Design considerations

Design procedure

The design procedure varies for each connection type, however the general procedure is as follows:

1. An initial plate size is chosen from the plate library, starting with the smallest size.
2. An initial bolt size and bolt count is chosen from the bolt library, starting with the smallest size. The bolt count depends on the bolt size, the plate size and the connection type.
3. An initial weld is chosen from the weld library, starting with the smallest size.
4. A number of checks are performed to determine the adequacy of each component and the overall adequacy of the connection. If everything passes then the design stops. If not, it continues as follows.
5. If any weld checks fail, the weld size is incremented (or is changed from a fillet to a butt weld) and the procedure returns to step 4. If the maximum weld size has been reached without a solution, the procedure continues as follows.
6. If any bolt checks fail, the bolt size is incremented and the procedure returns to step 3. If the maximum bolt size has been reached without a solution, the procedure continues as follows.
7. If any plate checks fail, the plate size is incremented and the procedure returns to step 2. If the maximum plate size has been reached without a solution then the connection fails.

Note that the actual procedure is somewhat more complicated than described above due to the differing nature of the interaction between the plates, bolts and welds for each connection type.

Design actions

Some of the design actions that occur at a connection are not relevant for every connection type. The design actions considered for each connection type are listed in the following table.

The design actions used in a connection design are taken only from the members that are selected by you for the design of the connection. The design actions from any other non-selected members attached to the connection are ignored. For example, if you are designing a web side plate connection that connects a beam to a column at a particular node N, and you have a bracing member (not selected) that in reality is attached to the end of the beam but in your SPACE GASS model you have attached it directly to node N then its design actions wouldn't be taken into account in the connection design. In cases such as this, if you want the design actions from the brace to be included in the connection design then you should change your SPACE GASS model so that the brace connects to the beam at a short distance away from the connection. This means that the brace design actions will go into the end of the beam and hence into the connection rather than directly to the beam-column node.

The only exception to this is that for pinned and moment baseplate connections in SPACE GASS 12.65.1452 and onwards, the design actions are now taken from all the members that connect to the baseplate node and which are on the same side of the baseplate as the selected column.

For apex and splice connections it is assumed that only two members are involved and the moment is the same on each side of the connection. SPACE GASS therefore takes the design moment just from the first member "Member 1" in the connection. If other members are also attached to the connection then they may also contribute some moment and cause the moments in the two members being connected to not be equal. In this case, the design moment for the connection will depend on which member is selected as "Member 1". Note that any other members attached to the connection along with their design actions will be ignored in the connection design.

Note that tubular connections containing a gusset plate and involving multiple members consider the shear forces and moments generated by the eccentricity of the connected members.

Zero member strength

During a connection design/check, the module also checks that the member has sufficient section capacity to transfer the design actions to the connection. If you get an error message stating that "The supporting or supported member has zero strength...", it means that the member's Fy or Fyw value is zero. To fix this, you should open the shape builder for the member in question, click the "Design Properties" button and then ensure that the Fy and Fyw values are non-zero. Note that if the Fy and Fyw are already non-zero, it means that the shape builder has obtained them and put them into the fields for you. You should save the new properties, re-analyse the model and then try the connection design again.