Elevated Storage Tanks Research Articles

Fluid Structure Interaction Analyses of Elevated Storage Tank under Seismic Load

Elevated storage tanks are used to store fresh and waste water, cereal, oil and petrochemical materials. Therefore they serve in a wide area of utilization in this day and age. Analysis of a half full with water elevated storage tank is performed in the scope of this study. The structure is composed of a steel circular storage tank and frame typed steel stager. The structure is under the effect of earthquake loads as well as operational ones. Numerical model is generated by Finite Elements Analysis (FEA) software including fluid and structure parts. The interaction of the parts is provided by Coupled Eulerian Lagrangian (CEL) technique. While the structure constitutes the Lagrangian part, the fluid constitutes the Eulerian part. Interaction of Eulerian and Lagrangian parts are provided by general contact algorithms. Free surface movement of the water, maximum displacements and natural frequency values with related mode shapes of the structure are obtained after numerical analysis. Numerical results are verified by semi-analytical model, where the structure is modelled as single degree of freedom system. The accordance between results is numerically and visually obtained. The turbulent movement of water under the influence of an earthquake is modelled by utilizing the CEL technique. So, the effect of the dynamic pressure induced by the turbulence on the tank and the structural system has been taken into consideration.

Microbial and physicochemical water quality changes within distribution and premise plumbing systems during a chlorine conversion

A strategy for nitrification control within chloraminated drinking water systems (CDWSs) is to temporarily switch from chloramine secondary disinfection to free chlorine, also known as a free chlorine conversion (FCC). However, the long-term and beneficial effects of FCCs are unclear, especially regarding opportunistic pathogen occurrence. In this study, the impacts to microbial and physicochemical parameters were monitored throughout a CDWS implementing a FCC. Water samples were collected weekly for 4–6 weeks before, during, and after a FCC at eight locations: four distribution system and four residential sites. Monochloramine residual (mean±standard deviation) before and after the FCC averaged 1.8±0.9 and 1.6±1.0 parts per million (ppm) for all sites, respectively. Free chlorine levels averaged 2.3±0.9 ppm. There were no significant differences in turbidity and hardness at each location during the three time periods, but some were noted for pH, temperature, and orthophosphate levels across various sites and sampling periods. For all locations, heterotrophic plate count levels were lower during the FCC compared to the periods before and after. All samples from one residence were culture positive for P. aeruginosa which exhibited high levels before the FCC, decreasing levels during, and steadily increasing levels after. Additionally, one week prior to the FCC, sediment samples from two elevated storage tanks, ET-1 and ET-2, were analyzed with ET-1 displaying higher levels of culturable heterotrophic bacteria and molecularly detected total bacteria, Legionella spp., and nontuberculous mycobacteria (NTM), as well as presence of culturable P. aeruginosa and total coliforms compared to ET-2. Fourteen P. aeruginosa and total coliform isolates were whole genome sequenced with genetic differences observed depending on the sampling location and timepoint. Collectively, the observed differences in chemical and microbial parameters advocates for a better understanding of the effects associated with implementing FCCs to determine both their effectiveness and potential risks/rewards to water quality.

Influence of the Behaviour Coefficient on the Damage Level of an RC Elevated Tank under Seismic Loading

In Algeria, the seismic design of elevated concrete storage tanks is carried out in accordance with seismic standard, involving a behavior coefficient of the structure. This behaviour coefficient is used to determine the internal forces and to estimate the inelastic deformations undergone by the structure. For the elevated water tank, considered as reverse pendulum structure, this coefficient assumes a constant value (R=2) in the Algerian seismic code. Taking into account a single value, whatever the seismic zone, the site of implantation and the geometric characteristics of the structure, can lead to design errors leading to oversizing, hence an additional cost of the structure. Thus, faced with the need to design resistant structures while minimizing construction costs, it is important to precisely determine the value of this behaviour coefficient to introduce into the evaluation of the structure's response. In this research, the seismic performance of an RC elevated tank is analyzed, using a nonlinear approach based on the Pushover method, initially using the behavior coefficient prescribed by the Algerian seismic code, then secondly using the behavior coefficient approximated by a power-type law, taking into account the seismic zone, the type of soil, the height of the structure and the storage capacity. The results of this study highlight the influence of the value of the behavior coefficient on the seismic performance and the level of damage to an elevated tank.

