GrillageCalc

Set up a grillage model

1. Lay out nodes in the global X–Z plane; vertical translation is global Y. Generate regular grids or paste a coordinate table to establish the deck layout.
2. Connect nodes into beam lines, assign section properties, and add supports with the intended vertical and rotational restraints.
3. Enter nodal or member loads and organise them into cases and combinations. Include self-weight only where material density and section data are defined.
4. Run the analysis and inspect displacements, member forces, reactions and the maximum-action envelope. Select a result row to identify the corresponding member in the model.
5. Add the relevant views and tables to the report and export the calculation sheet as PDF.

Useful features

• Node and member series generation, block copying, chain notation and spreadsheet-style editing help create repetitive grillage layouts.
• Section references keep member properties reusable across the model; load cases and combinations make alternative loading scenarios easy to compare.
• Result tables and diagrams show how the idealised grillage distributes applied actions to supports and between intersecting members.
• The report layout supports project information, diagrams and tables for a traceable calculation record.

Model limits and checks

A grillage is a simplified representation of a three-dimensional deck or slab. Results depend on the chosen member layout, stiffness distribution and support idealisation. Check mesh spacing, torsional stiffness, load distribution and equilibrium against the real structure and an independent assessment.

Information pop-ups

Model Information

Use this tab for the model title and project notes saved with the data file.

Node Coordinates

Enter grillage node coordinates in the global X-Z plane. Block generation: for a numeric node row, fill No. of Inc, Node Inc, X-inc and Z-inc to generate a series automatically. If End / Inc is Y, then X-inc and Z-inc are treated as end coordinates. To remove a generated sequence, enter its first Node, No. of Inc and Node Inc, then type Delete in End / Inc. For a copied block, enter B1 to copy the nodes generated by numeric row 1, or enter B1-2 to copy an explicit node set.

Member Connectivity

Enter member node chains such as 1-2-3. Section refs link to the Section Props tab. 1-2-3 creates members 1-2 and 2-3. Shorthand 1-2--6 expands automatically to 1-2-3-4-5-6 using the increment implied by the first two node numbers. Member generation: enter No. of extra and Node increment to copy the whole chain.

Support Conditions

Use Fixity Yxz for vertical-Y translation and rotations about global X/Z. Uppercase Y restrains vertical translation; lowercase x and z restrain rotation. Enter numerical elastic stiffnesses in Trans-Y, Rotation-x and Rotation-z. Gap-Y + is bearing/downforce-only; Gap-Y - is hold-down/uplift-only. Support generation copies the row using No. extra and Node increment.

Loadings

Enter nodal loads, member UDLs, member point loads, and combinations. Every populated load row requires an explicit case name. Global-Y loads are negative downward. Positive moments follow the right-hand rule about global X and Z. Nodal-load generation copies the case and actions using No. of extra and Node inc. Member load chains such as 1-2-3 apply to each segment. Point-load distance a is measured from the start node of each member. Use repeated combination names on adjacent rows. ULS factors apply to member forces and reactions; SLS factors apply to displacements. Blank definition rows are kept visible automatically.

Section Props

For grillage, Izz is the vertical-Y bending inertia and J is the torsion constant. A nonzero area and unit weight automatically generate SWT. Engineering notation such as 200E3 and 120E6 is accepted. Select a target row before opening the Section Props Helper if you want the helper result inserted into that row.

Displacements

Displacement results from the last analysis. Click a node row to highlight it and the matching node in the view; click again or press Esc to clear the selection.

Member End Forces

Member end forces from the last analysis. Click a table row or a canvas member to isolate its active force diagram. Click or drag along its member span or force diagram to position the in-member force cursor. Double-click the cursor or press Esc to remove it; click the selected row again, press Esc, or click empty canvas to show all members.

Reactions

Support reactions for the selected load case or combination. Click a reaction row to highlight the support/node in the view; click again or press Esc to clear the selection.

Member Force Envelope

Envelope table of maximum member end forces across all solved load cases and combinations. Click a member row to highlight it in the view.

Report

Build the printable A4 PDF output pack from selected input tables and session captures. Use Capture below the canvas for views, or Capture at the top right of result tables for selected table rows. Captures are kept only for the current app session and are not saved in the data file. Use Edit sheet layout if the PDF title-block/background needs adjusting.

Tips and field guidance

The five PDF fields are placed in the calculation-sheet title block. Their positions and the printable content area can be adjusted in the Report tab.

Block generation: for a numeric node row, fill No. of Inc, Node Inc, X-inc and Z-inc to generate a series automatically. If End / Inc is Y, then X-inc and Z-inc are treated as end coordinates. To remove a generated sequence, enter its first Node, No. of Inc and Node Inc, then type Delete in End / Inc. For a copied block, enter B1 to copy the nodes generated by numeric row 1, or enter B1-2 to copy an explicit node set.

1-2-3 creates members 1→2 and 2→3. Shorthand 1-2--6 expands automatically to 1-2-3-4-5-6 using the increment implied by the first two node numbers. Member generation: enter No. of extra and Node increment to copy the whole chain. For example 1-2-3-4 with No. of extra = 4 and Node increment = 5 also creates 6-7-8-9, 11-12-13-14, 16-17-18-19 and 21-22-23-24.

Fixity: uppercase Y restrains vertical translation; lowercase x and z restrain rotation. Enter numerical elastic stiffnesses in Trans-Y, Rotation-x and Rotation-z. Gap-Y + is bearing/downforce-only (no uplift); Gap-Y − is hold-down/uplift-only. Support generation copies the row using No. extra and Node increment.

Every populated load row requires an explicit case name. Positive moments follow the right-hand rule about global X and Z. Nodal-load generation copies the case and actions using No. of extra and Node inc.; node 101 with 4 extra and increment 10 loads nodes 101, 111, 121, 131 and 141. Six blank definition rows are kept visible automatically.

A chain such as 1-2-3 applies the same vertical UDL to members 1-2 and 2-3.

Point-load distance a is measured from the start node of each member in the chain.

Use repeated combination names on adjacent rows. ULS factors apply to member forces and reactions; SLS factors apply to displacements.

Izz is the second moment for vertical-Y bending and J is the torsion constant. A nonzero area and unit weight automatically generate the SWT load case. Engineering notation such as 200E3 and 120E6 is accepted.

Def × 20

Deformation scale: finer control at low values, faster increase to the right

Field guidance

Low-angle perspective view from the southwest; drag to orbit, Shift-drag to pan, and use the wheel to zoom

Field guidance

Reset view. In 3D, drag to orbit and Shift-drag to pan; wheel zooms and double-click resets.

Interactive perspective 3D grillage view

In 3D, drag to orbit and Shift-drag to pan. Wheel to zoom. In Member Forces, click or drag a member or diagram to probe it. Double-click the probe to remove it.

Areas in the app

Use these sections to locate the inputs, checks and results shown in the app:

• Info
• Nodes
• Members
• Supports
• Section Props
• Loadings
• Displacements
• Member Forces
• Reactions
• Envelope
• Report

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