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Polygon Section Beam Modules

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CALCULATOR MODULE : Polygon Beam Natural Vibration Frequency   ±

Calculate the damped and undamped natural vibration frequency for solid and hollow regular polygon beams (simply supported, fixed, and cantilever beams).

For lateral vibration with axial load 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. The axial load is calculated from temperature.

For longitudinal and torsional vibration, the natural frequency is independent of the cross section, and the general beam calculators can be used.

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. The polygon section is assumed to be symmetric along axis 1 and 2, and all sides and wall thickness are assumed to be equal. The minimum number of sides is 3. A regular polygon with 3 sides is equivalent to an equilateral triangle. A regular polygon with 4 sides is equivalent to a square. For beams with axial load the axis with minimum stiffness (I1 or I2) should be used unless the beam is constrained to deflect on the chosen axis (buckling normally occurs on the minimum stiffness axis).

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 : Polygon Beam Cross Section   ±

Calculate beam cross section properties for regular polygon beams: cross section area, moment of inertia, polar moment of inertia, mass moment of inertia, plastic modulus, section modulus, shape factor, radius of gyration, EI, EA, EAα, unit mass, total mass, unit weight and specific gravity.

The polygon section is assumed to be symmetric along axis 1 and 2, and all sides and wall thickness are assumed to be equal. The minimum number of sides is 3. A regular polygon with 3 sides is equivalent to an equilateral triangle. A regular polygon with 4 sides is equivalent to a square. Refer to the figures for more details.

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

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CALCULATOR MODULE : Polygon Beam Bending   ±

Calculate beam bending shear force, bending moment, slope and deflection for regular polygon beams.

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).

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 : Polygon Beam Buckling Load   ±

Calculate beam buckling load for regular polygon beams.

The polygon section is assumed to be symmetric along axis 1 and 2, and all sides and wall thickness are assumed to be equal. The minimum number of sides is 3. A regular polygon with 3 sides is equivalent to an equilateral triangle. A regular polygon with 4 sides is equivalent to a square.

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).

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

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