Seismic Response of Base-Isolated Liquid Storage Tanks

2003 ◽  
Vol 9 (10) ◽  
pp. 1201-1218 ◽  
Author(s):  
M. K. Shrimali ◽  
R. S. Jangid
Keyword(s):  
Seismic Response ◽  
Deformation Behavior ◽  
Seismic Isolation ◽  
Storage Tanks ◽  
Base Shear ◽  
Step Method ◽  
Isolation System ◽  
System Parameters ◽  
Liquid Mass ◽  
Liquid Storage

We investigate the seismic response of liquid storage tanks isolated by lead-rubber bearings. The force-deformation behavior of the bearings is considered as bi-linear modeled by the Wen equation. The continuous liquid mass of the tank is modeled as a sloshing mass, impulsive mass and rigid mass. The corresponding stiffness associated with these masses has been worked out depending upon the properties of the tank wall and liquid mass. The governing equations of motion of the three-degrees-of-freedom model of the isolated liquid storage tank are derived. Since the force-deformation behavior of the bearings is non-linear, as a result, the seismic response is obtained using the Newmark step-by-step method under several recorded earthquake ground motions. The responses of two types of tanks, namely slender and broad, are compared with the corresponding response without an isolation system in order to investigate the effectiveness of the isolation system. A parametric study is also carried out to study the effects of important system parameters on the effectiveness of seismic isolation for liquid storage tanks. The various important parameters considered are the aspect ratio of the tank, period, damping and the yield strength of the isolation system. It has been observed that the seismic isolation of the tanks is quite effective and the response of isolated liquid storage tanks is significantly influenced by the above system parameters. There is an optimum value of isolation damping for which the base shear in the tank attains the minimum value. Therefore, increasing the bearing damping beyond a certain value decreases the bearing and sloshing displacements but it increases the base shear.

scholarly journals Response of Base-Isolated Liquid Storage Tanks

2004 ◽  
Vol 11 (1) ◽  
pp. 33-45 ◽  
Author(s):  
M.B. Jadhav ◽  
R.S. Jangid
Keyword(s):  
Seismic Response ◽  
Seismic Isolation ◽  
Equations Of Motion ◽  
Approximate Model ◽  
Storage Tanks ◽  
Step Method ◽  
Earthquake Excitation ◽  
System Parameters ◽  
Liquid Storage ◽  
Isolation Systems

Seismic response of liquid storage tanks isolated by elastomeric bearings and sliding system is investigated under real earthquake ground motions. The continuous liquid mass of the tank is modeled as lumped masses known as sloshing mass, impulsive mass and rigid mass. The coupled differential equations of motion of the system are derived and solved in the incremental form using Newmark's step-by-step method with iterations. The seismic response of isolated tank is studied to investigate the comparative effectiveness of various isolation systems. A parametric study is also carried out to study the effect of important system parameters on the effectiveness of seismic isolation for liquid storage tanks. The various important parameters considered are: (i) aspect ratio of the tank and (ii) the time period of the isolation systems. It was observed that both elastomeric and sliding systems are found to be effective in reducing the earthquake forces of the liquid storage tanks. However, the elastomeric bearing with lead core is found to perform better in comparison to other systems. Further, an approximate model is proposed for evaluation of seismic response of base-isolated liquid storage tanks. A comparison of the seismic response evaluated by the proposed approximate method and an exact approach is made under different isolation systems and system parameters. It was observed that the proposed approximate analysis provides satisfactory response estimates of the base-isolated liquid storage tanks under earthquake excitation.

Dynamic Analysis of Liquid Storage Tanks with Sliding Systems

2003 ◽  
Vol 6 (2) ◽  
pp. 145-158 ◽  
Author(s):  
M. K. Shrimali ◽  
R. S. Jangid
Keyword(s):  
Seismic Response ◽  
Frictional Force ◽  
Seismic Isolation ◽  
Earthquake Ground Motion ◽  
Hysteretic Model ◽  
Storage Tanks ◽  
Step Method ◽  
Conventional Model ◽  
Liquid Mass ◽  
Liquid Storage

