15.6design procedure

AISC 358-22, Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications

Last Updated 29 Oct 2026

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Step 1. Choose trial sizes for the beam section(s) and column section. Confirm that the column-beam moment ratio is satisfied per Section 15.4.

Step 2. Compute the probable maximum force that will develop at the bottom flange level on each side, $V_{f e}$ :

V_{f e}=\frac{M_{p r}}{2\left(d_{b}+t_{p}\right)}

(15.6-1)

where

$M_{p r}=$ probable maximum moment at the fuse location, kip-in. (N-mm). This moment shall not exceed $M_{p}$ and shall not be less than the beam flexural demand defined by the applicable building code. If $M_{p r}$ is less than $M_{p}$ , analysis shall be performed to demonstrate the connection is fully restrained.

User Note: The fuse plate is proportioned in Step 19 to have an expected ultimate capacity corresponding to $M_{p r}$ .

$d_{b}$ = depth of the beam, in. (mm)

$\begin{aligned} t_{p} & =\text { thickness of the top plates, fuse plate, and external continuity plates, in. } \\ & \text { (mm). This thickness is typically equal to the beam flange thickness, } t_{b f} \\ & \text { rounded up to the next standard plate size. }\end{aligned}$

Step 3. Design the cover plates. Compute the required cover plate shear strength:

R_{u, c p}=\sum\left(V_{f e}+P_{d}\right)

(15.6-2)

where

$P_{d}=$ drag force to be transmitted through the cover plate, computed as the beam axial force defined by the applicable building code divided by 2, kips (N)

User Note: The drag force is divided by 2 because $P_{d}$ is the force resisted by one side of the connection (one of the two cover plates).

Check the limit state of shear yielding of the cover plates according to AISC Specification Section J4.2.

User Note: Because the cover plates will have shear strength greater than $\Sigma V_{f e}$ , the panel-zone check from the AISCE Seismic Provisions will be satisfied.

User Note: For built-up box and HSS columns, the sides of the column may function as cover plates.

The thickness of the cover plate, $t_{c p}$ , shall conform to

t_{c p} \geq \frac{\left(d_{z}+w_{z}\right)}{90}

where

$\begin{aligned} d_{z} & =\text { depth of the web of the deeper beam at the connection, in. (mm) } \\ & =d_{b}-2 t_{b f}\end{aligned}$

$\begin{aligned} w_{z} & =\text { width of the panel zone between column flanges, in. (mm) } \\ & =d_{c}-2 t_{c f}\end{aligned}$

For flanged cruciform columns without cover plates, the required shear strength of the panel zone shall be $2 R_{u, c p}$ .

User Note: $R_{u, c p}$ is the demand on one cover plate. The total panel-zone shear demand is $2 R_{u, c p}$ .

Step 4. Determine the maximum bolt diameter. Beam plastic hinging or net section fracture is not expected to occur, but to ensure that beam yielding will occur prior to fracture, the net section of the beam shall satisfy the following:

Z_{x, \text { net }} R_{t} F_{u b} \geq Z_{x} R_{y} F_{y b}

(15.6-4)

where

$F_{u b} \quad$ = specified minimum tensile strength of beam, ksi (MPa)

$\begin{aligned} R_{t} & =\text { ratio of expected tensile strength to the specified minimum tensile } \\ & \text { strength }\end{aligned}$

$Z_{x, \text { net }}=$ plastic section modulus of the net section of the beam, in. ${ }^{3}\left(\mathrm{~mm}^{3}\right)$

User Note: ASTM F3125/F3125M Grade F2280 bolts, or similar, with a diameter of 1 1/8 in. (28 mm) are reasonable for most beams weighing between 100 and 200 lb/ft (150 and 300 kg/m). A smaller bolt diameter may be more appropriate for lighter beams or a bigger bolt diameter for heavier beams.

$Z_{x, \text { net }}$ of the beam may be computed by accounting for only the holes in the tension flange, or more simply $Z_{x, \text { net }}$ of the beam may be computed by accounting for the holes in both flanges. Note that if the former approach is employed, the plastic neutral axis will not be at the mid-depth of the beam.

