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Spin-Lock Anchor Design Considerations
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For several decades Engineers have successfully based their Spin-lock designs on the 45˚ cone method that was presented in ACI 349 Appendix B (1985). This method has worked effectively for Spin-Locks when used in nuclear power plants, rocket launch pads, machinery tie downs, foundation repair anchors and many more applications.
At times, job conditions may dictate the necessity to place adjacent anchors closer than the minimum spacings (S) shown in the following table. When reduced spacing is desired it is then recommended to install the anchors by staggering the embedment depths. Adjacent anchors should be staggered as shown in the illustration below. After the deepest anchors have been drilled, installed, grouted, and the grout has cured; the adjacent anchors can be drilled and installed. This procedure would allow for (S) values to be reduced by half without the danger of fracture between holes during installation.
The ideal spacings are large enough to prevent blow out from anchor hole to anchor hole, but not to develop the full combined anchor capacities. Based on the 45˚ cone method in ACI 349 Appendix B (1985), the center to center spacing to develop the full shear cone should be 2 times the recommended embedment depth. Closely spaced anchors can be designed with a deeper embedment than what is listed in order to develop the combined anchor capacities.
Adequate safety factors should always be applied based on site and design conditions. For best results Williams Spin-Lock anchors should be used in high strength reinforced concrete.
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Prestressed Anchors for Tower or Column Supports |
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Prestressing New Concrete to Old Concrete |
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Spin-Lock Concrete Anchors - Minimum Spacing & Edge Distances |
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Edge distance (E) may be reduced from the following chart if special care is taken during installation, working loads are reduced, or heavy reinforcement is present in the side wall of the concrete. Williams has performed testing that gives the designer a basic idea of what concrete failure loads to expect in non-reinforced concrete for reduced edge distances. These numbers are not recommendations, they are simply meant to be used as a reference. The designer should compare the numbers below that are based on tests, to numbers determined from the design models of ACI 349 appendix B and/or values from ACI 318 Appendix D. Call the Williams Concrete Anchor Division for additional test info. |
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Spin-Lock Concrete Anchors - Minimum Spacing & Edge Distances |
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Head
Assembly
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Anchor
Type
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Anchor
Diameter
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Minimum
Embedment
|
Minimum
Spacing
to Prevent
Hole to Hole
Blowout
Failure (S)
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Minimum
Recomm.
Edge
Distance
(E)
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Average
Ultimate
Strength
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Concrete Failure Loads
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7 Bar Dia.
from the
Edge (Test)
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10 Bar Dia.
from the
Edge (Test)
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14 Bar Dia.
from the
Edge (Test)
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18 Bar Dia.
from the
Edge (Test)
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| A10 |
R1S |
1/2"
(12 mm) |
7"
(178 mm) |
6"
(152 mm) |
8"
(203 mm) |
17.1 kips
(75.8 kN) |
15 kips
(67 kN) |
17 kips
(75.8 kN) |
(1)
|
(1)
|
5/8"
(16 mm) |
8"
(203 mm) |
7-1/2"
(191 mm) |
9"
(229 mm) |
27.1 kips
(121 kN)
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15 kips
(67 kN) |
19 kips
(84.5 kN)
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22 kips
(98 kN)
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N.A.
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| R1V |
1/2"
(12 mm) |
7"
(178 mm) |
6"
(152 mm) |
8"
(203 mm) |
18 kips
(80.0 kN) |
15 kips
(67 kN) |
(1)
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(1)
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(1)
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| R1J |
1/2"
(12 mm) |
7"
(178 mm) |
6"
(152 mm) |
8"
(203 mm) |
12.7 kips
(56.5 kN) |
15 kips
(67 kN) |
(1)
|
(1)
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(1)
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5/8"
(16 mm) |
8"
(203 mm) |
7-1/2"
(191 mm) |
9"
(229 mm) |
20.3 kips
(90.3 kN)
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15 kips
(67 kN) |
19 kips
(84.5 kN)
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20 kips
(89 kN)
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(1)
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| B14 |
R1H |
1"
(25 mm) |
14"
(356 mm) |
12"
(305 mm) |
15"
(381 mm) |
66 kips.
(294 kN) |
35 kips
(156 kN)
|
66 kips.
(294 kN) |
(1)
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(1)
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| R1J |
3/4"
(20 mm) |
10"
(254 mm) |
9"
(229 mm) |
11"
(279 mm) |
30 kips
(134 kN)
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18 kips.
(80 kN) |
30 kips
(134 kN)
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(1)
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(1)
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7/8"
(22 mm) |
12"
(305 mm) |
10-1/2"
(227 mm) |
14"
(356 mm) |
41.5 kips
(185 kN)
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18 kips.
