Some Remarks on the Seismic Demand Estimation in the Context of Vulnerability Assessment of Large Steel Storage Tank Facilities
Author: Antonio Di Carluccio and Giovanni Fabbrocino | Size: 2 MB | Format:PDF | Quality:Unspecified | Publisher: International Scholarly Research Network ISRN Civil Engineering Volume 2012, Article ID 271414, 12 pages doi:10.5402/2012/271414 | Year: 2012 | pages: 13
The seismic behavior of steel tanks is relevant in industrial risk assessment because collapse of these structures may trigger other catastrophic phenomena due to loss of containment. Therefore, seismic assessment should be focused on for leakage-based limit states. From a seismic structural perspective, damages sufferedby tanks are generally related to large axial compressive stresses, which can induce shell buckling near the base and large displacements of unanchored structures resulting in the detachment of piping. This paper approaches the analysis of seismic response of sliding, nonuplifting, unanchored tanks subject to seismic actions. Simplified methods for dynamic analysis and seismic demand estimation in terms of base displacement and compressive shell stress are analyzed. In particular, attention is focussed on some computational issues related to the solution of the dynamic problem and on the extension of the incremental dynamic analysis (IDA) technique to storage tanks.
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VIBRATIONAL CHARACTERISTICS AND SEISMIC ANALYSIS OF CYLINDRICAL LIQUID STORAGE TANKS
Author: JOSEPH W. TEDESCO CELAL N. KOSTEM | Size: 7.2 MB | Format:PDF | Quality:Unspecified | Publisher: FRITZ ENGINEERING LABORATORY REPORT No. 433.5 | Year: 1982 | pages: 219
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The "uplift mecbanismn, developed in response to large overtuniing moment, is the dominant response behaviour of unanchored liquid-tank systems under seismic load. Associated wi t h the base plate uplift , significant deformation and intensive stresses are developed in the tank structure. intense iiquid motion, both the impulsive and the convective component, is also induced fiom the coupling effect. The uplift mechanism is highly nonlinear. Its significance and mechanism in contributing to the seismic behaviour is not fully understood. In this thesis, the seismic behaviour time history of an unanchored broad liquid- tank system is analyzed with the focus on the uplift mechanism. The 1940 El Centro
and the 1994 Northridge earthquakes are used as the ground excitations. The up- lift phenomenon of the base plate, its effects on the shell wall deformation and the dynamic characteristics of the liquid-tank system are studied. The liquid motion developed in the partially uplifted liquid- tank system and the corresponding hydro- dynamic loads are analyzed. The intensive stress developed in the tank structure and the failure mechanism are discussed. A parametric study is conducted to define the effects of the properties of the liquid-tank system on the uplift rnechanism. The seismic behaviour tirne history of mode1 liquid-tank systems with variant structural stiffness and liquid height to tank radius ratio are studied. By varying these parameters, the uplift behaviour, liquid motion and structural stress of the liquid-tank system are carefully compared 2nd deterrnined.
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Comparison between Static and Dynamic Analysis of Elevated Water Tank”
Author: Gaikwad Madhurar V. , Prof. Mangulkar Madhuri N. | Size: 1.1 MB | Format:PDF | Quality:Unspecified | Publisher: International Journal of Scientific & Engineering Research, Volume 4, Issue 6, June-2013 ISSN 2229-5518 | Year: 2013 | pages: 10
Abstract— In earthquake resigns, the elevated water tanks are one of the most important lifeline structures. In major cities & also in rural area, elevated water tanks forms an integral part of water supply scheme. The elevated water tank must functional even after the earthquakes as water tanks are required to provide water for drinking and firefighting purpose. The main object of this paper is, to compare the Static and Dynamic analysis of elevated water tank, to study the dynamic response of elevated water tank by both the methods, to study the hydrodynamic effect on elevated water tank, to compare the effects of Impulsive and Convective pressure results. From detail study and analysis it was found that, for same capacity, same geometry, same height, with same staging system, with same Importance factor & Response reduction factor, in the same Zone; response by equivalent static method to dynamic method differ considerably. Even if we consider two cases for same capacity of tank, change in geometric features of a container can shows the considerable change in the response of tank. As the capacity increases difference between the response increases. Increase in the capacity shows that difference between static and dynamic response is in increasing order. It is also found that, for small capacity of tank the impulsive pressure is always greater than the convective pressure, but it is vice- versa for tanks with arge capacity. Magnitude of both the pressure is different. The effect of water sloshing must be included in the analysis. Free board to be provided in the tank based on maximum value of sloshing wave height. If sufficient free board is not provided, roof structure should be designed to resist
the uplift pressure due to sloshing of water.
