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Pipeline Concrete Stiffness Factor Modules

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CALCULATOR MODULE : Beam Natural Vibration Frequency   ±

Calculate the damped and undamped beam natural vibration frequency for general beams (simply supported, fixed, and cantilever beams). For other beam types (eg circular beams) refer to the module links below.

The lateral natural vibration frequency beam end conditions are: pinned ends (simply supported beams), fixed ends, free fixed ends (cantilever beams), pinned fixed ends, and for beams with no load, pinned free ends, and free ends (unsupported beams). Added mass should be included for submerged or wet beams. The added mass coefficient can be calculated in accordance with DNVGL RP F105. The submerged natural frequency is calculated for still water conditions, with no vortex shedding. For beams on a soft foundation such as soil, use the effective length factor to allow for movement at the beam ends. For defined beam ends such as structures, the effective length factor should be set to one. The buckling load can be calculated using either the Euler equation (suitable for long beams), or the Johnson equation (suitable for short beams). The buckling load is dependent on the end type, and is used for mode 1 vibration only. Buckling normally occurs on the axis with lowest stiffness (I1 or I2). The bending stiffness for vibration and buckling can be defined separately for cases where vibration and buckling are not parallel.

`fn = ca.cd k / (2 π) √((EI) / (m . Le^4)) `
`ca =1 / (1 + F / (Fb))) `
`cd = √(1 - fd^2) `

where :

fn = lateral natural frequency [Hz]
ca = axial load coefficient
cd = damping coefficient
fd = damping factor (0 = undamped 1 = critical damping)
k = mode factor
L = effective beam length
EI = beam E I (bending modulus)
m = beam unit mass or mass per length
F = axial load (+ve in tension and -ve in compression)
Fb = buckling load

The longitudinal natural vibration frequency end conditions are: free fixed ends (cantilever), fixed ends, and free ends (unsupported). The fixed ends and free ends modes have the same natural frequencies, but different mode shapes. The longitudinal natural frequency is independent of cross section, and depends on the beam elastic modulus and density.

`fn = cd k / (2 π L) √(E / ρ) `

where :

fn = natural frequency [Hz]
cd = damping coefficient
k = mode factor
L = beam length
E = beam elastic modulus
ρ = beam density

The torsional natural vibration frequency end conditions are: free fixed ends (cantilever), fixed ends, and free ends (unsupported). The fixed ends and free ends modes have the same natural frequencies, but different mode shapes. The torsional natural frequency is independent of cross section, and depends on the beam shear modulus and density.

`fn = cd k / (2 π L) √(G / ρ) `

where :

fn = natural frequency [Hz]
cd = damping coefficient
k = mode factor
L = beam length
G = beam shear modulus
ρ = beam density

The mode factor k is dependent on the mode number, and the beam end type. The k factors have been taken from the Shock and Vibration handbook. The damping factor should be set to zero for undamped vibration or set greater than zero and less than or equal to one for damped vibration.

Use the Result Table and Result Plot options to display tables and plots. Refer to the figures and help pages for more details about the tools. Refer to the links below for other beam options.

References :

Shock And Vibration Handbook, Cyril M Harris, McGraw Hill
Roark's Formulas For Stress And Strain, Warren C Young, McGraw Hill

Change Module :

CALCULATOR MODULE : Beam Lateral Vibration Frequency   ±

Calculate the damped and undamped beam natural vibration frequency for lateral vibration (simply supported, fixed, and cantilever beams).

Added mass should be included for submerged or wet beams. The added mass coefficient can be calculated in accordance with DNVGL RP F105. The submerged natural frequency is calculated for still water conditions, with no vortex shedding. For beams on a soft foundation such as soil, use the effective length factor to allow for movement at the beam ends. For defined beam ends such as structures, the effective length factor should be set to one.

The mode factor k is dependent on the mode number, and the beam end type. The k factors have been taken from the Shock and Vibration handbook. The damping factor should be set to zero for undamped vibration or set greater than zero and less than or equal to one for damped vibration. For multi layer pipes the bending stiffness can be calculated with the concrete stiffness factor (CSF). The CSF accounts for the additional stiffness provided by the external concrete coating. The concrete stiffness factor is calculated in accordance with DNVGL RP F105. Enter the wall thickness for all layers. Only enter the elastic modulus for layers which affect the pipe stiffness.

