SEISMIC RESPONSE TESTING SYSTEM FOR LIQUID STORAGE TANK AND A METHOD THEREOF

Abstract

The present invention discloses a seismic response testing system designed to evaluate the seismic performance of liquid storage tanks, particularly with and without base isolation techniques. The system simulates real-world earthquake conditions using a servo-hydraulic shake table to replicate seismic forces. It measures the dynamic response of tanks with varying liquid levels through accelerometers strategically placed on the tank. Base isolation is achieved using elastomeric bearings to minimize seismic impact. The system's data acquisition and analysis software provide real-time insights into the tank's behavior during seismic events. This invention is critical for assessing the effectiveness of base isolation techniques in reducing seismic forces, particularly in industries like water, oil, and chemical storage. Test results demonstrate a significant reduction in seismic forces, especially at 50% liquid levels, highlighting the efficacy of base isolation in improving tank stability. The invention contributes to better earthquake-resistant designs for liquid storage tanks.

Specification

Description:FIELD OF THE INVENTION
The present invention relates to the seismic performance and protection of liquid storage tanks, particularly cylindrical ground-supported tanks used to store liquids such as water, petroleum, gases, and other industrial fluids. More particularly, the present invention relates to the pre-use of base isolation techniques, particularly elastomeric bearings, to reduce seismic forces and the resulting acceleration impacts on tanks containing various types of liquids.
BACKGROUND OF THE INVENTION
Liquid Storage Tanks (LST) has become critical life line structures during the recent decades. Liquid storage tanks are mainly used for storage of water, petrol, petroleum products, different gases like oxygen, nitrogen, high pressure fluids, highly flammable gases like hydrogen, LPG etc. These tanks may also be used in nuclear plants for storage of various types of liquids or gas chemical fluids and waste of different forms. The said Liquid storage tanks are geographically dispersed over broad area and after earthquake these tanks can provide services necessary for the emergency response for the community if appropriately designed against earthquakes. However, currently these tanks are exposed to a wide range of seismic hazards to community users.
Over the years, earthquakes have caused significant damage to liquid storage tanks, leading to economic losses, safety hazards, and environmental disasters. Historical seismic events, such as the 1940 El-Centro earthquake and the 1964 Alaska earthquake, have highlighted the vulnerability of these tanks to seismic forces.
Therefore, the Seismic performance of these tanks has been a matter of special importance, beyond the economic value of the structure, due to the requirement to remain functional after a major earthquake event. Water supply is essential immediately following destructive earthquakes, not only to cope with possible subsequent fires, but also to avoid outbreaks of disease. Another reason is the potential danger associated with the failure of tanks containing highly inflammable products, which can lead to extensive uncontrolled fire, while possible spillage of such contents might cause extensive environmental damage and affect populated areas.
The failure of numerous liquid storage tanks during past earthquakes has highlighted the critical need to protect these tanks from seismic forces. This issue has generated significant interest in developing methods to safeguard tanks, which are vital for storing liquids like water, petroleum, and industrial chemicals.
The determination of the seismic response of the tanks requires extensive & rigorous analysis which in most cases demands long computational time. Since early seventies the simplifying assumptions and analysis have been performed, the major issue of understanding their exact seismic behaviour is still incomplete and under investigation.
The main challenge in tank design is ensuring their functionality after an earthquake, particularly when dealing with the complex hydrodynamic forces that develop during seismic events. These forces can cause severe damage to tanks, leading to loss of stored materials and environmental hazards.
Another problem associated with the seismic behavior of liquid storage tanks involve the analysis of three systems: the tank, the soil, and the liquid, as well as the interaction between them along their boundaries.
Engineers often rely on conventional design methods and standard codes to ensure tank safety, but these approaches may not always provide adequate protection, especially in the face of strong earthquakes. Therefore, alternative methods, like the use of base isolation techniques, offer non-conventional but experimentally proven ways to improve tank safety. This motivates further exploration and development, especially for large industrial applications where tank integrity is critical for safety and continued operations.
