Keywords: cost optimization, reinforced concrete, slabs, nonlinear programming.

The majority of the structural optimization applied to reinforced concrete (RC) structures involves heuristic methods such as genetic algorithms, threshold accepting, tabu search, etc. [1,2,3,4]. A very limited number of research deals with exact methods which are based on the (non)linear programming approach.

In this work the cost optimization design of reinforced concrete one-way slabs was performed using the nonlinear programming (NLP) approach by taking into account design constraints defined by the European Building Code for RC structures [5]. A detailed objective function of the slab's manufacturing costs is given including the material and labour cost items. At the serviceability limit state Eurocode 2, allows two ways of design for deflection control, namely the limitation of the real calculated deflection and a simplified way where solely the slab's slenderness ratio is limited.

The task of the research was to perform a comprehensive comparison of the optimal cross-sections obtained as well as manufacturing costs of the slabs designed using the two different deflection controls. In order to do this a comparative multi-parametric non-linear programming (NLP) cost optimization of the RC slab was performed and the slab's optimal cost development as well as optimal depth was investigated for different spans of the slab (5, 6, 7, and 8m) and two different live loads (2 and 5 kN/m²). The NLP optimization model OPTIRCS (OPTImization of RC Slab) was developed. For the mathematical modelling and data input/outputs the high level language general algebraic modelling system (GAMS) was used.

The comparison of the results shows that if at the serviceability limit state the slab's deflection is limited, the depth of the obtained optimal slab is considerably higher than if the slab's slenderness ratio were limited. Consequently the manufacturing costs of the slabs designed with deflection control are much higher than of the slabs designed with slenderness control.

1

C.C. Coello, F.S. Hernandez, F.A. Farrera, "Optimal Design of Reinforced Concrete Beams using Genetic Algorithms", Expert Systems with Applications, 12(1), 101-108, 1997. doi:10.1016/S0957-4174(96)00084-X

2

C.C. Ferreira, M.H.F.M. Barrros, A.F.M. Barros, "Optimal design of reinforced concrete T-sections in bending", Engineering Structures, 25, 951-964, 2003. doi:10.1016/S0141-0296(03)00039-7

3

V. Govindaraj, J.V. Ramasamy, "Optimum detailed design of reinforced concrete continuous beams using Genetic Algorithms", Computers & Structures, 84, 34-48, 2005. doi:10.1016/j.compstruc.2005.09.001

4

A.M. Azmy, M.H. Eid, "Cost-Optimum Design for Shear Reinforced Concrete Beams", ACI Structural Journal, 96(1), 122-126, 1999.

5

Eurocode 2, "Design of concrete structures - Part 1-1: General - Common rules for building and civil engineering structures", EN 1992-1-1, European Committee for Standardization, Brussels, 2005.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £145 +P&P)