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The paper proposes a new methodology for the control of residual displacements in multi-storey steel structure frames. The work starts from the validation and extension of a mechanical model based on single degree of freedom systems, already proposed in previous work, following with analyses performed on a set of natural accelerograms. The same model is applied to multi-degree of freedom (MDOF) systems through an anlaytical design procedure. The procedure is used to dimension study cases composed of concentrically braced frames that are analysed through nonlinear dynamic analyses with earthquake records excerpted from the previous dataset. The results confirm the effectiveness and suitability of the proposed procedure for MDOF systems. ……

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUG Probably the biggest challenge for wave energy is to ensure survival in harsh offshore conditions, in order to reduce costs for offshore repair operations and downtime, and achieve economic viability. This work presents a reliable numerical tool that can be used to study the dynamics and survivability of wave energy converters in violent wave conditions, possibly cutting down the costs of experimental campaigns. Within the Smoothed Particle Hydrodynamics framework, this research identifies a detailed procedure to model a taut-moored point-absorber wave energy converter together with its inherent power take-off device, which seamlessly exploits its functions of energy harvesting and load bearing. A validation of the DualSPHysics code is provided by contrasting the numerical outcome with a thorough set of data obtained in physical tests with extreme waves, showing that the time-integrated numerical model can capture with good accuracy all the physics involved. The computational fluid dynamics tool is employed to perform a survivability study, modeling high-return period wave conditions for marine structures, and providing guidelines on how to create the numerically best setup to be used for design purposes. A real-like irregular sea state representation, comprising 500 waves, was used to draw insightful indications for the structure optimization to increase the structure’s life expectancy, or conversely, to reduce the initial and operational costs. Agencia Estatal de Investigación | Ref. PID2020-113245RB-I00 Xunta de Galicia | Ref. ED431C 2021/44 Xunta de Galicia | Ref. ED481A-2021/337

The presence downstream of a dam of either rigid or erodible obstacles may strongly affect the flood wave propagation, and this complex interaction may lead to further dramatic consequences on people and structures. The open-source Lagrangian-based DualSPHysics solver was used to simulate a three-dimensional dam-break in a closed domain including an oriented obstacle that deflects the flow, thus increasing the complexity of fluid dynamics. By comparing numerical results with experimental data, the effectiveness of the model was evaluated and demonstrated with an extensive sensitivity analysis based on several parameters crucial to the smoothed particle hydrodynamics method, such as the resolution, the boundary conditions, and the properties of the interaction weight function. Charts and summary tables highlight the most suitable conditions for simulating such occurrences in the DualSPHysics framework. The presence of the obstacle, being also an opportunity for observation and study of complex fluid dynamics, opens the way to investigate the fluid interaction with solid objects involved in dam-break events and, possibly, to predict their effect with respect to the relative position between them and the flood and other relevant parameters. Finally, the numerical model presents a good overall agreement.

Computational Fluid Dynamics simulations of planing hulls are generally considered less reliable than simulations of displacement hulls. This is due to the flow complexity around planing hulls, especially in the bow region, where the sprays are formed. The recent and constant increasing of computational capabilities allows simulating planing hull features, with more accurate turbulence models and advanced meshing procedures. However, mesh-based approaches based on the finite volume methods have shown to be limited in capturing all the phenomena around a planing hull. As such, the focus of this study is on evaluating the ability of the Smoothed Particle Hydrodynamics mesh-less method to numerically solve the 3-D flow around a planing hull and simulate more accurately the spray structures, which is a rather challenging task to be performed with mesh-based tools. A novel application of the DualSPHysics code for simulating a planing hull resistance test has been proposed and applied to the parent hull of the Naples warped planing hull Systematic Series. The drag and the running attitudes (heave and dynamic trim angle) are computed for a wide range of Froude’s numbers and discussed concerning experimental values.

