RAM Steel Beam Design calculates the number of studs required, accounting for the locations of maximum moments and zero moments and special distributions required due to the presence of point loads. These point loads may be caused by other beams, user input loads, or columns carried by the beam. It calculates the studs required for a uniform distribution along the entire length of the beam as well as for a segmented distribution where the segments are defined by the locations of the point loads. If there are no point loads on a member there will only be one segment. In this case the number of studs required for "segmented" distribution and "uniform" distribution will be identical. When determining the number of studs required for a uniform distribution, the highest stud density required in any segment is determined and then placed along the full beam length.

The program automatically defaults to a uniform distribution of studs unless fewer total studs are required by using the segmented distribution.

If there are more than four point loads, the program always defaults to uniform stud distribution.

Segments are determined based on the location of the point loads. If a segment is so short that no studs could be placed within it, it is combined with the adjacent segment.

If the point of maximum moment occurs at a point other than at the location of a point load, the number of studs in that segment is based on the greater of the densities required on either side of the maximum moment. This is also the case for beams with no point loads.

If the point of zero moment occurs at a point other than the support, the number of studs between the support and the point of zero moment is based on the density of studs required in the segment adjacent to the point of zero moment.

The point of zero moment used is that which corresponds to the load combination that produced the maximum moment.

For AISC 360, LRFD 3rd, Eurocode, CAN/CSA-S16-01 / S16-09 / S16-14, BS 5950, or AS 2723.1, when calculating the studs required between any concentrated load and the point of zero moment, a more exact approach is incorporated whereby the number of studs is based on that required to generate the moment capacity necessary to satisfy the actual design moment at the point of the concentrated load. This is done in lieu of the more simplified approach of calculating the studs based on ratios of the moments allowed by some codes.

Cantilevers are not considered as a segment nor are studs called out on cantilevers since the concrete on a cantilever is generally not in compression. Even when there is an uplift load at the end of the cantilever resulting in compression in the concrete on the cantilever, the cantilever beam is not designed as a composite section. As limited by AS 2327.1, cantilever beams are not designed as composite beams when that code is specified.

In the View/Update dialog of the RAM Steel Beam module, you can change the number of studs in each segment. When an analysis is performed with those studs the program will check the adequacy of those studs for the moments at each of the point loads as well as for the maximum moment.

RAM Steel Beam Design indicates the number of studs required for full composite action as well as minimum partial composite action. The number of studs shown for Partial composite action represents the greater of the number required for moment capacity at the point of maximum moment and at point loads, minimum percent of full composite, or maximum allowable stud spacing. If the number of studs required to produce full composite action exceeds the maximum number of studs that can be placed along the beam, the values shown for full composite are limited to that maximum number, and the output will indicate "Max" rather than "Full". This is based on the minimum stud spacing for deck parallel to the beam, and three studs per flute otherwise. If the number of studs you have specified exceeds the number shown for full composite, the additional studs are ignored. Additionally, the number of studs shown for full composite does not reflect minimum stud requirements, while the number of studs shown for partial composite does. Thus it is possible in some cases for the number of studs shown for partial composite to exceed the number of studs shown for full composite. An example of this is a girder loaded with equal loads at the third points; the Beam Design module will indicate that no studs are required in the middle segment for full composite but that some (minimum studs) are required for partial composite. It should be noted that consistent with the Code requirements, in calculating the properties Seff and Ieff of partially composite beams the value of Cf (for AISC 360 ASD, AISC 360 LRFD and LRFD 3^rd, and others) and Vh (for ASD 9th) is the total horizontal shear from the appropriate equations and is not the value limited by the number of studs that can be placed.

There is a provision in the AISC Codes which states, "Unless located directly over the web, the diameter of studs shall not be greater than 2‑1/2 times the thickness of the flange to which they are welded." The other codes have a similar provision. The Beam Design module checks this provision before selecting a member size requiring multiple rows of studs. If the provision is not met, RAM Steel Beam Design will select a larger size. In the case of CAN/CSA S16, the program will not select a beam for which the stud diameter is greater than 2-1/2 times the flange thickness.

There is a provision in the AISC Codes which states, "The minimum center‑to‑center spacing of stud connectors shall be… 4 diameters transverse to the longitudinal axis of the supporting composite beam." The other codes have a similar provision. RAM Steel Beam Design checks this provision when it specifies multiple rows of studs to determine if the beam width is adequate for the given number of rows. If not, a larger size will be selected.

In the RAM Modeler, composite decks can be specified as formed steel deck (profiled steel sheeting) of a particular brand, or they can be specified as flat slab. If specified as flat slab, the stud spacing is not impacted by rib spacing, and the allow stud shear capacity is not multiplied by the reduction factors applicable to studs in formed steel decks.

