PROFIS ENGINEERING
Figure
6.2.1a [ 52 ] shows the direct shear load distribution on each anchor( V ua, y, n) from V ua, y. Assume V ua, y acts equally on each anchor. V ua, y acts 6 in from the centroid of the anchors in the x- direction. This creates a torsion moment( M tor) about the centroid of the anchors, which creates a load on each anchor( F tor, n) that can be calculated using the anchor geometry and M tor. Figure 6.2.1b [ 52 ] shows the torsion load distribution on each anchor. The torsion load on each anchor can act in both the x direction( F tor, n, x) and y direction( F tor, n, y). The torsion load direction(+ or-) is used to calculate the net shear load acting on an anchor, and its direction. Table 6.2.1 [ 53 ] below shows the shear loads that have been calculated for each anchor. The net shear load acting on each anchor with respect to the x direction( V x, net) equals( V ua, x, n + F tor, n, x) and the sum of V x, net equals V ua, x. Note there is no torsion component acting in the x direction on anchor 2 and anchor 5. The net shear load acting on each anchor with respect to the y direction( V y, net) equals( V ua, y, n + F tor, n, y) and the sum of V y, net equals V ua, y.
Table 6.2.1.
anchor V ua, x, n( lb) F tor, n, x( lb)
V x, net( lb) = V ua, x, n + F tor, n, x
V ua, y, n( lb) F tor, n, y( lb)
V y, net( lb)
= V ua, y, n + F tor, n, y 1(-) 1000(-) 367(-) 1367(-) 500(-) 306(-) 806 2(-) 1000 0(-) 1000(-) 500(-) 306(-) 806 3(-) 1000(+) 367(-) 633(-) 500(-) 306(-) 806 4(-) 1000(-) 367(-) 1367(-) 500(+) 306(-) 194 5(-) 1000 0(-) 1000(-) 500(+) 306(-) 194 6(-) 1000(+) 367(-) 633(-) 500(+) 306(-) 194
ΣV x, net = V ua, x(-) 6000 ΣV y, net = V ua, y(-) 3000
Figure 6.2.1c. Figure 6.2.1d.
Figure 6.2.1e.
Reference Figure 6.2.1c [ 53 ]. The resultant shear load( V ua, res) is calculated using V ua, x and V ua, y. The distance“ x” corresponds to the eccentricity of V ua, y with respect to the centroid of the anchor group. Reference Table 6.2.1 [ 53 ]. Using the net load V y, net acting on each anchor and the distance of each anchor in the +/- x direction from the centroid of the anchor group, the distance“ x” can be determined.
Reference Figure 6.2.1d [ 53 ]. ACI 318 provisions would calculate the value for“ x” as follows:
3 anchors 806 lb / anchor −5 in * + 3 anchors 194 lb / anchor + 5 in * = V ua, y lb x in − 12, 090 in − lb + 2910 in − lb = 3000lb xin x = − 3.06in
* reference Figure 6.2 [ 51 ] for anchor geometry
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