This paper presents the results of an experimental study of the seismic response of buildings with supplemental fluid damping devices. These devices operate on the principle of fluid flow through orifices specially shaped so as to produce damping forces proportional to the velocity, i.e. the devices operate as linear viscous dampers. The experimental results demonstrate that the addition of fluid dampers to the tested steel model structure resulted in reductions of interstory drifts, floor accelerations and story shear forces by factors of two to three in comparison with the response of the same structure without the dampers.

Experimental study of seismic response of buildings with supplemental fluid dampers

Dynamic analysis of wind turbines including soil-structure interaction

Structural control of wind turbines with soil structure interaction included

Damping of structures resting on flexible foundations is affected by soil-structure interaction in two ways: (1) the structure gains damping through energy dissipation in soil, and (2) the damping the structure would have on a rigid foundation is reduced. These effects are evaluated using two approaches: an energy consideration which is a simple but approximate approach, and the complex eigenvalue analysis which is mathematically accurate but uses damped, non-classical vibration modes. These two methods are compared and the accuracy of the more convenient energy approach is assessed. Examples of modal damping are given for rigid structures, buildings and towers.

Effect of soil-structure interaction on damping of structures

While various porous scaffolds have been developed, the focused study about which structure leads to better mechanics is rare. In this study, we designed porous scaffolds with tetragonal, hexagonal and wheel-like structures under a given porosity, and fabricated corresponding poly(lactic acid) (PLA) scaffolds with three-dimensional printing. High-resolution micro-computed tomography was carried out to calculate their experimental porosity and confirm their high interconnectivity. The theoretical and experimental compressive properties in the longitudinal direction were characterized by finite element analysis method and electromechanical universal testing system, respectively. Thereinto, the scaffold with the tetragonal structure exhibited higher mechanical strength both theoretically and experimentally. Creep and stress relaxation behaviors of the scaffolds revealed that the tetragonal scaffold had less significant viscoelasticity. Immersion dynamic mechanical analysis was performed to test their cycle-loading fatigue behaviors in the simulated body fluid at 37 °C; the tetragonal scaffold exhibited the latest fatigue beginning point at 4400 cycles, which indicated a better anti-fatigue performance; the hexagonal and wheel-like ones exhibited the middle and earliest fatigue beginning points at 3200 and 2500 cycles, respectively. What is more, cytocompatibility and histocompatibility of the scaffolds with all of the structures were confirmed by cell counting kit-8 assay in vitro and three-month subcutaneous implantation in rats in vivo. Hence, the key property difference of the three examined structures comes from their mechanics; the tetragonal structure exhibited better mechanics in the longitudinal direction examined in this study, which could be taken into consideration in design of a porous scaffold for tissue engineering and regeneration.

https://iopscience.iop.org/article/10.1088/1758-5090/ab0f59/pdf

L. El Hifnawy

Papers

Effect of soil-structure interaction on damping of structures

Response of hammer foundations to pulse loading

Vibration of hammer foundations

Damping of structures due to soil-structure interaction