Williams Form Engineering Corp. - S-7 Reusable Concrete Anchor System Design Considerations

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S-7 Reusable Anchor Design Considerations

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Williams has listed recommended embedment depths that are minimum values for ductile steel failure design in 3000 psi concrete. Embedment depths will need to increase according to the values determined from anchor design models when spacing requirements are less than the values listed below (S). A reduction in anchor capacity should be used if the concrete thickness does not allow for deeper embedments. Appropriate reduction factors can be calculated from industry design models. When placing anchors that require a smaller edge distance than what is recommended in the table below, the designer should be aware of a reduction in anchor capacity. Table information below can be used as a reference when reduced edge distance is a factor in anchor design. The values for reduced edge distance are based on tests in 3000 to 4000 psi non-reinforced concrete and should only be used as a reference in combination with reduction values calculated from industry design models.

S-7 Reusable Anchor - Minimum Spacing & Edge Distance

Outer Stud Diameter	Minimum Embedment in 3000 PSI Concrete	Center to Center Spacing for Full Strength with no Reduction (S)	Minimum Recommended Edge Distance (E)	Minimum Ultimate Strength of Inner Stud	Concrete Failure Loads
Outer Stud Diameter	Minimum Embedment in 3000 PSI Concrete		Minimum Recommended Edge Distance (E)	Minimum Ultimate Strength of Inner Stud	4 Bar Dia. from the Edge (Test)	6 Bar Dia. from the Edge (Test)
1/2"-13 (12 mm)	3-3/4" (95 mm)	7-1/2" (191 mm)	5" (127 mm)	6.25 kips (27.8 kN)	4 kips (18 kN)	6.2 kips (31 kN)
3/4"-10 (20 mm)	5-1/4" (133 mm)	10-1/2" (267 mm)	5-3/4" (146 mm)	17 kips (75.6 kN)	11 kips (49 kN)	17 kips (76 kN)
1"-8 (25 mm)	7-1/4" (184 mm)	14-1/2" (368 mm)	9" (229 mm)	22.5 kips (100 kN)	15 kips (67 kN)	22 kips (98 kN)
1-1/4"-7 (32 mm)	7-3/4" (197 mm)	15-1/2" (394 mm)	12-1/2" (318 mm)	22.5 kips (100 kN)	19 kips (85 kN)	21 kips (93 kN)
1-3/4"-5 (45 mm)	12-1/2" (318 mm)	25" (635 mm)	16" (406 mm)	75 kips (334 kN)	18 kips (80 kN)	23 kips (102 kN)
2"-6 (51 mm)	16" (406 mm)	32" (813 mm)	21" (533 mm)	135 kips (600 kN)	N.A.	N.A.

(N.A.) No test data available
Recommended safe edge distance to be at least 10 bar diameters.
Concrete compressive strengths were between 3000-4000 psi unreinforced concrete.

Materials

The Williams S-7 Reusable Concrete Anchor is offered in diameters ranging from 1/2"-13 UN thru 2"-6 UN and a choice of materials including ASTM A108 standard commercial grade carbon steel and ASTM A193 Grade B8 Type 304 stainless steels in anchor sizes up to 1” diameter. The anchors shall be complete with stud, cone, and expansion shell.

Anchor assembly for S-7 consists of:
1. An anchor stud complying with ASTM A108 for carbon steel and ASTM A193 Grade B8 Type 304 for stainless steel.
2. A Williams cone in threaded engagement with the inner end of the anchor stud complying with ASTM A 29 for carbon steel and ASTM A193 Grade B8 Type 304 for stainless steel. The cone shall have an exterior conical surface continuous in cross section to deliver bearing pressure radially with respect to the axis of the anchor bar.
3. A Williams slotted expansion shell with an inner surface bearing on the cone, the outer surface initially of cylindrical curvature. The steel complies with ASTM A108 for carbon steel and ASTM A193 Grade B8 Type 304 for stainless steel.
The S97 Setting Tool is required for installation of S-7 Reusable Concrete Anchors.

Williams S-7 anchors are specially designed with a cone that threads into the bottom of the anchor stud. This threaded portion at the bottom of the anchor governs the ultimate tensile capacity of the system, which explains why the tensile loads are lower than Williams Spin-Lock anchor systems. However, shear loading at the base plate is resisted by the full diameter of the anchor stud rather than the smaller threaded diameter at the cone/stud interface. The picture above illustrates this point. This process is necessary to provide the user with a reusable detachable anchor stud. The outer stud diameter dictates the shear strength of the anchor, while the inner stud diameter dictates the anchor tensile strength.