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.

scholarly journals Dynamic time-history response of concrete rectangular liquid storage tanks

2021 ◽  
Author(s):  
Amirreza Ghaemmaghami
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Vertical Acceleration ◽  
Surface Boundary ◽  
Frequency Content ◽  
Seismic Behaviour ◽  
Structure Interaction ◽  
Earthquake Frequency ◽  
Wall Flexibility ◽  
Tank System

In this study, the finite element method is used to investigate the seismic behaviour of concrete, open top rectangular liquid tanks in two and three-dimensional spaces. This method is capable of considering both impulsive and convective responses of liquid-tank system. The sloshing behaviour is simulated using linear free surface boundary conditions. Two different finite element models corresponding with shallow and tall tank configurations are studied under the effects of all components of earthquake record. The effect of earthquake frequency content on the seismic behaviour of fluid-rectangular tank system is investigated using four different seismic motions including Northridge, El-Centro, San-Fernando and San-Francisco earthquake records. These records are scaled in such a way that all horizontal peak ground accelerations are similar. Fluid-structure interaction effects on the dynamic response of fluid containers are taken into account incorporating wall flexibility. A simple model with viscous boundary is used to include deformable foundation effects as a linear medium. Six different soil types are considered. In addition the application of slat screens and baffles in reducing the sloshing height of liquid tank is investigated by carrying out a parametric study. The results show that the wall flexibility, fluid damping properties, earthquake frequency content and soil-structure interaction have a major effect on seismic behaviour of liquid tanks and should be considered in design criteria of tanks. The effect of vertical acceleration on the dynamic response of the liquid tanks is found to be less significant when horizontal and vertical ground motions are considered together. The results in this study are verified and compared with those obtained by numerical methods and other available methods in the literature.

scholarly journals Dynamic time-history response of concrete rectangular liquid storage tanks

2021 ◽  
Author(s):  
Amirreza Ghaemmaghami
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Vertical Acceleration ◽  
Surface Boundary ◽  
Frequency Content ◽  
Seismic Behaviour ◽  
Structure Interaction ◽  
Earthquake Frequency ◽  
Wall Flexibility ◽  
Tank System

In this study, the finite element method is used to investigate the seismic behaviour of concrete, open top rectangular liquid tanks in two and three-dimensional spaces. This method is capable of considering both impulsive and convective responses of liquid-tank system. The sloshing behaviour is simulated using linear free surface boundary conditions. Two different finite element models corresponding with shallow and tall tank configurations are studied under the effects of all components of earthquake record. The effect of earthquake frequency content on the seismic behaviour of fluid-rectangular tank system is investigated using four different seismic motions including Northridge, El-Centro, San-Fernando and San-Francisco earthquake records. These records are scaled in such a way that all horizontal peak ground accelerations are similar. Fluid-structure interaction effects on the dynamic response of fluid containers are taken into account incorporating wall flexibility. A simple model with viscous boundary is used to include deformable foundation effects as a linear medium. Six different soil types are considered. In addition the application of slat screens and baffles in reducing the sloshing height of liquid tank is investigated by carrying out a parametric study. The results show that the wall flexibility, fluid damping properties, earthquake frequency content and soil-structure interaction have a major effect on seismic behaviour of liquid tanks and should be considered in design criteria of tanks. The effect of vertical acceleration on the dynamic response of the liquid tanks is found to be less significant when horizontal and vertical ground motions are considered together. The results in this study are verified and compared with those obtained by numerical methods and other available methods in the literature.