Dynamic response of liquid storage tanks isolated by the sliding systems is investigated under real earthquake ground motion. The frictional force of sliding systems is modelled by conventional and hysteretic models. The continuous liquid mass is lumped as convective mass, impulsive mass and rigid mass. The corresponding stiffness associated with these lumped masses is worked out depending upon the properties of the tank wall and liquid mass. The governing equations of motion of the tank with sliding system are derived and solved by Newmark's step-by-step method with iterations. The frictional force mobilized at the interface of the sliding system is assumed to be velocity dependent. For comparative study, the seismic response of isolated liquid storage tank obtained by the conventional model is compared with the corresponding response obtained by the hysteretic model. In order to measure the effectiveness of isolation system, the seismic response of isolated tank is compared with that of the non-isolated tank. A parametric study is also conducted to study the effects of aspect ratio of tank on the effectiveness of seismic isolation of liquid storage tanks. It is found that the sliding systems are quite effective in reducing the earthquake response of liquid storage tanks. In addition, the conventional and the hysteretic model of the sliding system predict the same seismic response of liquid storage tanks. However, the conventional model is relatively more computationally efficient as compared to the hysteretic model.

Comparison between standards for seismic design of liquid storage tanks with respect to soil-foundation-structure interaction and uplift

2012 ◽  
Vol 45 (1) ◽  
pp. 40-46 ◽  
Author(s):  
Miguel Ormeño ◽  
Tam Larkin ◽  
Nawawi Chouw
Keyword(s):  
Seismic Response ◽  
Seismic Design ◽  
Earthquake Engineering ◽  
Storage Tanks ◽  
Base Shear ◽  
Structure Interaction ◽  
Liquid Storage ◽  
Field Evidence ◽  
Soil Foundation ◽  
Foundation Structure

Field evidence has established that strong earthquakes can cause severe damage or even collapse of liquid storage tanks. Many tanks worldwide are built near the coast on soft soils of marginal quality. Because of the difference in stiffness between the tank (rigid), foundation (rigid) and the soil (flexible), soil-foundation-structure interaction (SFSI) has an important effect on the seismic response, often causing an elongation of the period of the impulsive mode. This elongation is likely to produce a significant change in the seismic response of the tank and will affect the loading on the structure. An issue not well understood, in the case of unanchored tanks, is uplift of the tank base that usually occurs under anything more than moderate dynamic loading. This paper presents a comparison of the loads obtained using “Appendix E of API STANDARD 650” of the American Petroleum Institute and the “Seismic Design of Storage Tanks” produced by the New Zealand Society for Earthquake Engineering. The seismic response assessed using both codes is presented for a range of tanks incorporating a range of the most relevant parameters in design. The results obtained from the analyses showed that both standards provide similar base shear and overturning moment; however, the results given for the anchorage requirement and uplift are different.

scholarly journals The seismic response of elevated liquid storage tanks isolated by lead-rubber bearings

2003 ◽  
Vol 36 (3) ◽  
pp. 141-164 ◽  
Author(s):  
M.K. Shrimali ◽  
R.S. Jangid
Keyword(s):  
Seismic Response ◽  
Seismic Isolation ◽  
Degree Of Freedom ◽  
Earthquake Ground Motion ◽  
Storage Tanks ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Liquid Storage ◽  
Tower Structure ◽  
Lumped Masses

The seismic response of elevated liquid storage tanks isolated by the lead-rubber bearing is investigated under real earthquake ground motion. Two types of isolated tank models are considered in which the bearings are placed at the base and top of the tower structure. The tank liquid is modelled as lumped masses referred as convective mass, impulsive mass and rigid mass. The corresponding stiffness associated with these lumped masses has been worked out using the properties of the tank wall and liquid mass based on simple single-degree-of-freedom concepts. The mass of the tower structure is lumped equally at top and bottom. The assembled equations of motion are solved by Newmark's step-by-step method with iteration. The seismic response of two types of tanks, namely slender and broad tanks is obtained and a parametric study is carried out to study the effects of important system parameters on the effectiveness of seismic isolation. The various important parameters considered are the tank aspect ratio, the time period of the tower structure, damping and the lime period of the isolation system. It has been observed that the earthquake response of the isolated tank is reduced significantly. Further, it is observed that the isolation is more effective for the tank with a stiff tower structure in comparison to flexible towers. In addition, a simplified analysis is also presented to evaluate the response of the elevated tanks using a two-degrees-of-freedom model and two single degree-of-freedom models. It is observed that the proposed methods predict accurately the seismic response of elevated liquid storage tanks with less computational efforts.

