Nizhou Bridge, China: an insight into deck erection gantries supported on main suspension cables

Abstract

The Nizhou waterway bridge, part of the Second Humen Bridge over the Pearl River in China's Guangdong province, is the second longest suspension bridge in the world (1688 m main span). The reinforced concrete towers are 260 m tall and the main cable spacing is 42·1 m. The deck is an aerofoil-shaped orthotropic steel box 49·7 m wide and 4 m deep. Deck erection took place during the spring of 2018. Three 500 t safe working load deck erection gantries, supported on the main cables, lifted 175 deck segments into position in 10 weeks. Strand jacks were used for deck lifting and gantry relocation. This paper describes the deck erection gantries, from concept development, through detailed design and testing, to operation on site. It focuses on the innovative movement system specifically developed for this project to reduce operating cycle times and overcome the design constraints, particularly the large range of relative positions between the deck erection gantry and the cable bands. Cast nylon wheels and aluminium ramps were designed for the gantry to roll smoothly over cable bands. Insufficient industry guidance on the design of cast nylon wheels and their interaction with the main cables required a multidirectional approach, which involved hand calculations, finite-element analysis and testing.