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.

scholarly journals Nonlinear seismic response of ground supported cylindrical reinforced concrete tanks

2021 ◽  
Author(s):  
Maryam Rafieeraad
Keyword(s):  
Seismic Behavior ◽  
Time History ◽  
Material Nonlinearity ◽  
Ground Acceleration ◽  
Response Modification Factor ◽  
R Factor ◽  
Earthquake Frequency ◽  
Modification Factor ◽  
Vertical Ground ◽  
Strength And Ductility

Seismic behavior of Liquid Containing Structures has been studied for decades. Being able to have these structures functioning during and after an earthquake is imperative for well-being of a society hence importance of their design. Response Modification Factor known as “R factor” is one of the key parameters in seismic design. However, in case of LCS’s, a justifiable guideline to determine the R factor is yet to be developed and current codes have utilized empirical values in design of these structures. The design intend for LCS’s is to meet the serviceability limits as opposed to life safety and collapse prevention which is the case of design of buildings. This study aims to investigate the effect of various parameters such as material nonlinearity, tank dimensions, base condition, concrete compressive strength, characteristics of seismic excitation records on the seismic behavior of concrete tanks. In this study, a finite element method is developed to investigate the seismic behavior of circular ground supported reinforced concrete tanks. First, the accuracy of current practice is investigated by employing the analytical and numerical methods, experimental studies. Finite element technique and pushover analysis are utilized to set up the pushover curve and achieve over-strength and ductility factors. The response modification factor (R) is then evaluated based on the nonlinear static analysis. Second, using the nonlinear dynamic analysis (time-history), the seismic behavioral aspects of full liquid tanks are studied taking into account the material nonlinearity, wall flexibility, effect of impulsive component, fluid-surface interaction and vertical ground acceleration. Thereafter, a parametric study is conducted to study the influence of tank dimensions, base fixity conditions and earthquake frequency content on the response modification factor. This study shows the over-strength and ductility factor of RC ground-supported tanks are significantly influence by tank size, height, height/diameter ratio and fundamental period. Also, fixed based tanks and shallow tanks have higher R values compared to hinged based and tall tanks respectively. The time history results show that the effect of material nonlinearity, vertical ground acceleration, base condition and earthquake frequency content on the dynamic behavior of liquid ground supported tanks is significant.

scholarly journals Nonlinear seismic response of ground supported cylindrical reinforced concrete tanks

2021 ◽  
Author(s):  
Maryam Rafieeraad
Keyword(s):  
Seismic Behavior ◽  
Time History ◽  
Material Nonlinearity ◽  
Ground Acceleration ◽  
Response Modification Factor ◽  
R Factor ◽  
Earthquake Frequency ◽  
Modification Factor ◽  
Vertical Ground ◽  
Strength And Ductility

Seismic behavior of Liquid Containing Structures has been studied for decades. Being able to have these structures functioning during and after an earthquake is imperative for well-being of a society hence importance of their design. Response Modification Factor known as “R factor” is one of the key parameters in seismic design. However, in case of LCS’s, a justifiable guideline to determine the R factor is yet to be developed and current codes have utilized empirical values in design of these structures. The design intend for LCS’s is to meet the serviceability limits as opposed to life safety and collapse prevention which is the case of design of buildings. This study aims to investigate the effect of various parameters such as material nonlinearity, tank dimensions, base condition, concrete compressive strength, characteristics of seismic excitation records on the seismic behavior of concrete tanks. In this study, a finite element method is developed to investigate the seismic behavior of circular ground supported reinforced concrete tanks. First, the accuracy of current practice is investigated by employing the analytical and numerical methods, experimental studies. Finite element technique and pushover analysis are utilized to set up the pushover curve and achieve over-strength and ductility factors. The response modification factor (R) is then evaluated based on the nonlinear static analysis. Second, using the nonlinear dynamic analysis (time-history), the seismic behavioral aspects of full liquid tanks are studied taking into account the material nonlinearity, wall flexibility, effect of impulsive component, fluid-surface interaction and vertical ground acceleration. Thereafter, a parametric study is conducted to study the influence of tank dimensions, base fixity conditions and earthquake frequency content on the response modification factor. This study shows the over-strength and ductility factor of RC ground-supported tanks are significantly influence by tank size, height, height/diameter ratio and fundamental period. Also, fixed based tanks and shallow tanks have higher R values compared to hinged based and tall tanks respectively. The time history results show that the effect of material nonlinearity, vertical ground acceleration, base condition and earthquake frequency content on the dynamic behavior of liquid ground supported tanks is significant.

