Selection of the optimal diagrid patterns in tall buildings within a multi-response framework: Application of the desirability function

Diagrids are efficient structural systems for tall building design and construction due to their high lateral stiffness. Their structural response can be optimized by changing the geometrical pattern of external diagonals. This has usually been carried out by looking for the diagonal pattern that employs the minimum amount of structural material, while complying with strength and stiffness requirements. However, other responses can be significant for the selection of the optimal pattern, such as the torsional flexibility and construction complexity of the building. In this work, the desirability function approach has been used for selecting the optimal diagonal pattern for diagrid tall buildings in a multi-response framework. The most desirable diagonal layout has been selected based on its overall desirability to minimize: (i) the wind-induced lateral displacement, (ii) the torsional rotation, (iii) the diagrid structural weight, and (iv) the construction complexity. The application of this methodology straightforwardly provides the optimal diagrid pattern considering the four responses simultaneously. The method has been applied initially to a limited set of uniform-angle patterns, and afterwards to a wider population of varying-angle geometries. Four different floor plan shapes were also taken into account. The outcomes of the analysis revealed that the specific plan shape plays only a minor role in the definition of the optimal structure, whereas the diagonal layout affects greatly the efficiency of the solution. Uniform-angle diagrids are generally the most desirable, even for taller buildings, due to their higher performance in terms of torsional rigidity and construction complexity. Among these, the patterns in which the diagrid triangular module spans over two-three floors, corresponding to diagonal inclinations of about 55°–65°, have the highest desirability. Notably, because of the competition between the different responses, this optimal inclination is not found to increase as the building becomes taller.