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Abstraction: This survey presents an idealisation strategy for the analysis of rectangular storage armored combat vehicles acted upon by temblor excitements. Above and below land armored combat vehicle, utilizations have been considered. A additive 3-dimensional finite component analysis has been used to foretell the natural frequences. The analysis parametric quantities are the ratio of tallness to length of the armored combat vehicle, the type of dirt, degree of H2O in the armored combat vehicle, and besides the wall thickness. The consequences for top supplanting and axial force constituents for a full armored combat vehicle above land instance have values greater than those in half- full ( 31 % ) and empty armored combat vehicle instances ( 75 % ) . At the antonym of that, the belowground armored combat vehicle demonstrate that top supplanting and axial force constituents for an empty armored combat vehicle instance have values greater than those in half- full ( 19 % ) and full armored combat vehicle instances ( 40 % ) . The base shear for above land armored combat vehicle instance has values greater than those in belowground armored combat vehicle instances ( 19 % to 37 % ) . The shear base for dirt type 2 is greater than those in dirt type 1 ( 17 % to 28 % ) .

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KEYWORDS: Seismic analysis, syrupy dampers, rectangular armored combat vehicles, finite component theoretical accounts, fluid-structure-soil interaction, clip history, free quiver, ANSYS.

1. Introduction

The harm to storage armored combat vehicles due to recent temblors has been extensively studied by ( Jennings 1971, Hanson 1973, and Monos and Clough 1985 ) . These armored combat vehicles are chiefly steel armored combat vehicles whose failure manners are edge effects in the signifier of elephant pes buckling at the base. ( Housner 1957 ) is the first who considers the hydrodynamic force per unit area distribution developed in stiff armored combat vehicles during horizontal base excitement. He formulates a dynamic theoretical account for gauging the liquid response in seismically aroused stiff, rectangular and round armored combat vehicles. The consequence due to blast flexibleness is subsequently incorporated in the theoretical account by ( Veletsos and Yang 1976 ) , ( Nash et al. 1978 ) , ( Haroun and Housner 1980 ) . ( Haroun and Tayel 1984 ) have investigated the consequence of soil-structure interaction. ( Veletsos and Tang 1986 ) and ( Luft 1984 ) have considered the consequence of perpendicular excitement on the hydrodynamic force per unit areas. ( Haroun and Chen 1989 ) have investigated the nonlinear splashing behaviour in rectangular armored combat vehicles by sing big amplitude sloshing. The finite component analysis of the liquid-tank system is studied by ( Haroun and Housner 1981 ) . Several surveies were besides carried out to look into that dynamic interaction between deformable wall of the armored combat vehicle and the liquid utilizing finite component analysis. ( ASCE 1984 ) comprehensively discusses the consequence of fluid-structure interaction on the hydrodynamic force per unit areas and ( ASCE 1981 ) provides first-class guidelines for the analysis and design of liquid storage constructions.

2. BASIC ASSUMPTIONS

The premises introduced in the present analysis are as follows:

the armored combat vehicle is symmetric in x-axis and symmetric in z-axis footings of geometry.

the stuff of the armored combat vehicle is linearly elastic, isotropic and homogenous.

the contained liquid is inviscid, incompressible and in a non-rotational gesture, within vass holding no net flow rate

the liquid represents solid elements.

the base is connected stiffly to the armored combat vehicle wall.

the dirt medium is represented as a system of closely separated independent additive springs, multitudes and dashpots.

the seismal consequence analogue to z-axis and perpendicular on x-axis

The symbols of the geometric parametric quantities used in this present paper are shown in Plate ( 1 ) .