You can limit the allowable shear in each stud by specifying a smaller value of the tensile strength, Fu, for the studs in the Modeler. The program limits the stud shear capacity to R_gR_pA_scF_u for AISC 360 (ASD and LRFD) where Rg is based on the deck dimensions and orientation and Rp is based on user specified criteria as described in Section 2.10.5 according to Sect. I8.2a in AISC 360-16 and AISC 360-10 and Sect. I3.2d(3) in AISC 360-05, A_scF_u for LRFD 3rd, 0.5AscFu for ASD 9th, Φ_scA_scF_u for CAN/CSA-S16-01 / S16-09 / S16-14, 0.63d_bs ²f_uc for AS 2327.1, and 0.8A_scF_u/ γv for Eurocode. A_sc is the area of the stud and Fu is the minimum specified tensile strength of a stud shear connector (normally specified as 65ksi in the US). This is in addition to the other equation and/or table values specified by Code. For BS 5950, Fu is not used by the program.

For CAN/CSA-S16-01, S16-09, and S16-014, when the rib height is between 38mm and 75mm and the deck is spanning perpendicular to the beam, the shear strength of the shear studs is determined by interpolating between the values given by the equations in Clause 17.7.2.3. Also, the value of Ap is determined using a common simplified approach that uses the average rib width and assumes that the rib edges are vertical.

For BS 5950, Qk is based on Table 5. No interpolation is performed for intermediate values. Qk is set to 0.0 kN if the stud shear connector or concrete properties fall outside of the table. Allowable values are modified as required for ribbed deck, accounting for the direction of deck relative to the beam. The program assumes that the studs are placed centrally in the rib, or in the favorable position. Concrete with a unit weight less than about 2320 kg/m³ is considered light weight, and the Qk values get multiplied by 0.90 per Clause 5.4.6.

Optionally, BS 5950-3.1:1990 Amendment 1:2010 can be selected. This particularly impacts the minimum percent composite (Na/Np), the shear capacity of the shear connectors, and the transverse reinforcement. In the calculation of the shear capacity of the shear connectors the Amendment distinguishes between open trough profiles and re-entrant trough profiles; the program recognizes these differences. In Criteria > Stud Criteria the stud placement, Unfavourable, Center or Favourable, is specified; this is used in calculating the connector capacity as well as the minimum percent composite. The number of rows of studs is limited to 2. Propped construction will always call out enough studs for 100% composite action.

For AS 2327.1, the program conservatively uses a k_n value of 1.0 in the calculation of the design shear capacity, f_ds, in the determination of the required number of studs.

You are given considerable control over the selection of studs. A number of parameters can be specified by selecting Criteria > Stud Criteria . You may specify the maximum percent of full composite allowed. The Code allows 100%. The minimum percent of full composite allowed may also be specified. ASD 9th Edition specifications require at least 25%. The AISC 360 (ASD and LRFD) and LRFD 3rd Edition specifications have no such requirement but the commentary indicates that less than 25% should not be used if the method for calculating IEff that is given there is used, which the progam does. RAM Steel Beam treats the 25% as a Code requirement for all AISC Codes.

If you specify a minimum percent of full composite greater than that required by code, but an adequate number of studs to satisfy that user-specified minimum will not physically fit on the beam, the program will select as many studs as will fit, and will give a design warning.

If the code-specified minimum percent composite is not met, either because you specified too few studs or the required studs will not physically fit on the beam, the program will design the beam as a noncomposite beam and a warning will be given. The number of studs will be shown as 0.

The Beam Design module allows three rows of studs (except for Composite slabs under AS 2327.1, which limits the number of rows to two) unless limited by the flange width or stud diameter/flange thickness ratio. You may also specify a maximum number of rows. If an adequate number of studs cannot fit within the number of rows specified, the program will select a larger member. You may specify the beam flange width required in order to fit double and triple rows of studs. If multiple rows are required on a beam with inadequate flange width, the program will select a larger member. Note that by using a staggered stud configuration, a smaller Minimum Flange Width may be specified. However, caution should be taken to avoid specifying a Minimum Flange Width narrower than can physically accommodate the multiple rows of studs.

When determining the occurrence of multiple rows of studs, RAM Steel Beam considers the deck orientation, flute spacing, web thickness, flange width and maximum number of rows allowed. When multiple rows of studs are required, the allowable shear value for those studs is reduced per the applicable Code requirements.

As indicated the orientation of the deck that crosses the beam will impact the stud spacing. The program assumes studs can only be placed at locations where the deck is physically supported on the beam (i.e. at the ribs). When the angle between the deck and the beam is very small, there are very few ribs crossing the beam in which to put studs. As a result, there are insufficient studs to satisfy the minimum required percent composite action, and the RAM Steel Beam module is unable to design the beam compositely.

