Seismic Analysis of Conventional and Isolated LNG Tanks Using Mechanical Analogs

2008 ◽  
Vol 24 (3) ◽  
pp. 599-616 ◽  
Author(s):  
Ioannis P. Christovasilis ◽  
Andrew S. Whittaker
Keyword(s):  
Seismic Isolation ◽  
Seismic Analysis ◽  
Numerical Models ◽  
Base Shear ◽  
Isolation System ◽  
Analysis And Design ◽  
Mechanical Analog ◽  
Wave Heights ◽  
Overturning Moment ◽  
Lng Tank

The seismic response of a conventional and an isolated vertical, cylindrical, Liquefied Natural Gas (LNG) tank is computed using a mechanical analog and a finite element code to judge the utility of the analog for preliminary design and of the effectiveness of seismic isolation. Data reported and statistically sorted include base shear, global overturning moment, and wave height in the tank. The results obtained from the two numerical models are in good agreement and demonstrate that the mechanical analog can be used with confidence for the preliminary analysis and design of conventional and isolated LNG tanks that have similar dimensions to the sample tank of this study. The base shear and overturning moment in the seismically isolated LNG tank are 10% to 15% of the values computed for the conventional tank; the wave heights are unaffected by the introduction of a seismic isolation system.

scholarly journals Response Quantities of Framed Buildings under Dynamic Excitation

2019 ◽  
Vol 8 (11) ◽  
pp. 3798-3804
Keyword(s):  
Seismic Analysis ◽  
Structural Response ◽  
Base Shear ◽  
Response Factors ◽  
Analysis And Design ◽  
Dynamic Excitation ◽  
Combination Methods ◽  
Time Period ◽  
Moment Resisting ◽  
Seismic Forces

Seismic analysis of structure is employed to make the structure enable to resist the seismic forces and perform against the factors causing the failure of the structure under dynamic excitation. Among various response factors, the base shear and time period of buildings are predominant factors used in the analysis and design of the structure. The prime objective of the paper is to present an analytical study on non-linear seismic analysis of moment resisting framed buildings (as per Indian code IS1893 – 2016) to evaluate the base shear of different configurations of buildings according to different mode combination methods. The obtained results have been presented the comparative analysis of different combination methods. The paper also presents the evaluated results in the form of the time period values of the different buildings depending upon variation in its configuration. As a result, the responses of multistoried moment-resisting framed buildings have been evaluated for various models of considered buildings based on different mode combination methods, and the results of obtained responses have been analyzed in a comparative manner to understand the behaviour of buildings under various methods and configuration conditions. The work presented in the paper can support to develop better understanding of structural response and efficient designing of structures.

scholarly journals Design and Seismic Analysis of Ground Supported Water Tank

10.29007/gqkl ◽  
2018 ◽  
Author(s):  
Rahul Patel ◽  
Rishi Dave ◽  
Prutha Vyas
Keyword(s):  
Program Analysis ◽  
Seismic Analysis ◽  
Hydrodynamic Pressure ◽  
Water Tank ◽  
Base Shear ◽  
Moment Capacity ◽  
Spreadsheet Program ◽  
Analysis And Design ◽  
Working Stress ◽  
Seismic Forces

The ground supported tanks are firmly attached with ground and tank walls are subjected to hydrostatic as well as hydrodynamic pressure due to seismic forces. Base of the tank is subjected to weight of water and pressure of soil. Top of the tanks may be covered and is designed by using IS 3370:2009 Part (I, II) [4] and IS 1893:2007 (part-2) draft code[3] is used for the seismic analysis of the tank. This paper gives idea behind the design of liquid retaining structure (rectangular ground supported water tank) using working stress method. This paper includes the seismic analysis and design of the tank. The values are obtained with the help of spreadsheet program. Analysis of ground supported water tank has been carried out and relationship between tank capacity with moment capacity and reinforcement area, base shear with impulsive height and overturning moment with convective height is derived.

Seismic Analysis of a Turbine on a Spring Isolated Pedestal

2006 ◽  
Author(s):  
Victor V. Kostarev ◽  
Andrei V. Petrenko ◽  
Peter S. Vasilyev ◽  
Alexander S. Lisyansky
Keyword(s):  
High Speed ◽  
Seismic Isolation ◽  
System Analysis ◽  
Seismic Analysis ◽  
Full Range ◽  
Coupled Model ◽  
Time History ◽  
Soil Conditions ◽  
Isolation System ◽  
Detailed Model

