Nonlinear behaviour of bottom plate in cylindrical liquid storage tanks for seismic applications

1995 ◽  
Vol 22 (1) ◽  
pp. 180-189 ◽  
Author(s):  
David T. Lau ◽  
Xianguang Zeng
Keyword(s):  
Bottom Plate ◽  
Response Analysis ◽  
Beam Model ◽  
Nonlinear Behaviour ◽  
Storage Tanks ◽  
One Dimensional ◽  
Nonlinear Springs ◽  
Liquid Storage ◽  
Cylindrical Tanks ◽  
Seismic Applications

The paper presents a simplified pseudostatic approach to model the nonlinear behaviour of the bottom plate in unanchored cylindrical liquid storage tanks for seismic applications. In this paper, the problem of axisymmetric uplift of the bottom plate is studied for tanks supported on both rigid and elastic Winkler foundations. In the analysis, the bottom plate is modelled by one-dimensional beam and two-dimensional plate models. By comparing the results, it is found that the one-dimensional beam model gives accurate results acceptable for all practical design purposes, in view of the many other uncertainties in the tank uplift problem. The analysis results also show that the support foundation flexibility may have significant effects on the uplift behaviour of the tanks. Based on the axisymmetric uplift results, the paper then presents a simple approach to model the seismic partial uplift problem of unanchored tanks by means of nonlinear springs. Modelling parameters for the nonlinear springs are generated for dynamic uplift response analysis. Sensitivities of the uplift behaviour and the nonlinear spring modelling parameters to the tank height-to-radius ratio and the soil stiffness are also studied. Key words: axisymmetric uplift, cylindrical tanks, earthquakes, pressure vessel, shell, soil effect.

Simplified Model for the Seismic Performance of Unanchored Liquid Storage Tanks

2015 ◽  
Author(s):  
Maria Vathi ◽  
Spyros A. Karamanos
Keyword(s):  
Bottom Plate ◽  
Storage Tanks ◽  
Mass System ◽  
Aspect Ratios ◽  
Liquid Storage ◽  
Stress And Deformation ◽  
Cylindrical Tanks ◽  
Welded Connection ◽  
Simplified Modeling ◽  
Different Levels

Ground-supported unanchored liquid-storage cylindrical tanks, when subjected to strong seismic loading may exhibit uplifting of their bottom plate, which has significant effects on their dynamic behavior and strength. Those effects mainly concern: (a) the increase of axial (meridional) compression at the tank base, resulting in premature buckling in the form of elephant’s foot and (b) the significant plastic deformation at the vicinity of the welded connection between the tank shell and the bottom plate that may cause failure of the welded connection due to fracture and fatigue. The present study focuses on base uplifting mechanics and tank performance with respect to the shell/plate welded connection through a numerical two-step methodology: (1) a detailed finite element shell model of the tank for incremental static analysis, capable of describing the state of stress and deformation at different levels of loading and (2) a simplified modeling of the tank as a spring-mass system for dynamic analysis, enhanced by a nonlinear spring at its base to account for the effects of uplifting. Two cylindrical liquid storage tanks of different aspect ratios are modeled and analyzed in terms of local performance of the welded connection. The results are aimed at better understanding of tank uplifting mechanics and motivating possible amendments in existing seismic design provisions.

The tapered beam model for bottom plate uplift analysis of unanchored cylindrical steel storage tanks

2009 ◽  
Vol 31 (3) ◽  
pp. 623-632 ◽  
Author(s):  
Masoud Nourali Ahari ◽  
Sassan Eshghi ◽  
Mohsen Ghafory Ashtiany
Keyword(s):  
Bottom Plate ◽  
Beam Model ◽  
Storage Tanks ◽  
Tapered Beam ◽  
Cylindrical Steel

Seismic response analysis of adjacent liquid-storage tanks

2016 ◽  
Vol 45 (11) ◽  
pp. 1779-1796 ◽  
Author(s):  
Konstantinos Mykoniou ◽  
Christoph Butenweg ◽  
Britta Holtschoppen ◽  
Sven Klinkel
Keyword(s):  
Seismic Response ◽  
Response Analysis ◽  
Storage Tanks ◽  
Seismic Response Analysis ◽  
Liquid Storage

Seismic Design of Cylindrical and Spherical Storage Tanks According to API and Eurocode: A Difficult Merge in Design Philosophies

2003 ◽  
Author(s):  
Ch. Botsis ◽  
G. Anagnostides ◽  
N. Kokavesis
Keyword(s):  
Seismic Design ◽  
Structural Design ◽  
Bottom Plate ◽  
Design Codes ◽  
The European Union ◽  
Storage Tanks ◽  
Member States ◽  
The World ◽  
Design Requirements ◽  
Cylindrical Tanks

