PROFIS ENGINEERING
Torsion
Moment
Figure 6.4a.
Reference Figure 6.4a [ 65 ]. It illustrates a hypothetical anchorage consisting of eight anchors. A torsion moment( M z) acts on the anchorage. This moment creates loads on each anchor, which have components that act in the x direction and in the y direction. There is one fixed edge in the y- direction; therefore, concrete breakout in shear must be considered with respect to this edge. A resultant shear load can be calculated from the torsion load components acting on each anchor. This load will be checked against the calculated design concrete breakout strength in shear.
For this example, the following design steps are taken:
• Determine the torsion load component in the x and y direction on each anchor.
• Calculate the resultant shear load( V res) due to the torsion load components and locate where it acts with respect to the centroid of the anchor group.
F tor, n = factored torsion load acting on anchor n F tor, n, x = torsion load component acting in the x direction F tor, n, y = torsion load component acting in the y direction α = tan-1( 5 in / 12 in) = 22.62 0 β = 90 0- α = 67.38 0 γ = tan-1( 5 in / 4 in) = 51.34 0
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