Keywords: optimization, concrete structures, tall bridge piers, ant colony, structural design, reinforced concrete.

This paper deals with the economic optimization of reinforced concrete bridge piers with rectangular hollow sections typically used in the construction of prestressed concrete viaducts for railways. Most traditional procedures based on a trial-and-error method, are not automatic and leads to safe designs. The cost of the pier is, consequently, highly dependent upon the experience of the structural designer. Model artificial intelligence procedures define the structure on the basis of design variables, automatically calculate and validate the structure and then redefine it by means of an optimization algorithm that controls the flow of iterations in the search for the optimum structure. This optimum structure has to satisfy the limit states prescribed by concrete codes [1,2]. The proposed ant colony optimization (ACO) algorithm follows an original formulation of the path followed by ants that includes both the trace followed by former ants and the random selection of new paths. This model for the optimum design of bridge piers with rectangular hollow sections was developed in previous papers [3].

This paper presents the characteristics of a pier of 100 m in height. The viaduct is a typical one of ten continuous bays and main spans of 60m (45-8x60-45m). All variables and parameters are discrete since the final solution of the optimization process has to be construable. Design variables define the geometry, the steel reinforcement and concrete type in the different parts of the pier. The variables include those to define the column as well as those to define the foundation. The column variables depend on the number of stages in which the column is built. Every stage is limited by two sections and they measure 5.00m in the middle, 3.00m in the top part and 2.00m at stage one of the column. The number of variables representing the column is 291 and 16 for the footing, so the total number of variables for the pier is 307. The size of the solution space is 2.77x1051. Variables for the column include geometrical values for the width of the pier, the thickness of the walls at different cross-sections, the concrete grades at different heights and the reinforcement of the column following a decrease in height setup. As for the footing, five variables define the geometry and eleven the reinforcement. The most important parameters are the vertical height, the transverse dimension of the pier which is 6.80m and the vertical and horizontal loads on the top bearings and the partial coefficients of safety. The main reactions include two vertical reactions spaced 5.00m apart and horizontal reactions arising from bearing friction and the wind. Design loads are in accordance with the European regulations for railway bridges.

1

M. Fomento, "EHE-08: Code of Structural Concrete (in Spanish)", M. Fomento, Madrid, 2008.

2

CEN, "Eurocode 2. Design of Concrete Structures. Part 1-1: General Rules and Rules for buildings", CEN, Brussels, 1991.

3

F.J. Martinez, F. González-Vidosa, A. Hospitaler and V. Yepes, "Heuristic optimization of RC bridge piers with rectangular hollow sections", Computers and Structures, 88(5-6), 375-386, 2010. doi:10.1016/j.compstruc.2009.11.009

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 £110 +P&P)