Herein a comprehensive review and comparison of the parameters used in design of cylindrical tanks according to API 650 and Eurocodes is presented. API 650 is extensively used in many countries, including Greece, for the design of storage tanks. The European Community has developed a set of structural design codes named Eurocodes. They are the gathering and combination of existing design knowledge of many member states. Some of these codes are already mandatory in many member states, whereas others are still under discussion and improvement. The design of storage tanks is covered in the last editions of Eurocodes. It was found that the seismic design according to Eurocodes is more conservative that of API 650. As compared to API 650, the thickness of the first, second, and third courses of storage tanks needs to be increased by 15% or 20% on average, when the seismic design requirements of Eurocodes is used. Similarly the thickness of the bottom plate under the first course, must also be increased to comply with the seismic design requirements of Eurocodes. Most likely Eurocodes will be mandatory in the European Union, and therefore it is important to study and discuss the main differences between API 650 and Eurocodes. Undoubtedly API 650 is a historic and well-tested code. It has been applied in the design of storage tanks all over the world, however compliance with local and European laws is required to issue an installation license.

scholarly journals Assessment of an edge type settlement of above ground liquid storage tanks using a simple beam model

2007 ◽  
Vol 31 (11) ◽  
pp. 2461-2474 ◽  
Author(s):  
M.N. Hamdan ◽  
Osama Abuzeid ◽  
Ahmed Al-Salaymeh
Keyword(s):  
Beam Model ◽  
Storage Tanks ◽  
Edge Type ◽  
Liquid Storage ◽  
Type Settlement

Generation and Use of Simplified Uplift Shape Functions in Unanchored Cylindrical Tanks

1996 ◽  
Vol 118 (3) ◽  
pp. 278-286 ◽  
Author(s):  
D. T. Lau ◽  
X. Zeng
Keyword(s):  
Mathematical Model ◽  
Bottom Plate ◽  
Shape Functions ◽  
Liquid Storage ◽  
Tilt Condition ◽  
Liquid Storage Tank ◽  
Cylindrical Tanks ◽  
Relationship Of ◽  
The Relationship ◽  
Simplified Mathematical Model

This paper presents a simplified mathematical model for modeling the flexible bottom plate in an unanchored cylindrical liquid storage tank partially uplifted under the static tilt condition. In this model, the cylindrical tank is divided into substructures according to the deformation-resistant mechanisms involved. The modeling of each substructure is based on the Ritz formulation. Numerical results are presented and compared with reported experimental measurements. The results show that the simplified mathematical model is efficient. Practical and accurate results can be obtained using the model leading to a better understanding of the uplift mechanism. The relationship of the uplift behavior with the static tilt angle is also presented and discussed.

The Formulations of Shear Force and Overturning Moment of the Large-Upright-Unanchored Industrial Liquid Storage Tanks Subjected to Horizontal Ground Excitations

2005 ◽  
Author(s):  
Mutlu Ozer
Keyword(s):  
Shear Force ◽  
Excitation Frequency ◽  
Response Analysis ◽  
Tank Wall ◽  
Storage Tanks ◽  
Base Shear ◽  
Ground Acceleration ◽  
Dynamic Coefficients ◽  
Liquid Storage ◽  
Overturning Moment

The dynamic response analysis is performed for the formulations of shear force and overturning moment of the large-upright-unanchored industrial liquid storage tanks subjected to horizontal ground acceleration. As the tank is accelerated in the horizontal direction, it tends to uplift from its foundation, and hydrodynamic pressures on the tank wall vary with height in non-linear fashion. In this study, the distribution of hydrodynamic pressures and its center are directly correlated to formulate shear force and overturning moment. Initially, the equations of shear force and overturning moment derived by assuming hydrodynamic pressures exerted on tank wall vary in parabolic trend. Then derived equations are multiplied by dynamic coefficients, which are basically the function of peak ground acceleration, excitation frequency and the ratio of liquid’s height to radius of tanks. Dynamic coefficients are formulated through the shake table experiment of the model tanks excited by computer generated ground motion. The equations proposed in this paper for base shear and overturning moment are only the function of total weight of tank, the ratio of liquid’s height to radius, specific weight of liquid and dynamic coefficients for shear force and overturning moment. Therefore, proposed equations are very simple, efficient and easy to perform in calculating of shear forces and overturning moments of the large-upright industrial liquid storage tanks subjected to lateral earthquake loads. The results are verified with different codes (e.g. Eurocode8, API and AWWA-100...).

Sign in / Sign up

Export Citation Format

Share Document