J3Bolts, threaded parts, and bolted connections

J3.1 Common Bolts

ASTM A307 bolts are permitted except where pretensioning is specified.

J3.2 High-Strength Bolts

Use of high-strength bolts and bolting components shall conform to the provisions of the RCSC Specification for Structural Joints Using High-Strength Bolts, hereafter referred to as the RCSC Specification, except where those provisions differ from this Specification. This Specification governs where provisions differ from the RCSC Specification.

User Note: Examples of provisions in the RCSC Specification that differ from this Specification’s provisions are shown in the Commentary.

High-strength bolts in this Specification are grouped according to material strength as follows:

• Group 120 ASTM F3125/F3125M Grades A325, A325M, F1852, and ASTM A354 Grade BC

Group 144 ASTM F3148 Grade 144

Group 150 ASTM F3125/F3125M Grades A490, A490M, F2280, and ASTM A354 Grade BD

Group 200 ASTM F3043 and ASTM F3111

Use of Group 144 bolting assemblies shall conform to the provisions of ASTM F3148.

Use of Group 200 high-strength bolting assemblies shall conform to the applicable provisions of their ASTM standard. ASTM F3043 and ASTM F3111 Grade 1 assemblies may be installed only to the snug-tight condition. ASTM F3043 and ASTM F3111 Grade 2 assemblies may be used in snug-tight, pretensioned, and slip-critical connections, using procedures provided in the applicable ASTM standard.

User Note: The use of Group 200 bolting assemblies is limited to specific building locations and noncorrosive environmental conditions by the applicable ASTM standard.

When assembled, all joint surfaces, including those adjacent to the washers, shall be free of scale, except tight mill scale.

• (a) Bolting assemblies are permitted to be installed to the snug-tight condition when used in

• (1) Bearing-type connections, except as stipulated in Section E6

• (2) Tension or combined shear and tension applications, for Group 120 bolts only, where loosening or fatigue due to vibration or load fluctuations are not design considerations

• (b) Bolts in the following connections shall be pretensioned:

• (1) As required by the RCSC Specification

• (2) Connections subjected to vibratory loads where bolt loosening is a consideration

• (3) End connections of built-up members composed of two shapes either interconnected by bolts, or with at least one open side interconnected by perforated cover plates or lacing with tie plates, as required in Section E6.1

• (c) The following connections shall be designed as slip-critical:

• (1) As required by the RCSC Specification

• (2) The extended portion of bolted, partial-length cover plates, as required in Section F13.3

The snug-tight condition is defined in the RCSC Specification. Bolts to be tightened to a condition other than snug tight shall be clearly identified on the design documents. (See Table J3.1 or J3.1M for minimum bolt pretension for connections designated as pretensioned or slip-critical.)

User Note: There are no specific minimum or maximum tension requirements for snug-tight bolts. Bolts that have been pretensioned are permitted in snug-tight connections unless specifically prohibited on design documents.

When bolt requirements cannot be provided within the RCSC Specification limitations because of requirements for lengths exceeding 12 diameters or diameters exceeding 1½ in. (38 mm), bolts or threaded rods conforming to Group 120 or Group 150 materials are permitted to be used in accordance with the provisions for threaded parts in Table J3.2.

When ASTM A354 Grade BC, ASTM A354 Grade BD, or ASTM A449 bolts and threaded rods are used in pretensioned connections, the bolt geometry, including the thread pitch, thread length, head, and nut(s), shall be equal to or (if larger in diameter) proportional to that required by the RCSC Specification. Installation shall comply with all applicable requirements of the RCSC Specification with modifications as required for the increased diameter and/or length to provide the design pretension.

J3.3 Size and Use of Holes

The following requirements apply for bolted connections:

• (a) The nominal dimensions of standard, oversized, short-slotted, and long-slotted holes for bolts are given in Table J3.3 or Table J3.3M.

User Note: Bolt holes with a smaller nominal diameter are permitted. See RCSC Specification Table 3.1 for bolt hole fabrication tolerances. See Section J9 for diameters of holes in base plates for anchor rods providing anchorage to concrete.

J3.4 Minimum Spacing

The distance between centers of standard, oversized, or slotted holes shall not be less than $2 \frac{2}{3}$ times the nominal diameter, $d$, of the fastener. However, the clear distance between bolt holes or slots shall not be less than $d$.

User Note: A distance between centers of standard, oversized, or slotted holes of 3d is preferred.