A COMPARATIVE STUDY OF PERFORMANCE OF VARIOUS ISOLATION SYSTEMS FOR LIQUID STORAGE TANKS

2002 ◽  
Vol 02 (04) ◽  
pp. 573-591 ◽  
Author(s):  
M. K. SHRIMALI ◽  
R. S. JANGID
Keyword(s):  
Comparative Study ◽  
Seismic Isolation ◽  
Deformation Behaviour ◽  
Storage Tanks ◽  
Step Method ◽  
Earthquake Excitation ◽  
Restoring Force ◽  
Liquid Storage ◽  
Wide Range ◽  
Isolation Systems

A comparative study of performance of various isolation systems for liquid storage tanks is investigated under real earthquake ground motions. The various base isolation systems considered are the laminated rubber bearings (with and without lead core) and sliding isolation systems (with and without restoring force). The isolated liquid storage tank is idealized with three-degrees-of-freedom associated with convective, impulsive and rigid mass under uni-directional earthquake excitation. Since the force-deformation behaviour of the isolation systems is non-linear, as a result, the equations of motion are solved numerically by step-by-step method. In order to measure the effectiveness of the isolation systems, the seismic response of the isolated liquid storage tanks is compared with the corresponding response of non-isolated tanks. Further, the effectiveness of the isolation is also explored for wide range of practical liquid storage tanks considering the influence of tank aspect ratio. It is observed that the isolation systems are quite effective in attenuating the earthquake acceleration transmitted to the tank, which reduces the design seismic forces significantly. Further, it is also found that the sliding type isolation systems are more effective in controlling the response of liquid storage tanks in comparison to the elastomeric bearings. Among the various sliding systems, the resilient-friction base isolator is found to be most effective for seismic isolation of the tanks.

Earthquake Protection of Liquid Storage Tanks by Sliding Isolation Bearings

2015 ◽  
Author(s):  
Eren Uckan ◽  
Bulent Akbas ◽  
Fabrizio Paolacci ◽  
Jashue Shen ◽  
Emre Abalı
Keyword(s):  
Base Isolation ◽  
Ground Motions ◽  
The Other ◽  
Lumped Parameter Model ◽  
Appreciable Amount ◽  
Storage Tanks ◽  
Base Shear ◽  
Isolation System ◽  
Liquid Storage ◽  
Sliding Isolation

Liquid storage tanks are critical components of industrial facilities since damage to such structures may cause spreading of hazardous material and environmental pollution. Tanks exhibit mainly two different seismic behaviors one of which is the long period movements due to sloshing of the liquid and the other is the impulsive vibrations generated as a result of the fluid structure interaction phenomena at higher frequencies. The overall base shear is the combination of these two loads. The seismic base isolation aims to control the impulsive load as it has appreciable amount of contribution to the base shear values. Among various types, the curved surface sliding bearings (FPS) are commonly used in liquid tanks since provide isolation periods which is independent of the tank weight (liquid height). In this paper a parametric analysis has been performed to investigate the efficiency of FPS bearings. The numerical model is based on the Haroun and Housner’s simplified lumped parameter model in which the sloshing and fluid-tank interactions are modeled by convective and impulsive masses, respectively. The effectiveness of the isolation system was investigated under a series of ground motions, isolation periods and tank aspect (slenderness) ratios. Results indicated that depending on the characteristics of the ground motion, the response of the isolated tank can be reduced in appreciable amounts as compared to the conventionally constructed one. On the other hand, some detrimental effects were also observed in lower isolation periods (Tb=2s) particularly in medium slender tanks under near fault ground motions. This undesirable situation was avoided by using higher isolation periods (Tb =3s) without much affecting the bearing displacements.