Step 5. Determine the number of bolts for each bolt line on the fuse plate and top plates, $n_{b}$ . The number of bolts required for the bolt shear limit state is determined as follows:

n_{b} \geq \frac{V_{f e}+p d}{\phi r_{n}}

(15.6-5)

where

$\phi_{r_{n}}=$ design shear strength of one bolt, assuming threads excluded from shear plane, kips (N)

Some of the bolts are on or to the right of the alignment line (Figure 15.3). The number of bolts on and ahead of the alignment line on the outside lines is $n_{p}$ (see Figure 15.6) and shall be sufficient to accommodate the depth of two fuse regions on the fuse plate with 3 in. (75 mm) spacing between.

n_{p} \geq \frac{2\left[\mathrm{F} 2_{a}\right]+3 \text { in. }-2 e_{d}}{s}+1

(15.6-6)

n_{p} \geq \frac{2\left[\mathrm{F} 2_{a}\right]+75 \mathrm{~mm}-2 e_{d}}{e}+1

(15.6-6M)

where

\begin{aligned} \left[\mathrm{F} 2_{a}\right] & =\text { the approximate longitudinal dimension of each fuse region on the plate, } \\ & \text { in. (mm) } \\ & =V_{f e} /\left[2\left(0.6 R_{t p} F_{u p} t_{p}\right)\right] \end{aligned}

$F_{u p}=$ specified minimum tensile strength of the plate, ksi (MPa) $R_{t p}=$ tensile overstrength factor of the plate, ksi (MPa) $e_{d}=$ minimum edge distance for bolt in oversized hole, in. (mm) $s=$ bolt spacing, in. (mm)

The number of bolts behind the alignment line on the outside lines, $n_{m}$ , is

n_{m}=n_{b}-n_{p}

(15.6-8)

where

$n_{b}=$ total number of bolts on the lines of the fuse plate

$\begin{aligned} n_{p} & =\text { number of bolts on or ahead of the alignment line on each outside line of the } \\ & \text { fuse plate }\end{aligned}$

The nominal slip resistance of each line of bolts using the slip coefficient determined in accordance with Section 15.5.2 and a resistance factor of 1.00 shall be less than $V_{f e}$ .

User Note: DuraFuse Frames moment connections accommodate inelastic deformations through a combination of fuse plate yielding and bolt slip. Because the number of bolts is based on bearing capacity, this check is performed to ensure that bolt slip will occur as part of the inelastic response.

Check bolts for the limit states of bearing and tearout according to AISC Specification Chapter J.

Step 6. Locate the alignment line. The beam-to-column gap and the single-plate shear connection slots in the connection shall accommodate a beam rotation, $\gamma_{\max }$ , of at least 0.06 rad.

\gamma_{\max } \geq 0.06 \mathrm{rad}

(15.6-9)

The alignment line is shown in Figures 15.3, 15.4, and 15.5. The distance from the column face to the alignment line [C1] is

[\mathrm{C} 1] \geq \gamma_{\max } d_{b}+e_{d}+\alpha[\mathrm{C} 3]

where

α = factor that accounts for overlap of beam flange and cover plates = 1.0, if the beam flange is wider than the column flange = 0, if the beam flange width is equal to or less than the column flange width [C3] = distance from the column face to the edge of the cover plate, in. (mm)

Step 7. When cover plates are used, size the cover plate-to-column flange weld, [W1]. The moment in the plane of the cover plate causes shear demands in the cover plate-to-column flange weld, $r_{u v 1}$ . A moment in the plane of the external continuity plates causes normal forces in the cover plate-to-column flange weld, $r_{u n 1}$ .

r_{u v 1}=\frac{\Sigma\left(V_{f e}+P_{d}\right)\left(d_{b}+t_{p}\right)}{d_{c}\left(d_{b}+2\left[\mathrm{C} 6\right]\right)}

r_{u n 1}=\frac{\Sigma\left(V_{f e}+P_{d}\right)[\mathrm{C} 5]}{l_{w e 1} d_{c}}

where

\begin{aligned} l_{w e 1} & =\text { length at each end of the weld between the cover plates and the column } \\ & \text { flanges that is considered effective for resisting normal forces, in. (mm). } \\ & =t_{p}+t_{c p}+\left[\mathrm{C} 6\right] \end{aligned}

(15.6-13)

[C5] = distance from the cover plate to the line of bolts on the external continuity plates, in. (mm). See Figure 15.3. [C6] = distance of the cover plate extension above and below the external continuity plates, in. (mm). See Figure 15.3.

