Wire fractures in the main cables of the Lysefjord Suspension Bridge display an approximate linear relationship with time. Uncertainties related to wire fractures in sublayers, reduction of load-carrying capacity and lifetime, and future development of wire fractures have prompted extensive investigations of the main cables. Failure analyses of fractured Z-wire samples and fracture mechanics analysis concluded that cracks have initiated and propagated from surface imperfections. The potential for hydrogen atom generation and absorption that causes hydrogen-induced cracking is discussed. Hydrogen atoms result from the hot-dip galvanization process, or due to corrosion. Evaluation of remaining load-carrying capacity and the need for strengthening of the main cables are briefly discussed and methods for surveillance of wire fractures are presented.

Abstract. Experimental laboratory testing of vortex-induced structural oscillations in flowing water is an expensive and time-consuming procedure, and the testing of high Reynolds number flow regimes is complicated due to the requirement of either a large-scale or high-speed facility. In most cases, Reynolds number scaling effects are unavoidable, and these uncertainties have to be accounted for, usually by means of empirical rules-of-thumb. Instead of performing traditional hydrodynamic measurements, wind tunnel testing in an appropriately designed experimental setup may provide an alternative and much simpler and cheaper framework for estimating the structural behavior under water current and wave loading. Furthermore, the fluid velocities that can be obtained in a wind tunnel are substantially higher than in a water testing facility, thus decreasing the uncertainty from scaling effects. In a series of measurements, wind tunnel testing has been used to investigate the static response characteristics of a circular and a rectangular section model. Motivated by the wish to estimate the vortex-induced in-line vibration characteristics of a neutrally buoyant submerged marine structure, additional measurements on extremely lightweight, helium-filled circular section models were conducted in a dynamic setup. During the experiment campaign, the mass of the model was varied in order to investigate how the mass ratio influences the vibration amplitude. The results show good agreement with both aerodynamic and hydrodynamic experimental results documented in the literature.

A custom-made monitoring system for long-term measurements of the wind field, surface pressures and structural response has been installed on the Gjemnessund Bridge in Norway. The monitoring system has been operating from 2018 to 2021. The scope was to investigate several topics within bridge aerodynamics in a fullscale environment, e.g. vortex shedding, gust response and span-wise correlations. Six cross-sectional strips with pressure taps were installed on the bridge. The pressure strips covered a span-wise distance equal to approximately six times the deck width. The upstream and the wake flow properties were measured in five locations along the same span. A case study showed that the ten-second gust correlations were stronger than the ten-minute correlations, both spanwise and section-wise. The gust impact on the bridge caused peak-to-peak midspan amplitudes of 1 m vertically and 2 m laterally.