Analysis of CO2 Emissions in the Topological Optimization of Floor Systems Composed by Composite Trusses

Resumo

The use of composite floor systems in steel buildings has been growing over the last few decades. However, this application usually takes place with full web composite beams and composite slabs with incorporated steel formwork, although there are other possibilities, such as, for example, trusses composite beams. The objective of this work is to present the formulation of the topological and sizing optimization problem for floor systems composed of composite trusses with tubular steel profiles and composite slabs. A structure for the floor, secondary trusses are proposed that directly support the slabs and main trusses that serve as support for the
secondary trusses. The trusses are simply supported and the upper compressed chord may or may not be filled with concrete. The objective function minimizes CO2 emissions from the manufacture of materials used in the floor. The optimization problem solution was obtained via Genetic Algorithm (GA) and the Particle Swarm Optimization (PSO). The algorithm selects, in addition to the topology of the truss (height and number of truss panels), the ideal number of secondary trusses, the compressive strength of the concrete slab and the filling of the upper chord, and finally, it selects the profiles of the chords, diagonals and verticals and composite slab formwork from manufacturers' catalogues. The results indicate that, when compared with composite floor systems composed of
full web beams, a reduction in CO2 emissions of over 20% can be obtained depending on the spans of the analyzed floors. In addition, tubular trusses with a concrete-filled upper chord provide better solutions than trusses with an unfilled tube.