The pivots of irrigation or the swiveling banisters of irrigation are metallic mobile devices with an important size intended for automatic irrigation of cultivated wide fields, they are composed by a central tower, mobile tower and a set of spans. In our country, these devices are made by a company having a complete line of production with a good level of integration of local raw materials including its production. However these devices do not really answer in global needs of a local market, indeed, the shape and the size of the produced and proposed model how is only the once receipts with the production unit. This work consists in clearing tools to modify and develop other models of more adapted pivots to reach this goal we proceed at first to checking the optimality of the shape of the current span, then, we propose the possibility of the weight reduction of this span by using the technique of the variation of geometrical form of the element defining the structure while assuring the quality of the product. The obtained results establish effective tools in the development of new pivots of irrigation; this also show the possibility of modification of the current geometrical configuration and gives relative importance of the choice of the geometrical variables and objectifs functions. In conclusion we were able to propose three models how in theory answer our aims.