The Truss Interface
The Truss (truss) interface (), found under the Structural Mechanics branch () when adding a physics interface, is used for modeling slender elements that can only sustain axial forces. It can be used for analyzing truss works where the edges are straight, or to model sagging cables like the deformation of a wire exposed to gravity. It is available in 3D and 2D. Geometric nonlinearity can be taken into account.
The Truss interface can also be used for modeling springs and dashpots.
The default material model is Linear Elastic Material. With the Nonlinear Structural Materials Module, you can also model Plasticity.
When this physics interface is added, these default nodes are also added to the Model Builder: Linear Elastic Material, Cross Section Data, Free (a condition where points are free, with no loads or constraints), Straight Edge Constraint (to ensure that the points lie on a straight line between the endpoints of the edge or boundary), and Initial Values. Then, from the Physics toolbar, you can add other nodes that implement, for example, loads and constraints. You can also right-click Truss to select physics features from the context menu.
Settings
The Label is the default physics interface name.
The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.
The default Name (for the first physics interface in the model) is truss.
Reference Point for Moment Computation
Enter the default coordinates for the Reference point for moment computation xref. The resulting moments (applied or as reactions) are then computed relative to this reference point. During the results and analysis stage, the coordinates can be changed in the Parameters section in the result nodes.
Dependent Variables
The dependent variable (field variable) is for the Displacement field u which has two components (u, v) in 2D and three components (u, v, and w) in 3D. The name can be changed but the names of fields and dependent variables must be unique within a model.
Discretization
The default is to use linear shape functions. If the truss elements share an edge with another structural mechanics interface, you may want to use quadratic shape functions instead, in order to get displacement compatibility.
Vibrating String: Application Library path Structural_Mechanics_Module/Verification_Examples/vibrating_string
In-Plane and Space Truss: Application Library path Structural_Mechanics_Module/Verification_Examples/inplane_and_space_truss