The present work addresses the need for an efficient, versatile, accurate and open-source numerical tool to be used during the design stage of wave energy converters (WECs). The device considered here is the heaving point-absorber developed and tested by Sandia National Laboratories. The smoothed particle hydrodynamics (SPH) method, as implemented in DualSPHysics, is proposed since its meshless approach presents some important advantages when simulating floating devices. The dynamics of the power take-off system are also modelled by coupling DualSPHysics with the multi-physics library Project Chrono. A satisfactory matching between experimental and numerical results is obtained for: (i) the heave response of the device when forced via its actuator; (ii) the vertical forces acting on the fixed device under regular waves and; (iii) the heave response of the WEC under the action of both regular waves and the actuator force. This proves the ability of the numerical approach proposed to simulate accurately the fluid–structure interaction along with the WEC’s closed-loop control system. In addition, radiation models built from the experimental and WAMIT results are compared with DualSPHysics by plotting the intrinsic impedance in the frequency domain, showing that the SPH method can be also employed for system identification. Xunta de Galicia | Ref. ED431C 2017/64 Ministerio de Economía y Competitividad | Ref. ENE2016-75074-C2-1-R European Commission

This work aims to provide a relationship to assess the residual displacements for one-storey buildings standing in seismic-prone areas. The maximum residual displacement that a structure can possibly sustain is clearly identified by means of its structural characteristics alone. It is demonstrated that the upper bound is independent of the peak displacement. The proposed procedure can help in controlling the structural residual deformations, which is an issue that is gaining momentum into the seismic community: a large body of research has been dealing with post-seismic damage. However, no general rule or theoretical mechanic model with general validity are reported in the literature. The solely valuable approach, though widely accepted, for predicting seismic-induced residual displacements is a statistical one. In order to frame the given relationship into the established probabilistic framework, an extensive numerical campaign has been carried out by means of nonlinear time-history analyses. Artificial spectrum-compatible accelerograms are used as proxies to account for seismic events. As a final result, residual displacement response spectra are proposed.

This study aims to evaluate the performance of a steel storage pallet racking system equipped with a novel seismic isolation system, which is effective along the cross-aisle direction alone. The isolation system consists of two IsolGOODS® isolators, which are curved surface slider bearings as framed into the European Standards for anti-seismic devices. The efficiency of the proposed device in reducing the seismic effects on pallet racks is investigated. Firstly, uniaxial real-time shake table tests are performed, showing a great reduction of floor accelerations. With the help of a herein validated numerical model, advanced knowledge is obtained. Six accelerograms, two normal-fault records, two pulse-like, and two spectrum-compatible series are selected for drawing generally valid statements. As proposed in this work, the outcomes confirm that the isolation system provides substantial reduction in terms of floor accelerations. In contrast, no up-lift of the base-connections is recorded: the uprights are always engaged in compression. On the whole, the most severe condition comes from the pulse-like record (Emilia 2012), in which displacement demand must be carefully considered while defining the isolators to be put in place.

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Smoothed Particle Hydrodynamics (SPH) method is used here to simulate a heaving point-absorber with a Power Take-Off system (PTO). The SPH-based code DualSPHysics is first validated with experimental data of regular waves interacting with the point-absorber. Comparison between the numerical and experimental heave displacement and velocity of the device show a good agreement for a given regular wave condition and different configurations of the PTO system. The validated numerical tool is then employed to investigate the efficiency of the proposed system. The efficiency, which is defined here as the ratio between the power absorbed by the point-absorber and its theoretical maximum, is obtained for different wave conditions and several arrangements of the PTO. Finally, the effects of highly energetic sea states on the buoy are examined through alternative configurations of the initial system. A survivability study is performed by computing the horizontal and vertical forces exerted by focused waves on the wave energy converter (WEC). The yield criterion is used to determine that submerging the heaving buoy at a certain depth is the most effective strategy to reduce the loads acting on the WEC and its structure, while keeping the WEC floating at still water level is the worst-case scenario. This work was partially financed by the Ministry of Economy and Competitiveness of the Government of Spain under project “WELCOME ENE2016-75074-C2-1-R″ and financed by Xunta de Galicia (Spain) under project ED431C 2017/64 ″Programa de Consolidación e Estructuración de Unidades de Investigación Competitivas (Grupos de Referencia Competitiva)" cofunded by European Regional Development Fund (ERDF). Dr. C. Altomare acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No.: 792370. Dr J. M. Domínguez acknowledges funding from Spanish government under the program “Juan de la Cierva-incorporación 2017” (IJCI-2017-32592).