The resultant demand is $r_{u 1}$ :

r_{u l}=\sqrt{r_{u v 1}^{2}+r_{u n 1}^{2}}

(15.6-14)

Alternatively, weld demands may be determined using the instantaneous center of rotation method.

Check weld strength according to AISC Specification Chapter J.

User Note: For built-up box and HSS columns where the sides of the column function as cover plates, [W1] is not required. For flanged cruciform columns without cover plates, [W1] is not required.

Step 8. Size the external continuity plate-to-cover plate weld, [W2]. The applied forces on each external continuity plate result in shear, $r_{t w 2}$ , and normal, $r_{t u n 2}$ , demands on the weld.

r_{u v 2}=\frac{\Sigma\left(V_{f e}+P_{d}\right)}{\left(d_{c}+2\left[\mathrm{C} 3\right]\right)}

r_{u n 2}=\frac{\Sigma\left(V_{f e}+P_{d}\right)[\mathrm{C} 5]}{l_{w e 2}\left(d_{c}+2[\mathrm{C} 3]-2 l_{h o l d b a c k}-l_{w e 2}\right)}

(15.6-16)

where

$\begin{aligned} l_{\text {holdback }} & =\text { length of the weld holdback, taken as the weld size }[\mathrm{W} 2], \text { in. (mm) } \\ l_{w e 2} & =\text { the length at each end of the weld between the external continuity } \\ & \text { plates and the cover plates that is considered effective for resisting } \\ & \text { normal forces, in. (mm) } \\ & =t_{f c}+t_{c p}+\left[\mathrm{C} 3\right]-l_{\text {holdback }} \quad(15.6-17)\end{aligned}$

The resultant demand is $r_{u 2}$ :

r_{u 2}=\sqrt{r_{u v 2}^{2}+r_{u n 2}^{2}}

(15.6-18)

Alternatively, weld demands may be determined using the instantaneous center of rotation method. Check weld strength according to AISC Specification Chapter J.

User Note: See the AISC Manual Part 8 for discussion of the instantaneous center of rotation method and design tables.

For flanged cruciform columns, [W2] demands are determined considering $V_{f e}+$ $P_{d}$ loading on the external continuity plate in both orthogonal directions acting simultaneously.

Step 9. Check external continuity plates for the limit state of tensile rupture in the net section according to AISC Specification Chapter D. Three modes shall be checked, corresponding to rupture through the bolt hole on the alignment line and the next two bolt holes in the direction of the column. For each check, the tension demand is $V_{f e}+P_{d}$ multiplied by the percentage of bolts that are ahead of the bolt in question— $n_{p} / n_{b},\left(n_{p}+1\right) / n_{b}$ , or $\left(n_{p}+2\right) / n_{b}$ -that have transferred load into the external continuity plate. Check external continuity plates for the limit state of block shear rupture according to AISC Specification Chapter J.

For flanged cruciform columns, continuity plate demands are determined considering $V_{f e}+P_{d}$ loading on the external continuity plate in both orthogonal directions acting simultaneously.

Step 10. The required shear strength, $V_{u}$ , for the beam and single-plate shear connection shall be determined in accordance with Section 2.5.

Check the design shear strength of the beam according to AISC Specification Chapter G.

Step 11. Compute the required block shear rupture strength of the beam flange

$R_{u, b f}=2\left(V_{f e}+P_{d}\right)$ (15.6-20)

Check the design strength of the beam flange for the limit state of block shear rupture according to AISC Specification Section J4.3.

