An active mass damper utilizing rotating masses to damp the vibrations of an oscillator with two translational degrees of freedom in a horizontal plane and one rotational degree of freedom about a vertical axis is presented along with a corresponding closed-loop control algorithm. The damper consists of two masses rotating about a single vertical axis, powered by two actuators. In a preferred mode of operation, these masses rotate with a nearly constant and equal angular velocity in opposite directions, thus producing a harmonic control force in a single horizontal direction. By varying the relative angular position of the rotating masses, this control force can be directed in an arbitrary direction and used to damp the translational motion. In previous research, a control algorithm was derived for this purpose. The rotational degree of freedom can additionally be controlled by producing a moment by imposing angular accelerations on the rotating masses. In this paper, the previous control algorithm is augmented such that the rotational degree of freedom is additionally controlled. The augmented control algorithm is verified with help of numerical simulations.

A novel active mass damper, the twin rotor damper (TRD), was presented in previous research, including control algorithms for monofrequent vibrations. In this paper, the steady-state damping performance is evaluated by applying a harmonic excitation force to a single degree of freedom (SDOF) oscillator with and without the action of the damping device. Using the velocity of the SDOF oscillator as feedback, adequate steady-state damping performance can be achieved with the TRD by setting the control force of the TRD in antiphase to the velocity of the SDOF oscillator. An analytic solution describing the steady-state damping performance is derived. The analytic solution allows for the comparison with a dynamic vibration absorber (DVA) of comparable size (stroke) and control mass. The analytic comparison shows that the TRD achieves greatly better damping performance than the DVA.

CIU triaxial tests are conducted on very pure kaolinite and illite clay powders using two different pore fluids to study differences in shear parameters. First, the two materials are characterized in-depth. Special attention was paid to sample preparation in order to generate high-quality samples. The evaluation of the test data reveals an increase in friction angle for both materials when using a 1M KCl solution as compared to demineralized water. Kaolinite shows a lower friction angle for the same pore fluid than illite. Future work will further investigate different salt concentrations and different salt types.

Floating offshore wind turbines (FOWTs) enable renewable energy generation in deep ocean locations and provide economic and ecological benefits. However, reliable anchoring remains challenging due to a limited understanding of seabed-anchor interactions. This study examines the extent to which drag embedment anchor (DEA) models can be simplified without impacting penetration depth results in CEL simulations. Five DEA models with varying complexity were tested in typical Baltic Sea soils, sand and clay, modeled within a hypoplastic and visco-hypoplastic framework. Results suggest that the most simplified model is sufficient for sand. However, precaution should be taken when altering the anchor model in a clay environment due to the nonlinear relationship between model complexity and performance. This study offers insights into optimizing model complexity and computational efficiency in DEA simulations, ultimately improving safety and effectiveness for floating anchor installations.

Geotechnical constructions often fail due to a localized shear failure. Shear zones are formed in the soil as a result of external loads. To increase the load bearing capacity of geotechnical constructions and to prevent a critical failure mechanism, it is possible to only strengthen the potential shear bands by injecting cement in the beginning of the potential shear bands. This local strengthening makes it possible to increase the load bearing capacity of constructions with a minimum use of material. The soil strengthening is numerically modelled for a strip foundation using FEM and implementing different strengthening criteria within a hypoplastic soil model which considers material transition from sand to strengthened soil. The necessity of realistic contact modelling is shown, and the results both with and without contact modelling are shown. The numerical results show a significant increase in the load bearing capacity compared to the results without shear band strengthening.

Given the context of climate change, it is imperative to adapt the majority of existing flood defence systems using sustainable methods. Multi-objective evolutionary algorithms, like NSGA-II, offer a valuable decision support tool for exploring different designs based on predefined objectives. This paper specifically examines the application of the NSGA-II optimization algorithm in geotechnical problems by integrating it with FEM simulations, where slope horizontal runs are considered as variables. Throughout the study, different sets of termination criteria are employed to optimize the reduction of structural exploitation and the expected CO2 footprint.