generalized equation to obtain the deflection profile. This method accounts for axial deflection of the vertical components and is, therefore, more accurate for very tall structures. The method provides a rapid estimate of the drift in a high-rise structure as well as allowing an easy means of comparing the suitability of different structural solutions for a tall building. The method also illustrates the fundamental dependence of the behavior of continuous type cantilevers on two characteristic parameters.