Nonlinear Seismic Analysis of RC Elevated Liquid Storage Tanks

Liquid storage tanks are strategically important due to their essential requirement of service in the post-earthquake situation. Numerical modeling of the liquid storage tank needs special attention and cannot be done in the same manner as that of the conventional buildings. In the present paper, a numerical simulation of the RC elevated liquid storage tank is presented. The staging of the tank is modeled as a multi-degree freedom system, and the container with contained liquid is modeled as a two-mass system. Free vibration analysis of the tank is carried out, and mode shapes are extracted. Further, to study the seismic response of the tank, nonlinear time history analysis is carried out. The tank is subjected to time histories of real earthquake ground motions. The varying level of the liquid in the container is another characteristic feature of tanks. The filled condition of the tank is taken into account by considering the aspect ratio (S), defined as the ratio of height of the liquid to the radius of the container. The response of the tanks with two different aspect ratios viz. 0.5 (broad) and 2.0 (slender) is studied. The linear modal analysis also carried out to understand the significance of nonlinear analysis, particularly in liquid storage tanks. Displacement, velocity, and acceleration response at the bracing levels, as well as at container levels, are obtained. Additionally, the base shear response is also obtained. The effect of aspect ratio on the free vibration analysis and the seismic response of the tanks are presented. Liquid storage tanks are special structures that have typically low fundamental natural frequencies. The nonlinear time history response of the tank showed that the higher displacement and velocity response occurs at the convective level. It is found that the linear modal analysis significantly underestimates the response of the liquid storage tank.

Seismic Analysis of Baffle-Reinforced Elevated Storage Tank Using Finite Element Method

The sloshing phenomenon is an important field of fluid dynamics in liquid storage tanks under earthquake excitation. When the sloshing frequency gets close to the liquid tank’s natural frequency, the resulting resonance could lead to instability and even damage to structures, followed by catastrophic economic losses and environmental damages. As passive control devices, baffles are a place for liquid energy dissipation. This study uses annular and horizontal baffles to evaluate the baffles’ relative effectiveness on the elevated storage tanks’ dynamic response. The analysis results are compared with those of elevated storage tanks with no baffles. The flexible and rigid storage tank analysis is examined here, where half of the tank height is filled with liquid. The structural interaction between the liquid, the (horizontal and annular) baffle, and the elevated storage tank affected by seismic action are investigated using Abaqus software. The results confirm that using the baffles, the maximum base shear force in flexible and rigid elevated storage tanks decreases as much as 26.43% and 31.90%, respectively, and the maximum hydrodynamic pressure reduction in the tank is 50.1%.

Performance of RC elevated liquid storage tanks installed with semi‐active pseudo‐negative stiffness dampers

The effect of semi-active pseudo-negative stiffness dampers (SAPNSDs) on the seismic response mitigation in the reinforced concrete (RC) elevated liquid storage tanks is investigated. The SAPNSDs are operated in two modes: Passive-ON and Passive-OFF. The effect of placement (location) of the dampers is also studied by placing the dampers in three different configurations. Two aspect ratios of the tanks, viz., 0.5 and 2.0, are considered to study the effect of the variable level of the liquid in the container. Time history analysis is carried out for total of 18 different earthquake ground motions. The differential equations of motion are solved by the state-space approach. The response quantities such as peak base shear, overturning moment, container level displacements, and bracing level displacements, along with the damper forces, are obtained. It is found that the SAPNSDs (Passive-ON) effectively control the response of the RC elevated liquid storage tanks. Further, seismic energy input to the structure without SAPNSDs and the percentage energy dissipated by SAPNSDs is obtained. The placement of the dampers plays a significant role in response reduction during ground motion with high peak ground acceleration (PGA) than that with low PGA. The SAPNSDs installed at alternate levels (Configuration II) is the most efficient configuration for response control of the RC elevated liquid storage tank installed with the SAPNSDs. The seismic input energy reduces considerably by the installation of the semi-active pseudo-negative stiffness dampers (SAPNSDs).