Representation of bolted joints in a structure using finite element modelling and model updating

2020 ◽  
Vol 14 (3) ◽  
pp. 7141-7151 ◽  
Author(s):  
R. Omar ◽  
M. N. Abdul Rani ◽  
M. A. Yunus
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Model Updating ◽  
Complex Structure ◽  
Bolted Joints ◽  
Model Parameters ◽  
Fe Model ◽  
Bolted Joint ◽  
Fe Modelling ◽  
Joint Structure

Efficient and accurate finite element (FE) modelling of bolted joints is essential for increasing confidence in the investigation of structural vibrations. However, modelling of bolted joints for the investigation is often found to be very challenging. This paper proposes an appropriate FE representation of bolted joints for the prediction of the dynamic behaviour of a bolted joint structure. Two different FE models of the bolted joint structure with two different FE element connectors, which are CBEAM and CBUSH, representing the bolted joints are developed. Modal updating is used to correlate the two FE models with the experimental model. The dynamic behaviour of the two FE models is compared with experimental modal analysis to evaluate and determine the most appropriate FE model of the bolted joint structure. The comparison reveals that the CBUSH element connectors based FE model has a greater capability in representing the bolted joints with 86 percent accuracy and greater efficiency in updating the model parameters. The proposed modelling technique will be useful in the modelling of a complex structure with a large number of bolted joints.

Bond Thickness Effects upon Dynamic Behaviour in Adhesive Joints

2010 ◽  
Vol 97-101 ◽  
pp. 3920-3923 ◽  
Author(s):  
Xiao Cong He
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Dynamic Behaviour ◽  
Adhesive Layer ◽  
Adhesive Joints ◽  
Response Functions ◽  
Frequency Range ◽  
Element Analysis ◽  
Cantilevered Beam ◽  
Different Thickness

The influence of adhesive layer thickness on the dynamic behaviour of the single-lap adhesive joints is investigated in this paper. The ABAQUS finite element analysis (FEA) software was used to predict the frequency response functions (FRFs) of the single-lap adhesive joints of different thickness of the adhesive layer. As a reference, the FRFs of a cantilevered beam without joint were investigated as well. It is clear that the FRFs of the four beams are close to each other within the frequency range 0~1000 Hz. It is also found that the composite damping of the single-lap adhesive joint increases as the thickness of the adhesive layer increases.

Nonlinear dynamic behaviour of guy cables in turbulent winds

2001 ◽  
Vol 28 (1) ◽  
pp. 98-110 ◽  
Author(s):  
Bruce F Sparling ◽  
Alan G Davenport
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Aerodynamic Drag ◽  
Numerical Study ◽  
Horizontal Displacement ◽  
Wind Loading ◽  
Second Phase ◽  
Nonlinear Coupling ◽  
Wide Range ◽  
Cable Vibrations

Large amplitude cable vibrations are difficult to predict using linear theory due to the presence of sag in the suspended profile. A numerical study was therefore undertaken to investigate the dynamic behaviour of inclined cables excited by imposed displacements. To model the nonlinear nature of cable response, a time domain finite element approach was adopted using nonlinear catenary cable elements. Two types of horizontal displacement patterns were enforced at the upper end of the guy. In the first phase of the study, harmonic displacement histories with a wide range of forcing frequencies were considered. In the second phase, random enforced displacements were used to simulate the motion of a guyed mast in gusty winds. The influence of aerodynamic drag and damping forces was investigated by performing analyses under still air, steady wind, and turbulent wind conditions. It was found that nonlinear coupling of related harmonic response components was significant at certain critical frequencies, particular when the excitation was harmonic and acted in the plane of the guy. Positive aerodynamic damping was shown to effectively suppress resonant and nonlinear coupling response.Key words: cables, structural dynamics, wind loading, finite element method, nonlinear analysis, guyed towers.

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