Seismic analysis of liquid-containing tanks differs from buildings in two ways: One is, during seismic excitation, the liquid inside the tank exerts a hydrodynamic force on tank walls and base. The other is, liquid-containing tanks are generally less ductile and have low redundancy as compared to buildings. Traditionally, hydrodynamic forces in a tank-liquid system are evaluated using a mechanical analogy in the form of a spring-mass system, which simulate the impulsive and convective mode of vibration of a tank-fluid system. Due to low ductility and redundancy, seismic forces for tanks are usually higher than that for buildings with "equivalent" dynamic characteristics, which is achieved by specifying lower values of the response modification factor or its equivalent factor. Since tanks have higher utility and damage consequences, codes specify a higher importance factor for liquid-containing tanks, which further increases design seismic forces for tanks.
All the codes and standards suggest modelling the tank-liquid system using the mechanical analogy, where liquid mass is divided into impulsive and convective masses. The impulsive liquid mass vibrates along with the tank wall and the convective liquid mass vibrates relative to the tank wall and undergoes sloshing motion. Liquid in the lower portion mostly contributes to impulsive mass and liquid in the upper portion undergoes sloshing motion.
Traditionally, liquid storage tanks are designed with a fixed base, making them susceptible to seismic-induced stresses, such as ground shaking and hydrodynamic pressure exerted by the stored liquid. These forces can lead to structural failure, including buckling of the tank walls, rupture, and base sliding, posing a significant risk to both the infrastructure and surrounding areas.
To mitigate these risks, base isolation techniques have emerged as an effective solution. Base isolation systems, such as elastomeric bearings, have been successfully applied to buildings and other structures to reduce seismic forces transmitted to the structure. However, their application in liquid storage tanks remains relatively underexplored. The unique challenge of liquid storage tanks lies in their dynamic interaction with the contained fluid, which generates complex impulsive and convective forces during seismic activity. In conventional liquid storage tank designs, particularly those with fixed bases, tanks are vulnerable to seismic forces due to their low ductility and the additional hydrodynamic forces generated by the stored liquid. Prior approaches, such as mechanical analogies using spring-mass systems, have limitations in accurately simulating the dynamic behavior of tanks under seismic loads. These systems often result in high seismic forces due to the impulsive and convective motion of the liquid, leading to tank failure, structural damage, and environmental hazards.
While base isolation has been explored for seismic protection in buildings and certain infrastructure, its application to liquid storage tanks has been limited. Previous studies on base isolation techniques, like Laminated Rubber Bearings (LRB) and Friction Pendulum Systems (FPS), have shown promise, but few have been experimentally verified for tanks under real-world seismic conditions. Additionally, while simulation models have been developed, the lack of time-history analysis and comprehensive experimental data in the prior art has limited the understanding of base isolation's full potential for tanks. Therefore, the need for an experimentally validated, reliable base isolation system tailored to the specific requirements of liquid storage tanks remains an unresolved challenge in the prior art.
Therefore, to address the limitations associated with prior art. The present invention discloses an advanced effective seismic protection system for liquid storage tanks by incorporating base isolation technology, specifically elastomeric bearings, to minimize the transmission of seismic forces to the tank. This invention aims to enhance the seismic resilience of these tanks, ensuring their structural integrity and continued functionality during and after an earthquake.
OBJECTIVES OF THE PRESENT INVENTION
The primary objective of the present invention is to improve the seismic resilience of liquid storage tanks by incorporating base isolation techniques, specifically elastomeric bearings, to mitigate the transmission of seismic forces to the tank structure.
Another objective of the present invention aims to reduce the impact of seismic vibrations on ground-supported cylindrical liquid storage tanks, ensuring structural integrity and continued functionality during and after earthquakes.
Another objective of the present invention to reduce the risk of structural failure, including buckling, rupture, and base sliding, in liquid storage tanks during seismic events by decoupling the tank from ground motion.