Seismic Performance of R. C. Elevated Water Storage Tanks

The primary basis for construction of structures for strong ground shaking is that it shall not collapse. However, permissible damage for structural components is permitted. If a structure is permitted to be damaged in the case of severe ground shaking, it shall be constructed for seismic forces considerably lesser than those expected in the event of severe shaking if it is to remain linearly elastic. Response reduction factor, R is the factor that should be used to lower the actual base shear in order to obtain the required design lateral force. In the case of seismic design of water tanks, different values of the “R” factor are suggested by various countries, such as IBC-2000 gives the value of the “R” factor varying from 2 to 4, whereas ACI 350.3 has given the values from 2 to 4.5, whereas AWWA (D-100) recommended the values in between 3 and 4. According to Eurocode 8, the behaviour factor, also known as the “R” factor, varies between 1 and 5. The values in the Indian code for seismic analysis, IS1893-(Part 2), range from 2 to 4.Hence, it is tempting to look into the real aspect of the ‘R’ factor evaluation. IS 1893, an Indian seismic code, calculates a design shear force for an elastic structure and divides it by twice R. In other words, the term “R” refers the amount of over-strength and ductility that a structure is predicted to possess. Thus, by considering the elements, over strength factor, redundancy factor, and ductility factor, the structure can be constructed for much lesser force than is predicted by the violent shaking, preventing the structure from collapsing. Available literature shows a sound recommendation does not exist for the values of “R” given in the seismic design codes of various countries, including India. There is currently no basis for the R-values in the codes. According to the available literature, limited research has been done on the influence of viscous dampers on “R,” which reflects a structure's ability of dissipation of energy through inelastic behaviour. The finite element (FE) approach must be used in conjunction with the study of material properties, the study of nonlinear hinge properties, the investigation of the seismic response of water tanks for different water heights, and the effect of including braces in staging to reduce the seismic response of the water tank to examine the nonlinear response of tanks under dynamic time-history and push-over analysis.

Seismic Response Control of Elevated Water Tank using Base Isolation: A Review

Earthquake events are not something which can be avoidable. The Indian subcontinent has a background marked by devasting quakes. Quakes are generally caused when the stone underground out of nowhere breaks along an issue. Ground shake is caused by seismic waves due to sudden release of energy. The Centre of earthquake vibration is known as epicentre. Due to earthquake millions of lives are lost which can never be affordable. Most of the structures are subjected to vibrations; it causes destruction of country’s infrastructure. In the recent earthquakes many well designed concrete structures have been severely damaged or collapsed. To protect structures from response reduction of structures and important harm under such serious earthquakes has become a vital theme in structural engineering. In this investigation, we evaluated seismic performance of staging system of elevated water storage tank with or without Base Isolation by using SAP2000. From this examination the powers following up on elevated water tank because of seismic powers are determined for zone IV.

Design and Development of Ram Pump

Due to A hydraulic ram (or water ram) pump is a simple, motorless device for pumping water at low flow rates. It uses the energy of flowing water to lift water from a stream, pond, or spring to an elevated storage tank or to a discharge point. It is suitable for use where small quantities of water are required and power supplies are limited, such as for household, garden, or livestock water supply. A hydraulic ram pump is useful where the water source flows constantly and the usable fall from the water source to the pump location is at least 3 feet.

