Horizontal Deck Research Articles

Shore-Side Downfall Pressures Due to Waves Impacting a Vertical Seawall: An Experimental Study

As part of an investigation into downfall impacts from violent overtopping waves, experimental data are presented for the impact pressures and forces generated by regular and focused waves breaking onto a vertical wall and impacting a landward horizontal deck at a scale of 1:38. Particular attention is given to the wave-by-wave uprush and impact downfall events. By selecting regular and focused wave conditions that produce impacts, new trends are identified for violent downfall phenomena that could easily be underestimated in current practice. The characteristics of the downfall impacts are investigated and three different types of downfall impact are identified and discussed. Using a Wavelet Filter to denoise the signal from pressure probes without losing the peak impact pressures or introducing a phase shift, the distinctive features and dynamic behaviours of the white-water impacts are considered, and it is shown that downfall pressure magnitudes of 30–40 ρgH are regularly achieved. Dynamic impulse times of the events are also presented with higher-impact events generally relating to shorter impulse times, highlighting the dynamic character of these impacts. The largest downfall pressures are found to occur further from the vertical wall than previously measured. Importantly, the spray travelling furthest from the point of the initial wave impact on the vertical wall causes some of the largest downfall pressures on the deck. The paper concludes that, while the dataset is small, there are strong indications that the effects of these types of impacts are structurally significant and present a risk to infrastructure located landward of seawalls.

Equivalent static methods for seismic design of straight integral abutment bridges

AbstractIntegral abutment bridges (IABs) are becoming the solution of choice in the low to mid‐length ranges because of their low cost compared with traditional solutions and their good performance under seismic actions. The main drawback of these bridges is the need to consider soil‐structure interaction to assess their performance, a problem that is more pronounced for actions implying horizontal deck movements, such as temperature or the specific focus of this paper, that is, seismic action. In IAB design, simplified models are often used, where soil‐structure interaction is modeled by means of beams on non‐linear Winkler springs for the evaluation of seismic behavior. This paper, starting from an existing non‐linear dynamic model (NLDM) that describes IABs longitudinal seismic response, derives two equivalent static models: one non‐linear and the other linear, for displacement‐ or force‐based design respectively. A parametric study is carried out to assess the static models performance in terms of the main design internal actions versus the NLDM. Finally, the assessed model errors are discussed in the context of partial factors safety format.

Laboratory studies of the impact of non-breaking waves on a horizontal emerged deck

The horizontal elements of maritime structures are susceptible to both wave impact and resulting vibrations. These vibrations can lead to a partial or complete failure of structures and require detailed investigations. To address this issue, laboratory experiments were conducted in a wave flume. The aim of this study was to investigate the problem of standing wave impact underneath a horizontal deck. The main focus was on the effect of the wave-induced vertical forces on the global response of the structure. The physical model of the deck was installed above a still water level in front of a vertical barrier. The model was supported by a system of strings and springs. The mechanical system had one degree of freedom corresponding to a small rotational displacement around rear deck edge. Among other physical parameters, the impact pressure generated under the structure due to wave impact was measured. The high sampling frequency of the data acquisition system allowed to capture momentary slamming pressure. The systems of accelerometers and displacement gauges were installed to measure induced vibrations. Thorough analysis of the influence of wave parameters and the deck clearance on the structure response was performed based on the measurements. The rapid slamming force increase, recorded at the moment of impact is not revealed in the dynamic response of the plate.

On Solitary Wave Breaking and Impact on a Horizontal Deck

The impact of waves and bores generated by broken solitary waves on horizontal decks of coastal structures was studied by solving the Navier–Stokes equations. Solitary waves of different amplitudes were considered, and submerged ramps were used to bring the waves to the breaking point. The horizontal fixed deck was located downwave of the ramp and placed at various elevations above and below the still-water level. The results include the surface elevation of the wave and the bore-induced horizontal and vertical forces on the deck. The results were compared with laboratory measurements and those due to the bore generated by breaking a reservoir, and a discussion is provided on the relative magnitude of the loads. It is found that breaking solitary waves and dam-break provide reasonable loading conclusions for tsunamis events.

