Novel Building Diaphragm Layouts Generated through Topology Optimization: Fid-Bau Portal

Novel Building Diaphragm Layouts Generated through Topology Optimization

Fischer, Astrid W. / Guest, James K. / Schafer, Benjamin W.

The objective of this paper is to explore the layout of floor diaphragms in steel buildings subject to demands generated from lateral loads, such as those from wind and earthquakes, optimized for shear stiffness and minimum weight. The design of floors is typically dominated by considerations for gravity loads. In some classical cases, e.g. the works of Nervi, optimized floor topologies have been expressed in non‐grid patterns, such as through ribs oriented in principal stress directions. Floor designs employing steel deck generally express only one‐way action spanning between joists. Layouts of floor diaphragms are investigated here for improved lateral stiffness through topology optimization. To handle the widely different equivalent stiffness properties of steel deck the classic topology optimization algorithm is augmented to allow for orthotropic material in the formulation and material orientation as a design variable. A range of possible orthotropic stiffness properties are developed from a database of existing designs for bare steel deck and composite steel‐concrete deck diaphragms. The floor designs are generally found to follow the principal stress trajectories developed in the model under the considered shear loading. This work is the first step in an effort to develop optimized floor layouts under combined gravity and lateral (seismic) load and is part of a larger initiative (www.steeli.org) that aims to better understand and optimize the role of diaphragms in the seismic response of steel buildings.