Automatic Mesh Settings for Floors

Form: Automatic Mesh Options (for Floors)

Click the Analyze menu > Automatic Mesh Settings for Floors command to access the Automatic Mesh Options (for Floors) form. This form is used to specify the typical automatic mesh options for floors with slab section properties. Floor meshes are used internally by the program to distribute vertical loads to beams, columns and walls, and to determine in-plane and out-of-plane stiffnesses. All shell objects used to model floors are automatically meshed by ETABS into the analysis model, but the type of mesh will depend upon the section property of the floor, i.e., slabs will have a different type of mesh than will decks and planks. See the Assign > Shell > Floor Auto Mesh Options command for additional information on the default mesh for each type of object.

Note: The Automatic Mesh Options (for Floors) form also displays when the Assign > Shell > Floor Auto Mesh Options command is used to access the Shell Assignment - Floor Auto Mesh Options form and the Advanced - Modify/Show Auto Mesh Settings button is clicked.

Use the Automatic Mesh Options (for Floors) form to specify how and where meshing will occur and the approximate maximum mesh size.

The meshing is applied to shell objects (not to be confused with shell behavior) that use auto meshing either by default or as part of an assignment.

Mesh Options for Slabs

Rectangular Mesh option. This is the default option and is typically the recommended option for most floor slab geometries, i.e., floors with linear edges. When this option is selected, the mesh generated will use 4 node quadrilateral elements.

Use Localized Meshing option. When this option is not used, an initial grid is defined that has lines passing in the two mesh directions through all joints in the structure. This can lead to closely spaced mesh lines and thus large meshes with many area elements.

When this option is used, an initial grid is not necessarily passed through all joints. Instead, it is passed through as many joints as possible while keeping mesh lines at least half the specified Approximate Maximum Mesh Size apart. Then, if specified, joints are merged where possible, as described in the next bullet item. Finally, localization then picks up joints that were not included in the original mesh grid.

Merge Joints Where Possible option. When this option is used, the merging of joints takes place as soon as the initial grid is defined. Joints on the initial grid are moved, if possible, to align with nearby joints, frames, or edges of shell objects. The maximum distance that a joint is allowed to move is 10% of the specified Approximate Maximum Mesh Size.

Many joints are not allowed to move at all. These include joints at joint object locations, joints that lie on frame objects, and joints that fall on shell object edges.

Approximate Maximum Mesh Size edit box. Input the target maximum size for the elements generated by the mesh - decreasing the size will create a finer mesh.

Use the Reset Defaults button to clear previously specified mesh settings.