Seismic Design Optimization of Concrete Cable-Stayed Bridges with "H"-Shaped Towers

An optimization-based strategy for designing concrete cable-stayed bridges under seismic action is presented.An initial designs module provides a convex optimization algorithm with multiple starting solutions from which local optimum solutions are obtained and the least cost solution is selected as the optimum design.The threedimensional analysis considers dead loads and road traffic live loads, geometrical nonlinearities and time-dependent effects.The modal response spectrum approach is used for seismic analysis.The design is formulated as the cost minimization subject to constraints on the displacements and stresses considering service and strength criteria defined according to the Eurocodes provisions.A constraint aggregation approach is adopted to solve the problem through the minimization of a convex scalar function obtained by an entropy-based approach.The discrete direct method is used for sensitivity analysis.The 64 design variables are the deck and towers' sizes, the cable-stays' cross-sectional areas and prestressing forces, and the towers' height.The optimization of a 312 m span bridge illustrates the features and applicability of the proposed strategy.The optimum design features a deck slenderness of 1/130 and a height of the towers (above the deck)-to-main span ratio of 0.205.