Hold a node with a support

Fix, pin or roll a node, turn its support to a sloping plane, or hold it on springs or on a bearing that can lift. One Support component does all of these.

Six columns, each held another way at its foot.

You need

• A point on a node of the model: the end of a beam, a vertex of a shell's mesh, a node of a solid.
• Assemble, whose Supports input takes the supports.

Steps

1. Place a Support and wire the point into Position.

2. Pick the type in its Support Type menu: Rigid (the default), Elastic or Compression Only.

3. Rigid: Tx to Rz are all true, held, to start with. Set to false what the node is free to do:

   Support	Set to false
   Fixed	nothing
   Pinned	Rx, Ry, Rz
   Roller sliding in X (preset Sliding in X + Rz restraint)	Tx, Rx, Ry
   Roller sliding in X and Y (preset Sliding in X and Y + Rz restraint)	Tx, Ty, Rx, Ry

4. Skewed: wire a Plane into Position instead of a point. The six directions are then the plane's own axes. For a roller on a sloping face, give a plane whose Z axis is square to the face, hold Tz and set Tx and Ty to false.

5. Elastic: give a stiffness for each direction the springs hold: Kx, Ky, Kz in kN/m, Krx, Kry, Krz in kNm/rad. Left empty, or zero, the node is free that way. Give at least one, or the component warns.

6. Compression Only: it holds along the plane's Z only while the node moves against Z: down, for a point. Leave Stiffness empty for a rigid bearing, or give one in kN/m. Gap, in m, is how far the node moves before the support takes hold. Analyse it with the Newton algorithm in Analysis Settings, in several steps.

Check

• In Model View, tick Show Supports in the Supports menu. The seven presets of the Support page get their own symbol; any other support, springs included, a text tag listing what it holds.
• After the analysis, Reaction Forces gives each support's reactions in its own axes. A released direction reads zero, and the vertical reactions add up to the load.

Good to know

• A support takes hold only within Assemble's Tolerance of a node. Two supports on one node are merged into one, with a remark, unless one of them is skewed or a spring.
• A spring support holds nothing it has no spring for. For a pinned bearing that can lift, put a Compression Only support and a Rigid one holding only Tx and Ty on the same point. Do not let the two act along the same direction: Assemble warns when they do.
• Turn the plane over for a Compression Only support that holds only in tension.
• A Compression Only support lets go only in a non-linear analysis. The component says so in a remark, and Run Analysis warns when the algorithm is Linear.

See also

• Support — every input, the seven presets, and what it writes for OpenSees
• Reaction Forces — what each support carries
• Assemble — two supports on one node
• Spring Link — a spring between two parts of the model rather than to the ground