PROFIS ENGINEERING
Eccentric Shear Load
Figure 6.3a.
Reference
Figure 6.3a [ 60 ]. It illustrates a hypothetical anchorage consisting of eight anchors. A shear load( V ua, y) acts towards the y- edge. This load is eccentric with respect to the x direction such that it acts at a point located 6 in in the-x direction from the centroid of the anchor group. Assume V ua, y = 8000 lb.
V ua, y acts eccentric to the centroid of the anchor group, so a torsion moment is created. Therefore, the anchors are subjected to direct shear load acting in the y- direction( V ua, y) as well as shear load due to torsion. The torsion load acting on these anchors has components in both the x +/- and y +/-directions. Torsion loads in the y +/- direction will be summed with the direct load in the y- direction acting on each anchor( V ua, y / 8 anchors). Based on the net anchor loading in the x and y directions, a resultant shear load can be calculated. The location of this resultant shear load with respect to the centroid of the anchor group will be determined, and the resultant shear load eccentricity in the x direction will be used to calculate the design concrete breakout strength with respect to the y- edge( ϕV cbg, y).
For this example, the following design steps are taken:
• Determine the torsion load component in the x and y direction on each anchor.
• Using sign conventions, sum the torsion load component in the y direction with the direct shear load acting on each anchor in the y direction( V ua, y / 8 anchors).
• direct shear on each anchor =( V ua, y / n anchors) =( 8000 lb / 8 anchors) = 1000 lb / anchor.
• Calculate the resultant shear load( V res) and locate where it acts with respect to the centroid of the anchor group.
• Use the resultant shear load eccentricity in the x direction to calculate design concrete breakout strength at the y- fixed edge( ϕV cbg, y).
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