Optimum design of steel structures with web openings

The objective of this work is to perform optimum design of 3D steel structures having perforated I-section beams. The optimization problem is formulated as a combined sizing, shape and topology optimization problem. The cross-sectional dimensions of the columns and beams constitute the sizing design variables, while the number and size of the web openings of the beams constitute the topology and shape design variables, respectively. Two distinctive formulations of the optimization problem are considered depending on the finite element discretization implemented for simulating the structural elements. The two formulations, corresponding to beam and shell discretization, are compared in terms of the optimum designs achieved. A characteristic test example considered, showed that a quantifiable reduction in the weight of the structure is accomplished by allowing web openings in the beams of the structure without reducing structural strength or serviceability requirements.