Evolutionary Optimization of Passive Compensators to Improve Earthquake Resistance

Evolutionary Optimization of Passive Compensators to Improve Earthquake Resistance

Rolf Steinbuch (Reutlingen University, Germany)
DOI: 10.4018/978-1-4666-2029-2.ch011
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Abstract

Compensators are widely used to influence the dynamic response of excited structures. The coupling of additional masses with defined stiffness and damping to the vibrating elements reduces or avoids unwanted oscillations. In earthquake engineering, compensators often consist of one or a small number of such additional mass-spring combinations. To come up with a good design of the compensators, a multidimensional optimization problem has to be solved. As there might be many local optima, evolutionary approaches are the appropriate choice of the optimization strategy. They start with some basic designs. Then a sequence of generations of design variants is studied. The members of each generation are derived from the parent generation by crossing and mutation. The best kids are the parents of the next generation. Optimization results show that the use of compensating systems may essentially reduce the impact of an earthquake.
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Improve The Structural Ability To Withstand Earthquake Impact

The earthquake loading of a building is understood as a base excitation of the building (Towhata 2008, pp. 67-71, Bozorgnia and Bertero 2004, pp. 2-9 - 2-15). Due to the large mass of the surrounding ground compared to the building’s mass, the excitation may be considered as displacement controlled. The interface between the surroundings and the building has to follow these displacements. Any approach to limit or reduce the impact on the building has to take into account this displacement history.

The improvement of the static strength by enforcing the load-carrying elements is not always feasible in an economic and aesthetic way. Consequently we need dynamic approaches. One of the often-used ideas to isolate the building’s base from the excited ground shows very promising results (Naeim 1999, pp. 93-119, Ordonez 2002). Isolation implies the uncoupling of the buildings’ base from the ground by some less stiff but damping components. Unfortunately, it is not easy and sometimes very expensive to design such an isolating base system for very large and high structures.

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