Multi-Objective Optimization Design of Control Devices to Suppress Tall Buildings Vibrations against Earthquake Excitations Using Fuzzy Logic and Genetic Algorithms - Design Optimization of Active and Passive Structural Control Systems - page 183

GENETIC ALGORITHMS AND MULTI-
OBJECTIVE OPTIMIZATION

• The columns are inextensible and weight-

less providing the lateral stiffness.

• The system is subjected to horizontal com-

ponents of the earthquake ground motion
(single-support excitation assumption).

The main purpose of this chapter is multi-objective
optimization design of control devices to reduce
the structural vibrations excited by the earthquake.
Most of the engineering optimization problems are
often very complex and difficult to solve without
considering many simplifications. In recent years,
the use of evolutionary algorithms is considered
by many researchers in different optimization
fields. Genetic algorithms (GAs) are effective
search methods in very large and wide space that
eventually lead to the orientation towards finding
an optimal answer. They can be used for solving
a variety of optimization problems that are not
well suited for standard optimization algorithms
including problems in which the objective function
is discontinuous, non-differentiable, stochastic
or highly nonlinear (Pourzeynali & Mousanejad,
2010). Genetic algorithms are very different with
the traditional optimization methods; one of these
differences is that GA works with a population
or set of points in a certain moment, while tradi-
tional optimization methods use a special point.
This means that the GA will be processed a large
number of schemes at a time. Unlike conventional
optimization methods that use derivative of func-
tion, genetic algorithms just use objective function

• No soil-structure interaction is considered

in the analyses.

EARTHQUAKE GROUND
MOTION TIME HISTORIES

In order to perform time history dynamic analyses,
the earthquake inputs must be specified in terms of
free field strong ground motion accelerogrames.
For this purpose, in present study to show the
performance of the base isolation systems, 18
worldwide strong ground motion accelerogrames
are selected in which after performing any neces-
sary corrections, filtering, and scaling are used
in the analyses. The most important earthquake
accelerogrames used for this purpose are given
in reference (Pourzeynali & Zarif, 2008). A part
of these accelerogrames may incorporate the near
fault effect in the analyses. As well, to study the
effect of STMD/TMD systems, 7 earthquake
accelerogrames are selected for which detail
descriptions are provided in Table 1.

Table 1. Earthquake accelerogrames considered to show the performance of STMD/TMD devices

Earthquake specifications

Earthquake

Date Station Magnitude (Ms) PGA (g) Duration (sec)

Kocaeli 1999 Ambarli 7.8 0.2228 150.405

Chi-Chi 1999 CHY022 7.62 0.64 121

Duze 1999 Sakarya 7.3 0.0215 60

Kobe 1995 Kakogawa 7.2 0.2668 40.96

Cape Mendocino 1992 Eureka - Myrtle & West 7.1 0.1668 44

90088 Anaheim - W
Ball Rd

Northridge 1994 6.7 0.0658 34.99

36229 Parkfield - Chol-
ame 12W

Coalinga 1983 6.5 0.0445 40