Paper deals with the detailed seismic analysis of powerful high-speed Russian turbine of Nuclear Power Plant. Dozens of patterns of such turbine work reliably since 70’s worldwide. Until last decade only simplified structural analyses were available due to a complicated overall structure and internals of such turbines. The current analysis considers detail geometry of the turbine itself as well as vibration and seismic isolation system within turbine’s pedestal and full range of operational, accident and seismic loads. To solve the problem of the turbine seismic and dynamic qualification the following steps have been done. On the first step detailed finite element models of turbine’s high and low pressure parts and rotor system with bearings were created. Using such models corresponding simplified models were developed to be included into the coupled model of the system: “Building – Vibroisolation Pedestal – Turbine” (BVT). The second step was the analysis of that coupled system. Soil-structure interaction was considered using actual soil conditions. Three components of time history acceleration were used to define seismic excitation. As the result of BVT system analysis a full picture of time history displacements and loads were determined. At the same time a non-linear problem of rotor’s axial and radial bearings behavior and gaps in the system was solved. On the final step determined loads were applied to the detailed model of turbine for seismic and dynamic qualification of the whole structure.

Study on Seismic Analysis Method of Fast Reactor Plant with Seismic Isolation System

2020 ◽  
Vol 2020 (0) ◽  
pp. S10107
Author(s):  
Shigeki OKAMURA ◽  
Takahiro KINOSHITA ◽  
Hiroyuki NISHINO ◽  
Hidemasa YAMANO ◽  
Kenichi KURISAKA ◽  
...  
Keyword(s):  
Fast Reactor ◽  
Seismic Isolation ◽  
Seismic Analysis ◽  
Analysis Method ◽  
Reactor Plant ◽  
Isolation System

Seismic Evaluation of Base Isolated System Equipped with Shape Memory Alloys

2013 ◽  
Vol 831 ◽  
pp. 110-114
Author(s):  
S. Alvandi ◽  
M. Ghassemieh
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Seismic Isolation ◽  
Passive Control ◽  
Structural Model ◽  
Base Isolation ◽  
Base Shear ◽  
Seismic Evaluation ◽  
Isolation System ◽  
Base Isolation System

Seismic isolation system is an example of passive control system that effectively improves the performance of structures. This research discusses the seismic performance of a elastomeric base isolation system which provide the combined features of vertical load support, horizontal flexibility and energy absorbing capacity, utilizing shape memory alloys that provides re-centering force and additional damping in the system. Also this paper compares the effect of such alloys with memory effect and/or superelasticity (with pre-straining) in base isolated structure. To provide such comparison, a nonlinear structural model has been developed on some benchmark control problems and some health monitoring evaluation criterias are used. The smart base isolation utilizes the different responses of shape memory alloys at several levels of strain to control the displacements of the rubber bearing and base shear at excitation level. Furthermore the proposed based isolation systems has enhanced performance in terms of response reduction and re-centering capacity.

Application of Annular Damper Reaction Wall in Seismic Isolated LNG Tank

2010 ◽  
Author(s):  
Rui-Fu Zhang ◽  
Da-Gen Weng ◽  
Wei-Bo Ni
Keyword(s):  
Equations Of Motion ◽  
Time Base ◽  
Base Shear ◽  
Lumped Mass ◽  
Mass Model ◽  
Isolation System ◽  
Lead Rubber Bearings ◽  
Lumped Mass Model ◽  
Lng Tank ◽  
Rubber Bearings

Most of the large LNG tanks have a fundamental frequency between 2 and 10 Hz which involves range of resonance of most earthquake ground motions. It is a fact that tanks could be damaged easily in the earthquake, which had been proved in many cases in the past few decades. It is an effective way to reduce the response for an isolation system being used for large LNG storage tanks in the strong earthquake. However, the displacement of the isolation story for actual project is very large in soft site so that the design of connection components is relatively difficult. In order to solve this problem, isolation system which is composed of annular damper reaction wall, viscous dampers, and lead rubber bearings mounted on the top of the piles is presented in this paper. The annular damper reaction wall which is not connected with the piles is embedded into the ground independently. The multi-degree-of-freedom lumped mass model is used to solve the governing equations of motion in which convective, impulsive and rigid masses are included. Simplified model of an actual LNG tank which can contain 160000m3 gases is analyzed by using isolators and annular damper reaction wall. The efficiency of the isolation system is investigated by analyzing various parameters such as displacement of the isolation story, base shear and so on. The results show that isolation system is very effective to control the displacement of isolation story, and at the same time base shear and other parameters are also effectively controlled.

