Wave Direction Classification for Advancing Ships Using Artificial Neural Networks Based on Motion Response Spectra

The independent support motion (ISM) response spectrum method is currently used in seismic analysis to calculate the response of piping systems subjected to independent excitations at several points of a supporting structure. This approach leads to considerable over estimation when the maximum responses by multiple excitations are combined by the absolute sum rule, while this may result in underestimation when the maximum responses by the multiple excitations are combined by the square root of sum of squares rule. Then authors have developed an advanced method of the ISM approach named SATH (spectrum method assisted by time history analysis), which was presented in PVP2020. In the SATH method, both floor response spectra and time histories of floor acceleration are used as independent inputs of support excitations. The maximum responses by multiple excitations are combined using correlation coefficients calculated by taking into account each time history of modal response due to independent inputs of support excitations. When the SATH method is applied to actual design using broadened FRS, the structural frequency uncertainty corresponding to broadened FRS should be considered in the calculation of correlation coefficients. The applicability of the SATH method to the structural frequency uncertainty was presented in ICONE2020. Furthermore, when piping systems are subjected independent excitations at several points of a supporting structure, the response of piping systems can be considered to have two different components. One is due solely to the inertia of the mass (the dynamic component) and the other is due to the time-varying differential motion of the support point (the pseudo-static component). Here, the dynamic component consists of two parts: the damped-periodic response (dynamic response) and the residual rigid response (high frequency response). Then authors have improved the SATH method to cope with above three responses (dynamic response, high frequency response and pseudo-static response), which was presented in ASME PVP 2023. Thus, since its presentation at ASME PVP 2020, the SATH method has been evaluated and improved several times and is now an appropriate method to use in design. In this paper, the entire procedure of the SATH method, which combines the dynamic response using broadened FRS, with the high-frequency response and the pseudo-static response, is described as an actual design method. In addition, the advantages of the SATH method in design are clarified by comparing the response by the SATH method with that by the conventional method (the uniform response spectrum analysis method and the independent support motion response spectrum analysis method) for a three-dimensional piping system model subjected to independent excitations at several points of a supporting structure.

A synthesis of ground motion and corresponding design response spectrum is presented here. A semi-empirical Green’s function approach based on envelope summation technique is used to model ground motion for evaluation of expected peak ground acceleration (PGA) from future large earthquake in Garhwal Himalaya, northeast (NE) and south India. The synthetic site-specific response spectra for the single degree of freedom (SDOF) structures corresponding to the synthetic ground motion records are obtained for both rock and soil conditions for engineering design of reservoir and nuclear power plant in different parts of India. The predicted PGA for NE India is found to be ~ 3.5 m/s2 at 60 km, decaying to ~ 0.1 m/s2 at 500 km distance, while it is ~ 3.0 m/s2 at 15 km, decaying to ~ 1.4 m/s2 at 80 km distance for Garhwal Himalaya. These PGA estimates are in good agreement with those obtained from the Global Seismic Hazard Assessment Program (GSHAP) exercise. The response spectrum attains its maximum relatively earlier for rock site than for soil site. The response spectra decay gradually at periods later than 0.5 s and approach asymptotically constant values at longer periods. The synthetic ground motions are used to perform seismic response analysis of engineering structures. For such analysis, a PGA of 0.027 g is estimated for the Tail pond reservoir in south India for a target earthquake of M 6.5 at 50 km distance, while a PGA of 0.015 g is found for the Gorakhpur nuclear power plant in north India for similar magnitude and distance. The difference in the PGA estimates between the two is mostly attributed to regional difference in attenuation and site response. The findings of this study are expected to facilitate the seismic design of engineered structures, safe from seismic hazard, in regions where strong motion data are sparse.

