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

Advancements in Design, Analysis, and Retrofitting of Structures Exposed to Blast

The objective of this special issue is to provide an overview on the current trends and recent advancements in terms of design, analysis, experimental testing, and retrofitting of structural systems and assemblies exposed to exceptional loads such as explosions

Understanding the response of reinforced concrete slabs due to contact explosion of TNT

Evaluating response of reinforced concrete (RC) structures to blast loads is now a matured field of research. The United Facilities Criteria (UFC) 3-340 design manual and similar other manuals lay out the design practice for blast resistant structures. However, most of the design methodologies are restricted to far-field (scaled distance > 1.18 m/kg 1/3 ) blast loading. The semi-empirical charts and equations presented in design manuals for far-field blast loading are not accurate in the near-field events and furthermore very little research is available on contact explosions. Contact explosions are more complex than the far-field explosion effects due to the spatially and temporally non-uniform overpressure. There are limited experimental studies available in the literature as many gauges do not survive the harsh near-field environment. Thus, most finite element models in the near-field events are validated based on post blast damage photos. This paper presents the results from field tests conducted on RC slabs with embedded piezo-electric based concrete vibration sensors (CVS). A correlation has been shown between the concrete strains and the voltage recorded by the sensors. These results have further been compared to the numerical results obtained from LS-DYNA. The contact explosion was modeled using the arbitrary-Lagrangian-Eulerian (ALE) element formulation. The study shows that contact explosion can be reliably modeled using the presented parameters. The readings obtained from CVS could capture the shock wave propagation and the strain time history in the slab at required locations