J3.5 Minimum Edge Distance

The distance from the center of a standard hole to an edge of a connected part in any direction shall not be less than either the applicable value from Table J3.4 or Table J3.4M, or as required in Section J3.11. The distance from the center of an oversized or slotted hole to an edge of a connected part shall be not less than that required for a standard hole to an edge of a connected part plus the applicable increment, C₂, from Table J3.5 or Table J3.5M.

J3.6 Maximum Spacing and Edge Distance

The maximum distance from the center of any bolt hole to the nearest edge of elements in contact shall be 12 times the thickness of the connected element under consideration, but shall not exceed 6 in. (150 mm). The longitudinal spacing of bolt holes between elements consisting of a plate and a shape, or two plates, in continuous contact shall be as follows:

• (a) For painted members or unpainted members not subject to atmospheric corrosion, the spacing shall not exceed 24 times the thickness of the thinner part or 12 in. (300 mm).
• (b) For unpainted members of weathering steel subject to atmospheric corrosion, the spacing shall not exceed 14 times the thickness of the thinner part or 7 in. (180 mm).

User Note: The dimensions in (a) and (b) do not apply to elements consisting of two shapes in continuous contact.

J3.7 Tensile and Shear Strength of Bolts and Threaded Parts

The design tensile or shear strength, $\phi R_{n}$, and the allowable tensile or shear strength, $R_{n} / \Omega$, of a snug-tightened or pretensioned high-strength bolt or threaded part shall be determined according to the limit states of tension rupture and shear rupture as

(J3-1)

$\phi=0.75$ (LRFD) $\quad \Omega=2.00$ (ASD)

where

$\begin{aligned} A_{b} & =\text { nominal unthreaded body area of bolt or threaded part, in. }^{2}\left(\mathrm{~mm}^{2}\right) \\ F_{n} & =\text { nominal tensile stress, } F_{n t} \text {, or shear stress, } F_{n v} \text {, from Table J3.2, ksi (MPa) }\end{aligned}$

The required tensile strength shall include any tension resulting from prying action produced by deformation of the connected parts.

User Note: The available strength of a bolt in shear depends on whether the bolt is sheared through its shank or through the threads or thread runout. Bolts that are relatively short may be produced as fully threaded, without a shank, and thus may not be able to be installed in the “threads excluded” condition.

User Note: The force that can be resisted by a snug-tightened or pretensioned high-strength bolt or threaded part may be limited by the bearing or tearout strength at the bolt hole per Section J3.11. The effective strength of an individual fastener may be taken as the lesser of the fastener shear strength per Section J3.7 or the bearing or tearout strength at the bolt hole per Section J3.11. The strength of the bolt group is taken as the sum of the effective strengths of the individual fasteners.

J3.8 Combined Tension and Shear in Bearing-Type Connections

The available tensile strength of a bolt subjected to combined tension and shear shall be determined according to the limit states of tension and shear rupture as

(J3-2)

$\phi=0.75$ (LRFD) $\quad \Omega=2.00$ (ASD)

where

$F_{n t}^{\prime}=$ nominal tensile stress modified to include the effects of shear stress, ksi (MPa)

$F_{n t}=$ nominal tensile stress from Table J3.2, ksi (MPa)

$F_{n v}=$ nominal shear stress from Table J3.2, ksi (MPa)

$f_{r v}=$ required shear stress using LRFD or ASD load combinations, ksi (MPa)

The available shear stress of the fastener shall equal or exceed the required shear stress, $f_{r y}$.

User Note: Note that when the required stress, $f$, in either shear or tension, is less than or equal to $30 \%$ of the corresponding available stress, the effects of combined stress need not be investigated. Also note that Equations J3-3a and J3-3b can be rewritten so as to find a nominal shear stress, $F_{n v}^{\prime}$, as a function of the required tensile stress, $f_{t}$.

J3.9 High-Strength Bolts in Slip-Critical Connections

Slip-critical connections shall be designed to prevent slip and for the limit states of bearing-type connections. When slip-critical bolts pass through fillers, all surfaces subject to slip shall be prepared to achieve design slip resistance.