Improvement of the polyurethane spring isolation device for HV post insulators and its evaluation by fragility curves

2021 ◽  
pp. 875529302098196
Author(s):  
Tansu Gökçe ◽  
Engin Orakdöğen ◽  
Ercan Yüksel
Keyword(s):  
Seismic Isolation ◽  
Base Isolation ◽  
Numerical Models ◽  
Fragility Curves ◽  
Low Cost ◽  
Steel Plates ◽  
Isolation System ◽  
Base Isolation System ◽  
Isolation Device ◽  
Seismic Base Isolation

A novel seismic base isolation system has been developed for high-voltage (HV) porcelain post insulators. The seismic isolation device consists of two steel plates, four polyurethane springs, and a steel rod, which are low-cost components compared to the post insulators. Two alternative designs of the device are experimentally and numerically assessed in this article. A simple and robust numerical model consisting of linear line elements and nonlinear springs was generated, and subsequently validated using the experimental results. Incremental dynamic analyses (IDAs) were then performed to obtain fragility curves. Ten historical earthquake profiles, scaled to intensities between 0.1 and 2.0 g, were then applied to the numerical models. The fragility curves, generated according to the latest version of IEEE-693, demonstrate that the seismic isolation devices are highly effective in diminishing the base moment of the porcelain insulator. It should be noted that relatively large displacements at the top of the pole must be accounted for by ensuring adequate slackness in the flexible conductors.

Seismic Isolation of the IRIS Nuclear Plant

2009 ◽  
Author(s):  
Massimo Forni ◽  
Alessandro Poggianti ◽  
Fosco Bianchi ◽  
Giuseppe Forasassi ◽  
Rosa Lo Frano ◽  
...  
Keyword(s):  
Seismic Isolation ◽  
Seismic Analysis ◽  
Wide Spectrum ◽  
Seismic Excitation ◽  
Fragility Analysis ◽  
Pressurized Water ◽  
Isolation System ◽  
Order Of Magnitude ◽  
Safety Features ◽  
The Impact

The safety-by-design™ approach adopted for the design of the International Reactor Innovative and Secure (IRIS) resulted in the elimination by design of some of the main accident scenarios classically applicable to Pressurized Water Reactors (PWR) and to the reduction of either consequences or frequency of the remaining classical at-power accident initiators. As a result of such strategy the Core Damage Frequency (CDF) from at-power internal initiating events was reduced to the 10−8/ry order of magnitude, thus elevating CDF from external events (seismic above all) to an even more significant contributor than what currently experienced in the existing PWR fleet. The same safety-by-design™ approach was then exported from the design of the IRIS reactor and of its safety systems to the design of the IRIS Nuclear Steam Supply System (NSSS) building, with the goal of reducing the impact of seismically induced scenarios. The small footprint of the IRIS NSSS building, which includes all Engineered Safety Features (ESF), all the emergency heat sink and all the required support systems makes the idea of seismic isolation of the entire nuclear island a relatively easy and economically competitive solution. The seismically isolated IRIS NSSS building dramatically reduces the seismic excitation perceived by the reactor vessel, the containment structure and all the main IRIS ESF components, thus virtually eliminating the seismic-induced CDF. This solution is also contributing to the standardization of the IRIS plant, with a single design compatible with a variety of sites covering a wide spectrum of seismic conditions. The conceptual IRIS seismic isolation system is herein presented, along with a selection of the preliminary seismic analyses confirming the drastic reduction of the seismic excitation to the IRIS NSSS building. Along with the adoption of the seismic isolation system, a more refined approach to the computation of the fragility analysis of the components is also being developed, in order to reduce the undue conservatism historically affecting seismic analysis. The new fragility analysis methodology will be particularly focused on the analysis of the isolators themselves, which will now be the limiting components in the evaluation of the overall seismic induced CDF.

scholarly journals Effect of a Near Fault on the Seismic Response of a Base-Isolated Structure with a Soft Storey

2017 ◽  
Vol 25 (4) ◽  
pp. 34-46
Author(s):  
B. Athamnia ◽  
A. Ounis ◽  
M. Abdeddaim
Keyword(s):  
Seismic Isolation ◽  
Seismic Analysis ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Base Shear ◽  
Rc Structures ◽  
Soft Storey ◽  
Near Fault ◽  
Nonlinear Time History ◽  
Far Fault

AbstractThis study focuses on the soft-storey behavior of RC structures with lead core rubber bearing (LRB) isolation systems under near and far-fault motions. Under near-fault ground motions, seismic isolation devices might perform poorly because of large isolator displacements caused by large velocity and displacement pulses associated with such strong motions. In this study, four different structural models have been designed to study the effect of soft-storey behavior under near-fault and far-fault motions. The seismic analysis for isolated reinforced concrete buildings is carried out using a nonlinear time history analysis method. Inter-story drifts, absolute acceleration, displacement, base shear forces, hysteretic loops and the distribution of plastic hinges are examined as a result of the analysis. These results show that the performance of a base isolated RC structure is more affected by increasing the height of a story under nearfault motion than under far-fault motion.

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.

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