Mass, direct cost and energy life-cycle cost optimization of steel-concrete composite floor structures
Building use
Office building
Country/Region
Slovenia
Overview
The scope of the research is to push the optimization of composite floor systems further. Optimization studies are usually limited to the mass of the materials use, while the research also looks at direct cost and lifecycle cost of the designed solution. By assessing a great variability of conditions (imposed loads from 2 to 10 km/sqm, spans from 5 to 50 m, three steel classes, seven concrete classes, and multiple variations of steel profiles, welded wire mesh and concrete slab depth), the study adopts Mixed integer non linear programming to assess a total of 1,743E08 options.
Issue and/or innovation
The main innovation proposed by the study is the consideration not only of mass optimization, but also:
– Direct cost objective function
– Energy Life-cycle cost objective function of three alternative design scenarios to simulate the energy consumption of the building during its life phase
Most importantly, the study also presents design recommendations that can be used by engineers and designers to determine the most efficient alternative based on the various parameters considered in the study.
Technical details
The supplemental document presents a study showing the optimization of the mass, direct (self-manufacturing) costs, and energy life-cycle costs of composite floor structures composed of a reinforced concrete slab and steel I-beams. In a multi-parametric study, mixed-integer non-linear programming (MINLP) optimizations are carried out for different design parameters, such as different loads, spans, concrete and steel classes, welded, IPE and HEA steel profiles, and different energy consumption cases. Different objective functions of the composite structure are defined for optimization, such as mass, direct cost, and energy life-cycle cost objective functions. Moreover, three different energy consumption cases are proposed for the energy life-cycle cost objective: an energy efficient case (50 kWh/m2), an energy inefficient case (100 kWh/m2), and a high energy consumption case (200 kWh/m2). In each optimization, the objective function of the structure is subjected to the design, load, resistance, and deflection (in)equality constraints defined in accordance with Eurocode specifications. The optimal results calculated with different criteria are then compared to obtain competitive composite designs. Comparative diagrams have been developed to determine the competitive spans of composite floor structures with three different types of steel I beam: those made of welded sections and those made of IPE or HEA sections, respectively. The document answers the question of how different objective functions affect the amount of the calculated costs and masses of the structures. It has been established that the higher (more wasteful) the energy consumption case is, the lower the obtained masses of the composite floor structures are. In cases with higher energy consumption, the energy life-cycle costs are several times higher than the costs determined in direct cost optimization. At the end of the document, a recommended optimal design for a composite floor system is presented that has been developed on the multi-parametric energy life-cycle cost optimization, where the energy efficient case is considered. An engineer or researcher can use the recommendations presented here to find a suitable optimal composite structure design for a desired span and uniformly imposed load.
References / Technical Papers Content
Kravanja, S.; Klanšek, U.; Žula, T. Mass, Direct Cost and Energy Life-Cycle Cost Optimization of Steel-Concrete Composite Floor Structures. Appl. Sci. 2021, 11, 10316. https://doi.org/10.3390/app112110316
Categories
Building, Floor (slab)