Conoscenza di base

How to model a single bolt connection (Model type)

Steel

Connection

Bolts

Modeling

Geometry

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In this article we will discuss the different model types defined for connected members and how to correctly set the type in case of one bolt connection.

Bearing member and supports

One member of the joint is always set as "bearing". All other members are "connected". The bearing member can be chosen. The bearing member can be "continuous" or "ended" in the joint. "Ended" members are supported on one end, "continuous" members are supported on both ends. Supports are depicted as red squares at the continuous ends of the bearing member.

For more, read the Equilibrium and supporting member.

Defining the Model type

Connected members can be of several types, according to the load, which the member can take:

Type N-Vy-Vz-Mx-My-Mz – member is able to transfer all 6 components of internal forces
Type N-Vy-Mz – member is able to transfer only loading in XY plane – internal forces N, V_y, M_z
Type N-Vz-My – member is able to transfer only loading in XZ plane – internal forces N, V_z, M_y
Type N-Vy-Vz – member is able to transfer only normal force N and shear forces V_y and V_z

Appropriate support types respecting the type of the individual members should be defined at the ends of the connected members to prevent the occurrence of unstable mechanisms or unrealistic deformations.

Based on the selected model type, the corresponding cells in the load table are "locked" (prevented from defining).

One bolt connection

Sometimes, the engineer needs to make a joint with one bolt only, especially if e.g. a hinge, a bracing, a rod, or a diagonal is expected. To model and calculate this kind of operation, you need to define a proper Model type of the member.

If you use the standard Model type: N-Vy-Vz-Mx-My-Mz for a member connected only with a single bolt, the mechanism/singularity can occur or the analysis fails.