Static and dynamic numerical analysis studies of hemispheres and spherical caps. Part I: Background and theory

Shao, Wei; Frieze, P A

doi:10.1016/0263-8231(89)90038-4

Cited by 7 publications

(6 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The test results obtained on the shells are also given for purposes of comparison. Table 3, the employment in equation (15) of an imperfection having an amplitude of 6, = O.O5,/(Rt) gave calculated collapse pressures for the DTMB hemispherical shells that were in satisfactory agreement with the test results. The ratios pexpJpc were all in the range 0.98-1.30, that is all the calculated collapse pressures (except one) were lower than the test values and were thus on the safe side.…”

Section: Computer Analysis Of Imperfect Spherical Shellssupporting

confidence: 55%

“…As an example, consider the following tabulation: In the above two cases, the value of dolt given by equation (4) (and which assumed increased-radius imperfections) is 5&75 per cent higher than the maximum value recommended by DASt 013. Thus, for 12 Comparison of collapse pressures p, as given by equations (13) and (15), assuming simp = 3.5J(Rt) these cases, the predicted collapse pressures can be significantly lower than those shown by the DnV and DASt curves in Fig. 6.…”

Section: Increased-radius Versus Legendre Polynomialmentioning

confidence: 89%

“…The ratios pexpJpc were all in the range 0.98-1.30, that is all the calculated collapse pressures (except one) were lower than the test values and were thus on the safe side. This means that equation (15) [and also equation (1311 would be satisfactory for estimating the collapse pressures of welded hemispherical shells-at least for initial design purposes.…”

Section: Computer Analysis Of Imperfect Spherical Shellsmentioning

confidence: 99%

“…When using equation (15), it is necessary to know the value of p;, for the corresponding perfect hemispherical shell. While there is no difficulty in calculating this p:, (using a program like BOSOR 5), it is probably easier for the designer when the collapse pressures are normalized with respect to pyp instead of prr [as is the case with equation (13)].…”

Section: Another Equation For the Collapse Pressures Found Bymentioning

confidence: 99%

See 3 more Smart Citations

Buckling Design of Imperfect Welded Hemispherical Shells Subjected to External Pressure

Galletly

Błachut

1991

Proceedings of the Institution of Mechanical Engineers, Part C:

View full text Add to dashboard Cite

Welded hemispherical or spherical shells in practice have initial geometric imperfections in them that are random in nature. These imperfections determine the buckling resistance of a shell to external pressure but their magnitudes will not be known until after the shell has been built. If suitable simplified, but realistic, imperfection shapes can be found, then a reasonably accurate theoretical prediction of a spherical shell's bucklinglcollapse pressure should be possible at the design stage.The main aim of the present paper is to show that the test results obtained at the David Taylor Model Basin (DTMB) on 28 welded hemispherical shells (having diameters of 0.75 and 1.68 m) can be predicted quite well using such simplified shape imperfections. This was done in two ways. In the jirst, equations for determining the theoretical collapse pressures of externally pressurized imperfect spherical shells were utilized. The only imperfection parameter used in these equations is 6,, the amplitude of the inward radial deviation of the pole of the shell. Two values for 6 , were studied but the best overall agreement between test and theory was found using 6, = 0.05J(Rt). This produced ratios of experimental to numerical collapse pressures in the range 0.98-1.30 (in most cases the test result was the higher). The second approach also used simplified imperfection shapes, but in conjunction with the shell buckling program BOSOR 5. The arc length of the imperfection was taken as simp = kJ(Rt) (with k = 3.0 or 3.5) and its amplitude as 6 , = O.O5J (Rt) . Using this procedure on the 28 D T M B shells gave satisfactory agreement between the experimental and the computer predictions (in the range 0.92-1.20). These results are very encouraging. The foregoing method is, however, only ajirst step in the computerized buckling design of welded spherical shells and it needs to be checked against spherical shells having other values of Rlt. I n addition, more experimental information on the initial geometric imperfections in welded spherical shells (and how they vary with Rlt) is desirable.A comparison is also given in the paper of the collapse pressures of spherical shells, as obtained from codes, with those predicted by computer analyses when the maximum shape deviations allowed by the codes are employed in the computer programs. The computed collapse pressures arefrequently higher than the values given by the buckling strength curves in the codes. On the other hand, some amplitudes of imperfections studied in the paper give acceptable results. It would be helpful to designers i f agreement could be reached on an imperfection shape (amplitude and arc length) that was generally acceptable. Residual stresses are not considered in this paper. They might be expected to decrease a spherical shell's buckling resistance to external pressure. However, experimentally, this does not always happen.{ 12(1 -v ' ) }~/~~J ( R /~) z 1.82a,/(R/t) for v = 0.3 slenderness parameter = J(pyp/pcr) = 1.285J{(R/t)(ay,,/E)} for a spherical shell Poisson ratio...