Another objective of the present invention to maintain the operational integrity of liquid storage tanks during and after seismic events to ensure the storage and supply of essential liquids such as water, petroleum, and industrial fluids without interruption.
Another objective of the present invention is to counteract the hydrodynamic forces generated by the liquid inside the tank during seismic activity to reduce the impulsive and convective accelerations that contribute to the structural stress.
Another objective of the present invention is to experimentally and numerically validate the effectiveness of elastomeric bearing isolation through shake table tests and simulation studies under varying liquid levels and seismic conditions.
Another objective of the present invention is to provide a practical, cost-effective solution through both experimental and simulation methods, validating the effectiveness of base isolation in reducing seismic acceleration at different liquid levels.
SUMMARY OF THE INVENTION
The present invention discloses a seismic response testing system designed to evaluate the seismic performance of liquid storage tank particularly under varying conditions with and without base isolation techniques. This system is essential for understanding how such tanks behave under earthquake-induced forces and how seismic isolation methods can mitigate potential damage. The invention simulates real-world earthquake conditions using a servo-hydraulic shake table to assess the effects of seismic activities on ground-supported tanks. The system can accurately simulate different earthquake magnitudes and apply controlled horizontal forces to the tank, replicating seismic ground motion.
The system comprises a liquid storage tank mounted on a support system that can be configured either as a fixed base or with base isolation using elastomeric bearings. An accelerometers mounted at different points on the tank (such as the base and top) to capture the dynamic response of the tank under seismic activity. These accelerometers are highly sensitive and can measure both impulsive and convective responses from the interaction between the tank and the liquid. A servo-hydraulic system to simulate seismic ground motion by applying controlled forces to the tank. A data acquisition system to gather real-time data from the accelerometers and analyse the tank's seismic response with the assistance of software on a desktop PC.
The primary objective of the present invention is to focus on testing the effectiveness of base isolation techniques. Elastomeric bearings are used to isolate the tank from seismic forces, allowing for the reduction of horizontal forces transmitted to the tank during an earthquake. This system is versatile and can evaluate different liquid levels, providing insights into the dynamic behavior of the tank under different fill conditions, ranging from empty to partially filled.
In conclusion, the present invention addresses the critical need to evaluate seismic responses of liquid storage tanks, particularly those used in industries like water supply, oil storage, and chemical processing. The testing system, with its ability to simulate earthquakes and measure responses with and without seismic isolation, offers key insights into how such tanks can be better protected during earthquakes.
BRIEF DESCRIPTION OF THE FIGURES
Fig. 1 illustrates a schematic diagram of experimental test set-up designed to evaluate the seismic behavior of liquid storage tank and effectiveness of isolation system in reducing seismic impact according to an embodiment of the present invention.
Fig. 2(a) & 2(b) is a diagrammatic and actual representation of liquid storage tank according to an embodiment of the present invention.
Fig. 3 illustrates an Acceleration vs. Time graph for the El-Centro earthquake wave, demonstrating its intensity and frequency characteristics.
Fig. 4 illustrates a bottom view of the liquid storage tank equipped with elastomeric bearing according to an embodiment of the present invention.
Fig. 5 illustrates an Acceleration vs. Time graph for the sample test for liquid storage tank without base isolation according to an exemplary embodiment of the present invention.
DETAILED DECSRIPTION OF THE INVENTION
The present invention discloses a seismic response testing system and a method thereof to test the seismic response of liquid storage tanks and evaluate the effectiveness of seismic isolation systems. The seismic response testing system of the present invention provides a controlled environment for simulating seismic activities and measuring the tank's response in real-time. The system is configured to assess the behavior of ground-supported liquid storage tanks under seismic conditions, and provide critical data on how the tank and the stored liquid react to such external forces.
