Seismic Design of Structures by Bundled Columns

A practical technique to protect structures against the effects of earthquakes is examined and proposed for use in design. The technique involves the bundling of slender steel members to form columns that are stiff and strong vertically, yet stable and quite flexible horizontally, leading to significant deamplifications of the main effects of the earthquake excitation. Because of its lateral deformation capacity, the proposed system can be designed to remain elastic even under severe ground motions. A number of analyses are made to identify the main properties of the proposed column system, and the use of the bundled column concept as a base isolation system is also explored. Example problems representative of realistic earthquake-excited structures are reported, elucidating the main features of the proposed technique and the implications of its implementation. The presentation focuses on the fundamentals, avoiding unnecessary modeling complications, to highlight the main factors involved.