Plate ( 1 ) Rectangular storage armored combat vehicle and co-ordinate system

3. DESCRIPTION OF STRUCTURE

The construction analyzed in the present survey, shown in Plate ( 1 ) , is a typical rectangular storage armored combat vehicle with a volume of 767.6m3. The contained liquid is assumed to be H2O with the denseness of 10kN/m3, Ew= 2.0684 x109 kN/m2 and Viscosity = 1.2379 x10-12kN/m.s, I…w= 0.19. The armored combat vehicle has a length of 12.6m, a width 6.3m, a tallness 12.6m and a shell thickness of 0.45m and is constructed from a concrete with Ec= 20x 106kN/m2, I…c= 0.15 and I?c= 24kN/m3. The muffling coefficient of the overall construction has been assumed equal to 5 % . The dirt has been chosen, harmonizing to ( Prakash 1981 ) categorization, four different theoretical accounts of dirt types are carried out. The four types of dirt are classified in Table ( 1 ) .

Table ( 1 ) Parametric surveies of dirt type

No.

Soil type

Mass denseness

kN.s2/m4

Shear faculties kN /m2

1

Loess at natural wet

1.67

112892

2

Medium-sized crushed rock

1.8

58320

3

Medium-grained sand

1.65

42240

4

Powdered sand

1.65

19965

4. SEISMIC GROUND EXCITATION

In the present survey a seismal land gesture, the land acceleration has continuance of 31.18sec and a peak land acceleration ( PGA ) of 0.318g. A rectangular concrete armored combat vehicle has been analyzed due to north-south component El-Centro temblor of Fig. ( 1 ) , taken the first five seconds for analysing theoretical accounts of armored combat vehicles, which is assumed to move in the horizontal way ( z-axis ) .

Figure ( 1 ) Accelerogram N-S El Centro temblor, 18-May-1940

5. SOIL-STRUCTURE Interaction

Harmonizing to ( Clough 2003 ) , the soil-structure interaction ( SSI ) effects on the dynamic response of a rectangular armored combat vehicle can be taken into history by patterning each of the physical degrees-of freedom, i.e. horizontal and perpendicular, of the environing dirt system as distinct system with six degrees-of-freedom. The invariables of all the distinct elements are computed as listed in Table 2.

Table ( 2 ) Dirt belongingss of all concrete theoretical accounts considered in the analysis

Soil type

unit

dirt type 1

dirt type 2

dirt type 3

dirt type 4

Directions

R

m

0.5085

0.5085

0.5085

0.5085

Gram

kN/m

112892

58320

42240

19965

??›Zs

0.45

0.2

0.3

0.35

Vertical

Ks

kN/m2

417495.1

148278.6

122737.4

62475.1

Cesium

kN.s/m

542.0

335.3

305.1

208.4

MS

kN.s2/m

0.33

0.36

0.36

0.33

Horizontal

Ks

kN/m

346811.0

159921.2

123092.0

59554.0

Cesium

kN.s/m

298.0

210.1

184.3

122.8

MS

kN.s2/m

0.06

0.07

0.07

0.06

6. FEM Model

The numerical analysis of the rectangular storage armored combat vehicle construction is performed on the footing of elaborate FEM theoretical account developed with the aid of the modus operandis available in the ANSYS Finite Element plan ( ANSYS 2008 ) , as shown in Plate ( 2 ) . The rectangular storage armored combat vehicle is modeled by 26485 or 19093 severally, for the two instances of armored combat vehicle considered in this work, i.e. the belowground armored combat vehicle and the armored combat vehicle above land, four-noded shell elements ( SHELL63 ) with six DOFs per node. The eight node solid fluid component ( FLUID80 ) , with three DOFs per node, has been chosen to pattern the incompressible fluid content. A sum of 4368 or 8736 FLUID80 elements are used, severally, for the three degrees of armored combat vehicle comprehensiveness considered in this work, i.e. empty, half full and full. In order to fulfill the continuity conditions between the fluid and solid media at the rectangular armored combat vehicle boundary, the coincident nodes of the fluid and shell elements are constrained to be coupled in the way normal to the interface, while comparative motions are allowed to happen in the digressive waies. The uniaxial “ tenseness merely ” behaviour of the braces is simulated by agencies of the 3-D spar elements LINK10, which feature a bilinear stiffness matrix, i.e. the stiffness is removed if the component goes into compaction. The syrupy fluid damper devices are modeled utilizing the 1-D non-linear damper elements COMBIN37. Finally, concentrated mass elements ( MASS21 ) and additive spring-damper elements ( COMBIN14 ) are used to pattern the distinct elements for the simulation of soil-structure interaction. The above FEM rectangular armored combat vehicle theoretical account is numerically analyzed by agencies of a full transient additive analysis. The regulating equations of gesture can be expressed in matrix signifier as ( Chopra 1996 ) .

