Dynamic analysis of multiple liquid-storage tanks

• Dynamische Analyse multipler flüssigkeitsgefüllter Tankbauwerke

Mykoniou, Konstantinos; Klinkel, Sven (Thesis advisor); Könke, Carsten (Thesis advisor)

Aachen : Lehrstuhl für Baustatik und Baudynamik (2015, 2016)
Book, Dissertation / PhD Thesis

In: Schriftenreihe des Lehrstuhls für Baustatik und Baudynamik der RWTH Aachen 2015,04
Page(s)/Article-Nr.: XVI, 164 S. : Ill., graph. Darst.

Zugl.: Aachen, Techn. Hochsch., Diss., 2014

Abstract

The seismic analysis of liquid-storage tanks proceeds ordinarily on the basis of neglecting the dynamic interaction with adjacent tanks, although they are frequently arranged next to each other, for instance in tank farms. In this work, a study on the dynamic behavior of tanks is therefore carried out, which takes into account group interaction effects.To this aim, a refined substructure technique in the frequency domain is developed, which permits consideration of the interaction effects among adjacent containers through the supporting deformable soil medium. The tank-liquid systems are represented by means of mechanical models, whereas discrete springs and dashpots stand for the soil beneath the foundations. The properties assigned to the models for the superstructures result from a semi-analytical method for the dynamic analysis of circular, cylindrical shells, which takes into account both coupled free surface-shell vibrations and liquid’s compressibility. The coefficients for the dynamic impedance functions of the foundations are obtained with the aid of a coupled FEM-BEM formulation, which incorporates the solution of a three-dimensional wave propagation problem for the soil medium into the surface foundations equation of motion.The proposed model is employed to assess the responses of adjacent tanks for harmonic and seismic excitations over wide range of tank proportions and soil conditions. The influence of the number, spatial arrangement of the containers and their distance on the overall system’s behavior is addressed. The results indicate that the cross-interaction effects can substantially alter the impulsive components of response of each individual element in a tank farm. The degree of this impact is primarily controlled by the tank proportions and the proximity of the predominant natural frequencies of the shell-liquid-soil systems and the input seismic motion. The group effects should not a priori disregarded, unless the tanks are founded on shallow soil deposit overlying very stiff material or bedrock.With a focus on issues concerning engineering practice, a simplified seismic design process is proposed for the determination of the hydrodynamic pressures exerted on liquid-storage tanks in fixed-base conditions. A guideline for preliminary evaluation of group effects for general, dynamic structure-soil-structure interaction problems is also provided.