Seismic Analysis and Comparative Study of Elevated Storage Tank by GSDMA Guidelines

A container to store water in a huge amount of capacity can simply be called as the water tank. During the earthquakes, all these liquid storage tanks get collapsed or damaged heavily. 40 to 65 years is the feasible lifetime of an ESR in general. Shortage of drinking water, utilizing water, uncontrolled fires, etc are some unexpected events caused due to any damage or collapse of the tanks. Water tank parameters include various designs of tanks and different way of construction, materials, linings etc. Different materials are used for the construction and development of water tanks such as: - plastic, concrete, steel, fiberglass, etc. Therefore, to avoid all those unwanted events in the future various studies have been carried out regarding different types, shapes of water tanks. In this research, Elevated Service Reservoir (E.S.R) is being compared of shape Rectangular & Circular water tanks of capacity 5lakh litres and a total height of 18m with 3m, 4.5m staging height in Earthquake Zone V by Equivalent static analysis using STAAD.PRO software and referring GSDMA guidelines for the design of a tank and IS 1893 PART2-2014 code. By studying all the observations and results, it shows that Circular water tank is more preferable and economical for use.

Temporal analysis of the performance of an elevated concrete tank considering the corrosion of the steel reinforcement

Reinforced concrete water storage tanks are civil engineering structures subject to very aggressive atmospheric conditions that expose them to harmful corrosion risk. This dangerous phenomenon caused by the penetration of chloride ions causes pitting corrosion and leads to the reduction of the section of the reinforcements and consequently to the loss of strength and the structure performance. In this study, we are interested in analyzing the performance of an elevated storage tank, taking into account the corrosion of the reinforcements subjected to tensile stress, by considering environments with different rates of aggressiveness. A method based on Housner's model is used to evaluate the tension stresses in the reinforced concrete (RC) pedestal (supporting system) of the tank, subjected to the seismic actions. A pitting corrosion model is developed in order to determine the evolution in time of the reinforcements section in different environments. Several parameters influencing corrosion are taken into account, such as concrete cover and the concentration of chlorides ions.

Influence of Nonlinear Fluid Viscous Dampers on Seismic Response of RC Elevated Storage Tanks

The numerical investigation on the seismic response of RC elevated liquid storage tanks installed with viscous dampers is presented. A discrete two-mass model for the liquid and multi-degree of freedom system for staging, installed with the dampers are developed for Reinforced Concrete (RC) elevated liquid storage tanks. The elevated tank is assessed for seismic response reduction when provided with Linear Viscous Damper (LVD) and Nonlinear Viscous Damper (NLVD), installed in the staging. The RC elevated liquid storage tanks are analyzed for two levels of liquid containment in the tank, 100% and 25% of the tank capacity. Three Configurations of placements of dampers viz. dampers at alternate levels (Configuration I and Configuration II) and dampers at all the panels of the staging of the tank (Configuration III) are considered. To study the effect of peak ground acceleration, eight real earthquake time histories with accelerations varying from 0.1 g to 0.93 g are considered. The nonlinearity in the viscous damper is modified by taking force proportional to various velocity exponents. It is found that the nonlinear viscous dampers with lower damping constant result in a comparable reduction in the response of RC elevated liquid storage tank, to that of linear viscous dampers with higher damping constant. A lower damping constant signifies compact the size of the damper. Doi: 10.28991/cej-2020-SP(EMCE)-09 Full Text: PDF

Failure analysis of reinforced concrete elevated storage tanks

Assessing the condition of existing structures, with a particular focus on analysing the degradation level, is a complex issue for those responsible for maintenance and monitoring. Elevated storage tanks (water towers) are particularly prone to suffering obsolescence and degradation. As many of these structures are no longer in use and in a poor state of conservation, researchers and local administrators need new tools to achieve a complete overview of the tank condition on a regional scale with limited resources.This paper presents a large-scale structural degradation analysis on the specific structural typology of storage tanks. Firstly, the tanks performances and degradation level are analysed by using a multicriteria approach useful to include both qualitative and quantitative data in the analysis. Secondly, 32 case studies in Valencia (Spain) are investigated to demonstrate the method’s potential. Thirdly, the results of the degradation analysis were used to identify the most frequent damage, the related causes and the structures in the worst conditions. Finally, the best maintenance and intervention strategies to extend the tanks’ remaining life and protect them from further damage are proposed.