Arch and Cable Suspended Bridges

An arch bridge is a mainly horizontal deck with an arch as its load-carrying structure. The arch works by transferring the weight and other external vertical loads into a horizontal thrust on the abutments placed at both sides. When the main load on the arch is the homogeneously distributed deck weight, and the arch is properly shaped, the arch rib is subjected to pure compression along its whole extension. Both tensile forces along the arch rib and shear forces transversal to it are absent. Bending moments vanish as well. This has made possible the use of masonry for arch bridges, which uses materials such as stone, brick, and concrete that are strong in compression but very weak to tension and shearing. In the following sections, we determine mathematically this optimal arch shape, which turns out to be a parabola. The novelty is that these well-known results are obtained using just basic algebra and trigonometry, without any mention of infinitesimal calculus, including in the demonstration of the absence of shearing forces. Subsequently, the method is extended to cable suspended bridges.

Tuned Liquid Column for Dampering Rotational Motion of a Nonlinear Horizontal Deck

Tuned Liquid Column for Dampering Rotational Motion of a Nonlinear Horizontal Deck

Two-phase SPH–FD depth-integrated model for debris flows: application to basal grid brakes

In some cases, debris flow consists of low-permeability soils in which run-out distances, velocities and lateral spreading are highly influenced by pore-water pressures. Basal screens are energy dissipation structures designed to reduce these velocities and run-out distances. These structures consist of grids built on horizontal decks where basal pore pressures of debris flows are made equal to the atmospheric pressure, which increases basal friction. Once the debris flows exit the structure, basal pore pressure increases as the basal surface is impermeable again, but the values have been reduced. In order to model these phenomena, it is necessary to use debris flow simulation models considering two phases and pore-water pressures. Here, a depth-integrated two-phase smooth particle hydrodynamics (SPH) model, previously developed by the authors, is improved by including the vertical structure of pore-water pressure. This is done by incorporating finite-differences meshes associated to each SPH node that represents a solid particle. In this way, a higher precision is obtained in describing excess pore pressure along depth, including the influence of vertical consolidation, height variation and changes in basal permeability. The proposed model is applied to describe debris flows with two different ranges of soil permeability propagating over grid structures. The authors have used laboratory tests run at the Norwegian University of Science and Technology and studied the efficiency of the basal grids by comparing cases equipped by them and cases without any obstacle. The results obtained from the proposed numerical experiments suggest that the proposed two-phase coupled model is able to properly reproduce the behaviour of debris flows, describing more accurately the time–space evolution of pore-water pressures during the whole propagation stage, considering both propagation impermeable beds and pore pressure dissipation structures such as grids.

A study of the wave impact loads on a fixed column-slab combined structure with a GPU-accelerated SPH method

ABSTRACT Wave impacts on a semi-submerged platform have a great influence on the structure. Physical experiments and numerical simulations are carried out based on fixed horizontal deck and column-slab combined structures. During the physical experiments, the impact pressures acting on the horizontal decks are measured to verify the accuracy of the numerical models. In the SPH program, by equipping with GPU parallel acceleration processing framework and adopting the dynamic boundary particles method, the total calculation time shortens more than 6 times and the gap near the wavemaker has been eliminated, improving the efficiency and accuracy of numerical calculation significantly. The similarities and differences of the pressure amplitude and distribution between the two structures are summarised and compared. Due to the presence of the columns, the wave energy transmission is largely influenced, and the relationship between the peak pressure and velocity distribution is also demonstrated. The influence of the columns is both considerable and crucial.

