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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FEM SEISMIC ANALYSIS OF STEEL TANKS FOR OIL STORAGE IN INDUSTRIAL FACILITIES
Author: A. Di Carluccio , G. Fabbrocino , G. Manfredi | Size: 712 KB | Format:PDF | Quality:Unspecified | Publisher: The 14 th World Conference on Earthquake Engineering October 12-17, 2008, Beijing, China | Year: 2008 | pages: 08
ABSTRACT :
Structural and seismic engineering are involved in the design of new industrial facilities, but have certainly a
primary role in the evaluation and upgrading of existing plants. Atmospheric steel tanks for oil and other
hazardous material storage are commonly used in power plants, airports, and other critical plants. Their design is
somehow very standardized worldwide and thus they represent a challenging topic in the context of an industrial
risk assessment related to external hazards like earthquakes. In fact, their dynamic response is not trivial, since
fluid/structure interactions are relevant and influence the susceptibility to seismic damage. A full stress analysis
is certainly the more accurate way to design and to evaluate the risk of steel tanks under earthquake loads, but is
generally demanding in terms of computational effort. This approach leads to the direct computation of the
interaction between shell deformations and content motion during earthquakes. In the present paper, seismic
evaluation according to Eurocode 8 is discussed and some global results of Finite Element Analyses (FEM)
analyses are compared with those obtained according to simplified design procedures by Eurocode 8.
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Nonlinear Winkler-based shallow foundation model for performance assessment of seismically loaded structures
Author: Raychowdhury, Prishati | Size: 20.6 MB | Format:PDF | Quality:Original preprint | Publisher: UNIVERSITY OF CALIFORNIA, SAN DIEGO | Year: 2008 | pages: 326
Abstract:
When a structure supported on shallow foundations is subjected to inertial loading due to earthquake ground motion, the foundation may undergo sliding, settling and rocking movements. If the capacity of the foundation is mobilized, the soil-foundation interface will dissipate significant amounts of vibrational energy, resulting in a reduction in structural force demand. This energy dissipation and force demand reduction may enhance the overall performance of the structure, if potential consequences such as excessive tilting, settlement or bearing failure are accounted for.
Despite this potential benefit, building codes, particularly for new construction, discourage designs that allow foundation capacity mobilization. This lack of acceptance to embrace soil- foundation structure interaction (SFSI) as a design inelastic mechanism may stem from the well founded concern that significant uncertainties exist in characterization of soils. More importantly, the lack of well-calibrated modeling tools, coupled with parameter selection protocols cast in a simplistic fashion are lacking. In this work, a numerical model based on the Beam-on-Nonlinear-WinklerFoundation (BNWF) concept is developed to capture the above mentioned foundation behavior.
The BNWF model is selected due to its relative simplicity, ease of calibration, and acceptance in engineering practice. The soil-foundation interface is assumed to be an assembly of discrete, nonlinear elements composed of springs, dashpots and gap elements. Spring backbone curves typically used for modeling soil-pile response are taken as a baseline and further modified for their usefulness in shallow footing modeling. Evaluation of the model and associated parameter selection protocol is conducted using a suite of centrifuge experiments involving square and strip footings, bridge and building models, static and dynamic loading, sand and clay tests, a range of vertical factors of safety and aspect ratios. It is observed that the model can reasonably predict experimentally measured footing response in terms of moment, shear, settlement and
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Providing the main tools used for preliminary design of composites, this concise text covers all design aspects such as fiber and matrix selection, fabrication processes, prediction of material properties, and structural analysis of beams, plates, shells, and other structures.
Powerful preliminary-design tools, such as "carpet plots," are used in examples throughout the book, and software, entitles Computer Aided Design Environment for Composites (CADEC), is provided, which includes all of the design equations.