Referring now to Fig. 1 illustrates the seismic response testing system for liquid storage according to an embodiment of the present invention. The system comprises a liquid storage tank positioned on a supporting system that can simulate either a fixed base or a base-isolated configuration, depending on the experiment's needs; an accelerometer mounted on the walls of the liquid storage tank to measure the accelerations experienced by the tank during the simulated seismic activity, wherein the said sensors are highly sensitive and capable of capturing the detailed dynamics of the tank's motion, including both impulsive and convective responses due to interaction between the tank structure and the liquid content; and a data acquisition system in communication with the accelerometers, configured to collect real-time data generated by the accelerometers. The said data acquisition system gathers precise measurements of the tank's response, including the acceleration data corresponding to different modes of vibration (impulsive and convective). The data acquisition system stores and processes the measured data for transmission to the desktop PC for further analysis.
The system further comprises a desktop PC connected to the data acquisition system for receiving real-time acceleration data from liquid storage tank. The desktop PC comprises software that analyzes the collected data, allowing researchers to observe the tank's behavior during seismic events. The desktop PC is also responsible for controlling the servo hydraulic system, sending commands to simulate different seismic scenarios. The said servo hyrdualic system comprises an actuator that is connected to the supporting system of the liquid storage tank. The actuator applies controlled horizontal forces to the tank, simulating ground motion experienced during seismic events. The movements are precisely managed by the controller and the desktop PC, ensuring that the simulated seismic forces accurately replicate real-world earthquake conditions. The system is capable of varying the magnitude and frequency of the forces to simulate different earthquake intensities and characteristics. Furthermore, a controller is position between the desktop PC and the servo hydraulic system. It receives instructions from the PC and translates them into operational commands for the hydraulic system. The controller ensures that the correct force profiles are applied to the actuator, replicating the desired seismic conditions. It also helps regulate the actuator's performance, ensuring smooth and accurate delivery of simulated seismic forces.
The liquid storage tank mounted on a supporting system is designed to facilitate different experimental configurations. For experiments evaluating fixed-base tanks, the supporting system holds the tank rigidly to the ground. For base-isolated configurations, the supporting system incorporates elastomeric bearings or other isolation devices, allowing the tank to move independently from the ground motion and simulate the effects of seismic isolation techniques.
During operation, the servo hydraulic system, controlled by the desktop PC, applies horizontal forces to the liquid storage tank, simulating seismic ground motion. The accelerometers attached to the tank walls record the tank's movements and the accelerations generated by the seismic forces. These measurements capture both the impulsive behavior (where the tank and liquid move together) and the convective behavior (where the liquid undergoes sloshing).
The data acquisition system collects the data from the accelerometers in real time and transmits it to the desktop PC, where it is processed and analyzed. The analysis software on the PC allows researchers to evaluate how the tank structure responds under various seismic conditions, including examining the effectiveness of base isolation in reducing seismic forces transmitted to the tank. The system is versatile, allowing the simulation of different earthquake magnitudes and durations.
The earthquake simulator can produce a variety of earthquake ground motion within its own capacity. One series of input seismic wave was considered in the present invention.
According to preferred embodiment of the present invention, the seismic response testing system comprises a shake table, servo hydraulic drive system with controller, tank model, accelerometers and data acquisition system as shown in Figure 1. The said shake table has operating frequency up to 50 Hz and the centre of gravity of the test object can be anywhere within the table and elevated up to 1000mm above the table. The cylindrical liquid storage tank is most commonly used in India and hence it is selected in the present study to investigate the seismic response under earthquake excitations. The dimension of the shake table is 1m x 1m and load carrying capacity is 1 ton. The dimensions selected for the tank are diameter 0.75m and height 0.63m. The thickness of the tank wall and bottom plate is 6mm as shown in the Figure 2(a). The actual tank manufactured for the test purpose is represented in Figure 2(b).