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A Computational Framework for Sloshing in Liquid Storage Tank: Theory and Application
Author: Pavan Kumar Sriram – 530144 MSc Computational Mechanics June 2010 | Size: 2.1 MB | Format:PDF | Quality:Unspecified | Publisher: Civil and Computational Engineering School Of Engineering | Year: 2010 | pages: 89
On one hand, the mathematical analysis of some free surface flows is considered. A model problem in one space dimension is first investigated. The Burgers equation with diffusion has
to be solved on a space interval with one free extremity. This extremity is unknown and moves in time. The main work is concerned with the simulation of the incompressible
Newtonian fluid flow problem. The space discretisation is based on the stabilized velocitypressure finite element method. The movement and the deformation of the domain are accounted for by employing the arbitrary Lagrangian-Eulerian (ALE) description of the fluid kinematics. The time discretisation is carried out by using implicit, explicit and semi implicit
scheme. The stability and the convergence of time splitting scheme are investigated. A partitioned solution procedure is developed based on the Newton-Raphson methodology
which incorporates full linearization of the overall incremental problem. Accuracy and stability of the solutions are demonstrated in example for which the analytical solutions are known. In the example, the Burger’s equation analogue to 1-D fluid flows is solved without and with FE mesh motion, to show that the mesh motion practically does not affect the solutions. All solutions presented show that the proposed algorithm is sufficiently accurate and stable. Since the algorithm is implicit, high accuracy of results can be achieved with a relatively large time step.A numerical example is provided to demonstrate the efficiency of the methodology by modeling large amplitude sloshing in a rectangular tank.
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Seismic evaluation of fluid-elevated tank-foundation/soil systems in frequency domain
Author: R. Livaoglu† and A. Dogangun‡ Karadeniz Technical University, Department of Civil Engineering, 61080, Trabzon, Turkey | Size: 867 MB | Format:PDF | Quality:Unspecified | Publisher: Structural Engineering and Mechanics, Vol. 21, No. 1 (2005) 000-0001 | Year: 2005 | pages: 19
Abstract. An efficient methodology is presented to evaluate the seismic behavior of a Fluid-Elevated Tank-Foundation/Soil system taking the embedment effects into accounts. The frequency-dependent cone model is used for considering the elevated tank-foundation/soil interaction and the equivalent spring-mass model given in the Eurocode-8 is used for fluid-elevated tank interaction. Both models are combined to
obtain the seismic response of the systems considering the sloshing effects of the fluid and frequencydependent
properties of soil. The analysis is carried out in the frequency domain with a modal analysis procedure. The presented methodology with less computational efforts takes account of; the soil and fluid interactions, the material and radiation damping effects of the elastic half-space, and the embedment effects. Some conclusions may be summarized as follows; the sloshing response is not practically affected by the change of properties in stiff soil such as S1 and S2 and embedment but affected in soft soil. On the other hand, these responses are not affected by embedment in stiff soils but affected in soft soils.
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Author: N. S. Potty*, Universiti Teknologi Malaysia, MALAYSIA S. Nambissan, Advanced Defence Laboratory, Bangalore, INDIA | Size: 189 MB | Format:PDF | Quality:Unspecified | Publisher: ICCBT 2008 - C - (09) – pp99-108 | Year: 2008 | pages: 10
The Indian Standard “Criteria for Earthquake Resistant Design of Structures: IS 1893-1984” has been revised. Areas in earthquake zone 1 have been merged to earthquake zone 2 and Killari is now in earthquake zone 3. The seismic zone factors have been also changed. Response spectra are now specified for 3 types of founding soil strata and a response reduction factor has been introduced. Elevated water tanks are vulnerable to earthquake, owing to large mass concentrated at the top of a relatively slender supporting structure. Existing elevated steel water tanks in India designed using IS 1893-1984 is checked for safety as per revised code (IS 1893-2002) by carrying out static and forced dynamic analysis. It is observed that the structure is unsafe due to under-estimation of seismic load as per old code provisions. Retrofit measures such as additional structural elements and passive devices like viscous and friction dampers are modelled and structure analysed again to check for compliance with the revised code. Conclusions drawn from this study are presented.
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As known from very upsetting experiences, elevated water tanks were heavily damages or collapsed during
earthquake. This was might be due to the lack of knowledge regarding the proper behaviour of supporting system of
the tank again dynamic effect and also due to improper geometrical selection of staging patterns. Due to the fluidstructure interactions, the seismic behaviour of elevated tanks has the characteristics of complex phenomena. The
main aim of this study is to understand the behaviour of supporting system which is more effective under different
response spectrum method with SAP 2000 software. In this Paper different supporting systems such as radial
bracing and cross bracing.
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Performance of elevated tanks in Mw 7.7 Bhuj earthquake of January 26th, 2001
Author: Proc. Indian Acad. Sci. (Earth Planet. Sci.), 112, No. 3, September 2003, pp. 421{429 | Size: 988 KB | Format:PDF | Quality:Unspecified | Publisher: Durgesh C Rai Department of Civil Engineering, Indian Institute of Technology, Kanpur 208 016, India. | Year: 2013 | pages: 09
The current designs of supporting structures of elevated water tanks are extremely vulnerable under lateral forces due to an earthquake and the Bhuj earthquake provided another illustration when a great many water tank stagings su ered damage and a few collapsed. The more popular shaft type stagings su er from poor ductility of thin shell sections besides low redundancy and toughness whereas framed stagings consist of weak members and poor brace-column joints. A strength analysis of a few damaged shaft type stagings clearly shows that all of them either met or exceeded the strength requirements of IS:1893{1984, however, they were all found de cient when compared with requirements of the International Building Code. IS:1893{1984 is unjusti ably low for these systems which do not have the advantage of ductility and redundancy and are currently being underestimated at least by a factor of 3 and need an upward revision of forces immediately.
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