Locating and Quantifying Damage in Deck Type Arch Bridges Using Frequency Response Functions and Artificial Neural Networks

Vibration-based methods can be used to detect damage in a structure as its vibration characteristics change with physical changes in the structure. Arch bridge is a popular type of bridge with rather complex vibration characteristics which pose a challenge for using existing vibration-based methods to detect damage in the bridge. Further, its particular geometry with a curved arch rib and vertical members (either in compression or tension) to support the horizontal deck makes the process of damage quantification using vibration-based methods harder and challenging. This paper develops and presents a vibration-based method that utilizes damage pattern changes in frequency response functions (FRFs) and artificial neural networks (ANNs) to locate and quantify damage in the rib of deck-type arch bridge, which is the most important load bearing component in the bridge. Principal component analysis, which is performed to reduce the dimension of original FRF data series and to obtain limited principal component analysis (PCA)-compressed FRF data is used in the development of the proposed method. FRF change, which is the difference in the FRF data between the intact and the damaged structure, is compressed to a few principal components and fed to ANNs to predict the location and severity of structural damage. The process and the hierarchy of developed ANN systems are presented, including the “fusion network” concept, which individually analyses FRF-based damage indicators separated by sensor locations. Finally, results obtained for many tested damage cases (inverse problems) are presented, which demonstrate the applicability of the proposed method for locating and quantifying damage in the rib of deck type arch bridge.

Experimental study of vertical wave-in-deck force and pressure on a thin plate due to regular and focused waves

Offshore platforms and ocean structures endure wave impact loads due to transient steep waves, including wave breaking events during their design life. The present study aims to understand the nature of the impact pressure and vertical wave-in-deck impact force on a horizontal deck under the action of the regular and breaking waves through experimental investigations. The model details, wave simulation, vertical wave-in-deck load, and pressure variation along the wave direction on a thin plate are presented in the present paper. The maximum breaking wave impact pressure on the plate increases with the air gap up to about one-eighth of the maximum wave height and further decreases with an increase in the air gap.

Wave Front Steepness and Influence on Horizontal Deck Impact Loads

In design storm sea states, wave-in-deck forces need to be analysed for fixed and floating offshore platforms. Due to the complex physics of wave impact phenomena, numerical analyses should be complemented by model test data. With a large statistical variability, such experiments usually involve running many 3-h storm realisations. Efforts are being done to establish efficient procedures and still obtain improved statistical accuracy, by means of an initial simplified screening based on parameters derived from the incident wave record only. Here, we investigate the vertical rise velocity of the incident wave elevation at a fixed point in space, which indirectly measures both the local slope and the near-surface orbital velocity. A derived simple deck slamming model is also suggested, to support the check of the physical basis of the approach. Correlation against data from a GBS wave-in-deck model test is used for checking this model. The results show that, although there is a significant random scatter in the measured impact forces, especially in the local slamming forces but also in the global forces, there is a correlation to the rise velocity. Comparisons to the simple load model also show promising results when seen on background of the complex physics and random scatter of the impact problem.

Experimental Study on Wave Impact under Deck due to Regular Waves

Duong, T.T.; Jung, K.-H.; Lee, G.-N.; Kim, D.-S.; Suh, S.-B., and Kim, M.-S., 2019. Experimental study on wave impact under deck due to regular waves. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 81-85. Coconut Creek (Florida), ISSN 0749-0208.Wave forces acting on the lower decks of offshore platforms can cause significant structural damage and play an important role in the design of offshore structures. In this study, the wave impact phenomena under horizontal decks of offshore structures were investigated with a series of laboratory experiments measuring vertical global forces and local pressure distributions on fixed horizontal plate subjected to regular waves varying wave height, wave period, and deck clearance. The local pressure data under the deck was used to assess the impulsiveness at each location for various wave conditions and deck clearances. Particle image velocimetry (PIV) technique was employed to obtain the velocity fields under the deck, which were synchronized with vertical forces and local pressure data. The water velocity profiles during wave loading under deck were compared with velocity profiles of incoming regular waves without the deck and presented the deformation of wave kinematics at each phase of the predominant vertical force change to understand the wave impact phenomena.