Vulnerability-Based Design of Sliding Concave Bearings for the Seismic Isolation of Steel Storage Tanks

2016 ◽  
Author(s):  
Hoang Nam Phan ◽  
Fabrizio Paolacci ◽  
Silvia Alessandri ◽  
Phuong Hoa Hoang
Keyword(s):  
Liquid Steel ◽  
Seismic Isolation ◽  
Failure Modes ◽  
Fragility Curves ◽  
Time History ◽  
Probability Of Failure ◽  
Design Parameters ◽  
Economic Losses ◽  
Storage Tanks ◽  
Isolation System

Liquid steel storage tanks are strategic structures for industrial facilities and have been widely used both in nuclear and non-nuclear power plants. Typical damage to tanks occurred during past earthquakes such as cracking at the bottom plate, elastic or elastoplastic buckling of the tank wall, failure of the ground anchorage system, and sloshing damage around the roof, etc. Due to their potential and substantial economic losses as well as environmental hazards, implementations of seismic isolation and energy dissipation systems have been recently extended to liquid storage tanks. Although the benefits of seismic isolation systems have been well known in reducing seismic demands of tanks; however, these benefits have been rarely investigated in literature in terms of reduction in the probability of failure. In this paper, A vulnerability-based design approach of a sliding concave bearing system for an existing elevated liquid steel storage tank is presented by evaluating the probability of exceeding specific limit states. Firstly, nonlinear time history analyses of a three-dimensional stick model for the examined case study are performed using a set of ground motion records. Fragility curves of different failure modes of the tank are then obtained by the well-known cloud method. In the following, a seismic isolation system based on concave sliding bearings is proposed. The effectiveness of the isolation system in mitigating the seismic response of the tank is investigated by means of fragility curves. Finally, an optimization of design parameters for sliding concave bearings is determined based on the reduction of the tank vulnerability or the probability of failure.

Floating Roof Influence on Seismic Response of Large Vertical Storage Tank

2013 ◽  
Vol 671-674 ◽  
pp. 1399-1402
Author(s):  
Ying Sun ◽  
Jian Gang Sun ◽  
Li Fu Cui
Keyword(s):  
Seismic Response ◽  
Storage Tank ◽  
Numerical Solutions ◽  
Fluid Pressure ◽  
Seismic Intensity ◽  
Site Conditions ◽  
Storage Tanks ◽  
Analysis Model ◽  
Base Shear ◽  
The Impact

To study the impact of floating roof on seismic response of vertical storage tank structure system subjected to seismic excitation, select 150000m3 storage tanks as research object, and the finite element analysis model of storage tanks with and without floating roof were established respectively. The seismic response of these two types of structure in different site conditions and seismic intensity were calculated and the numerical solutions were compared. The results show that floating roof has little impact on base shear and base moment in different site conditions and seismic intensity. Floating roof can effectively reduce the sloshing wave height. The influence of floating roof on dynamic fluid pressure decreases with the increase of seismic intensity, which is less affected by ground conditions.

Shaking Table Test Study on Mid-Story Isolation Structures

2012 ◽  
Vol 446-449 ◽  
pp. 378-381
Author(s):  
Jian Min Jin ◽  
Ping Tan ◽  
Fu Lin Zhou ◽  
Yu Hong Ma ◽  
Chao Yong Shen
Keyword(s):  
Seismic Response ◽  
Seismic Isolation ◽  
Shaking Table Test ◽  
Base Isolation ◽  
Shaking Table ◽  
Natural Period ◽  
Isolation System ◽  
Isolation Layer ◽  
Lead Rubber Bearing ◽  
Complex Structural

Mid-story isolation structure is developing from base isolation structures. As a complex structural system, the work mechanism of base isolation structure is not entirely appropriate for mid-story isolation structure, and the prolonging of structural natural period may not be able to decrease the seismic response of substructure and superstructure simultaneously. In this paper, for a four-story steel frame model, whose prototype first natural period is about 1s without seismic isolation design, the seismic responses and isolation effectiveness of mid-story isolation system with lead rubber bearing are studied experimentally by changing the location of isolation layer. Respectively, the locations of isolation layer are set at bottom of the first story, top of the first story, top of the second story and top of the third story. The results show that mid-story isolation can reduce seismic response in general, and substructure acceleration may be amplified.

Sign in / Sign up

Export Citation Format

Share Document