( 1 )

with [ M ] , and being the mass, muffling and stiffness matrices of the construction, severally, an influence coefficient matrix, and the land acceleration. Eq. ( 1 ) is integrated straight in clip utilizing the Newmark-I? method.

Plat ( 2 ) Finite component rectangular armored combat vehicle theoretical account

7. NUMERICAL Survey

The seismal response of the rectangular liquid storage armored combat vehicle above land and resistance is investigated by executing two types of analyses: ( I ) modal analysis and ( two ) clip domain analysis. The job is solved for four types of dirt.

7.1 Modal Analysis

The first measure in the dynamic analysis of any structural system is to find the free quiver response such as natural frequences and manner forms, which are of import in ciphering the seismal response of the liquid storage armored combat vehicles. The Block Lanczos method is used in ANSYS for the Eigenvalue and Eigenvector extractions to cipher natural frequences including the fluid manners ( Hallquist 1998 ) .

7.1.1 Effect of Tank Height to Length Ratio Variation

For this intent, two instances of storage armored combat vehicles are considered, the armored combat vehicle above land and buried armored combat vehicle, for each instance it has been used empty and wholly full armored combat vehicles. The consequences of natural frequences are given in Fig. ( 2 ) and ( 3 ) for empty and wholly full armored combat vehicles, after utilizing four different types of dirt, it has been observed that weakest the dirt ( holding low shear faculties ( Gs ) ) , for this ground the natural frequences acquiring less for the weakest dirt, that become clear in dirt type No. 4.

Above land Underground

Figure ( 2 ) Fundamental natural frequences versus aspect ratio ( Ht/lx ) fluctuation of empty armored combat vehicle

Above land Underground

Figure ( 3 ) Fundamental natural frequences versus aspect ratio ( Ht/lx ) fluctuation of full armored combat vehicle

In comparing the consequences between the two instances of the armored combat vehicles ( the armored combat vehicle above land and buried armored combat vehicle ) , it has been found that the inhumed armored combat vehicle has natural frequences less than the armored combat vehicle above land, because the mass of the armored combat vehicle will increase and that will do the natural frequences acquiring less. It is besides noticed by analyzing these tabular arraies and secret plans, that the natural frequences of the empty armored combat vehicle are much larger than those of the full armored combat vehicles irrespective of the type of dirt.

7.1.2 Effect of Liquid Height to Tank Length Ratio Variation

To show the consequence of liquid tallness fluctuation ( HL/Ht ) , two instances of the armored combat vehicles ( the armored combat vehicle above land and buried armored combat vehicle ) were considered for this intent. The ensuing natural frequences are given in Fig. ( 4 ) for above land and inhumed armored combat vehicles severally.

Above land Underground

Figure ( 4 ) Fundamental natural frequences versus make fulling ratio ( HL/Ht )

It can be observed from these tabular arraies and secret plans that, as the degree of fluid in the armored combat vehicle additions, the natural frequences lessening for both instances of armored combat vehicles and for all four types of the dirt. This behaviour is obvious since the mass of the construction system increases with the degree of fluid.

7.1.3 Effect of Wall Thickness Variation

To show the consequence of wall thickness fluctuation, empty armored combat vehicle and wholly full armored combat vehicle, is studied for the free quiver features when its wall thickness varies from 450mm to 1350mm with one type of the environing dirt ( dirt type 1 ) , and besides for two instances ( above land and buried armored combat vehicle ) .

