Defining Members in BCDsteel

BCDsteel uses the bending moments, axial force and shear forces from beam elements to check a Strand7 model of a structure using either linear or non-linear analysis. The model can include all the usual features including plate and brick elements and links, different freedom cases, staged analysis and tapered beam elements. The steel design solvers check the strength of individual members. In general, each member is defined as a number of beam elements joined end-to-end, with appropriate restraints assigned to the nodes along the length of the member.

Assign material

Clicking “Assign material” opens a form that allows materials to be assigned to each of the beam properties.

IBoxed BXS dimensions

BCDsteel will analyse an equal flanged I-section that is boxed-in each side with plates. These must be modelled as BXS sections in the Strand7 model. For BCDsteel to calculate the properties of these sections, the dimensions must be entered within BCDsteel. Clicking “IBoxed BXS dimensions” opens a form that allows these dimensions to be assigned.

Automatic member definition

BCDsteel will automatically define members and restraints. There is an option to define all of the model, those not yet defined, or those selected.

The program defines members and restraints based on the geometry of the structure and taking into account node restraints, beam end release, orientation / alignment etc. It calculates effective lengths from these restraints. BCDsteel will correctly define all members and restraints for many structures. However, complicated machine structures can have some members for which it is very difficult even for experienced engineers to determine the appropriate member lengths. The restraints and or effective lengths may need to be manually changed for such members. The user therefore needs to check all members when they are defined.

Automatically defining all members typically takes only 1 – 2 secs. For typical structures such as trusses or bulidings, each member will take the user a few seconds to check. Some members in complex structures can take many minutes to decide what to do and make any changes required.

Manually checking members

In practice, each member can be checked in turn by clicking the scroll button.

Alternatively, a particular member may be selected with the mouse or by entering the member number in the text box.

The selected member is highlighted in the Strand7 model window and the restraints assigned to the nodes along it are displayed. The Sound option “speaks” the effective length factors out loud when the member is changed. This can speed up the checking process significantly.

The effective lengths for compression are calculated by the program from the restraints along the member assuming an effective length factor of 1.0. For cantilevers, this factor is: 2.2 for AS 4100, 2.0 for EC3, 1.0 for AISC 360. Changing the restraints will result in the effective lengths being updated automatically. The user can over-rule either the effective lengths or effective length factors if required.
Tools are provided to allow the user to create, delete or split a member, and to change the restraint at any nodes along the length of a member.