Step 12. Determine the required number of shear plate bolts, $n_{n}$ , for the limit state of bolt shear:

n_{n} \geq \frac{V_{u}}{\phi r_{n}}

(15.6-21)

The required length of the shear plate is determined as follows:

l_tab ≤ T - 1 in.	(15.6-22)
l_tab ≤ T - 25 mm	(15.6-22M)

where

$T=$ flat distance on the beam web, in. (mm)

The 1 in. (25 mm) buffer is to ensure that the single-plate shear connection remains clear of the $k$ -area during seismic response.

User Note: The single-plate shear connection is as long as possible, without encroaching on the k-area of the beam, to maximize connection stiffness.

Step 13. The required shear strength of the single-plate shear connection is $V_{u}$ (Step 10). Compute the required normal strength of the single-plate shear connection:

P_{u}=n_{n} F_{b}

(15.6-23)

where

$F_{b}=$ maximum slip force that can develop in one bolt, kips (N), calculated as 1.5 times the nominal slip capacity assuming Class A faying surface.

Compute the required flexural strength of the single-plate shear connection:

$M_{u}=V_{u}[\mathrm{C} 1]$ (15.6-24)

where

[C1] = distance from the column face to the single-plate shear connection bolts, in. (mm)

Design the shear connection for the required strength meeting the requirements of the AISC Specification.

Step 14. Determine the single-plate shear connection slot dimensions. The single-plate shear connection slot dimension, [S1], shall accommodate the maximum beam rotation from Step 6 for the critical case where the center of rotation is assumed at the top flange level.

[\mathrm{S} 1] \geq \gamma_{\max }\left(\frac{d_{b}}{2}+\frac{l_{\text {tab }}}{2}-e_{d}\right)+\frac{d_{\text {bolt }}}{2}

(15.6-25)

where

[S1] = distance from alignment line to inside edge of slot, in. (mm); see Figure 15.4 $d_{\text {bolt }}=$ diameter of the single-plate shear connection bolt, in. (mm) $e_{d}=\quad$ edge distance at bottom of single-plate shear connection, in. (mm) $l_{t a b}=\quad$ length of the shear connection plate, in. (mm) $\gamma_{\max }=$ maximum beam rotation considered for design, rad

The slot dimension [S2], from the alignment line to the outside edge of the slot, is typically the same as [S1].

[\mathrm{S} 1]=[\mathrm{S} 2]

(15.6-26)

Step 15. Compute the required shear strength of the top plates, $V_{u, t p}$ :

$V_{u, t p}=V_{f e}+P_{d}$

V_{u, t p}=V_{f e}+P_{d}

(15.6-27)

Check the top plate for shear yielding and shear rupture according to AISC Specification Section J4.2.

User Note: If the top plate has insufficient shear capacity, the plate can be thickened, the bolt size can be reduced, or the bolt spacing can be increased.

Step 16. Compute the required tensile strength of the top plates in the narrow portion:

R_{u, t p n}=\left(\frac{n_{m}}{n_{b}}\right)\left(V_{f e}+P_{d}\right)

(15.6-28)

Check the top plate for the limit states of tensile yielding and tensile rupture in the net section of the narrow portion according to AISC Specification Chapter D.

Step 17. Check that [P2], as shown in Figure 15.6, is sufficient for entering and tightening requirements:

[\mathrm{P} 2] \geq k_{1}+d_{h}

(15.6-29)

where

$k_{1}=$ distance from web center line to flange toe of fillet, in. (mm)

$d_{h}=$ hole diameter used for rupture limit state calculations, in. (mm)

Check that [P2] is sufficient to preclude yielding of the top plate due to combined flexure and shear:

[\mathrm{P} 2] \geq[\mathrm{P} 10]-\frac{\left(0.9 F_{y p}\right) e(m+e) t_{p}}{V_{f e}+P_{d}}

where

$\begin{aligned} F_{y p} & =\text { specified minimum yield stress of end-plate material, ksi (MPa) } \\ \text { [P10] } & =\text { distance from beam flange centerline to outer bolt line, in. (mm); see } \\ & \text { Figure 15.6 } \\ e & =\frac{[\mathrm{P} 8]-m}{2} \quad(15.6-31)\end{aligned}$

