Seismic design forces for cylindrical tanks on ground

1985 ◽  
Vol 12 (1) ◽  
pp. 12-23
Author(s):  
W. K. Tso ◽  
A. Ghobarah ◽  
S. K. Yee
Keyword(s):  
Radius Ratio ◽  
Hydrodynamic Effect ◽  
Tank Wall ◽  
Base Shear ◽  
Ground Acceleration ◽  
Liquid Storage ◽  
Wall Flexibility ◽  
Flexibility Effect ◽  
Predicted Values ◽  
Cylindrical Tanks

A study is made on the hydrodynamic effect caused by seismic ground motions on the design of cylindrical on-ground liquid-storage tanks. The current techniques for determining the design base shear and overturning moment of the tank are reviewed, first treating the tank wall as rigid and then including the wall flexibility effect. By means of examples, these calculations are compared with those suggested by the National Building Code of Canada (NBCC). In addition, theoretically predicted values are compared with experimental data.It was found that in the case of tanks of high height to radius ratio and small wall thickness to radius ratio, the interaction of the fluid and wall flexibility can cause responses as high as two to three times those calculated based on rigid tank wall assumptions. The range of tank geometries under which the tank can be considered rigid is given. It is shown that the NBCC formula to establish seismic loads for tanks on ground is in general conservative, provided the acceleration ratio in the NBCC formulae takes on the value of maximum peak ground acceleration of the site. Key words: seismic, earthquake, hydrodynamic force, response, cylindrical tanks, design code.

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...).

scholarly journals Seismic Response of Ground Cylindrical and Elevated Conical Reinforced Concrete Tanks

2021 ◽  
Author(s):  
Mehdi Moslemi
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Cone Angle ◽  
Tank Wall ◽  
Frequency Content ◽  
Ground Acceleration ◽  
Earthquake Frequency ◽  
Wall Flexibility ◽  
Elevated Tanks ◽  
Vertical Ground

In this study, the seismic performance of concrete ground-supported cylindrical as well as liquid-filled elevated water tanks supported on concrete shaft is evaluated using the finite element method. The effects of a wide spectrum of parameters such as liquid sloshing, tank wall flexibility, vertical ground acceleration, tank aspect ratio, base fixity, and earthquake frequency content on dynamic behaviour of such structures are examined. Furthermore, the adequacy of current practice in seismic analysis and design of liquid containing structures is investigated. A comprehensive parametric study covering a wide range of tank capacities and aspect ratios found in practice today is also carried out on elevated tanks. Two different innovative strategies to reduce the seismic response of elevated tanks are examined, in the first strategy the inclined cone angle of the lower portion of the vessel is increased while in the second strategy the supporting shaft structure is isolated either from the ground or the vessel mounted on top. The results of this study show that capability of the proposed finite element technique. Using this method, the major aspects in the fluid-structure interaction problems including wall flexibility, sloshing motion, damping properties of fluid domain, and the individual effects of impulsive and convective terms can be considered. The effects of tank wall flexibility, vertical ground acceleration, base fixity, and earthquake frequency content are found to be significant on the dynamic behaviour of liquid tanks. The parametric study indicates that the results can be utilized with high level of accuracy in seismic design applications for conical elevated tanks. This study further shows that increasing the cone angle of the vessel can result in a significant reduction in seismically induced forces of the tank, leading to an economical design of the shaft structure and the foundation system. It is also concluded that the application of passive control devices to conical elevated tanks offers a substantial benefit for the earthquake-resistant design of such structures.

scholarly journals Seismic Response of Ground Cylindrical and Elevated Conical Reinforced Concrete Tanks

2021 ◽  
Author(s):  
Mehdi Moslemi
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Cone Angle ◽  
Tank Wall ◽  
Frequency Content ◽  
Ground Acceleration ◽  
Earthquake Frequency ◽  
Wall Flexibility ◽  
Elevated Tanks ◽  
Vertical Ground

In this study, the seismic performance of concrete ground-supported cylindrical as well as liquid-filled elevated water tanks supported on concrete shaft is evaluated using the finite element method. The effects of a wide spectrum of parameters such as liquid sloshing, tank wall flexibility, vertical ground acceleration, tank aspect ratio, base fixity, and earthquake frequency content on dynamic behaviour of such structures are examined. Furthermore, the adequacy of current practice in seismic analysis and design of liquid containing structures is investigated. A comprehensive parametric study covering a wide range of tank capacities and aspect ratios found in practice today is also carried out on elevated tanks. Two different innovative strategies to reduce the seismic response of elevated tanks are examined, in the first strategy the inclined cone angle of the lower portion of the vessel is increased while in the second strategy the supporting shaft structure is isolated either from the ground or the vessel mounted on top. The results of this study show that capability of the proposed finite element technique. Using this method, the major aspects in the fluid-structure interaction problems including wall flexibility, sloshing motion, damping properties of fluid domain, and the individual effects of impulsive and convective terms can be considered. The effects of tank wall flexibility, vertical ground acceleration, base fixity, and earthquake frequency content are found to be significant on the dynamic behaviour of liquid tanks. The parametric study indicates that the results can be utilized with high level of accuracy in seismic design applications for conical elevated tanks. This study further shows that increasing the cone angle of the vessel can result in a significant reduction in seismically induced forces of the tank, leading to an economical design of the shaft structure and the foundation system. It is also concluded that the application of passive control devices to conical elevated tanks offers a substantial benefit for the earthquake-resistant design of such structures.