Referring now to Fig. 3 illustrates the Acceleration V/s Time graph for El-Centro earthquake wave. According to the preferred embodiment of the present invention El-Centro earthquake wave is used for seismic analysis. In seismic design analysis for complex liquid-containing structures, selecting appropriate time history data is crucial. Accurate representation of seismic events ensures that the structural response can be effectively analyzed, particularly under severe ground motion scenarios which are essential for understanding potential damage. Naeim and Anderson (1993) conducted an extensive study of over five thousand significant strong earthquake ground motions from around the world. Their analysis highlighted the El-Centro (1940) earthquake as one of the most critical datasets due to its severe ground motion characteristics. The El-Centro earthquake data has been widely adopted in research due to its representation of high-damage potential ground motions.
According to another embodiment of the present invention, the accelerometers selected for the current study is highly sensitive and accurate to make them a valuable tool for measurement of seismic data. The accelerometers that are the parts of standard MTL-32 shake table test are selected in the present study. The range of frequency of these accelerometers ranges is 0.1 Hz to10 Hz (BISS machine manual).
To verify whether the relevant value of Peak Ground Acceleration (PGA) are given as the input to the liquid storage tank mounted on the shake table, it was decided to place one accelerometer at the base plate of the shake table. Based on the input PGA, to understand the behaviour of the liquid storage tank during the test it was decided to place another accelerometer at the top of the tank.
According to another embodiment of the present invention, the method for evaluating the seismic response of liquid storage tank comprises the steps of: preparing the liquid storage tank for testing by ensuring that the tank is properly mounted on the shake table. To investigate the effects of varying liquid levels on the seismic response of the tank, the tank is filled with water at multiple levels. Due to setup constraints and concerns about liquid sloshing, which could damage sensitive electronic instruments, the test for the 100% liquid level is not conducted. The liquid levels for the test are empty tank (0 m); 25% liquid level 0.15m); 50% liquid level (0.30m); 75% liquid level (0.45m); and 100% liquid level (0.60m) (only for preliminary analysis; full testing excluded). Then, One accelerometer is placed at the base of the shake table to record the Peak Ground Acceleration (PGA) that is applied during testing. This ensures that the input seismic forces are measured accurately, and a second accelerometer is mounted at the top of the liquid storage tank to measure the tank's response to seismic excitation. The data recorded by this accelerometer will provide insight into how the liquid level affects the tank's behavior during ground motion. Time history data corresponding to known seismic events, such as the El-Centro (1940) earthquake, is selected for the testing. This earthquake wave has been widely used in seismic analysis due to its severity, making it an ideal candidate for this study. The shake table is programmed to simulate the seismic ground motion using the El-Centro earthquake wave, applying varying levels of seismic forces to replicate real-world earthquake conditions. The first set of tests is conducted without any base isolation. The tank is rigidly connected to the shake table to simulate the behavior of a fixed-base tank during seismic activity. The tank is subjected to seismic ground motion at each of the pre-defined liquid levels (empty, 25%, 50%, 75%). The accelerometers capture real-time data on the tank's movement and response. The data acquisition system collects and stores the acceleration data for further analysis.
After completing the fixed-base tests, the same set of tests is repeated with the implementation of base isolation techniques. Elastomeric bearings are used for base isolation due to their high energy dissipation capacity and ability to reduce seismic force transmission. Four elastomeric bearings (laminated bearing, Type B, dimensions: 200 mm x 150 mm x 20 mm) are installed under the tank at diametrically opposite locations to allow movement in two perpendicular directions. The shake table is used to apply the same seismic input as in the fixed-base tests, with the accelerometers recording the tank's behavior under base isolation conditions at each liquid level. The data acquisition system continuously collects real-time acceleration data from the accelerometers during each test. This data includes both the input PGA (from the base) and the tank's response (from the top of the tank). The acceleration vs. time data for different liquid levels and test configurations (with and without base isolation) is stored for analysis. Peak acceleration values are identified, and the effectiveness of base isolation is evaluated by comparing the seismic response of the tank in both configurations. The data collected from the tests is processed and analyzed using specialized software. The behavior of the tank under different seismic forces and liquid levels is studied, and the effect of base isolation techniques in mitigating seismic damage is assessed. Graphs of acceleration vs. time are generated for each test, highlighting peak acceleration values and significant trends in tank movement under seismic forces. The results of the tests are compiled to evaluate the overall seismic performance of the liquid storage tank at different water levels. The effectiveness of the base isolation technique is determined by comparing the peak acceleration values of the tank with and without isolation. This allows for conclusions on how seismic isolation can reduce the structural impact during an earthquake.