Use the Result Table and Result Plot options to display tables and plots. Refer to the figures and help pages for more details about the tools.

References :

Shock And Vibration Handbook, Cyril M Harris, McGraw Hill
Roark's Formulas For Stress And Strain, Warren C Young, McGraw Hill

Change Module :

CALCULATOR MODULE : Beam Lateral Vibration Frequency With Axial Load   ±

Calculate the damped and undamped beam natural vibration frequency for lateral vibration with axial load (simply supported, fixed, and cantilever beams).

For beams with axial load the axis with minimum stiffness (I1 or I2) should be used unless the beam is constrained to deflect on an alternative axis (buckling normally occurs on the minimum stiffness axis). Use the general beam calculators for cases where vibration and buckling are not parallel. The buckling load can be calculated using either the Euler equation (suitable for long beams), or the Johnson equation (suitable for short beams). The buckling load is dependent on the end type, and is used for mode 1 vibration only.

Added mass should be included for submerged or wet beams. The added mass coefficient can be calculated in accordance with DNVGL RP F105. The submerged natural frequency is calculated for still water conditions, with no vortex shedding. For beams on a soft foundation such as soil, use the effective length factor to allow for movement at the beam ends. For defined beam ends such as structures, the effective length factor should be set to one. For pipes the axial load is calculated from temperature and pressure. For general beams the axial load is user defined.

The mode factor k is dependent on the mode number, and the beam end type. The k factors have been taken from the Shock and Vibration handbook. The damping factor should be set to zero for undamped vibration or set greater than zero and less than or equal to one for damped vibration. For multi layer pipes the bending stiffness can be calculated with the concrete stiffness factor (CSF). The CSF accounts for the additional stiffness provided by the external concrete coating. The concrete stiffness factor is calculated in accordance with DNVGL RP F105. Enter the wall thickness for all layers. Only enter the elastic modulus for layers which affect the pipe stiffness.

Use the Result Table and Result Plot options to display tables and plots. Refer to the figures and help pages for more details about the tools.

References :

Shock And Vibration Handbook, Cyril M Harris, McGraw Hill
Roark's Formulas For Stress And Strain, Warren C Young, McGraw Hill

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CALCULATOR MODULE : Beam Vibration Concrete Stiffness Factor CSF   ±

Calculate beam concrete stiffness factor and effective EI from the concrete beam EI ratio.

`CSF = kc ((EIc) / (EIp))^0.75 `
`EIe = EIc (1 + CSF) `

where :

CSF = concrete stiffness factor
kc = coating factor (kc = 0.33 for asphalt and 0.25 for PP/PE coating)
EIc = concrete bending stiffness
EIb = pipe bending stiffness
EIe = eqivalent bending stiffness

The concrete stiffness factor is used to account for the effect of the concrete layer on the natural frequency, deflection and bending stress. The concrete stiffness factor is calculated from the ratio of concrete EI over pipe EI. The concrete stiffness factor is calculated in accordance with DNVGL RP F105. The method is suitable for circular pipes. The method may not be valid for other profiles (engineering judgment is required).

Use the Result Table and Result Plot options to display tables and plots. Refer to the help pages for more details about the tools.

References :

Shock And Vibration Handbook, Cyril M Harris, McGraw Hill
Roark's Formulas For Stress And Strain, Warren C Young, McGraw Hill

Change Module :

CALCULATOR MODULE : Beam Cross Section   ±

Calculate beam cross section properties for circular pipes: cross section area, moment of inertia, polar moment of inertia, mass moment of inertia, section modulus, EI, EA, EAα, unit mass, total mass, unit weight and specific gravity.

Unit mass can be calculated with or without added mass. Added mass is included in the unit mass for submerged beams to account for the fluid which is displaced by the beam. The added mass coefficient can be calculated in accordance with DNVGL RP F105. For multi layer pipes the bending stifness can be calculated with the concrete stiffness factor (CSF). The CSF accounts for the additional stiffness provided by the external concrete coating. Use the Result Table option to display the cross section properties versus wall thickness. Refer to the help pages for more details.

