I. DELIGHT.STRUCT: A COMPUTER-AIDED DESIGN ENVIRONMENT FOR STRUCTURAL ENGINEERING. II. OPTIMAL DESIGN OF SEISMIC-RESISTANT PLANAR STEEL FRAMES

The first report describes an expandable software system for optimization-based, interactive computer-aided design of structures. This system can be used for the design of statically and/or dynamically loaded structures which exhibit linear or nonlinear response.;The software is the union of: (1) an interactive base code for the management of the computer-aided design process named DELIGHT, (2) a dynamic nonlinear general purpose structural analysis package named ANSR, (3) a library of optimization algorithms specialized for the type of mathematical programming problems characteristic of structural design, and (4) specialized software for the design of seismic-resistant planar steel frames.;Flexibility has been emphasized in the development of this system so that a wide range of structural problems can be considered. The user describes his problem to the system by supplying a minimal amount of software or by selecting software from expandable libraries.;The second report presents a method for the seismic-resistant design of planar, rectangular braced or unbraced steel frames. An important feature of the method is that nonlinear step-by-step integration is used as the analysis technique within the design process itself.;The method directly quantifies the accepted seismic-resistant design philosophy that a properly designed structure: (1) resists moderate ground motion without structural damage, and (2) resists severe ground motion without collapse. Actual ground motion accelerograms are selected and scaled to levels representing moderate and severe ground motions. Constraints quantifying structural damage and limited non-structural damage are constructed for the case of moderate ground motion, along with constraints quantifying collapse and limited structural damage for the case of severe ground motion. In addition serviceability constraints are imposed on structural behavior under gravity loads only. Possible objective functions range from the minimization of structural volume to the minimization of response quantities such as story drifts or inelastically dissipated energy. Sophisticated optimization algorithms are utilized to solve the resulting mathematical programming problem.;The frame design method is illustrated by application to a 4-story, 3-bay moment-resisting steel frame. The practicality and reliability of the method for this example problem are assessed.