Consistent Modal Calibration of a Pendulum-Type Vibration Absorber

Pendulum absorbers are installation in offshore wind turbines to mitigate excessive vibration amplitudes from wind and wave loading. The pendulum damper is placed inside the tower and attached to the structure at two distinct points: The tower top, where the pendulum arm is fixated, and at the position of the pendulum mass, which is connected to the tower wall by the damper. The present paper derives a modal calibration principle, which consistently accounts for different points of attachment for the absorber stiffness and damping.

Numerical Simulation of Dynamic Response of Submerged Floating Tunnel under Regular Wave Conditions

A submerged floating tunnel (SFT) is considered an innovative alternative to conventional bridges and underground or immersed tunnels for passing through deep water. Assessment of hydrodynamic performance of SFT under regular wave loading is one of the important factors in the design of SFT structure. In this paper, a theoretical hydrodynamic model is developed to describe the coupled dynamic response of an SFT and mooring lines under regular waves. In this model, wave-induced hydrodynamic loads are estimated by the Morison equation for a moving object, and the simplified governing differential equation of the tunnel with mooring cables is solved using the fourth-order Runge–Kutta and Adams numerical method. The numerical results are successfully validated by direct comparison against published experimental data. On this basis, the effects of the parameters such as the cable length, buoyancy-weight ratio, wave period, wave steepness, and water/submergence depth on the dynamic response of the SFT under wave loading are studied. The results show that tunnel motions and cable tensions grow with wave height and period and decrease with submergence depth. The resonance of the tunnel will be triggered when the wave period is close to its natural vibration period, and the estimation formula of wave period corresponding to tunnel resonance is proposed in this paper.

Численное моделирование поведения карбидов при высокоэнергетическом воздействии

The results of research on modeling thermodynamic parameters of shock-wave loading of carbides with different stoichiometric ratios are presented. The carbides are considered as a mixture of carbon with the corresponding component. The calculations of pressure, compression and temperature values under shock-wave loading for solid and porous carbides in the range of pressure values above 3 GPa are performed. The model calculations are compared with the known experimental results on the shock-wave loading of carbides with different porosity values. The possibility of modeling the behavior according to the proposed method for carbides for which there are no experimental data at high dynamic loads is shown.

Calibration of Load and Resistance Factors for Breakwater Foundation Design. Application on Different Types of Superstructures

Load and resistance factor design is an efficient design approach that provides a system of consistent design solutions. This study aims to determine the load and resistance factors needed for the design of breakwater foundations within a probabilistic framework. In the study, four typical types of Korean breakwaters, namely, rubble mound breakwaters, vertical composite caisson breakwaters, perforated caisson breakwaters, and horizontal composite breakwaters, are investigated. The bearing capacity of breakwater foundations under wave loading conditions is thoroughly examined. Two levels of the target reliability index (RI) of 2.5 and 3.0 are selected to implement the load and resistance factors calibration using Monte Carlo simulations with 100,000 cycles. The normalized resistance factors are found to be lower for the higher target RI as expected. Their ranges are from 0.668 to 0.687 for the target RI of 2.5 and from 0.576 to 0.634 for the target RI of 3.0.

STUDY OF STEEL BARRIER SURFACE AFTER HIGH-SPEED EXPOSURE OF W AND TIC POWDERS

The surface layer of an obstacle made of U8 steel is investigated after high-speed exposure to a flow of powder particles. After analyzing the frames of high-speed photography, the average velocities of movement of particles of tungsten and titanium carbide powders were determined. It is shown that the shock-wave loading of the barrier material and the effect of particles accelerated by the explosion energy provide a change in the physical and mechanical properties of the surface and the volume of the steel barrier material.

SHOCK-WAVE INITIATION OF SYNTHESIS IN NI-AL POWDER MIXTURE INSIDE TITANIUM MATRIX

This study presents the results of studying the effect of shock-wave loading on the initiation of synthesis in Ni-Al powder mixture inside titanium matrix. X-ray phase analysis (XRD) and measurement of the microhardness of the intermetallic layer showed that this layer consists of a monophase product NiAl, which is formed directly during explosive loading at a given impact velocity of the plate. Thus, the use of shock-wave loading made it possible to obtain a layered material with a strengthening intermetallic layer. The results obtained are promising for the development of new structural materials with special performance properties.