Hanger Length Adjustment in Network Arch Bridges – General Methodology and Real Case Study

Network arch bridges have inclined hangers with multiple intersections. The hanger force distribution is very sensitive to construction imperfections. To guarantee correct hanger forces, these forces must be measured and adjusted during the construction. The necessary length adjustments are calculated using an influence matrix to solve a multi-objective optimisation problem. The objectives include, but are not limited to, ensuring that all hanger forces are within the safe range, minimising the difference to the theoretical values, and minimising the number of hangers that need to be adjusted. At the Manchuria Bridge in Chile, the hanger forces were measured using strain gauges and the vibrating string theory, identifying five hangers with forces outside the safe limits. The required hanger length adjustments were approximately 4 mm.