Selection and scaling of earthquake motions for input into dynamic analyses

Suites of earthquake ground motions are critical parts of the seismic design and analysis process. The selection of these ground motions typically requires extensive trial of combinations by hand. The proposed methodology replaces the trial of combinations by hand with a semi-automated process that selects and scales ground motions to fit a target acceleration response spectrum, while at the same time controlling the standard deviation. The methodology selects motions for the suite based on matching the target spectral shape, and then fits the amplitude and standard deviation of the target by adjusting the scale factors. The trial of combinations is performed through both a rigorous method that tries each possible combination and an iterative approach that iteratively searches the full trial space in an effort to find combinations that provide an acceptable fit to the target spectrum. While the rigorous approach may determine the best combination, the time required to compute every combination may be too long to be practical, and thus the iterative approach is required. The developed methods are used to generate a number of possible combinations from which an engineer selects the final suite. An example of the process is carried out for both the rigorous and iterative procedures. (authors)