Forces due to Beam Prestress dialog

Use this dialog to generate forces resulting from prestressing tendons.

Access

• Click Loads Special Loads Prestress Forces.

Case

Displays the name of the case.

Eccentricities (in)

Specifies the local axis of a bar section.

Prestressing force

Specifies the value of the prestressing force.

Bars

Specifies the bars to which the defined load is applied.

Calculations and designations

The following displays how the values of the equivalent load are calculated.

• Data defined by the user:

  N - Prestressing force

  e1 - Eccentricity at the bar beginning

  e2 - Eccentricity at the bar midpoint

  e3 - Eccentricity at the bar end

  L - Length of the bar to which the load is applied

• Calculated load:

  M1 - Concentrated moment at the bar beginning

  M2 - Concentrated moment at the bar end

  F1 - Shear force at the bar beginning

  F2 - Shear force at the bar end

  q - Uniform load

  N1 - Axial force at the bar beginning

  N2 - Axial force at the bar end

• Calculated force values:

  q = 8 * N * e / (L * L)

  Where: e = | (e1 + e3) / 2 - e2 |

The sense of the load q depends on the following:

• For a convex parabola - (e1 + e3) / 2 > e2) - It is compatible with the sense of the axis selected with the Along local axis option.
• For a concave parabola - (e1 + e3) / 2 < e2 - It is opposite to the sense of the axis selected with the Along local axis option.

When the z axis is selected (Along local axis option):

My1 = N * e1

Nx1 = N

Fz1= - q * L / 2

My2 = - N * e3

Nx2 = - N

Fz2= - q * L / 2

When the y axis is selected (Along local axis option):

Mz1 = - N * e1

Nx1 = N

Fy1= - q * L / 2

Mz2 = N * e3

M = -N

Fy2= - q * L / 2.