OPTIMAL DESIGN OF THREE-DIMENSIONAL REINFORCED CONCRETE AND STEEL BUILDINGS SUBJECTED TO STATIC AND SEISMIC LOADS (ATC-03 PROVISIONS, CRITERIA, MULTI-COMPONENT EXCITATION, MULTIPLE CONSTRAINTS, SENSITIVITY ANALYSES)

A structural optimization algorithm based upon an optimality criteria approach is presented for three-dimensional statically and dynamically loaded steel and/or concrete structures. The theoretical work is presented in terms of scaling, sensitivity analyses, optimality criteria, and Lagrange multiplier determination. The structures can be subjected to a combination of static and/or dynamic displacement and stress, and natural frequency constraints. The dynamic analyses are based upon the ATC-03 provisions or multi-component response spectra modal analyses. Using the algorithm presented, a computer program called ODRESB-3D was developed for both analysis and design of building systems. Several examples are provided to illustrate the rapid convergence and the effects of the ATC-03 provisions and multi-component seismic loads. Several significant results are: (1) ATC-03 modal and equivalent lateral force provisions produce similar stiffness distributions with different magnitudes for both regular and irregular structural configurations, (2) ATC-03 stability function values are much less than the value of 0.1 within the ATC-03 provisions, and (3) multi- and single component excitation solutions can be quite different and are affected by the relative location of the mass and stiffness centers on each level.