Sustainable optimum design of trussed composite floors considering vibrations constraints

Over the past decades, the search for more economically and environmentally efficient construction systems has become essential to reduce civil construction costs and greenhouse gas emissions. Within this context, composite floor systems composed of tubular composite trusses present an attractive solution, as they can span larger spans with relatively lower steel usage compared to other floor systems. This study aims to present the formulation of the topological optimization problem for composite floor systems composed of tubular trusses and steel deck slabs with additional reinforcement, considering the effect of floor vibrations. The objective functions considered were the minimization of CO2 emissions and the final costs of the floor system. The Particle Swarm Optimization algorithm was employed to solve the optimization problem. The proposed method was compared with examples from the literature that utilized different beam typologies to demonstrate the formulation’s application. Additionally, a parametric analysis was conducted to identify the factors with the most significant impact on the final solutions. The results indicate reductions in both emissions and final costs when using systems with filled tubular trusses with concrete with different solutions in the final geometry, but with final CO2 emission and cost similar. The best solutions were achieved using concrete-filled tubes in the upper chord and reinforcing steel in the slabs. For systems with filled tubes, concrete with a strength above 35 MPa was used, resulting in minimal emissions and final costs. Moreover, the results of the study indicate that, although several limit states are considered in the optimization process, including those related to axial force, bending moment, combined axial force and bending, excessive floor-beam deflection, as well as the relevant slab verifications, it was the excessive floor vibration serviceability limit state that proved to be decisive for most optimal solutions. The analysis showed that, particularly in the main structural elements, the peak acceleration limit was the most critical criterion, governing the final design and directly influencing the truss geometry and the spacing between beams.