To download CADEC, visit Dr. Barbero’s book website
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Advanced Modeling and Evaluation of the Response of Base-Isolated Nuclear Facility Structures to Vertical Earthquake Excitation
Author: Eric Scott Keldrauk | Size: 12.9 MB | Format:PDF | Quality:Unspecified | Publisher: University of California, Berkeley | Year: 2012
The commissioning and construction of new nuclear power plants in the United States has dwindled over the past 30 years despite signi cant innovation in reactor technology. This
is partially due to the ever-increasing seismic hazard estimates, which increases the demand on and risk to nuclear power plant structures. Seismic base isolation is a mature technology which introduces a laterally- exible and vertically-sti layer between the foundation and superstructure to signi cantly reduce the
seismic response of the structure, systems, and components therein. Such devices have also been noted to concentrate the displacement response in one plane, reduce higher-mode
participation, and provide damping to protect against excessive displacements, all of which aid in increasing safety margins for seismically-isolated nuclear structures. Despite numerous
studies analyzing the applicability of seismic base isolation to nuclear power plant structures, some of which are discussed herein, no seismically-isolated nuclear plant has been constructed in the United States. This study presents a time-domain procedure for analyzing the performance of seismicallyisolatednuclear structures in response to design-basis earthquake events using ALE3D. The simulations serve as a parametric study to assess the e ects of soil column type, seismic isolation model, superstructure mesh, and ground motion selection on global displacements, rotations, and accelerations, as well as internal oor accelerations. Explicit modeling of the soil columns and superstructures enables detailed analysis of soil-structure interaction. The
soil columns analyzed have constant properties over the height of the nite element soil mesh
and include rock, soft rock, and sti soil sites, as well as a \no soil" case for comparison.
Four separate 3-dimensional seismic isolation bearing models were coded into ALE3D and validated. These include models for friction pendulum, triple friction pendulum, simpli ed lead rubber, and robust lead rubber bearings. Lastly, two superstructure nite element meshes were considered: a cylindrical plant design meant to represent a typical conceptual
design for advanced reactors, and a rectangular plant design meant to represent an advanced
boiling water reactor. The ground motions considered include 30 three-component time his
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Seismic Testing and Analytical Studies for the Development of New Seismic Force Resisting Systems for Metal Buildings /
Author: Smith, Matthew Douglas | Size: 12.8 MB | Format:PDF | Quality:Unspecified | Publisher: UNIVERSITY OF CALIFORNIA, SAN DIEGO | Year: 2013 | pages: 434
Abstract:
Metal buildings (MB) are a prevalent form of low-rise construction in the U.S. They are built in a
variety of geographic locations, including high seismic regions. It is desirable to understand the seismic performance of such a prevalent structural system. There is a general lack of experimental data available concerning the seismic performance of metal buildings and the web-tapered Ishaped
beams of which they are typically composed. In order to improve the seismic performance of the moment resisting frames in these buildings new Seismic Force Resisting Systems (SFRS) need to be developed. But first, several key issues required research. The MB moment frames
are often controlled by lateral-torsional buckling (LTB) and current design methodologies do not provide adequate LTB flexural strength prediction equations for the full range of member geometries commonly used. Single-story MB frames deviate significantly from the buildings used to define approximate fundamental period equations in the current building codes and the applicability of those equations to MB frames is questionable. Partial-floors, called mezzanines, are often attached to MB frames, yet no clear guidance is given in the current building codes to address the seismic analysis and design of these structures. Finally, experimental data for the
dynamic characteristics of MB moment frames at the system level and their cyclic post-buckling behavior at the member level was needed. This research provided experimental data through two testing programs. Shake table testing was performed on two full-scale metal buildings. Results of those tests led to two concepts for new SFRS for MB frames, one of which relies on LTB for inelastic hinging. Experimental data was provided in support of the development of the new SFRS through cyclic tests of ten web-tapered rafter specimens. The cyclic performance of LTB was investigated and results used to outline a new design procedure. In addition, new approximate
period equations and seismic design methods for mezzanines were developed. This research
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