As per the Code IRC-83-2018 (Part - II) and manufacturer's catalogue of MAURER and Sanfield India Limited, elastomeric bearings are selected which are more suitable to transmit vertical loads including combined effects of earthquake forces in horizontal and vertical components. The elastomeric bearing selected for experimental investigation is laminated bearing - Type B and its dimensions are 200mm X 150mm X 20mm. The material is Neoprene rubber with modulus of elasticity 15N/mm2 and modulus of rigidity of 5 MPa with Poison's ratio 0.4. The orientation of the bearing mounting has been selected by referring AASHTO [American Association of State Highway & Transportation Officials]. The four bearings have been mounted on diametrical opposite axes which are equidistant from centre of the tank as shown in the Figure 4. The reason to provide four bearing pads is to resist seismic forces in two mutually perpendicular directions.
Referring now to Fig. 5 illustrating the result of sample test for Liquid storage tank without base isolation. From this data sheet a peak value of acceleration has been identified and for convenience, the region where the peak value lies has been highlighted in Table 1. (ACC4) represents the reading of accelerometer mounted at the top of the tank.

Table 1: Peak Acceleration Value for Sample Test
The above table shows the the acceleration data captured during a sample test conducted on a liquid storage tank without base isolation (BI) under an empty condition. The table provides acceleration values measured by two accelerometers:
• ACC3: Represents the accelerometer mounted at the base plate of the shake table.
• ACC4: Represents the accelerometer mounted at the top of the liquid storage tank.
The columns in the table show a series of acceleration values (in "g") for both accelerometers (ACC3 and ACC4). These measurements reflect the seismic response during the sample test.
• The highlighted value of 0.135036g under ACC4 represents the peak acceleration recorded at the top of the tank during the test. This is identified as the highest acceleration in the entire dataset for the tank.
• The data from ACC3 (base plate) shows relatively consistent acceleration values, ranging between 0.28g and 0.30g, indicating the input force applied to the shake table.
• The data from ACC4 (top of the tank) shows varying acceleration values, with the peak reaching 0.135g, suggesting that the tank's seismic response at the top is significantly dampened compared to the base.
This table helps in understanding how the empty liquid storage tank behaves under seismic conditions without base isolation. Specifically, it shows how the seismic force is transmitted from the base (ACC3) to the top (ACC4), with a noticeable reduction in acceleration at the top.
In a similar way, the test has been conducted for different liquid levels (25%, 50%, and 75%) in the tank. These tests comprise tanks subjected to without and with base isolation technique.
Table 2: Experimental Results for Acceleration at the top of the tank without and with base isolation
Liquid Level in metres and percentage Empty Tank (0%) H= 0.15m (25%) H= 0.3m (50%) H= 0.45m (75%)
Acceleration(g)
(without base isolation)
0.135
0.175
0.165
0.171
Acceleration(g)
(with base isolation)
0.118
0.171
0.121
0.169
Acceleration Reduced 13% 2% 27% 1%

