Estimating ice forces on a bridge pier using field observations and a deformation model

Abstract

This technical note qualitatively and quantitatively describes the ice run that took place in Sokna river, Trøndelag, Norway on 23 January 2020. Metrological and hydrological data are described. Stranded ice floe size distribution data are presented and analysed. It is shown that the maximal ice floe dimension is well described by generalized exponential (shape parameter = 2.77, scale parameter = 1.42) or log-logistic distributions (alpha = 3.57, lambda = 1.15). A custom-built steel load panel had been mounted on Sokna bridge preceding the ice run; however, due to technical difficulties no forces were recorded. Hindcast calculations using Solidworks based on the permanent deflections experienced by this load panel have been carried out to estimate ice forces experienced by Sokna bridge. These hindcast calculations conclude that the real peak ice force experienced by the 0.8 m diameter cylindrical bridge piers must have been within the range 1.1 to 5.5 MN. This range is compared to predictions made by standards for predicting ice forces on bridge piers. This comparison reveals that the Norwegian standard, the lower bound of the SNiP standard, and the upper bound of the CSA S6:19 standard are consistent with this range, while the Swedish and Finnish standards predict too low forces.