The proposed work aims to prove the capability of the DualSPHysics numerical code to deal with the interaction of slamming waves with a Wave Energy Converter (WEC). In particular, the analysed device is a point-absorber that consists of a cylindrical heaving-buoy equipped with an air damper in order to reproduce the effect of the Power Take-Off (PTO) system. Numerical vertical displacement of the cylinder under regular waves is found to be in good agreement with experimental data for different PTO systems. Different scenarios are considered to compute the loads of focused waves acting on the device with its PTO system set on hold. The yield criterion is used to determine that keeping the WEC fixed at still water level is the worst-case scenario and submerging the heaving buoy deep enough is the best-case scenario. This work was partially financed by the Ministry of Economy and Competitiveness of the Government of Spain under project “WELCOME ENE2016-75074-C2-1-R” and financed by Xunta de Galicia (Spain) under project ED431C 2017/64 ″Programa de Con-solidación e Estructuración de Unidades de Investi-gación Competitivas (Grupos de Referencia Com-petitiva)" cofunded by European Regional Development Fund (FEDER). Fruitful discussion was held during the Course 'Mod-eling free surface flows with DualSPHysics' funded by the University of Salerno, Italy under the project N. 300393CIC19VICCIONE. Dr. C. Altomare acknowledges funding from the Eu-ropean Union’s Horizon 2020 research and innova-tion programme under the Marie Sklodowska-Curie grant agreement No.: 792370.

The efficiency of a low-reflective caisson built at the Outer Port of Punta Langosteira (A Coruña, Spain), with a front-wall porosity of ˜ 5%, has been numerically investigated by means of OpenFOAM® for different chamber configurations and different sea states. The numerical model is validated with data coming from experimental tests performed on a scaled prototype. First, two different water levels, low and mean tide levels, are analysed. Results show that the caisson is inefficient when the water level inside the chamber is low, and suggest its proper installation taking into account the tidal regime of the area. For mean tide level inside the chamber, the efficiency of the caisson shows to be strongly dependent on the wave period and height. However, it is shown to be more sensitive to the period for low wave heights than for the high ones. Overall, the reflection coefficient ranged from 0.365 ( s, m) to 0.660 ( s, m). Alternative configurations with one and two chambers are also examined instead of three. Overall, the reflection coefficient is very high ( > 0.95) for the configuration with only one chamber. For the two and three-chambered caissons the mean reflection coefficient is similar ( ˜ 0.5) but the dispersion of the values is much higher for the two-chambered caisson, with values ranging from 0.176 to 0.794. The first author of this manuscript wishes to express his gratitude to the IT support provided by Orlando Garcia-Feal, who made possible the use of the HPC system at monkey-island.uvigo.es. This work was partially financed by Xunta de Galicia (Spain) under project ED431C 2017/64 ”Programa de Consolidación e Estructuración de Unidades de Investigación Competitivas” and under project ED431F 2016/004 ”NUMANTIA”. This work was also funded by European Regional Development Fund under Interreg project ”MarRISK” (0262_MARRISK_1_E).

In this work, the capabilities of the open source code DualSPHysics coupled with the multiphysics library Project Chrono are shown. The framework is validated through an experimental campaign performed on a wave energy converter, which consists of a cylindrical heaving-buoy and a power take-off unit. The numerical model proves to correctly reproduce the hydrodynamic response of the wave energy converter under regular waves, and with three different damping coefficients of the power take-off. With this validated setup, the sensitivity of a wave energy converter to the lateral stiffness of the anchoring system is investigated. The outcomes of this numerical campaign show that the correct design of the anchoring structure should develop along with the design of the system. Enough lateral stiffness is able to avoid excessive displacements to limit the loss of efficiency. DualSPHysics is a toolbox ready to manage complex simulations, including mechanical constraints, high energetic sea states. Various scenarios along the lifespan of a floating structure can be investigated. More importantly, the model supports the preliminary studies that are of vital importance to design a test campaign. The first author’s Ph.D. scolarship is granted by the Italian Ministry for Education, University and Research (MIUR) as part of the program ”Dottorati Innovativi a caratterizzazione industriale”, ID DOT 1328490–3, funded by the European Union (Structural Funding ERDF-ESF for ”Research and Innovation” 2014-2020). The authors are grateful for the support.

