In the present paper, a new algorithm to achieve optimum lateral load pattern for inelastic steel shear‐building structures is proposed and the efficiency of the proposed algorithm in terms of convergence speed and stability is investigated. Then, by conducting this algorithm on 28,800 elastic and inelastic steel shear‐building structures having different dynamic characteristics subjected to 40 design compatible earthquakes, a new seismic force pattern incorporating higher modes effect is proposed, and the adequacy of the proposed load pattern is parametrically investigated on the basis of the concepts of structural weight and dissipated energy and cumulative damage index. Through conducting numerous nonlinear dynamic analyses, the effects of uncertainties in story shear strength, structural fundamental period, and damping ratio by using the Monte Carlo simulation are parametrically investigated. Result indicates that optimum structures are in general more sensitive to the random variation of fundamental period and story lateral strength, whereas up to 40% of damping ratio variation does not affect the seismic performance of the optimum design frames. Finally, compared with recently proposed optimum structures without consideration of higher modes and code‐complaint design structures, the proposed mean optimum designed buildings of this study exhibit up to 42% less cumulative damage under the design earthquakes.