Realistic currents in seas and oceans are almost always changing in depth thus indicating on the presence of shear in the mean ambient flow. However, analysis methodologies interpreting directional wave data gathered by in-situ measurement devices such as: buoys, pressure gauges and Acoustic Doppler Current Profilers (ADCPs) utilize potential irrotational flow theory which cannot account for the rotational shearing currents. The effects of shearing currents on the wave direction estimations were studied on synthetic ADCP data of waves propagating in a predetermined spread. The synthetic data was generated employing the Rayleigh Boundary Value Problem (BVP) and a selected ambient current profile. The potential data processing led to significant errors in wave directional spread estimation for common shearing currents (~10°  in mean wave direction for the presented example). This finding is of great importance, as it addresses the influence of an ambient current profile on wave propagation direction. The obtained results suggest that there is an uncertainty with the confidence of any wave directional spread ever presented by in-situ wave measurement devices. A new methodology was developed for estimating directional wave spectra based on rotational flow physics by acquiring new terms emanate from wave-shearing current interaction governing equations. This included a derivation of new numerical transfer functions for the fluid’s physical properties based on the Rayleigh BVP. Then, by applying classical cross- and auto-spectral analysis on time-series data sets, the directional spread function was numerically reconstructed. The newly derived data processing methodology was applied to the same synthetic ADCP data sets. It was found to be capable of reconstructing the spread with great accuracy (0.4° in mean wave direction for the presented example). In addition, to modeling and synthetic data, field measurement data from several campaigns were also analyzed showing the importance of accounting for the vertical shear. This makes it a prominent methodology for estimating directional wave spectra in realistic oceanic conditions.

Site-specific ground motion modeling for a historical Cairo site as a step towards computation of seismic input at cultural heritage sites

Abstract. We present an overview of the Naypyitaw station (NPW) in Myanmar, which is managed by the Department of Meteorology and Hydrology (DMH) and is part of the GEOFON (GE) network (https://doi.org/10.5281/zenodo.15921214, Bindi et al., 2025). The station is equipped with both strong-motion and broadband sensors and is situated 2.6 km from the Sagaing Fault, providing an exceptional near-fault recording of the Mw 7.7 earthquake that occurred on 28 March 2025. The installation and ongoing maintenance of NPW are the result of a collaborative effort between DMH and the GFZ Helmholtz Centre for Geosciences (GFZ), prompted by the GFZ International Training Course on seismology and seismic hazard assessment (ITC) in 2016. In this study, we provide background information on the collaborative effort that led to the installation of the only station providing near-fault, on-scale measurements of the 2025 Myanmar earthquake. Given the widespread interest in the data recorded by the station, we describe the instrumental settings in detail and how to access data and metadata for station NPW. Given the relevance of the near-fault recordings at NPW not only for constraining the rupture process of the mainshock but also for engineering seismology applications, we analyze key features of the mainshock from an engineering seismology perspective. This includes an examination of ground motion amplitudes, frequency content, response spectra, and near-fault effects such as the fling effect and pulse-like motion. The high-quality near-field data at NPW provide valuable information for seismic hazard assessment in the region and offer useful constraints for studies investigating the rupture characteristics of the mainshock, which preliminary findings suggest propagated at supershear speed.

Different structural forms of TLP have different capacities and different scopes of application. Each type of TLP is globally designed. The hydrodynamic parameters and dynamic responses of different types of TLPs are studied considering the effect of different directions of wave and tendon stiffness. The unsteady potential flow theory and boundary element method are used to analyze flow field and hydrodynamic calculation. The software AQWA suite which is a set of advanced hydrodynamic analysis programs is used to perform the numerical simulation of TLP motion response. The results show that the dynamic responses of different types of TLPs are observably different. Changes of wave directions and added stiffness from tendons have certain effect on the motion response of a TLP.

Comparison of modal combination methods

In this paper, the full nonlinear method based on the three-dimensional potential flow theory and the dynamic analysis method of flexible components are combined to simulate the motion and load response of a FPSO in waves. On the boundary of the hull body, the coupled motions are considered in the impenetrable condition. An improved Eulerian method is adopted to trace strongly nonlinear 3-D free surface deformation. In the far field, artificial damping zone is applied to eliminate reflected wave. Rankine source method is adopted to solve the velocity potential in time domain. Hydrodynamic mesh on hull body is generated by using accumulative chord length cubic parameter spline function. After solving Poisson equation, the initial mesh on free surface becomes orthogonal. In each time step, elastic-mesh-technique (EMT) is used to optimize the mesh on free surface. Several auxiliary functions are introduced to decouple the motions and load, and then the fourth-order Runge-Kutta method is adopted to update the numerical model in time domain. For the forces of the mooring system on the hull at each time step, the dynamic equation of the flexible member is established by the dynamic analysis method based on the elastic slender rod mechanical model, and then the equation is discretized into matrix form by the finite element discretization method and solved. The coupled motion of FPSO hull and mooring system in regular waves of various frequencies in various directions is simulated, and the time domain solutions are obtained. RAO of heave motion in each wave direction is given. The load response at the midship section is analyzed.

