Tekla Structural Designer checks shear connectors to Section I1-3 (360-05), or Section I8 (360-10).

The nominal strength of headed stud shear connectors in a solid slab or a composite slab is determined in accordance with Section I3.2d (360-05), or Section I3.2d with shear connector strength from I8.2a (360-10).

Ribs perpendicular

The reduction factor R_p is taken as,

• 0.6 for any number of studs and e_mid-ht < 2 in
• 0.75 for any number of studs and e_mid-ht >= 2 in

In Tekla Structural Designer you are therefore not required to input the actual value of e_mid-ht instead you simply indicate if it is less than 2 in.

Ribs parallel

R_p = 0.75 in all cases

Ribs at other angles

Where the ribs are at an angle θ_r to the beam there is no guidance in the AISC Specification. The approach adopted by Tekla Structural Designer is to apply a geometric adjustment of the reduction factors R_g and R_p which for the purposes of this adjustment are combined into one “k” factor. The combined reduction factor is calculated for perpendicular and parallel separately and then adjusted as shown below.

k_s = k₁ * sin²θ_r + k₂ * cos²θ_r

Where:

k_s = the adjusted value of the combined reduction factor R_g * R_p

k₁ = the value of the combined reduction factor R_g * R_p for ribs perpendicular

k₂ = the value of the combined reduction factor R_g * R_p for ribs parallel

Degree of shear connection

For efficient design the number of studs should be minimized. If the number provided has an overall capacity greater than the capacity of the concrete flange or steel beam (whichever is the lesser) then this is full shear connection. Anything less than this, is partial shear connection. There are, however, limits on the amount of partial interaction that are recommended by the AISC Specification – see note “3” (p.16.1-311 of the 2005 Commentary, or p.16.1-356 of the 2010 Commentary).

For all beams, the number of connectors required for full shear connection is,

N_s = (min(T_s, (C_c1 + C_c2)))/Q_n rounded up to the next group size above

Where:

T_s = the tensile yield strength of the steel section

C_c1 = the strength of the concrete flange above the ribs

C_c2 = strength of the concrete in the ribs (zero for perpendicular decks)

Q_n = the nominal strength of an individual shear connector

The degree of partial shear connection is given by,

I_nt = N_a * Q_n / (min((C_c1 + C_c2), T_s))

Where:

N_a = the number of shear connectors provided from the nearer point of support to the position under consideration

The degree of partial shear connection is checked at the point of maximum bending moment or the position of a point load if at that position the maximum utilization ratio occurs.

To determine the status of the check Tekla Structural Designer applies the following rules:

• If the partial interaction ratio at the position of maximum moment is less than the absolute minimum interaction ratio (default 25%), then this generates a FAIL status,
• If the partial interaction ratio at the position of maximum utilization ratio when this is at a different position to the maximum moment, is less than the absolute minimum interaction ratio, then this generates a WARNING status,
• If the partial interaction ratio at the position of maximum moment, or maximum utilization ratio if this is different, is greater than the absolute minimum interaction ratio, then this generates a PASS status,
• If the partial interaction ratio at any point load position that is not the maximum utilization ratio is less than the absolute minimum interaction ratio, then this does not affect the status in any way.
• If the partial interaction ratio at any position is less than the advisory minimum interaction ratio (default 50%) then this is given for information only and does not affect the status in any way.

Dimensional requirements

The dimensional limits given below are either recommendations or code limits:

• the nominal rib height of the profiled deck, h_r should be not greater than 3 in
• the mean width of the ribs of the profiled sheet, w_r should be not less than 2 in (for re-entrant decks the “mean” is taken as the minimum opening at the top of the rib)
• the nominal diameter of stud connectors, d_sc should be not greater than ¾ in
• the height of the stud after welding, H_s should be at least 1½ in greater than the nominal rib height of the profiled deck – see Section I3.2c(b) (360-05), or Section I3.2c(2) (360-10).
• the total depth of the composite slab, d_cs should not be less than 3¾ in
• the thickness of concrete above the main flat surface of the top of the ribs of the sheeting, d_cs - h_r should not be less than 2 in
• concrete cover, d_cs – H_s over the connector should not be less than ½ in – see Section I3.2c(b) (360-05), or Section I3.2c(2) (360-10).
• the longitudinal spacing should not exceed the lesser of 36 in or 8 * the slab depth, d_cs (see Section 6.2.6.2 of Structural Steel Designer's Handbook. Second Edition (Ref. 5))
• where studs are spaced at greater than 18 in centers puddle welds or other appropriate means are required to ensure anchorage of deck – see Section I3.2c (360-05), or Section I3.2c(4) (360-10).
• the clear distance between the edge of a connector and the edge of the steel beam flange should be not less than ¾ in (as universal good practice).
• Section I8.2d of the AISC Specification (360-10) requires that the minimum edge distance from the center of an anchor to a free edge in the direction of the shear force shall be 8 in for normal weight concrete and 10 in for lightweight concrete. This requirement will apply only in a limited number of configurations and therefore is not checked.
• the spacing of connectors in the direction of shear i.e. along the beam should be not less than, 6 * the stud diameter
• the spacing of connectors transverse to direction of shear i.e. across the beam should be not less than 4 * the stud diameter except for the condition given in the next item
• where rows of studs are staggered, the minimum transverse spacing between longitudinal lines of studs should be not less than 3 * the stud diameter with the amount of stagger such that the diagonal distance between studs on adjacent longitudinal lines is not less than 4 * the stud diameter
• the stud connector diameter should not exceed 2.5 times the flange thickness unless located directly over the web.