Journal of Waterway, Port, Coastal, and Ocean Engineering

As an unsupported structure, a berthing monopile is often expected to work under harsh conditions. Approaching vessels may introduce considerable berthing energy, resulting in substantial tensile stress on the pile. This vessel impact occurs frequently as a primary load over the service life of the berthing monopile. In this situation, the fatigue safety of circumferential butt welds on piles becomes a crucial aspect in monopile design. This paper evaluates linear elastic fracture mechanics (LEFM)–based fatigue reliability for circumferential splice welds on steel monopiles. Studied monopiles are those installed in inland waterways, for which the predominant fatigue loading is vessel berthing. Important factors involved in the fatigue reliability assessment are addressed. A geometry function for determining the range of stress intensity factor is identified, an approximate stress concentration factor for piles under bending moment is mathematically formulated, and the beta distribution is applied to characterize the doubly bound hot-spot stress range caused by operational water-level constraints. A detailed case study is presented for illustrative purposes. This paper provides a practical approach to assessing LEFM–based fatigue reliability for steel berthing monopiles.

In this paper, an experimental methodology is described to assess the structural strength of unreinforced concrete armor units (CAUs). The methodology is applied to measure the structural integrity under impact loads of the new Cubipod CAU compared with the conventional cube CAU. The casting systems and clamps are described for manufacturing and handling the 15-t conventional cubic block and 16-t Cubipod prototypes used for the drop tests. Two separate reinforced concrete platforms were used for overturning and for free-fall tests, respectively. Compared with conventional cubes of similar size and concrete strength, Cubipods withstand drops that are more than 50% higher. Two extreme free-fall tests confirmed the structural robustness of Cubipod armor units. Manufacturing cycle time, as well as storage and handling procedures, are similar for both Cubipods and conventional cubic blocks.

The viscous, two-dimensional, free-surface flow induced by the propagation of nonlinear water waves over a rigid rippled bed was simulated numerically. The simulations were based on the numerical solution of the Navier-Stokes equations subject to fully nonlinear free-surface boundary conditions and appropriate bottom, inflow, and outflow boundary conditions. The equations were properly transformed so that the computational domain became time-independent. A hybrid scheme was used for the spatial discretization with finite differences in the streamwise direction and a pseudospectral approximation with Chebyshev polynomials in the vertical direction. A fractional time-step scheme was used for the temporal discretization. Over the rippled bed, the wave boundary layer thickness increased significantly, while vortex shedding at the ripple crest generated alternating circulation regions over the ripple trough. The velocity of the Eulerian drift profile was opposite to the direction of wave propagation far above the ripples, whereas close to the bed, its magnitude was influenced by the ripples up to a height of about six times the ripple height above the ripple crest. The amplitude of the wall shear stress on the ripples increased with increasing ripple steepness, whereas the amplitude of the corresponding friction drag force on a ripple was insensitive to this increase. The amplitude of the form drag force attributable to the dynamic pressure increased with increasing ripple steepness; therefore, the percentage of friction in the total drag force decreased with increasing ripple steepness. The period-averaged drag forces on a ripple were very weak, while the influence of form drag increased with increasing ripple steepness.

Quay walls are one of the key elements of port and harbor facilities; however, their collapse and unexpected displacements during earthquakes have caused disastrous damage and economic consequences. Therefore, adequate design and assessing the seismic performance of waterfront quay walls continues to be a concern to the waterborne transportation industry. In this paper, the seismic displacement of broken-back quay walls is studied through eight reduced-scale shaking table model experiments. The experimental results indicate that backfill settlement is smaller in a region behind a broken-back quay wall in which coastal and port facilities located in this area would undergo less deformation and damage during earthquakes. The observations from the model tests also show that for walls on loose seabed materials, seabed softening may significantly contribute to quay wall horizontal displacement, and rotation. Moreover, the sliding displacements estimated using an improved sliding block model that incorporates the pseudostatic method of Mononobe-Okabe for lateral earth pressures, agree well with quay walls’ sliding displacements measured in the shaking table model tests.

This paper describes kinetic aspects of surface waves propagating with or without a current in a constant water depth. Physical properties of the velocity and trajectory of a water particle during one wave cycle were investigated experimentally using intrusive and nonintrusive measuring techniques. Two optical devices were used for the nonintrusive measuring technique: particle image velocimetry (PIV) and particle tracking velocimetry (PTV). The techniques provided the velocity fields and distributions at various phases and the trajectory of the water particle over one cycle, respectively. The instantaneous velocity from the PIV measurement was compared with that given by a third-order Stokes wave theory. Suitable agreement between the two velocity profiles proves the ability of the PIV technique to accurately measure both temporal and spatial variations of the velocity. The PIV technique was applied to the prediction of particle trajectories in an Eulerian scheme. The significant novel element of our technique is the use of the velocities at surrounding Eulerian grid points to identify a Lagrangian point.

A process is described for computation of bathymetry in and near the surf zone, from spatially varying celerity and breakpoint location data. The procedure involves the use of three submodels: (1) a wave shoaling model (outside of the surf zone); (2) a wave breaking model (defining the offshore boundary of the surf zone); and (3) a wave dissipation model (inside the surf zone). Influence of wave amplitude on the wave dispersion relation and celerity is included. Output includes wave height and water depth throughout the domain. In the application described here, oblique digital video served as the initial data source, although the model could be applied to data derived from other sources. Results are compared with data recorded by in situ sensors and beach profile survey data acquired by traditional means. Results suggest that water depths can be computed within 15% normalized error (equally, less than 0.1 m in biased depth error) for in and near the surf zone characterized by high wave nonlinearity.