Seismic response of concrete rectangular tanks for liquid containing structures

2005 ◽  
Vol 32 (4) ◽  
pp. 739-752 ◽  
Author(s):  
J Z Chen ◽  
M R Kianoush
Keyword(s):  
Time History ◽  
Hydrodynamic Pressure ◽  
Rigid Wall ◽  
Tank Wall ◽  
Base Shear ◽  
Lumped Mass ◽  
Sequential Method ◽  
Wall Flexibility ◽  
Current Design ◽  
Impulsive Response

In this paper, a procedure for computing hydrodynamic pressures in rectangular tanks is proposed. The procedure, which is referred to as the sequential method, considers the effect of the flexibility of the tank wall in determining the hydrodynamic pressures. In this study, only the impulsive response of the tank is considered. Based on a two-dimensional model of the tank wall, dynamic time-history analysis is carried out to study the effect of wall flexibility on the response. In the analysis, both a tall tank and a shallow tank are considered. The results of analysis are compared with those obtained based on current design practice codes and standards. The well-known Housner's model, which assumes that the mass of liquid is lumped on the wall based on rigid wall boundary condition in the calculation of hydrodynamic pressure, is widely used in practice. A comparison shows that in most cases, the lumped mass approach overestimates the base shear. The effect of wall flexibility on wall displacements, base shears, and moments are also discussed.Key words: reinforced concrete, liquid containing, rectangular tank, seismic, dynamic analysis, tank flexibility.

Dynamic Analysis of Liquid Storage Cylindrical Tanks due to Earthquake

2014 ◽  
Vol 969 ◽  
pp. 119-124 ◽  
Author(s):  
Kamila Kotrasova ◽  
Ivan Grajciar
Keyword(s):  
Dynamic Analysis ◽  
Seismic Response ◽  
Seismic Design ◽  
Response Spectrum ◽  
Theoretical Background ◽  
Earthquake Activity ◽  
Liquid Storage ◽  
Cylindrical Tanks

Ground-supported tanks are used to store a variety of liquids. This paper provides theoretical background of seismic design of liquid storage ground-supported circular tanks. During earthquake activity the liquid exerts impulsive and convective (sloshing) actions on the walls and bottom of the circular tank. Seismic response was calculated by using the seismic response spectrum. Knowledge of these inner forces is important for design of reservoirs.

The effects of input earthquake characteristics on the nonlinear dynamic behavior of FPS isolated liquid storage tanks

2016 ◽  
Vol 24 (7) ◽  
pp. 1264-1282 ◽  
Author(s):  
Saman Bagheri ◽  
Mostafa Farajian
Keyword(s):  
Passive Control ◽  
Base Isolation ◽  
Ground Motions ◽  
Storage Tanks ◽  
Ground Acceleration ◽  
Pendulum System ◽  
Aspect Ratios ◽  
Liquid Storage ◽  
Isolation Systems ◽  
Friction Pendulum

There are several methods to reduce the seismic damages in liquid storage tanks. One of these methods is to use passive control devices, in particular seismic base isolators. Among the different base isolation systems, the Friction Pendulum System (FPS) whose period does not depend on the weight of the system is more appropriate for isolation of liquid storage tanks. The aim of this paper is to investigate the effects of peak ground acceleration (PGA) and pulselike characteristics of earthquakes on the seismic behavior of steel liquid storage tanks base isolated by FPS bearings. In addition, impact effects of the slider with the side retainer are investigated, as well as effects of tank aspect ratio, isolation period and friction coefficient. The obtained results of tanks with different aspect ratios indicate that the responses get more reduced due to isolation under far-field ground motions compared to near-fault ground motions. It is also seen that the response of a base isolated tank is affected when contact takes place with the side retainer of the FPS.