Average Isolation : 11%

It can be seen that in empty tank (0% liquid level), the acceleration is reduced by 13% by applying base isolation technique. Similarly, the acceleration has reduced by 2% in case of H= 0.15m (25% liquid level) and the acceleration has reduced by 1% in case of H = 0.45m (75% liquid level). But, in case of H =0.3m (50% liquid level) the acceleration has reduced by 27% which is maximum amongst all the other liquid filled conditions by applying base isolation technique. It has been observed that the reduction in acceleration in case of empty tank is higher than 25% liquid level. It happens because there is no dynamic effect of liquid inside the tank. At higher levels of liquid, means at 75% liquid level there is hardly any reduction in acceleration because, at higher level of liquid in the tank the effect of convective acceleration is predominant as compared to impulsive acceleration. It can be clearly seen that the acceleration at 50% liquid level has reduced maximum because, both the impulsive and convective accelerations equally balance each other. In total, the average reduction in acceleration or isolation is observed to be 11% from the experimental investigation. , Claims:1. A seismic response testing system for evaluating the seismic behavior of liquid storage tanks, the system comprises:
a. a liquid storage tank mounted on a support system that allows testing under either fixed-base or base-isolated conditions;
b. one or more accelerometers positioned at different points on the liquid storage tank to capture the dynamic seismic response;
c. a servo-hydraulic system configured to simulate seismic ground motion by applying controlled horizontal forces to the tank;
d. a data acquisition system in communication with the accelerometers to collect real-time data on the tank's behavior during simulated seismic events; and
e. a desktop PC with software to analyze the collected data, including controlling the servo-hydraulic system to replicate different seismic scenarios.

2. The system as claimed in claim 1, wherein the base isolation is achieved using laminated elastomeric bearings comprising neoprene rubber that are installed under the tank to reduce seismic force transmission.

3. The system as claimed in claim 1, wherein the liquid storage tank is tested under varying liquid levels to evaluate the effect of different fill conditions on its seismic response.

4. The system as claimed in claim 1, wherein the accelerometers measure both impulsive and convective accelerations resulting from the interaction between the tank structure and the liquid content.
5. The system as claimed in claim 1, wherein the servo-hydraulic system applies seismic forces that replicate real-world earthquake data, such as the El-Centro (1940) earthquake wave.

6. The system as claimed in claim 1, wherein the shake table has a frequency range up to 50 Hz and a load carrying capacity of up to 1 ton to simulate varying earthquake magnitudes.

7. The system as claimed in claim 1, wherein the liquid storage tank has a cylindrical shape with specific dimensions of 0.75m diameter and 0.63m height, as representative of commonly used tanks in industries like water supply and oil storage.

8. A method for evaluating the seismic response of a liquid storage tank using the system described in claim 1, comprising the steps of:
a. preparing the liquid storage tank for testing by mounting it on the shake table;
b. filling the tank with liquid at various levels, from empty to partially filled;
c. applying seismic forces to the tank using the servo-hydraulic system to simulate real-world earthquake ground motion;
d. measuring the tank's seismic response using accelerometers positioned at the base and top of the tank; and
e. collecting real-time data using the data acquisition system for further analysis.

9. The method as claimed in claim 8, further comprising the step of repeating the test with base isolation by mounting elastomeric bearings under the tank and comparing the tank's seismic response with and without isolation.

10. The method as claimed in claim 8, wherein the effectiveness of base isolation is determined by comparing peak acceleration values at the top of the tank under different liquid levels.

11. The method as claimed in claim 8, wherein seismic testing is conducted for liquid levels of 0%, 25%, 50%, and 75%, and the reduction in acceleration is analyzed for each condition with and without base isolation.

12. The method as claimed in claim 8, wherein the greatest reduction in acceleration occurs at 50% liquid level due to the balanced effect of impulsive and convective accelerations, as recorded by the accelerometers.

13. The method as claimed in claim 8, wherein the data collected is processed to generate acceleration vs. time graphs for each liquid level and base configuration to evaluate the seismic performance of the tank.

Documents