Approximate Preliminary Methods for Design of Lateral Load Resisting Systems in High Rise Buildingsby Charles H. Thornton, Thornton-Tomasetti, New York, United States,
Leonard Joseph, Thornton-Tomasetti, New York, United States,
Thomas Z. Scarangello, Thornton-Tomasetti, New York, United States,
Abstract: A new group of optimization programs uses the speed and power of modern computers to eliminate the need for guessing preliminary sizes. Starting with any arbitrary sizes and a fixed geometry, the programs determine 'optimum' member sizes which use the least material to meet specified strength and deflection criteria. By comparing the 'optimum' materials quantities for a variety of framing schemes the best scheme can be selected for further study. In this way structural efficiency can be explored early in the design process. The new program also offers the ability to continue on to final member selection and connection force determination, if desired. 'Optimization' uses the virtual work approach to determine each member's influence on the defection(s) of interest. For each member the deflection contribution per unit volume of material is rated. If additional material must be added to meet a target deflection it is added to the most efficient members first. The authors have used the optimization programs to study and develop efficient lateral load resisting systems on several recent projects and found results which sometimes seemed to run against 'engineering intuition,' illustrating the value of this powerful tool on complex schemes.
Subject Headings: Lateral loads | Building design | Displacement (mechanics) | Load factors | Strength of materials | Numerical methods | Optimization models
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