Validation of dynamic response of a 2-MW hybrid-spar floating wind turbine during typhoon using full-scale field data

Effects of damping plate on the motion response of transport ships under waves

Multi-peaked directional wave spectra based on extensive field measurement data in the Gulf of Oman

A series of experiments were done to test theoretical predictions that an acoustically small, rigid (aluminum) hemisphere and semicircular cylinder excited by a plane acoustic wave in water would each produce a rocking motion perpendicular to the incident wave direction about the axis parallel to the incident wave. A plane standing wave was generated in a short open-ended thick-walled cylindrical waveguide with the waveguide's axis perpendicular to the symmetry axis of the hemisphere. Measurements were taken along the hemisphere from top to bottom to determine if any rocking motion occurred. The expected vibrational motion in the incident direction and symmetry-forbidden perpendicular vibrational motion were also measured. The transverse displacement of the hemisphere at each point was determined by using an ultrasonic vibrometer. The incident wave direction motion was measured using a hydrophone, an accelerometer, and a Laser Doppler Vibrometer (LDV). The motion in the incident wave direction was found t...

Indonesia is surrounded by three major tectonic plates which are Indian-Australian, Eurasian and Pacific tectonic plates. Consequently, Indonesia is prone to seismic hazard. Horizontal ground motion has taken a major role in conducting nonlinear time histories analysis or in assessing liquefaction potential. However, for site near fault area, vertical ground motion can be quite significant and cannot be neglected. This paper aims to evaluate the effect of vertical ground motion in the near fault area by conducting dynamic analysis using MIDAS GTS NX. UBC Sand model is employed to model liquifiable material. Standard penetration test, laboratory test and downhole seismic tests are conducted at the site in order to characterize the shear wave velocities and properties of the soil at the area and to determine the thickness of the liquifiable layer. For this paper, two dynamic analyses will be conducted. For first analysis, only horizontal ground motion is applied to the model while in the second analysis, both horizontal and vertical ground motion will be applied. Based on dynamic analysis result, the horizontal surface motion and horizontal surface response spectrum that is propagated using bi-directional time histories will have bigger acceleration if being compared by only using horizontal time histories.

There are significant risks in the construction sector, with falls from height identified a greater hazard than in most other industries. Efforts to improve working conditions and reduce accident rates have driven research into real-time monitoring technologies to reduce the risk of falls. The main objective of this research is to review existing real-time monitoring technologies, identify the most relevant, and analyse their benefits and impact on reducing workplace accidents in the construction sector. A systematic review was conducted using PRISMA methodology to investigate the use of real-time monitoring technologies in the construction industry. Only studies specifically investigating real-time fall risk assessment were included. Of the initial 446 articles reviewed, 39 were considered highly relevant to the research objectives. Various wireless and computer vision technologies were identified for real-time worker monitoring, often integrated with BIM to improve workplace safety. The findings suggest that a combination of technologies may produce more effective results for worker monitoring. However, further research is needed to verify the applicability of these technologies on construction sites.

An isotropic elastic solid reinforced with two families of aligned fibres behaves anisotropic to any deformation. For arbitrary orientation of fibres in either family, one set of fibres may be inclined obliquely to the aligned fibres in other family. A plane that contains the two families of aligned fibres becomes the plane of symmetry for composite material to exhibit monoclinic anisotropy. For this fibrous anisotropy, a fourth‐order elastic tensor is derived to define the constitutive relations between stress tensor and strain tensor. Components of this elastic tensor involve two Lame's moduli, eight fibroelastic coefficients and the angular deviation between two obliquely inclined fibre‐families. The velocities of bulk waves are calculated for propagation along general direction in this anisotropic composite. Propagation of surface wave is considered along the stress‐free plane boundary of anisotropic elastic half‐space. In a coordinate system with coordinate planes deviating from the plane boundary of the medium and/or plane of anisotropic symmetry, the fibrous composite is treated as triclinic for mathematical convenience. Mathematical model is derived to calculate the phase velocity of the surface wave, which varies with direction on the plane boundary. Horizontal energy flux at the boundary is calculated to determine the group velocity and ray direction of the surface wave. Effects of fibre‐orientations are analysed, numerically, on the wave velocities and ray direction of surface wave.