(80 kN) |
41.5 kips
(185 kN)
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(1)
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(1)
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1"
(25 mm) |
15"
(381 mm) |
12"
(305 mm) |
15"
(381 mm) |
54 kips
(240 kN)
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35 kips
(156 kN)
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54 kips
(240 kN)
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(1)
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(1)
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| B20 |
R1H |
1-3/8"
(35 mm) |
24"
(610 mm) |
16-1/2"
(419 mm) |
22"
(559 mm) |
138 kips
(614 kN) |
N.A.
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90 kips
(400 kN)
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102 kips
(508 kN)
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N.A.
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| R1V |
1-3/8"
(35 mm) |
24"
(610 mm) |
16-1/2"
(419 mm) |
22"
(559 mm) |
154 kips
(684 kN)
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N.A.
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90 kips
(400 kN)
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102 kips
(508 kN)
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N.A.
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| R1J |
1-3/8"
(35 mm) |
22"
(559 mm) |
16-1/2"
(419 mm) |
22"
(559 mm) |
110 kips
(489 kN)
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N.A.
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90 kips
(400 kN)
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102 kips
(508 kN)
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(1)
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| R7S |
1-1/4"
(32 mm) |
18"
(457 mm) |
15"
(381 mm) |
20"
(508 mm) |
145 kips
(649 kN)
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82 kips
(365 kN)
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87 kips
(387 kN)
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N.A.
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N.A.
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| B24 |
R7S |
1-1/2"
(38 mm) |
26"
(662 mm) |
19-1/2"
(495 mm) |
27"
(686 mm) |
210 kips
(932 kN)
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N.A.
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90 kips
(400 kN)
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102 kips
(508 kN)
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208 kips
(925 kN)
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| C14 |
R1S |
3/4"
(20 mm) |
12"
(305 mm) |
9"
(229 mm) |
11"
(279 mm) |
40.1 kips
(178 kN)
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33 kips
(147 kN)
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42 kips
(187 kN)
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(1)
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(1)
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7/8"
(22 mm) |
14"
(356 mm) |
10-1/2"
(227 mm) |
14"
(356 mm) |
55.4 kips
(246 kN)
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33 kips
(147 kN)
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42 kips
(187 kN)
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(1)
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(1)
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1"
(25 mm) |
16"
(406 mm) |
12"
(305 mm) |
15"
(381 mm) |
72.7 kips
(323 kN)
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55 kips
(245 kN) |
67 kips
(298 kN) |
(1)
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(1)
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| R1V |
3/4"
(20 mm) |
11"
(279 mm) |
9"
(229 mm) |
11"
(279 mm) |
42 kips
(187 kN)
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33 kips
(147 kN)
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42 kips
(187 kN)
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(1)
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(1)
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1"
(25 mm) |
16"
(406 mm) |
12"
(305 mm) |
15"
(381 mm) |
76 kips
(338 kN)
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55 kips
(245 kN) |
67 kips
(298 kN) |
N.A.
|
N.A.
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| R7S |
1"
(25 mm) |
18"
(457 mm) |
13"
(330 mm) |
17"
(432 mm) |
90 kips
(400 kN) |
55 kips
(245 kN) |
67 kips
(298 kN) |
91 kips
(405 kN) |
(1)
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| C18 |
R1S |
1-1/4"
(32 mm) |
20"
(508 mm) |
15"
(381 mm) |
20"
(508 mm) |
102 kips
(508 kN)
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82 kips
(365 kN)
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92 kips
(409 kN)
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102 kips
(508 kN)
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(1)
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| R1J |
1-1/8"
(30mm) |
16"
(406 mm) |
13-1/2"
(343 mm) |
18"
(457 mm) |
68 kips
(303 kN)
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N.A.
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68 kips
(303 kN)
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(1)
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(1)
|
1-1/4"
(32 mm) |
23"
(584 mm) |
16"
(406 mm) |
22"
(559 mm) |
87 kips
(387 kN)
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82 kips
(365 kN)
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92 kips
(409 kN)
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(1)
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(1)
|
| C28 |
R7S |
1-7/8"
(48 mm) |
36"
(914 mm) |
24"
(610 mm) |
35"
(889 mm) |
360 kips
(1598 kN)
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N.A.
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180 kips
(801 kN)
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283 kips
(1259 kN)
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330 kips
(1467 kN)
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| R1V |
2"
(51 mm) |
35"
(889 mm) |
24"
(610 mm) |
32"
(813 mm) |
330 kips
(1467 kN)
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N.A.
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180 kips
(801 kN)
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283 kips
(1259 kN)
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330 kips
(1467 kN)
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| R1H |
2"
(51 mm) |
33"
(838 mm) |
24"
(610 mm) |
32"
(813 mm) |
300 kips
(1334 kN) |
N.A.
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180 kips
(801 kN)
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283 kips
(1259 kN)
|
300 kips
(1334 kN) |
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(1) Ultimate Strength of the steel was reached.
(N.A.) No test data is available
Concrete compressive strengths were between 3000-4500 psi with the exception of the C28 tests which were performed in high strength 5000 psi concrete.
All tests were performed in unreinforced concrete. |
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 Williams Form Engineering Corp. All rights reserved. |
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