Abstract
The applicability of pressure-impulse theory is evaluated for predicting wave impact loading magnitudes for non-breaking standing wave impacts on vertical hydraulic structures with relatively short overhangs. To this end, tests were carried out on a schematized but realistic configuration with low steepness regular wave impacts on a straight overhang perpendicular to a vertical wall. This paper aims to fill the existing knowledge gap on this type of wave impact with reliable and simple expressions. Pressure-impulses and force-impulses are the wave impact loading magnitudes considered in this study, which are defined as the integral of the impulsive pressures/forces over time during a wave impact. These impulses can be used to determine the resulting stresses in a structure for sudden, impulsive loads. The proposed theoretical model is based on the pressure-impulse theory and validated with laboratory experiments. The laboratory tests are done with regular waves for relatively short overhangs, with ratios of wave length to overhang length between 12.1 and 43.6, and ratios of overhang height to overhang length of 3 and 6. Thus, the theory is verified for conditions where the wave impact takes place along the full length of the overhang. From the experimental results, a mean effective bounce-back factor β=1.17 is obtained, accounting for the bounce-back effect of entrapped air and other secondary sources of discrepancies between theoretical and experimental results. The standard deviation of β for all the different tests is σβ=0.11. This method seems suitable for carrying out preliminary loading estimations, including the pressure-impulse profile at the wall and the total force-impulse at the wall. This study also shows that the force-impulse is a more stable magnitude compared with the force peaks, with about half the relative standard deviation. The impulses predicted by this model are recommended to be coupled with fluid-structure interaction models for analysing the response of the loaded structure.
Highlights
In the coming years and decades, various new hydraulic structures will be constructed around the world at coastal areas, delta regions, lakes or reservoirs
The use of the pressure-impulse theory for estimating wave impact load magnitudes caused by standing regular waves on vertical structures with relatively short overhangs is evaluated
This addresses an existing knowledge gap on wave impact loading estimations on such structures, since such an experimental validation of the pressure-impulse theory is not known to the authors
Summary
In the coming years and decades, various new hydraulic structures will be constructed around the world at coastal areas, delta regions, lakes or reservoirs. Several of the existing hydraulic struc tures will be renovated after reaching the end of the envisaged design lifetime or due to increasing safety standards and/or loading conditions. Wave loads often play a key role in the design of these structures. This leads to a demand for extended knowledge on the design of hydraulic structures subjected to wave impacts. Among these three types of wave impacts, this study addresses wave impacts on overhang configurations, caused by non-breaking reflecting waves
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