Parametric study of nonlinear wave loads on submerged decks in shallow water

This study is concerned with calculations of nonlinear wave loads on submerged, horizontal decks in shallow water. Solitary and cnoidal wave loads on submerged decks are determined by use of the Level I Green–Naghdi (GN) equations. Results of the GN equations are compared with the linear theory, CFD, and with available laboratory measurements. Variation of the horizontal and vertical wave-induced loads and the overturning moment on submerged decks is studied through an extensive parametric study. In total, 240 cases are considered for cnoidal waves and 84 cases for solitary waves. The variable parameters include the wave height, wave period, deck submergence depth and deck length. Based on the parametric study results, two empirical, design-type equations are suggested for estimating the vertical and horizontal forces on submerged decks. Results of the empirical equations are compared with the available laboratory measurements and CFD calculations and good agreement is observed. Examples are provided to demonstrate the use of the empirical equations for prototype cases. The parametric study and the empirical equations provide engineers with the preliminary determination of wave loads on submerged decks.

Probabilistic Seismic Vulnerability Assessment of Tall Horizontally Curved Concrete Bridges in California

The seismic performance of bridge structures is significantly affected by their column height, design era, and horizontal deck curvature. However, existing risk assessment platforms do not appropriately account for the effect of column height and horizontal deck curvature. This paper investigates the effect of column height, design era, and deck curvature on probabilistic seismic demand models and fragilities of bridges. This paper selects a typical configuration of horizontally curved concrete box-girder bridges in California: two-frame five-span bridges with single-column bents. Extensive nonlinear time history analysis results for the bridges including the uncertainties are initially compared using a statistical technique, analysis of covariance. Results from the analysis of covariance are used to estimate the influence of column height, design era, and horizontal deck curvature on bridge performance. An increase in the deck horizontal curvature is found to increase the bridge vulnerability irrespective of the design era and height range. Although the seismic vulnerability of bridges constructed prior to 1970 increases with the increase in the column height, there is no specific trend in the change in vulnerability with respect to column height for bridges constructed after 1970. This research also shows that the implementation of seismic design principles reduces the seismic vulnerability of the bridges.

Probability Analysis of the Wave-Slamming Pressure Values of the Horizontal Deck with Elastic Support

This paper presents the probability distribution of the slamming pressure from an experimental study of regular wave slamming on an elastically supported horizontal deck. The time series of the slamming pressure during the wave impact were first obtained through statistical analyses on experimental data. The exceeding probability distribution of the maximum slamming pressure peak and distribution parameters were analyzed, and the results show that the exceeding probability distribution of the maximum slamming pressure peak accords with the three-parameter Weibull distribution. Furthermore, the range and relationships of the distribution parameters were studied. The sum of the location parameter D and the scale parameter L was approximately equal to 1.0, and the exceeding probability was more than 36.79% when the random peak was equal to the sample average during the wave impact. The variation of the distribution parameters and slamming pressure under different model conditions were comprehensively presented, and the parameter values of the Weibull distribution of wave-slamming pressure peaks were different due to different test models. The parameter values were found to decrease due to the increased stiffness of the elastic support. The damage criterion of the structure model caused by the wave impact was initially discussed, and the structure model was destroyed when the average slamming time was greater than a certain value during the duration of the wave impact. The conclusions of the experimental study were then described.

Accurate green water loads calculation using naval hydro pack

An extensive verification and validation of Finite Volume based CFD software Naval Hydro based on foam-extend is presented in this paper for green water loads. Two-phase numerical model with advanced methods for treating the free surface is employed. Pressure loads on horizontal deck of Floating Production Storage and Offloading vessel (FPSO) model are compared to experimental results from [1] for three incident regular waves. Pressure peaks and integrals of pressure in time are measured on ten different locations on deck for each case. Pressure peaks and integrals are evaluated as average values among the measured incident wave periods, where periodic uncertainty is assessed for both numerical and experimental results. Spatial and temporal discretization refinement study is performed providing numerical discretization uncertainties.

Probabilistic Performance Assessment of Retrofitted Horizontally Curved Multi-Frame RC Box-Girder Bridges

Bridge horizontal deck curvature and the prevalence of in-span hinges in multi-frame RC box-girder bridges have reinforced this class of bridge to response with unique dynamic behavior during seismic excitations. This paper assesses the impacts of 10 different retrofit strategies on the vulnerability of curved multi-frame RC box-girder bridges with multi-column bents based on nonlinear time history analyses in OpenSEES. Consistent with HAZUS-MH definitions, fragility curves corresponding to four damage states at the component and system levels are developed for various bridge deck radii. The results indicate that combinations of retrofit strategies should be used to enhance the desirable level of bridge performance. Moreover, the most effective retrofit strategy in reducing probable damage for a given intensity is dependent on the bridge deck radius and is a function of the damage state of interest.