Reference : Roark's Formulas For Stress And Strain, Warren C Young, McGraw Hill

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Related Modules :

CALCULATOR MODULE : Pipe Beam Bending   ±

Calculate beam bending shear force, bending moment, slope and deflection for pipe beams using the Euler Bernoulli beam equation.

The Euler Bernoulli beam equation is suitable for slender beams (it does not include the effect of shear), and for small angles (θ < 0.5 rad). The calculations are not valid past the beam end points. For combined loads, the shear force, bending moment, slope and deflection are assumed to be additive. The beam end conditions are of the form left end - right end (for example Pin-Fix is left end pinned and right end fixed). All distances are measured from the left end of the beam.

Beam end types include: free fixed (cantilever), guided fixed, pinned fixed, fixed fixed (built in or fixed), pinned pinned (simply supported), and guided pinned beam ends.

Combined loads include axial loads, point loads, distributed loads, weight loads, concentrated moments, angular displacements, lateral displacements, and uniform temperature gradient.

For beams with compressive axial loads the bending moment, slope and deflection tend to infinity as the axial load tends to the buckling load. For tension loads, the bending moment, slope and deflection decrease with increasing tension. The buckling load can be calculated using either the Euler equation (suitable for long beams), the Johnson equation (suitable for short beams), or the buckling load equation can be determined from the transition length.

The effective length factor should be used for beams on a soft foundation such as soil, where the beam ends are poorly defined. For defined beam ends, such as structures, the effective length factor should be set to one (fe = 1).

For multi layer beams the concrete stiffness can be included in EI by multiplying EI by a factor (1 + CSF). The bending stress at the field joint should also be multiplied by the factor (1 + CSF) to account for stress localisation (select the pipe joint option for bending stiffness) . The concrete stiffness factor is calculated from the ratio of concrete EI over beam EI in accordance with DNVGL RP F105. The method is suitable for circular beams and pipes. For other profile shapes engineering judgement is required.

The stress check includes longitudinal stress, Tresca combined stress, and von Mises equivalent stress. The bending stress is calculated at the pipe mid wall. The hoop stress is calculated using the Barlow mid wall equation with the nominal wall thickness.

:

`Sh = (P - Pe) (OD - tn) / (2 tn) `

where :

Sh = hoop stress
P = internal pressure
Pe = external pressure
OD = pipe outside diameter
tn = pipe nominal thickness

Use the Result Plot option to plot the bending moment, shear force, slope, deflection and stress versus position x. Refer to the figures and help pages for more details.

Reference : Roark's Formulas For Stress And Strain, Warren C Young, McGraw Hill

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CALCULATOR MODULE : Pipe Beam Buckling Load   ±

Calculate beam buckling load for pipe beams.

Beam end types include: free fixed (cantilever), guided fixed, pinned fixed, fixed fixed (built in or fixed), pinned pinned (simply supported), and guided pinned beam ends. The beam end conditions are of the form left end - right end (for example Pin-Fix is left end pinned and right end fixed).

The buckling load can be calculated using either the Euler equation (suitable for long beams), the Johnson equation (suitable for short beams), or the buckling load equation can be determined from the transition length. The buckling load is positive. The axial load is negative in compression. Buckling will generally occur about the axis with the lowest EI, depending on constraints.

The effective length factor should be used for beams on a soft foundation such as soil, where the beam ends are poorly defined. For defined beam ends, such as structures, the effective length factor should be set to one (fe = 1).

Concrete stiffness can be included in EI by multiplying EI by a factor (1 + CSF). The concrete stiffness factor is calculated from the ratio of concrete EI over beam EI in accordance with DNVGL RP F105. The method is suitable for circular beams and pipes. For other profile shapes engineering judgement is required.

Use the Result Plot option to plot the buckling load versus nominal length. Use the Result Table option to plot the buckling load versus end type. Refer to the figures and help pages for more details.

Reference : Roark's Formulas For Stress And Strain, Warren C Young, McGraw Hill

Change Module :

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