Goods and products are stored in framed systems, such as pallet racks, used for industrial and commercial activities. In the last years, pallet rack code provisions for seismic loads have been significantly improved, but there are still relevant aspects that need attention for guaranteeing a safer structural design. For example, in the current European and American standards, no indications are given about the seismic isolation systems applied to these structures. Only two ways to enhance the performance of racks in seismic zones are reported: rack netting and structural strengthening. Both methodologies present logistic and technical problems. For this reason, researchers are investigating more efficient solutions, like the base isolation systems. An accurate isolation system can bring benefits in terms of reduction of the structural damage and improving the safety of the stored items. Since the cost of the structural frame is often negligible, with respect to the cost of the stored products, avoiding the overturning of merchandise is an important challenge. Moreover, falling pallets can bring to the overall global collapse due to an impact given on beams or columns. In the paper, a critical overview of base isolation systems developed for different steel storage rack typologies is presented and discussed, highlighting the main characteristics and the advantages associated with their use in practical cases. Furthermore, four different applications of energy dissipation devices are briefly discussed, comparing these systems with the previously introduced devices.

It has been often observed, as outcome of non-linear dynamic analyses that structures designed according to the force distribution proposed by Eurocode8, i.e. proportional to first mode shape, show a displacement demand at the top storey higher than those occurring at other intermediate storeys, thus increasing the probability of premature failure at this very storey. The scope of this work is to propose a new force design distribution that allows for the higher mode effects and therefore further structural dynamic characteristics.

Today, the use of modern high-performance computing (HPC) systems, such as clusters equipped with graphics processing units (GPUs), allows solving problems with resolutions unthinkable only a decade ago. The demand for high computational power is certainly an issue when simulating free-surface flows. However, taking the advantage of GPU’s parallel computing techniques, simulations involving up to 109 particles can be achieved. In this framework, this chapter shows some numerical results of typical coastal engineering problems obtained by means of the GPU-based computing servers maintained at the Environmental Physics Laboratory (EPhysLab) from Vigo University in Ourense (Spain) and the Tier-1 Galileo cluster of the Italian computing centre CINECA. The DualSPHysics free package based on smoothed particle hydrodynamics (SPH) technique was used for the purpose. SPH is a meshless particle method based on Lagrangian formulation by which the fluid domain is discretized as a collection of computing fluid particles. Speedup and efficiency of calculations are studied in terms of the initial interparticle distance and by coupling DualSPHysics with a NLSW wave propagation model. Water free-surface elevation, orbital velocities and wave forces are compared with results from experimental campaigns and theoretical solutions.

An improved Relaxation Zone (RZ) method has been implemented in the meshless SPH-based DualSPHysics model. Final purpose of this work is to have a general wave generation scheme that allows coupling SPH-based models to other models, e.g. Eulerian based wave models, besides employing the RZ as alternative wave generation in SPH as a stand-alone scheme. Using RZ in SPH, the movement of the fluid particles is controlled by correcting their orbital velocity by means of a weighting function in a specified generation area. In the present work, the new technique is used to couple DualSPHysics to the non-hydrostatic wave-flow model SWASH. The results of RZ employed both as stand-alone wave generation technique and as coupling framework with SWASH model are validated for wave generation and wave reflection for monochromatic waves. Then, the method is tested successfully for generation and absorption of irregular waves. Finally, the coupling between DualSPHysics and SWASH using RZ is validated against experimental data concerning the wave flow impacts on vertical walls. A procedure for a proper design of the RZ (i.e. shape of the weighting function, size of the RZ) is described in the present work. Overall, the results indicate that the proposed improved RZ technique is among the most effective alternatives for wave generation in SPH-based models for coastal engineering application.