[P8] = inside length of the top plate, in. (mm); see Figure 15.6

m=\frac{V_{f e}+P_{d}}{0.9\left(0.6 F_{y p}\right) t_{p}}

(15.6-32)

Step 18. The width of the yielding regions in the fuse plates, [F6], shall not exceed 4 in. (100 mm) and shall not be less than 1½ in. (38 mm). The width-to-thickness ratio, [F6]/[T2], of the yielding region in the fuse plates shall not exceed 4.25 and shall not be less than 1.5.

Compute the required strength of the fuse plate ahead of the first yielding region (YR):

R_{u f p}=2\left(\frac{n_{m}}{n_{b}}\right)\left(V_{f e}+P_{d}\right)

(15.6-33)

Check the fuse plate for the limit states of tensile yielding and tensile rupture in the net section ahead of the first YR according to AISC Specification Chapter D.

User Note: The expected tensile strength of the plate, $R_{t p} F_{u p}$ , may be used when calculating the capacity for rupture of the net section.

Check the fuse plate for edge distances according to AISC Specification Chapter J.

Step 19. Determine the yielding region (YR) depth, [F2]. The YR depth is determined such that the maximum force that will develop in the strain-hardened regions on one side of the fuse plate will not exceed $V_{f e}$ . The expected strain-hardening in the fuse is a function of the width-to-depth ratio and the width-to-thickness ratio. The formula for [F2] that accounts for strain hardening is

[\mathrm{F} 2]=\frac{0.95 V_{f e}+2 t_{p}\left(0.6 R_{t p} F_{u p}\right) B[\mathrm{F} 6]}{2 t_{p}\left(0.6 R_{t p} F_{u p}\right)\left(A-\frac{C[\mathrm{F} 6]}{t_{p}}\right)}

(15.6-34)

where

$A=1.52$ , a coefficient in the strain hardening expression, calibrated from experiments
$B=0.16$ , a coefficient in the strain hardening expression, calibrated from experiments
$C=0.09$ , a coefficient in the strain hardening expression, calibrated from experiments

The width-to-depth ratio of the yielding regions in the fuse plates, [F6]/[F2], shall not exceed 1.25 and shall not be less than 0.5.

Step 20. The required tensile strength of the fuse plates in the narrow extensions is:

R_{u f p n}=\left(\frac{n_{m}}{n_{b}}\right)\left(V_{f e}+P_{d}\right)

(15.6-35)

Check the fuse plate for the limit states of tensile yielding and tensile rupture in the net section of the narrow extension according to AISC Specification Chapter D.

User Note: The expected tensile strength, $R_{t p} F_{u p}$ , of the plate may be used when calculating the capacity for rupture of the net section for the fuse plate extension.

End of chapter · NextAppendix A Casting requirements

15.6design procedure

AISC 358-22, Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications

Last Updated 29 Oct 2026

Hover any section to copy its link or text, ask Copilot about it, or bookmark it.

Step 1. Choose trial sizes for the beam section(s) and column section. Confirm that the column-beam moment ratio is satisfied per Section 15.4.

Step 2. Compute the probable maximum force that will develop at the bottom flange level on each side, $V_{f e}$ :

V_{f e}=\frac{M_{p r}}{2\left(d_{b}+t_{p}\right)}

(15.6-1)

where

User Note: The fuse plate is proportioned in Step 19 to have an expected ultimate capacity corresponding to $M_{p r}$ .

$d_{b}$ = depth of the beam, in. (mm)

$\begin{aligned} t_{p} & =\text { thickness of the top plates, fuse plate, and external continuity plates, in. } \\ & \text { (mm). This thickness is typically equal to the beam flange thickness, } t_{b f} \\ & \text { rounded up to the next standard plate size. }\end{aligned}$

Step 3. Design the cover plates. Compute the required cover plate shear strength:

R_{u, c p}=\sum\left(V_{f e}+P_{d}\right)

(15.6-2)

where

$P_{d}=$ drag force to be transmitted through the cover plate, computed as the beam axial force defined by the applicable building code divided by 2, kips (N)

User Note: The drag force is divided by 2 because $P_{d}$ is the force resisted by one side of the connection (one of the two cover plates).