show abstract

Section: Computer Analysis Of Imperfect Spherical Shellssupporting

confidence: 55%

Section: Increased-radius Versus Legendre Polynomialmentioning

confidence: 89%

Section: Computer Analysis Of Imperfect Spherical Shellsmentioning

confidence: 99%

Section: Another Equation For the Collapse Pressures Found Bymentioning

confidence: 99%

See 2 more Smart Citations

Buckling Design of Imperfect Welded Hemispherical Shells Subjected to External Pressure

Galletly

Błachut

1991

Proceedings of the Institution of Mechanical Engineers, Part C:

View full text Add to dashboard Cite

show abstract

“…On the other hand, the dynamic stability analysis of spherical caps has not received the same attention from investigators, possibly because of the difficulties in approaching this problem in a systematic manner, and criteria for dynamic buckling are not well established. Moreover, most of the studies on the axisymmetric dynamic buckling of shallow spherical caps have focused their attention on the snap-through buckling under step loading of infinite or finite duration [4][5][6][7][8][9]. Relatively little work has been done on the dynamic behavior of spherical caps under harmonic loading [10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Chaotic Behavior Resulting in Transient and Steady State Instabilities of Pressure-Loaded Shallow Spherical Shells

Soliman¹,

Gonçalves

2003

Journal of Sound and Vibration

View full text Add to dashboard Cite

Ultimate Strength Assessment of Steel-Welded Hemispheres under External Hydrostatic Pressure

Cho

Muttaqie

Lee

et al. 2020

J. Marine. Sci. Appl.

View full text Add to dashboard Cite

This paper focusses on steel-welded hemispherical shells subjected to external hydrostatic pressure. The experimental and numerical investigations were performed to study their failure behaviour. The model was fabricated from mild steel and made through press forming and welding. We therefore considered the effect of initial shape imperfection, variation of thickness and residual stress obtained from the actual structures. Four hemisphere models designed with R/t from 50 to 130 were tested until failure. Prior to the test, the actual geometric imperfection and shell thickness were carefully measured. The comparisons of available design codes (PD 5500, ABS, DNV-GL) in calculating the collapse pressure were also highlighted against the available published test data on steel-welded hemispheres. Furthermore, the nonlinear FE simulations were also conducted to substantiate the ultimate load capacity and plastic deformation of the models that were tested. Parametric dependence of the level of sphericity, varying thickness and residual welding stresses were also numerically considered in the benchmark studies. The structure behaviour from the experiments was used to verify the numerical analysis. In this work, both collapse pressure and failure mode in the numerical model were consistent with the experimental model.

show abstract

Static and dynamic numerical analysis studies of hemispheres and spherical caps. Part I: Background and theory

Cited by 7 publications

References 22 publications

Buckling Design of Imperfect Welded Hemispherical Shells Subjected to External Pressure

Buckling Design of Imperfect Welded Hemispherical Shells Subjected to External Pressure

Chaotic Behavior Resulting in Transient and Steady State Instabilities of Pressure-Loaded Shallow Spherical Shells

Ultimate Strength Assessment of Steel-Welded Hemispheres under External Hydrostatic Pressure

Contact Info

Product

Resources

About