Time History Analysis of Circular and Rectangular Elevated Water Storage Tank using Baffle Wall

In the world, there are large number of storage tanks which are used as water and oil storage facilities. Elevated water tank is one of the most important structures in earthquake event. As known from very upsetting experiences, elevated water tanks were heavily damaged or collapsed during earthquake Hence different configurations of liquid storage tanks have been constructed. Water tanks are play an important role in municipal water supply and firefighting systems. Due to post earthquake useful desires, seismic safety of water tanks is most important. In the current study time history analysis of rectangular and circular elevated water storage tank were analyzed using SAP 2000 software. In this study the concrete baffle wall was used to reduce sloshing effect of the water tank. The tank responses such as maximum nodal displacement, base shear and result were compared for empty and full tank water fill condition. From IS 11682:1985 provision when seismic loading is considered only two cases may be taken one is tank empty condition and other is tank full condition. Finally, study discloses the importance of suitable supporting baffle wall to remain withstand against heavy damages of circular and rectangular elevated water tanks during earthquake. As per IITK-GSDMA guidelines for seismic design of liquid storage tanks, hydrodynamic pressure for impulsive and convective mode was calculated.

Time History Analysis of Circular and Rectangular Elevated Water Storage Tank using Baffle Wall

In the world, there are large number of storage tanks which are used as water and oil storage facilities. Elevated water tank is one of the most important structures in earthquake event. As known from very upsetting experiences, elevated water tanks were heavily damaged or collapsed during earthquake Hence different configurations of liquid storage tanks have been constructed. Water tanks are play an important role in municipal water supply and firefighting systems. Due to post earthquake useful desires, seismic safety of water tanks is most important. In the current study time history analysis of rectangular and circular elevated water storage tank were analyzed using SAP 2000 software. In this study the concrete baffle wall was used to reduce sloshing effect of the water tank. The tank responses such as maximum nodal displacement, base shear and result were compared for empty and full tank water fill condition. From IS 11682:1985provision when seismic loading is considered only two cases may be taken one is tank empty condition and other is tank full condition. Finally, study discloses the importance of suitable supporting baffle wall to remain withstand against heavy damages of circular and rectangular elevated water tanks during earthquake. As per IITK-GSDMA guidelines for seismic design of liquid storage tanks, hydrodynamic pressure for impulsive and convective mode was calculated.

Structural reliability of elevated water reservoirs under wind loading

In the field of civil engineering, concrete water storage tanks are considered as hydraulic structures occupying a special place among other structures. The location of these tanks is based on hydraulic considerations related to the desired service pressure for subscribers whose solution is obtained by a compromise with the topographical constraints. In southern Algeria and the highlands; in order to ensure adequate pressure in the drinking water supply networks, the tanks are then elevated to high heights, which puts them under significant stress during windstorms and sandstorms conditions that are frequent in the South Algerian. As the severe weather conditions due to high winds are common, the elevated water storage tanks are designed to withstand to winds speeds included between 25 and 31 m/s according to the Algerian Wind Code. Given the uncertain and randomness of this phenomenon, the classical deterministic calculations of the engineer become limited since they do not integrate the notion of failure probability of the structure. In this study, a probabilistic approach based on Monte Carlo simulations is used to analyze the reliability of elevated water tanks submitted to hazard storm of wind loading. The limit state functions are related to the ultimate and serviceability limit states of the concrete elevated tank under wind analysis. This reliability approach, takes into account mainly two parameters which are the wind speed and the concrete compressive strength considered as random variable. Fragility curves depending on wind zones are obtained, where they demonstrate the dominant failure modes that can cause the structural failure.