Check the limit state of shear yielding of the cover plates according to AISC Specification Section J4.2.

User Note: Because the cover plates will have shear strength greater than $\Sigma V_{f e}$ , the panel-zone check from the AISCE Seismic Provisions will be satisfied.

User Note: For built-up box and HSS columns, the sides of the column may function as cover plates.

The thickness of the cover plate, $t_{c p}$ , shall conform to

t_{c p} \geq \frac{\left(d_{z}+w_{z}\right)}{90}

where

$\begin{aligned} d_{z} & =\text { depth of the web of the deeper beam at the connection, in. (mm) } \\ & =d_{b}-2 t_{b f}\end{aligned}$

$\begin{aligned} w_{z} & =\text { width of the panel zone between column flanges, in. (mm) } \\ & =d_{c}-2 t_{c f}\end{aligned}$

For flanged cruciform columns without cover plates, the required shear strength of the panel zone shall be $2 R_{u, c p}$ .

User Note: $R_{u, c p}$ is the demand on one cover plate. The total panel-zone shear demand is $2 R_{u, c p}$ .

Z_{x, \text { net }} R_{t} F_{u b} \geq Z_{x} R_{y} F_{y b}

(15.6-4)

where

$F_{u b} \quad$ = specified minimum tensile strength of beam, ksi (MPa)

$\begin{aligned} R_{t} & =\text { ratio of expected tensile strength to the specified minimum tensile } \\ & \text { strength }\end{aligned}$

$Z_{x, \text { net }}=$ plastic section modulus of the net section of the beam, in. ${ }^{3}\left(\mathrm{~mm}^{3}\right)$

Step 5. Determine the number of bolts for each bolt line on the fuse plate and top plates, $n_{b}$ . The number of bolts required for the bolt shear limit state is determined as follows:

n_{b} \geq \frac{V_{f e}+p d}{\phi r_{n}}

(15.6-5)

where

$\phi_{r_{n}}=$ design shear strength of one bolt, assuming threads excluded from shear plane, kips (N)

n_{p} \geq \frac{2\left[\mathrm{F} 2_{a}\right]+3 \text { in. }-2 e_{d}}{s}+1

(15.6-6)

n_{p} \geq \frac{2\left[\mathrm{F} 2_{a}\right]+75 \mathrm{~mm}-2 e_{d}}{e}+1

(15.6-6M)

where

\begin{aligned} \left[\mathrm{F} 2_{a}\right] & =\text { the approximate longitudinal dimension of each fuse region on the plate, } \\ & \text { in. (mm) } \\ & =V_{f e} /\left[2\left(0.6 R_{t p} F_{u p} t_{p}\right)\right] \end{aligned}

The number of bolts behind the alignment line on the outside lines, $n_{m}$ , is

n_{m}=n_{b}-n_{p}

(15.6-8)

where

$n_{b}=$ total number of bolts on the lines of the fuse plate

$\begin{aligned} n_{p} & =\text { number of bolts on or ahead of the alignment line on each outside line of the } \\ & \text { fuse plate }\end{aligned}$

The nominal slip resistance of each line of bolts using the slip coefficient determined in accordance with Section 15.5.2 and a resistance factor of 1.00 shall be less than $V_{f e}$ .

Check bolts for the limit states of bearing and tearout according to AISC Specification Chapter J.

Step 6. Locate the alignment line. The beam-to-column gap and the single-plate shear connection slots in the connection shall accommodate a beam rotation, $\gamma_{\max }$ , of at least 0.06 rad.

