Journal of Waterway, Port, Coastal, and Ocean Engineering

A test program consisting of 13 steel tubular brace specimens with dent damage and various diameter-to-thickness ( D/t ) ratios was conducted to assess the residual strength and repair of damaged tubular braces used in offshore platforms. Specimens were inflicted with a dent having a depth of 0.10 D , with internal full grouting and grouted steel clamps, respectively, used to repair specimens. A baseline of unrepaired, damaged specimens subjected to concentric axial loading showed a significant reduction in residual strength due to the dent. A further reduction in axial load capacity was found in specimens subjected to combined loading. The use of grout to repair specimens was found to inhibit a growth in dent depth under axial loading and restore the capacity of the dented member to a level greater than the undamaged strength. A comparison with existing and modified analytical methods for strength prediction of unrepaired and grout repaired braces showed that these methods provided reasonable results.

Traditional elliptic harbor wave models are based on the assumptions that the exterior sea region (i.e. the region outside the computational grid) is of constant depth and that the exterior coastlines are collinear and fully reflecting. This paper demonstrates that for most coastal regions, where these assumptions are generally not true, their effect on model results is substantial. This leads to unreliable simulations. Enlarging the model domain to overcome their effects is cumbersome and often prohibitive. To overcome these difficulties, the use of parabolic approximations of the mild-slope wave equation as open boundary conditions is explored. Suitable parabolic equations are derived and interfaced with an elliptic finite-element model. Since the parabolic approximation does not describe wave scattering as rigorously as the traditional method, the new model is tested against analytical and other solutions for cases where scattering is extensive. Errors resulting from the parabolic approximation are found to be extremely small. Further model tests show that for the generally realistic case where exterior reflection coefficients are less than unity, the new method requires considerably smaller domains than the traditional method, resulting in reduced modeling effort. The model is also applied to Toothacher Bay, Maine, and the use of the parabolic boundary conditions eliminates many spurious features in the simulation.

This paper describes a systematic methodology for predicting the fate and stability of dredged material disposal sites over long periods of time, ranging from months to years. The approach is based on the generation and use of databases of wave and current time series that describe environmental conditions specific to the site. These boundary conditions are used to drive a coupled hydrodynamic, sediment transport, and a bathymetry change model that provides a prediction of the long-term behavior of a disposal site of arbitrary dimensions. An example of an application of this approach is made for a moderately dispersive disposal mound located offshore of the entrance to Mobile Bay, Ala.

The forces and overturning moments on a vertical wall due to the reflection of solitary waves, undular bores, turbulent bores, and surges on a dry bed were determined experimentally. The incident wave celerity, wave profile, runup, force, overturning moment, and pressures were measured. The wave profiles and runup time histories were obtained with a laser-induced fluorescence system. The transition from undular to turbulent bores exhibits a large increase in the maximum measured wave slope, runup, force, and moment. For all cases, the maximum measured force and overturning moment were always less than that computed from the maximum measured runup using hydrostatic considerations. When properly normalized, the runup and force on a vertical wall due to the impingement of bores on a mildly sloping beach and a horizontal bed are shown to agree quite well. The results of this study may be used to estimate the forces on a vertical wall due to turbulent bores traveling on beaches with slopes no steeper than 1/50.

A simplified approach is presented to use Dean's method for determining dry-beach (subaerial) width after equilibrium for arbitrary sediment size. A simple equation is developed relating a key parameter in Dean's method to sediment diameter. Closure depth is shown to be simply related to nearshore mean annual significant wave height. Dean's equations for dry-beach width are dimensionalized and simplified. The key parameter, closure depth, and the equations for dry-beach width are all presented in simple forms that can be solved easily using a hand calculator. Examples are presented for all cases including fill sediment with a mean diameter the same size, larger, and smaller than the native sediment. When the fill sediment is finer than the native sediment a minimum quality of sediment has to be placed before there is any resulting dry beach, and an equation is provided to determine this minimum quantity. The simplified method presented allows an engineer to easily evaluate a large number of scenarios at the feasibility stage of a project.

Based on Kakuno and Liu's perturbation theory, the formula for wave forces acting on an array of vertical cylinders is derived. The perturbation approach is based on the small amplitude and simple harmonic wave theory. Furthermore, the distance between two adjacent cylinders is assumed to be smaller than the wave length of incident waves so that flow separations and energy dissipation are confined with the neighborhood of cylinders. The wave forces are calculated from the pressure differences in front and behind the array. Laboratory experiments are performed by using square cylinders. Theoretical results agree with the experimental data very well over a range of water depths.

Seven tests consisting of 72 runs were conduced to measure wave reflection, overtopping, and overwash of dunes. The measured reflection coefficients and overtopping rates are compared with the empirical formulas developed for coastal structures. The equivalent uniform slope for reflection is assumed to be the beach slope at the still water shoreline. The equivalent uniform slope for overtopping is assumed to be the overall slope between the dune crest and the point where the water depth equals the significant wave height. The toe depth of the coastal structure is assumed to correspond to the water depth immediately seaward of the breaker zone on the beach. The formulas with these adjustments are then shown to predict the order of magnitude of the measured reflection coefficients and overtopping rates. Furthermore, the average volumetric sand concentration in the overwash flow was measured to be approximately 0.04 for these small-scale tests.