Keywords: cost optimization, structural optimum design, harmony search algorithm, reinforced concrete structures, heuristics.

The emergence of robust and innovative non-gradient based search techniques has provided designers with tools that are efficiently used in obtaining the optimum solution of engineering design optimization problems. These techniques simulate the paradigm of a biological, chemical, or social system such as evolution, immune system, swarm intelligence, music improvisation or annealing process. The design algorithms developed using these meta-heuristic search techniques are particularly suitable for obtaining rapid and accurate solutions to design problems in the structural engineering discipline. This is particularly true in the optimum design of structures where the design problem turns out to be a discrete optimization problem when it is formulated according to design codes used in practice.

This study deals with the problem of optimizing Special Seismic Moment reinforced concrete (RC) frames subject to ACI 318-05 [1] and ASCE 7-05 [2]. Reinforced concrete special moment frames are used as part of seismic force-resisting systems in buildings that are designed to resist earthquakes. Beams, columns, and joints in moment frames are proportioned and detailed to resist flexural, axial, and shearing actions during an earthquake. RC frames with special proportioning and detailing requirements are capable of resisting strong earthquake shaking without significant loss of stiffness or strength. These moment-resisting frames are called "special moment frames" because of these additional requirements. A novel optimum design algorithm is developed for the RC special seismic moment frames and the design variable pool is assembled to obtain constructible optimum designs. In the design formulation, the objective function is selected as the cost of the RC structure. The design constraints are implemented according to ACI 318-05 [1] and checked to obtain feasible designs. This study does not only consider the flexural design constraints, but also the shear and seismic design constraints. Furthermore, the detailing of the flexural and shear reinforcement in the concrete members is considered. The lateral seismic forces are calculated according to ASCE 7-05 [2] and it is updated in each iteration according to the selected design. The solution of the design problem formulated is obtained using the harmony search (HS) method which is one of the recent meta-heuristic optimization techniques. A number of design examples is considered to demonstrate the efficiency of the optimum design algorithm developed.

1

ACI 318-05, "Building code requirements for structural concrete and commentary", ACI Committee 318, Structural Building Code, American Concrete Institute, Farmington Hills, MI, USA, 2005.

2

ASCE 7-05, "Minimum design loads for buildings and other structures", American Society of Civil Engineers, Virginia, USA, 2005.

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