Keywords: cable-stayed bridges, optimisation, optimal design, asymmetric, single-tower, concrete, cable tensioning forces, sizing design variables, shape design variables.

An optimisation-based approach is presented for the optimal design of asymmetric single-tower cable-stayed concrete bridges. The original non-convex optimisation problem is addressed using a gradient-based algorithm combined with a multi-start procedure that automates the definition of initial designs. The finite element method is used for the three-dimensional analysis considering geometric nonlinearities, dead load and road traffic live load, and the time-dependent effects of concrete. The design is formulated as a cost minimisation problem subject to constraints on the displacements and stresses, considering service and strength criteria defined in accordance with the Eurocodes’ provisions. This problem is addressed using a constraint aggregation approach by minimising a convex scalar function derived from an entropy-based formulation. The structural response to variations in the design variables is obtained using the discrete direct sensitivity analysis method. The design variables are the tower height, the deck and tower cross-sectional sizes, and the prestressing forces of cable-stays' and deck’s internal prestressing tendons’ and their cross-sectional areas. The optimisation of a 220 m bridge, with a main span of 128 m, illustrates the features and applicability of the proposed approach. The optimum design features a tower height-to-main span ratio of 1/1.82 and a deck slenderness of 1/80.

download the full-text of this paper (PDF, 14 pages, 953 Kb)

go to the previous paper
go to the next paper
return to the table of contents
return to the volume description