en Optimal design Optimal design پژوهشي Research <span style="font-size:11.5pt"><span new="" roman="" style="font-family:" times="">In most practical cases, structural design variables are linked to a discrete list of sections for optimal design. Cardinality of such a discrete search space is governed by the number of alternatives for each member group. The present work offers an adaptive strategy to detect more efficient alternatives and set aside redundant ones during optimization. In this regard, the difference between the lower and the upper bounds on such variables is gradually reduced by a procedure that adapts history of the selected alternatives in previous iterations. The propsed strategy is implemented on a hybrid paritcle swarm optimizer and imperialist competitive algorithm. The former is a basic swarm intelligent method while the later utilizes subpopulations in its search. Spatial and large-scale structures in various shapes are treated showing successive performance improvement. Variation of a diversity index and resulting band size are traced and discussed to declare behavior merits of the proposed adaptive band strategy.&nbsp;&nbsp;</span></span><br> &nbsp; Adaptive-band sizing, discrete structural optimization, truss, swarm intelligence, imperialist competitive algorithm, efficiency improvement. 155 176 http://ijoce.iust.ac.ir/browse.php?a_code=A-10-66-368&slc_lang=en&sid=1 M. Shahrouzi shahruzi@khu.ac.ir 180031947532846002584 180031947532846002584 Yes Civil Engineering Department, Faculty of Engineering, Kharazmi University, Tehran, Iran A. Salehi 180031947532846002585 180031947532846002585 No Civil Engineering Department, Faculty of Engineering, Kharazmi University, Tehran, Iran