Use of ceramic pot filter (CPF) technology under pressure in an in-line pumping system

Abstract Ceramic pot filters (CPFs) are an effective point of use water treatment device in developing nations due to their low cost and effectiveness. CPFs are gravity fed, typically making water production a major limiting factor to a CPF's lifetime and acceptability. Directly connecting CPFs to in-line pumping systems or systems with an elevated storage tank would allow filter usage for constant water treatment at increased pressures, increasing the quantity of treated water. Ceramic disks were manufactured for testing in a specially designed housing apparatus. Filters of varying thicknesses and clay to sawdust mass ratios were manufactured to fit tightly. Flowrate and microbiological removal efficacy (logarithmic reduction value (LRV)) were determined over the testing period at various pressures. Flowrate values ranged from 2.44 to 9.04 L per hour, significantly higher than traditional CPF technology. LRVs ranged from 1.1 to 2.0, lower than traditional CPF technology but still effective at removing most Escherichia coli and total coliform bacteria. Filters proved effective at removing total and fecal coliforms at pressures less than 70 kilopascals. The optimum filter had a thickness of 3.2 cm and clay to sawdust ratio of 6:1 by mass. Filters proved to be ineffective if flowrates were above 5 L/h.

Seismic fragility analysis of elevated steel storage tanks supported by reinforced concrete columns

This study aims to investigate the seismic vulnerability of elevated steel storage tanks rested upon reinforced concrete columns through a probabilistic seismic assessment approach. In particular, an elevated steel storage tank which collapsed during the 1999 Kocaeli earthquake in Turkey is considered. In this respect, in order to evaluate the earthquake performance of the tank components during earthquakes, nonlinear time history analyses are conducted on a three-dimensional finite element stick model. Then, probabilistic seismic demand models incorporating uncertainty parameters for the tank components are established using two sets of ground motion records that represent the near-source and far-field characteristics of the earthquakes. Relevant fragility curves which present the most likely damage states of the tank components are derived using both cloud and incremental dynamic analysis methods. The efficiency and sufficiency of different ground motion intensity measures are also evaluated, leading to the conclusion that in analyzed case, the peak ground acceleration demonstrates the best performance among selected intensity measures.

A Study of Energy Optimisation of Urban Water Distribution Systems Using Potential Elements

Energy use in water supply systems represents a significant portion of the global energy consumption. The electricity consumption due to the water pumping represents the highest proportion of the energy costs in these systems. This paper presents several comparative studies of energy efficiency in water distribution systems considering distinct configurations of the networks and also considers implementation of the variable-speed pumps. The main objective of this study is the energy optimisation of urban systems using optimal network configurations that reduce energy consumption and improve energy efficiency. The paper describes in detail four strategies for improving energy efficiency of water pumping: control systems to vary pump speed drive according to water demand, pumped storage tanks, intermediary pumping stations integrated in the network, and elevated storage tanks floating on the system. The improving energy efficiency of water pumping is briefly reviewed providing a representative real case study. In addition, a different approach for the hydraulic analysis of the networks and the determination of the optimal location of a pumped storage tank is provided. Finally, this study compares the results of the application of four water supply strategies to a real case in Romania. The results indicate high potential operating costs savings.

Seismic vulnerability mitigation of liquefied gas tanks using concave sliding bearings

The aim of this paper is to evaluate the effectiveness of a concave sliding bearing system for the seismic protection of liquefied gas storage tanks through a seismic fragility analysis. An emblematic case study of elevated steel storage tanks, which collapsed during the 1999 Izmit earthquake at Habas Pharmaceutics plant in Turkey, is studied. Firstly, a fragility analysis is conducted for the examined tank based on a lumped-mass stick model, where the nonlinear shear behaviour of support columns is taken into account by using a phenomenological model. Fragility curves in terms of an efficient intensity measure for different failure modes of structural components demonstrate the inevitable collapse of the tank mainly due to insufficient shear strength of the support columns. A seismic isolation system based on concave sliding bearings, which has been demonstrated a superior solution to seismically protect elevated tanks, is then designed and introduced into the numerical model, accounting for its non-linear behaviour. Finally, a vulnerability analysis for the isolated tank is performed, which proves a high effectiveness of the isolation system in reducing the probability of failure within an expected range of earthquake intensity levels.