\gamma_{\max } \geq 0.06 \mathrm{rad}

(15.6-9)

The alignment line is shown in Figures 15.3, 15.4, and 15.5. The distance from the column face to the alignment line [C1] is

[\mathrm{C} 1] \geq \gamma_{\max } d_{b}+e_{d}+\alpha[\mathrm{C} 3]

where

r_{u v 1}=\frac{\Sigma\left(V_{f e}+P_{d}\right)\left(d_{b}+t_{p}\right)}{d_{c}\left(d_{b}+2\left[\mathrm{C} 6\right]\right)}

r_{u n 1}=\frac{\Sigma\left(V_{f e}+P_{d}\right)[\mathrm{C} 5]}{l_{w e 1} d_{c}}

where

\begin{aligned} l_{w e 1} & =\text { length at each end of the weld between the cover plates and the column } \\ & \text { flanges that is considered effective for resisting normal forces, in. (mm). } \\ & =t_{p}+t_{c p}+\left[\mathrm{C} 6\right] \end{aligned}

(15.6-13)

The resultant demand is $r_{u 1}$ :

r_{u l}=\sqrt{r_{u v 1}^{2}+r_{u n 1}^{2}}

(15.6-14)

Alternatively, weld demands may be determined using the instantaneous center of rotation method.

Check weld strength according to AISC Specification Chapter J.

User Note: For built-up box and HSS columns where the sides of the column function as cover plates, [W1] is not required. For flanged cruciform columns without cover plates, [W1] is not required.

r_{u v 2}=\frac{\Sigma\left(V_{f e}+P_{d}\right)}{\left(d_{c}+2\left[\mathrm{C} 3\right]\right)}

r_{u n 2}=\frac{\Sigma\left(V_{f e}+P_{d}\right)[\mathrm{C} 5]}{l_{w e 2}\left(d_{c}+2[\mathrm{C} 3]-2 l_{h o l d b a c k}-l_{w e 2}\right)}

(15.6-16)

where

The resultant demand is $r_{u 2}$ :

r_{u 2}=\sqrt{r_{u v 2}^{2}+r_{u n 2}^{2}}

(15.6-18)

Alternatively, weld demands may be determined using the instantaneous center of rotation method. Check weld strength according to AISC Specification Chapter J.

User Note: See the AISC Manual Part 8 for discussion of the instantaneous center of rotation method and design tables.

For flanged cruciform columns, [W2] demands are determined considering $V_{f e}+$ $P_{d}$ loading on the external continuity plate in both orthogonal directions acting simultaneously.

For flanged cruciform columns, continuity plate demands are determined considering $V_{f e}+P_{d}$ loading on the external continuity plate in both orthogonal directions acting simultaneously.

Step 10. The required shear strength, $V_{u}$ , for the beam and single-plate shear connection shall be determined in accordance with Section 2.5.

Check the design shear strength of the beam according to AISC Specification Chapter G.

Step 11. Compute the required block shear rupture strength of the beam flange

$R_{u, b f}=2\left(V_{f e}+P_{d}\right)$ (15.6-20)

Check the design strength of the beam flange for the limit state of block shear rupture according to AISC Specification Section J4.3.

Step 12. Determine the required number of shear plate bolts, $n_{n}$ , for the limit state of bolt shear:

n_{n} \geq \frac{V_{u}}{\phi r_{n}}

(15.6-21)

The required length of the shear plate is determined as follows:

l_tab ≤ T - 1 in.	(15.6-22)
l_tab ≤ T - 25 mm	(15.6-22M)

where

$T=$ flat distance on the beam web, in. (mm)

The 1 in. (25 mm) buffer is to ensure that the single-plate shear connection remains clear of the $k$ -area during seismic response.

User Note: The single-plate shear connection is as long as possible, without encroaching on the k-area of the beam, to maximize connection stiffness.

Step 13. The required shear strength of the single-plate shear connection is $V_{u}$ (Step 10). Compute the required normal strength of the single-plate shear connection:

P_{u}=n_{n} F_{b}

(15.6-23)

where

$F_{b}=$ maximum slip force that can develop in one bolt, kips (N), calculated as 1.5 times the nominal slip capacity assuming Class A faying surface.

Compute the required flexural strength of the single-plate shear connection:

$M_{u}=V_{u}[\mathrm{C} 1]$ (15.6-24)

where

[C1] = distance from the column face to the single-plate shear connection bolts, in. (mm)

Design the shear connection for the required strength meeting the requirements of the AISC Specification.

