Optimal design of building structures using genetic algorithms

A general framework for multi-criteria optimal design is presented which is well-suited for automated design of structural systems. A systematic computer-aided optimal design decision process is developed which allows the designer to rapidly evaluate and improve a proposed design by taking into account the major factors of interest related to different aspects such as design, construction, and operation.

The proposed optimal design process requires the selection of the most promising choice of design parameters taken from a large design space, based on an evaluation using specified criteria. The design parameters specify a particular design, and so they relate to member sizes, structural configuration, etc. The evaluation of the design uses performance parameters which may include structural response parameters, risks due to uncertain loads and modeling errors, construction and operating costs, etc. Preference functions are used to implement the design criteria in a "soft" form. These preference functions give a measure of the degree of satisfaction of each design criterion. The overall evaluation measure for a design is built up from the individual measures for each criterion through a preference combination rule. The goal of the optimal design process is to obtain a design that has the highest overall evaluation measure - an optimization problem.

Genetic algorithms are stochastic optimization methods that are based on evolutionary theory. They provide the exploration power necessary to explore high-dimensional search spaces to seek these optimal solutions. Two special genetic algorithms, hGA and vGA, are presented here for continuous and discrete optimization problems, respectively.

The methodology is demonstrated with several examples involving the design of truss and frame systems. These examples are solved by using the proposed hGA and vGA.

Stress and load calculation for unknown building

Not available.

The effect of earthquakes on reinforced concrete building design

The building under consideration was the Pasadena Furniture Building, on East Colorado St., Pasadena, California. It is a modern reinforced concrete building that may be classed as a warehouse of flat-slab construction.

The unsteady forces on slender delta wing hydrofoils oscillating in heave

The investigations described herein are both experimental and theoretical. An experimental technique is described by which the models tested could be oscillated sinusoidally in heave. The apparatus used to gather the unsteady lift, drag and pitching moment data is also described.

The models tested were two flat delta wings with apex angles of 15° and 30° and they had sharp leading edges to insure flow separation. The models were fabricated from 0.25 inch aluminum plate and were approximately one foot in length.

Three distinct types of flow were investigated: 1) fully wetted, 2) ventilated and 3) planing. The experimental data are compared with existing theories for steady motions in the case of fully wetted delta wings. Ventilation measurements, made only for the 30° model at 20° angle of attack, of lift and drag are presented.

A correction of the theory proposed by M.P. Tulin for high speed planing of slender bodies is presented and it is extended to unsteady motions. This is compared to the experimental measurements made at 6° and 12° angle of attack for the two models previously described.

This is the first extensive measurement of unsteady drag for any shape wing, the first measurement of unsteady planing forces, the first quantitative documentation of unstable oscillations near a free surface, and the first measurements of the unsteady forces on ventilated delta wings. The results of these investigations, both theoretical and experimental, are discussed and further investigations suggested.