Modal response of free spanning pipelines based on dimensional analysis

Sollund, Håvar A.; Vedeld, Knut; Fyrileiv, Olav

doi:10.1016/j.apor.2014.12.001

Cited by 18 publications

(13 citation statements)

References 16 publications

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“…For an effective axial force equal to zero, Eq. (39) is fulfilled for the second mode when βE1.2 (Sollund et al, 2015). As a result, it makes little sense to evaluate higher order modal stresses for βo1.2, as the frequency of all higher order modes will be the same, and the VIV problem is reduced, more or less, to an onset problem.…”

Section: Dynamic Response Of An Axially Loaded Beam On An Elastic Foumentioning

confidence: 95%

“…(9) and (14), closed analytical expressions for the modal frequency and associated modal stress may be determined if the surfaces G f and G κ can be determined. A transcendental equation for obtaining the exact frequency and mode shape for an axially loaded free spanning pipeline was recently derived by Sollund et al (2015). However, in the present context a semianalytical solution (Vedeld et al, 2013) to the free span problem with the same level of accuracy as finite element (FE) solutions will be preferred for calculation of frequencies and modal stresses.…”

Section: Expressions For the Response Surfaces G F And G κmentioning

confidence: 97%

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Modal response of short pipeline spans on partial elastic foundations

2015

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Section: Dynamic Response Of An Axially Loaded Beam On An Elastic Foumentioning

confidence: 95%

Section: Expressions For the Response Surfaces G F And G κmentioning

confidence: 97%

Modal response of short pipeline spans on partial elastic foundations

2015

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“…For any straked segments, the excitation and added mass functions available in [19] are used. Mode Shape ϕ = ϕ(x) Determined from analytical solution for a single span from [17,18] with N/(k EI) 1/2 = -0.01508 and L (k/EI) 1/4 = 27.47. Plotted in Figure 8.…”

Section: Cross-flow Excitation Function By Inversion Of F10response Functionmentioning

confidence: 99%

Simplified VIV Response of Partially Strake-Covered Pipe Spans

Peek¹,

Yin²,

Wu³

et al. 2021

Preprint

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A simplified method for the fatigue assessment for partially strake-covered pipeline spans is provided and calibrated so that for the bare pipe case it is consistent with the current DNVGL Recommended Practice (DNVGL-RP-F105). It is based on a Rayleigh-Ritz approximation using the first undamped mode shape. In that sense it is equivalent to a single-mode analysis using Shear7, except that it accounts for frequency-dependent added mass, and the formulation is presented in a compact and convenient non-dimensional form. The method presented may also be considered a simplification of that in Vivana in that it does not account for propagating wave effects, and is therefore named “Sivana”.Like any frequency-domain method Sivana is based on the assumption of harmonic response. This requires excitation and added mass functions that define a harmonic hydrodynamic force as a function of the harmonic motion. On the other hand, current practice by DNVGL-RP-F105 is based on a response function, which gives VIV amplitude as function of reduced velocity and the Scruton mass-damping parameter Ks. To bridge this gap, an inversion technique is developed whereby the excitation function for bare pipe is derived from the DNVGL-RP-F105 response function, such that for bare pipe the Sivana calculation will lead to the same response amplitudes as DNVGL-RP-F105. The Sivana method is illustrated by an example involving a single span with different degrees of strake coverage centered at midspan.Although the Sivana method might be considered a natural and straight-forward extension of current span assessment practice to include partial strake coverage, caution is in order for certain approximations in the DNVGL-RP-F105 response function may be less appropriate for the use in this paper, than for the use envisioned by the developers of the DNVGL guidance.

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“…With the above properties, in-line natural frequencies of 0.95 and 5.37 Hz are calculated, for the first and third mode respectively, using the in-line analytical solution in [11], [12]. (The 2 nd mode is antisymmetric and not expected to be excited by pulling and releasing at midspan.…”

Section: Spanmentioning

confidence: 99%

Pluck Tests on Operating Deepwater Pipeline Spans

Peek¹,

Bernardo²,

Hong³

et al. 2020

Preprint

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Key uncertainties in the assessment of subsea pipeline spans for fatigue due to vortex-induced vibrations (VIV) are the effective axial force, the soil spring stiffness, and the soil damping. To reduce these uncertainties, pluck tests have been carried out, to determine the natural frequency and damping of single and multiple spans. These are carried out by pulling the span laterally at midspan with the ROV, until a 6mm or 8mm PP rope that serves as a weak link in the connection from the pipeline and the ROV breaks. The free vibrations resulting from this pluck are measured with accelerometers attached to the pipeline. The paper presents selected results from these tests and their interpretation in terms modal frequencies and damping ratios. Already at the achieved amplitudes of vibration of up to about 0.01D, the results already show considerable nonlinearity and inelasticity that is thought to come from the soil supporting the pipe at the shoulders of the span, and can be captured in FE models by making the soil springs nonlinear and inelastic.

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Modal response of free spanning pipelines based on dimensional analysis

Cited by 18 publications

References 16 publications

Modal response of short pipeline spans on partial elastic foundations

Modal response of short pipeline spans on partial elastic foundations

Simplified VIV Response of Partially Strake-Covered Pipe Spans

Pluck Tests on Operating Deepwater Pipeline Spans

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