A MULTI-NODE APPROACH TO SIMULATE THIN COASTAL STRUCTURES IN THE SPH CONTEXT

We propose an improvement in modeling solid boundary
 conditions for 2D weakly-compressible Smoothed Particle Hydrodynamics (SPH) simulations for cases in
 which the thickness of the body is small compared to the desired
 particle size and the fluid surrounds the body from more than one
 side. Specifically, the fixed ghost particles technique developed by 
 Marrone et al. (2011), based on interpolation nodes located within the
 fluid domain, is here extended to a multi-node approach. The fluid
 domain is thus divided into various sub-areas and an interpolation
 node for the considered solid particle is associated to every
 sub-area. Consequently, the solid particles present an array of
 values interpolated at different sub-areas for the same physical
 quantity. When a fluid particle located in a specific region
 interacts with a multi-node fixed ghost particle, the last assumes
 the field values interpolated in the reference area through the
 associated node. The present modeling allows to adopt a coarser
 spatial resolution to model the same physical problem, resulting in
 a reduction of the computational cost.
 The proposed solid boundary treatment is applied to horizontal decks and perforated
 wall-caisson breakwaters subjected to regular waves. In this
 context, an automatic hybrid diffusive formulation is introduced in order to prevent shock
 waves during water impacts and preserve the hydrostatic pressure.
 The formulation is obtained by defining a variable parameter
 detecting the occurrence of relevant density gradients induced by
 fluid impacts, resulting in an automatic switch between the two
 formulations.

Numerical study of nonlinear freak wave impact underneath a fixed horizontal deck in 2-D space

Freak waves are extreme and unexpected surface waves with huge wave heights that may lead to severe damage to ships and offshore structures. However, few researches have been conducted to investigate the impact underneath fixed horizontal decks caused by freak waves. To study these phenomena, a 2-D numerical wave tank is built in which nonlinear freak waves based on the Peregrine breather solution are generated. As a validation, a regular-wave-induced underneath impact is simulated and compared to the existing experimental measurements. Then the nonlinear freak-wave-induced impact is investigate with different values of deck clearance above the mean free surface. In addition, a comparative simulation of a “large” regular wave based on the 2nd-order Stokes wave theory with the same crest height and wave length of the nonlinear freak wave is carried out to reveal the unique features of the nonlinear freak-wave-induced impact. By applying a fluid–structure interaction (FSI) algorithm in which the bottom deck and front side wall are simplified as Euler beams in 2-D and discretized by the finite element method (FEM), the hydroelastic effects are considered during the impact event. The vertical force acting underneath the bottom deck, the transversal force acting on the front side wall, the structural displacements of the elastic deck and wall are analyzed and discussed respectively, from which meaningful conclusions are drawn.

A combined wave-dam-breaking model for rogue wave overtopping

Although great efforts have been devoted to revealing the formation mechanisms of rogue waves, the study of wave–structure interaction such as the green water phenomenon is still not sufficient. Since the traditional Ritter׳s solution of dam-breaking model gives improper estimations on the rogue wave overtopping, a combined wave-dam-breaking (CWDB) model is proposed. The CWDB model is deduced from the Ritter׳s solution, by including the influence of the rogue wave propagation as well as the delayed effect of the dam-breaking problem. Various rogue waves, which are based on the Peregrine breather solution of nonlinear Schrödinger (NLS) equation, are generated in a numerical wave flume. The rogue waves impinge onto a horizontal deck placed at the center part of the tank, creating green water on the deck surface. The CWDB model is validated by making comparisons with both numerical results and existing experimental measurements. Great improvement can be revealed by contrasting the results of the CWDB model with those of the Ritter׳s solution.