In these situations the engineer will typically specify that the deck is split along the beam to allow studs to be added at a more desirable spacing. This split in the deck can either be created by compressing the deck that runs over the top of the beam, or by physically cutting or starting the metal deck on the beam. You can assign the appropriate construction detail to the beam as described in Ignore Rib Spacing . For beams to which the assignment has been made, the stud spacing is not limited to the rib spacing; rather, the minimum allowable stud spacing is used instead. The program will however consider these construction conditions differently when calculating the stud capacities on the beam.

If the option for Altered Ribs is selected, the Stud Capacity will not be modified from what is currently calculated; the reduction for rib configuration will still be applied.

If the option for Split Deck is selected, the Stud Capacity may be modified: the normal reduction for the steel deck profile will not be applied if the beam width is at least 8" for AISC code design or at least 140mm for BS 5950 design. 8" was chosen for AISC because in AISC 360-05 User Note in Section I3.2d(3) it indicates that for split deck there is no reduction due to the deck configuration if less than one-half of the flange is covered by deck; since the required bearing length for deck is 2", this requires an 8" flange: (2")(2 sides)(2) = 8". The normal reduction for the steel deck profile will always be applied to CAN/CSA S16, AS 2327.1 and Eurocode; the stud capacity is not affected by the Split Deck designation.

The Beam Design report and Summary report indicate those beams to which the assignment has been made.

There are certain maximum stud spacing requirements based on the orientation of the deck and the Code selected. The Beam Design module selects studs conforming to these requirements. You may specify a more stringent requirement by specifying that the maximum spacing be limited to a certain value; in the case of the deck not parallel to the beam you can specify that there be at least one stud in every rib.

Item (1) indicates that stud ductility is not an issue for beams with spans less than or equal to 30 ft, so no further investigation is required for those beams. For beams with spans greater than 30 feet, in the Stud > Criteria command the Commentary methodology can be satisfied by specifying a Minimum % of Full Composite Allowed for Long Spans of 50%, and by specifying that Long Span is defined as Span Greater than 30 ft. This will satisfy Item (2). Alternatively, Item (3) can be satisfied in most cases by specifying a Maximum Stud Spacing of 12" for deck parallel to the beam and a Maximum Spacing equal to the Rib Spacing for deck not parallel to the beam; note that with this approach the maximum spacing limits are applied to beams of all spans, and further note that if the deck is severely skewed with respect to the beam, placing a stud in every rib may not satisfy Item (3) because so few ribs will cross such beams. Instead of specifying the Minimum % composite or the maximum stud spacing, the most convenient method of satisfying the Commentary’s stud ductility requirements is to select the option to Enforce AISC 360-16 Commentary I3.2d(1) for Spans greater than 30 ft. When this option is selected the program will ensure that an adequate number of studs are specified to satisfy either Item (2) or Item (3), whichever results in the fewer number of studs. If this option is selected it is not necessary to also specify a Minimum % composite for long spans of 50%. Beware that this is an option, it is not automatically enforced, since the engineer may choose to enforce the stud ductility requirements with some other method outside of the program, some of which are mentioned in the Commentary to the manual. This option is available for all AISC 360 codes even though the requirement is only in AISC 360-16; it may be advisable to select that option even if designing to an early AISC 360 version. If the option is selected but those additional studs won’t fit on the beam (because for example too few ribs cross the beam), a design warning will be given.

The default values used for these parameters were specified in the Defaults Utility in RAM Manager. They may be modified for the current model using the Criteria commands, or modified for all future models using the Defaults Utility. See the Installation manual for information about modifying these defaults.

All of these criteria are considered within the optimization loop, and only members that conform to all criteria simultaneously are selected. Care should be taken, therefore, not to specify conflicting criteria. If conflicting criteria are set, the program will select the member whose noncomposite section is adequate to carry the loads. One example of a possible conflict is to set the value for Minimum Percent of Full Composite Allowed to a high value, while setting Maximum Rows of Studs Allowed to a low value. It may be impossible to achieve the percent of composite required without exceeding the number of rows specified. Another conflict may occur if the Maximum Percent of Full Composite Allowed is set low and the Maximum Stud Spacing is set to a small value. For smaller beams, the studs required to satisfy the Maximum Spacing may result in percent of full composite exceeding that specified.

If the number of studs that can be placed on a member is controlled by a Code or User specified restriction, "Max" is indicated rather than "Full." You can, however, override any restrictions by specifying an "Actual" number of studs that exceeds the number shown for "max" in View/Update. The composite properties will be based on the actual number of studs, not to exceed full composite.