Optimized seismic design of passively damped outriggers considering perimeter column flexibility

This paper presents a formal optimization methodology for the damped outrigger problem under stochastic seismic excitations. An efficient analytical model is developed utilizing a Maxwell model connection between the core and the columns reducing the computational effort. A novel damping distribution function (DDF), representing the damped outriggers, is introduced in order to decrease the number of design variables significantly, reducing computational cost as well. The root mean square responses are obtained according to Lyapunov's equation. Accounting for several different responses as design criteria is done by formulating a single aggregated constraint in an efficient manner. The adjoint analytical method is adopted to execute the gradient-based optimization. Finally, demonstrating usage of the optimization methodology is shown for an example of a 50-story building with different perimeter column sizes. It is shown that the flexibility of the perimeter columns and outriggers have a large influence on the behavior of the structure and the optimized solutions, reaffirming the importance of an optimization methodology for the damped outrigger.