[\mathrm{S} 1] \geq \gamma_{\max }\left(\frac{d_{b}}{2}+\frac{l_{\text {tab }}}{2}-e_{d}\right)+\frac{d_{\text {bolt }}}{2}

(15.6-25)

where

The slot dimension [S2], from the alignment line to the outside edge of the slot, is typically the same as [S1].

[\mathrm{S} 1]=[\mathrm{S} 2]

(15.6-26)

Step 15. Compute the required shear strength of the top plates, $V_{u, t p}$ :

$V_{u, t p}=V_{f e}+P_{d}$

V_{u, t p}=V_{f e}+P_{d}

(15.6-27)

Check the top plate for shear yielding and shear rupture according to AISC Specification Section J4.2.

User Note: If the top plate has insufficient shear capacity, the plate can be thickened, the bolt size can be reduced, or the bolt spacing can be increased.

Step 16. Compute the required tensile strength of the top plates in the narrow portion:

R_{u, t p n}=\left(\frac{n_{m}}{n_{b}}\right)\left(V_{f e}+P_{d}\right)

(15.6-28)

Check the top plate for the limit states of tensile yielding and tensile rupture in the net section of the narrow portion according to AISC Specification Chapter D.

Step 17. Check that [P2], as shown in Figure 15.6, is sufficient for entering and tightening requirements:

[\mathrm{P} 2] \geq k_{1}+d_{h}

(15.6-29)

where

$k_{1}=$ distance from web center line to flange toe of fillet, in. (mm)

$d_{h}=$ hole diameter used for rupture limit state calculations, in. (mm)

Check that [P2] is sufficient to preclude yielding of the top plate due to combined flexure and shear:

[\mathrm{P} 2] \geq[\mathrm{P} 10]-\frac{\left(0.9 F_{y p}\right) e(m+e) t_{p}}{V_{f e}+P_{d}}

where

[P8] = inside length of the top plate, in. (mm); see Figure 15.6

m=\frac{V_{f e}+P_{d}}{0.9\left(0.6 F_{y p}\right) t_{p}}

(15.6-32)

Compute the required strength of the fuse plate ahead of the first yielding region (YR):

R_{u f p}=2\left(\frac{n_{m}}{n_{b}}\right)\left(V_{f e}+P_{d}\right)

(15.6-33)

Check the fuse plate for the limit states of tensile yielding and tensile rupture in the net section ahead of the first YR according to AISC Specification Chapter D.

User Note: The expected tensile strength of the plate, $R_{t p} F_{u p}$ , may be used when calculating the capacity for rupture of the net section.

Check the fuse plate for edge distances according to AISC Specification Chapter J.

[\mathrm{F} 2]=\frac{0.95 V_{f e}+2 t_{p}\left(0.6 R_{t p} F_{u p}\right) B[\mathrm{F} 6]}{2 t_{p}\left(0.6 R_{t p} F_{u p}\right)\left(A-\frac{C[\mathrm{F} 6]}{t_{p}}\right)}

(15.6-34)

where

$A=1.52$ , a coefficient in the strain hardening expression, calibrated from experiments
$B=0.16$ , a coefficient in the strain hardening expression, calibrated from experiments
$C=0.09$ , a coefficient in the strain hardening expression, calibrated from experiments

The width-to-depth ratio of the yielding regions in the fuse plates, [F6]/[F2], shall not exceed 1.25 and shall not be less than 0.5.

Step 20. The required tensile strength of the fuse plates in the narrow extensions is:

R_{u f p n}=\left(\frac{n_{m}}{n_{b}}\right)\left(V_{f e}+P_{d}\right)

(15.6-35)

Check the fuse plate for the limit states of tensile yielding and tensile rupture in the net section of the narrow extension according to AISC Specification Chapter D.

User Note: The expected tensile strength, $R_{t p} F_{u p}$ , of the plate may be used when calculating the capacity for rupture of the net section for the fuse plate extension.

End of chapter · NextAppendix A Casting requirements