Generalized SDOF system for dynamic analysis of concrete rectangular liquid storage tanks: effect of tank parameters on response

2010 ◽  
Vol 37 (2) ◽  
pp. 262-272 ◽  
Author(s):  
J. Z. Chen ◽  
M. R. Kianoush
Keyword(s):  
Dynamic Response ◽  
Natural Frequencies ◽  
Hydrodynamic Pressure ◽  
Characteristic Parameter ◽  
Added Mass ◽  
Tank Wall ◽  
Storage Tanks ◽  
Effective Height ◽  
Sdof System ◽  
Liquid Storage

This paper presents the results of parametric studies on the seismic response of concrete rectangular liquid storage tanks using the generalized single-degree-of-freedom (SDOF) system. The effects of height of liquid and width of tank on the dynamic response of liquid storage tanks are investigated. The liquid level varies from the empty condition to a full tank. Also, instead of the commonly used ratio of width of tank to liquid height, Lx/HL, the ratio of width of tank to full height of the tank wall, Lx/Hw, is used as a characteristic parameter of tanks to study the effect of tank size on the dynamic response. The trends of added mass of liquid, effective height, and natural frequencies for different sizes of tanks are established. The values of the added mass of liquid due to impulsive hydrodynamic pressure and the effective height in the relationship with the ratios Lx/Hw and HL/Hw are determined and can be used in the seismic design of liquid storage tanks. Since the natural frequencies of liquid-containing structures are within a band of frequencies between that of a full tank and that of an empty tank, the recommended frequency to be used in the design of the tank wall is the frequency that causes the maximum dynamic response .

Probabilistic Estimates of Maximum Seismic Horizontal Ground Acceleration on Rock in Alaska and the Adjacent Continental Shelf

1985 ◽  
Vol 1 (2) ◽  
pp. 285-306 ◽  
Author(s):  
Paul C. Thenhaus ◽  
Joseph I. Ziony ◽  
William H. Diment ◽  
Margaret G. Hopper ◽  
David M. Perkins ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Return Period ◽  
Chukchi Sea ◽  
Poisson Model ◽  
Seismic Source ◽  
Gulf Of Alaska ◽  
Historical Record ◽  
Peak Acceleration ◽  
Ground Acceleration ◽  
Predicted Values

Estimates of ground motion hazard from earthquakes in Alaska and the adjacent continental shelf indicate that, for all the exposure times considered, the predicted values of peak acceleration are highest in the Gulf of Alaska and near the major active strike-slip faults of southern Alaska. The evaluations assume a Poisson model of earthquake occurrence and are based on seismic source zones delineated from regional geologic considerations and the historical record of earthquakes. Calculated peak acceleration values for a return period of 100 years range as high as 0.4 g in the Gulf of Alaska sector between Kodiak and Kayak Islands, are about 0.2 g near Anchorage, and 0.1 g near Fairbanks. Values for most of the rest of the state are estimated to be less than .04 g; however, most of the southern Alaska industrial and population base lies within the 0.2 g contour. For a return period of 500 years, peak accelerations are estimated as high as 0.8 g for parts of southeastern Alaska near the Fairweather fault, 0.6 g or greater for part of the Gulf of Alaska, and are about 0.45 g and 0.2 g, respectively, for the Anchorage and Fairbanks areas. Values of acceleration for a return period of 2,500 years exceed 0.6 g for much of southern Alaska and are 0.8 g or greater near the Fairweather and central Denali faults; estimated values are 0.1 g or greater for nearly all of onshore Alaska and for the continental shelf areas of the Bering Sea, Norton and Kotzebue Sounds, southern Chukchi Sea and southeastern Beaufort Sea.

Combined seismic base shear and torsional loading provisions in the 1990 edition of the National Building Code of Canada

1991 ◽  
Vol 18 (6) ◽  
pp. 945-953
Author(s):  
A. M. Chandler
Keyword(s):  
Ground Motions ◽  
Building Code ◽  
Soil Conditions ◽  
Building Structures ◽  
Base Shear ◽  
Ground Acceleration ◽  
Period Range ◽  
Natural Period ◽  
Short Period ◽  
Edge Response

This paper evaluates the earthquake-resistant design provisions of the 1990 edition of the National Building Code of Canada (NBCC 1990) for asymmetric building structures subjected to combined lateral shear and torsional dynamic loadings arising from earthquake base excitation. A detailed parametric study is presented, evaluating the dynamic edge displacement response in the elastic range, for the side of the building which is adversely affected by lateral–torsional coupling. A series of buildings is studied, with realistic ranges of the fundamental natural period, structural eccentricity, and uncoupled frequency ratio. These buildings are evaluated under base loadings arising from a total of 45 strong motion records taken from earthquakes in North America, Mexico, Europe, the Middle East, and Southern Pacific, categorized according to site soil conditions and the ratio a/v of peak ground acceleration to velocity. The latter parameter together with the uncoupled lateral period are found to influence strongly the combined dynamic edge response, with the greatest forces on edge members arising from earthquakes with high a/v ratio in structures with natural periods below 0.8 s. In this case the NBCC 1990 loading provisions significantly underestimate the elastic dynamic response. For buildings with periods longer than 0.8 s, the conservatism of the base shear provisions leads to overestimation of combined dynamic edge response in asymmetric systems, and this is also true in the short-period range for buildings subjected to ground motions with low a/v ratio. The NBCC 1990 provisions are reasonably conservative for short-period systems subjected to ground motions with intermediate a/v ratio. Key words: earthquakes, seismic, design, response, spectra, base, shear, torsional, provisions.

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