Influence of Nonlinear Fluid Viscous Dampers on Seismic Response of RC Elevated Storage Tanks

The numerical investigation on the seismic response of RC elevated liquid storage tanks installed with viscous dampers is presented. A discrete two-mass model for the liquid and multi-degree of freedom system for staging, installed with the dampers are developed for Reinforced Concrete (RC) elevated liquid storage tanks. The elevated tank is assessed for seismic response reduction when provided with Linear Viscous Damper (LVD) and Nonlinear Viscous Damper (NLVD), installed in the staging. The RC elevated liquid storage tanks are analyzed for two levels of liquid containment in the tank, 100% and 25% of the tank capacity. Three Configurations of placements of dampers viz. dampers at alternate levels (Configuration I and Configuration II) and dampers at all the panels of the staging of the tank (Configuration III) are considered. To study the effect of peak ground acceleration, eight real earthquake time histories with accelerations varying from 0.1 g to 0.93 g are considered. The nonlinearity in the viscous damper is modified by taking force proportional to various velocity exponents. It is found that the nonlinear viscous dampers with lower damping constant result in a comparable reduction in the response of RC elevated liquid storage tank, to that of linear viscous dampers with higher damping constant. A lower damping constant signifies compact the size of the damper. Doi: 10.28991/cej-2020-SP(EMCE)-09 Full Text: PD

Localized Vibrations of Bi Bilayer Leading to Ultralow Lattice Thermal Conductivity and High Thermoelectric Performance in Weak Topological Insulator <i>n-</i>Type BiSe

Realization of high thermoelectric performance in <i>n</i>-type semiconductors is of imperative need on account of the dearth of efficient <i>n</i>-type thermoelectric materials compared to the <i>p</i>-type counterpart. Moreover, development of efficient thermoelectric materials based on Te-free compounds is desirable because of the scarcity of Te in the Earth’s crust. Herein, we report the intrinsic ultralow thermal conductivity and high thermoelectric performance near room temperature in <i>n-</i>type BiSe, a Te-free solid, which recently has emerged as a weak topological insulator. BiSe possesses a layered structure consisting of a bismuth bilayer (Bi₂) sandwiched between two Bi₂Se₃ quintuple layers [Se–Bi–Se–Bi-Se], resembling natural heterostructure. High thermoelectric performance of BiSe is realized through the ultralow lattice thermal conductivity (κ_lat of ∼0.6 W/mK at 300 K), which is significantly lower than that of Bi₂Se₃ (κ_lat of ∼1.8 W/mK at 300 K), although both of them belong to the same layered homologous family (Bi₂)_<i>m</i>(Bi₂Se₃)_<i>n</i>. Phonon dispersion calculated from first-principles and the experimental low-temperature specific heat data indicate that soft localized vibrations of bismuth bilayer in BiSe are responsible for its ultralow κ_lat. These low energy optical phonon branches couple strongly with the heat carrying acoustic phonons, and consequently suppress the phonon mean free path leading to low κ_lat. Further optimization of thermoelectric properties of BiSe through Sb substitution and spark plasma sintering (SPS) results in high ZT ∼ 0.8 at 425 K along the pressing direction, which is indeed remarkable among Te-free <i>n-</i>type thermoelectric materials near room temperature