Simple innovative comparison of costs between tied-arch bridge and cable-stayed bridge

Abstract

The proposed paper compares tied-arch bridge alternatives and cable-stayed bridge alternatives based on needed load-bearing construction material amounts in the superstructure. The comparisons are prepared between four tied arch bridge solutions and four cable-stayed bridge solutions of the same span lengths. The sum of the span lengths is 300 m. The rise of arch as well as the height of pylon and cable arrangements follow optimal dimensions. The theoretic optimum rise of tied-arch for minimum material amount is higher than traditionally used for aesthetic reason. The optimum rise for minimum material amount parabolic arch is shown in the paper. The mathematical solution uses axial force index method presented in the paper. For the tied-arches the span-rise-ration of 3 is used. The hangers of the tied-arches are vertical-The tied-arches are calculated by numeric iteration method in order to get moment-less arch. The arches are designed as constant stress arch. The area and the weight of the cross section follow the compression force in the arch. In addition the self-weight of the suspender cables are included in the calculation. The influence of traffic loads are calculated by using a separate FEM program. It is concluded that tied-arch is a competitive alternative to cable-stayed bridge especially when asymmetric bridge spans are considered.