The single bolt available slip resistance for the limit state of slip shall be determined as follows:

(J3-4)

• (a) For standard size and short-slotted holes perpendicular to the direction of the load $\phi=1.00$ (LRFD) $\quad \Omega=1.50$ (ASD)
• (b) For oversized and short-slotted holes parallel to the direction of the load

$\phi=0.85$ (LRFD) $\quad \Omega=1.76$ (ASD)

• (c) For long-slotted holes

$\phi=0.70$ (LRFD) $\quad \Omega=2.14$ (ASD)

where

• $D_{u}=1.13$, a multiplier that reflects the ratio of the mean installed bolt pretension to the specified minimum bolt pretension. The use of other values are permitted if approved by the engineer of record.
• $T_{b}=$ minimum fastener pretension given in Table J3.1 or Table J3.1M, kips (kN)

$h_{f}=$ factor for fillers, determined as follows:

• (1) For one filler between connected parts

$h_{f}=1.0$

• (2) For two or more fillers between connected parts

$h_{f}=0.85$

• $n_{s}=$ number of slip planes required to permit the connection to slip

• $\mu$ = mean slip coefficient for Class A or B surfaces, as applicable, and determined as follows, or as established by tests:

• (1) For Class A surfaces (unpainted clean mill scale steel surfaces or surfaces with Class A coatings on blast-cleaned steel or hot-dipped galvanized steel whether as-galvanized or hand roughened)

• (2) For Class B surfaces (unpainted blast-cleaned steel surfaces or surfaces with Class B coatings on blast-cleaned steel)

$\mu=0.50$

J3.10 Combined Tension and Shear in Slip-Critical Connections

When a slip-critical connection is subjected to an applied tension that reduces the net clamping force, the available slip resistance per bolt from Section J3.9 shall be multiplied by the factor, $k_{s c}$, determined as follows:

(J3-5a)

where

$T_{a}=$ required tension force using ASD load combinations, kips (kN)

$T_{u}=$ required tension force using LRFD load combinations, kips (kN)

$n_{b}=$ number of bolts carrying the applied tension

J3.11 Bearing and Tearout Strength at Bolt Holes

The available strength, $\phi R_{n}$ and $R_{n} / \Omega$, at bolt holes shall be determined for the limit states of bearing and tearout, as follows:

$\phi=0.75$ (LRFD) $\quad \Omega=2.00$ (ASD)

The nominal strength of the connected material, $R_{n}$, shall be determined in accordance with Section J3.11a or Section J3.11b.

J3.11a Snug-Tightened or Pretensioned High-Strength Bolted Connections

All plies of the connected elements shall be in firm contact.

• (1) The nominal strength of a connected element at a bolt in a connection with standard, oversized, and short-slotted holes, independent of the direction of loading, or a long-slotted hole with the slot parallel to the direction of the bearing force, shall be the lesser of the following:
• (a) Bearing
• (i) When deformation at the bolt hole at service load is a design consideration

$R_{n}=2.4 d t F_{u}$ (J3-6a)

• (ii) When deformation at the bolt hole at service load is not a design consideration

(J3-6b)

• (b) Tearout
• (i) When deformation at the bolt hole at service load is a design con- sideration

(J3-6c)

• (ii) When deformation at the bolt hole at service load is not a design consideration

(J3-6d)

• (2) The nominal strength of a connected element at a bolt in a connection with long-slotted holes with the slot perpendicular to the direction of force is the lesser of the following:
• (a) Bearing

(J3-6e)

• (b) Tearout

(J3-6f)

J3.11b Connections Made Using Bolts or Rods that Pass Completely Through an Unstiffened Box Member or HSS

• (1) Bearing shall satisfy Section J7 and Equation J7-1
• (2) Tearout
• (i) For a bolt in a connection with a standard hole or a short-slotted hole with the slot perpendicular to the direction of force
• (a) When deformation at the bolt hole at service load is a design consideration

(J3-6g)

• (b) When deformation at the bolt hole at service load is not a design consideration

(J3-6h)

• (ii) For a bolt in a connection with long-slotted holes with the slot perpendicular to the direction of force

$R_{n}=1.0 l_{c} t F_{u}$ (J3-6i)

where

• $F_{u}=$ specified minimum tensile strength of the connected material, ksi (MPa)
• $d \quad$ = nominal diameter of fastener, in. (mm)
• $l_{c}=$ clear distance, in the direction of the force, between the edge of the hole and the edge of the adjacent hole or edge of the material, in. (mm)
• $t \quad$ = thickness of connected material, in. (mm)

Bearing strength and tearout strength shall be checked for both bearing-type and slip-critical connections. The use of oversized holes and short- and long-slotted holes parallel to the line of force is restricted to slip-critical connections per Section J3.3.

J3.12 Special Fasteners

The nominal strength of special fasteners other than the bolts presented in Table J3.2 shall be verified by tests.

J3.13 Wall Strength at Tension Fasteners

When bolts or other fasteners in tension are attached to an unstiffened box or HSS wall, the strength of the wall shall be determined by rational analysis.