Above land Underground

Figure ( 5 ) Consequence of thickness fluctuation on natural frequences of empty armored combat vehicle

Above land Underground

Figure ( 6 ) Consequence of thickness fluctuation on natural frequences of full armored combat vehicle

The ensuing natural frequences are given in Fig. ( 5 ) and ( 6 ) . It can be seen clearly from these consequences that, the natural frequences increases when the thickness of the wall increases without altering the tallness of the armored combat vehicle ( the wall stiffness additions with increasing its thickness ) .

7.2 Time Domain Analysis

A clip history analysis utilizing the first five seconds of the north-south constituent of the 1940 El Centro temblor was used for the additive elastic theoretical account. Peak land acceleration values were adjusted to 0.318g. Model clip history analysis under additive elastic, little distortion premises included rating of H2O surface profiles top supplantings, axial force, and ensuing base shear. The undermentioned subdivisions summarize consequences.

The four sets of figures drawn for the different two types of environing dirt are assumed ( dirt type 1, and 2 as mentioned in article ( 5 ) ) , with different degrees of H2O ( full, half -full, and empty armored combat vehicle ) are considered, as shown in Figs. ( ( 7 ) – ( 10 ) ) . The secret plans presented for temblor response of the rectangular armored combat vehicle above land demonstrate that top supplanting and axial force constituents for a full armored combat vehicle instance have values greater than those in half- full ( 31 % ) and empty armored combat vehicle instances ( 75 % ) . At the antonym of that, the belowground rectangular armored combat vehicle demonstrate that top supplanting and axial force constituents for an empty armored combat vehicle instance have values greater than those in half- full ( 19 % ) and full armored combat vehicle instances ( 40 % ) .

It is besides interesting to detect that the base shear for above land armored combat vehicle instance have values greater than those in belowground armored combat vehicle instances ( 19 % to 37 % ) . The shear base for dirt type 2 is greater than those in dirt type 1 ( 17 % to 28 % ) . It is found that the environing dirt type has a important influence on the armored combat vehicle response, as shown in Fig. ( 11 ) and ( 12 ) .

Soil type 1 Soil type 2

Figure ( 7 ) Plot of the top displacement-versus wall height ratio above the base ( tank above land )

Soil type 1 Soil type 2

Figure ( 8 ) Plot of the top displacement-versus wall height ratio above the base ( inhumed armored combat vehicle )

Soil type 1 Soil type 2

Figure ( 9 ) Axial Force- wall tallness ratio for relationships above the base in long wall

Soil type 1 Soil type 2

Figure ( 10 ) Axial Force- wall tallness ratio for relationships above the base in long wall

Soil type 1 Soil type 2

Figure ( 11 ) Plot of basal shear-height of H2O ( tank above land )

Soil type 1 Soil type 2

Figure ( 12 ) Plot of basal shear-height of H2O ( buried armored combat vehicle )

8. CONCLUSIONS

It is concluded that the dirt armored combat vehicle interaction is represented by an elastic half-space medium. Variations of the belongingss of environing dirt medium are found to hold an of import influence on the free and forced vibrational response ( seismal excitement ) for the storage armored combat vehicles.

The frequences in the above land armored combat vehicle are greater than those for inhumed armored combat vehicle about ( 26 % to 27 % ) , and the frequences in type 1 instance have values greater than those in type 2 about ( 29 % to 31 % ) .

The shear base for above land armored combat vehicle have values greater than those in belowground armored combat vehicle by ratio ( 19 % to 37 % ) , The shear base for dirt type 2 is greater than those in dirt type 1 by ratio ( 17 % to 28 % ) . It is found that the environing dirt type has a important influence on the armored combat vehicle response.

It is besides found that, the natural frequence is relative to the wall thickness of the armored combat vehicle. This behaviour is related to the fact that the dynamic stiffness of a armored combat vehicle is a map of its wall thickness.

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