Weight placement on a bridge span significantly impacts structural reinforcement requirements. A load positioned at the midpoint demands more reinforcement than the same load near a supporting pier. For a 3,000m+ (free span) suspension bridge, this effect becomes particularly pronounced, with indirect costs exceeding the direct cost of the item itself. This paper explores material choices for the main structure, and ancillary components at the midpoint of a 3,000m+ span. It examines the direct costs of these materials and the potential for reducing indirect costs through weight reduction. The materials considered include standard steel grades, high-strength steels, aluminium, glass fibre, carbon fibre, and other lightweight alternatives. For a suspension bridge of this scale, aeroelastic stability is a critical factor. While weight reduction can lower material costs, it also decreases stiffness, thereby reducing the critical wind €speed. This paper presents a simplified method for estimating the cost savings achieved through weight reduction.
Forsberg et al. (Wed,) studied this question.