Application guide

3DFrameCalc

A 3D space-frame modeller and solver with generated geometry, local member orientation, load cases, cable compatibility analysis and interactive result views.

What this tool does

3DFrameCalc analyses a three-dimensional space-frame model and displays the model and structural results interactively. Review the geometry, restraints and loading directions alongside the calculated response.

Open 3DFrameCalc Contact support

Build a space frame

Create nodes in X, Y and Z. Straight-series generators build regular grids; block-copy rows duplicate groups, and polar rows create rotated node arrays around a selected centre and axis.
Connect nodes into member chains. Set sections, releases, local Beta rotations and any rigid-link or one-way axial member behaviour.
Define supports using global or generated radial axes. Enter nodal, member point, member distributed or cable loads in named cases.
Create combinations and run the analysis. Cable loads are solved through compatibility using the entered cable properties and pretension; one-way support conditions may require direct combination re-analysis.
Use the 3D view, sections, diagrams and result tables to inspect the load path. Export the selected calculation information from the Output tab.

Features for complex geometry

Straight and polar node generation, node-number offsets, member-chain expansion and copy operations reduce repetitive 3D data entry.
Automatic radial section-depth alignment supports members generated around a single polar axis; Beta remains available for additional orientation control.
Cable properties, pretension and cable UDLs are handled with a nonlinear compatibility solution, while regular frame members retain full axial, shear, bending and torsional response.
The canvas, local-axis display, properties preview, member-force tables and diagrams help trace section orientation and results through the model.

Interpretation and limits

Check the generated geometry and local axes before applying loads. Tension-only and compression-only members carry axial action only; distributed loads on them are converted to equivalent end-node forces and do not model span bending.

Confirm cable stiffness, pretension, restraints and load combinations independently. The model is an engineering analysis aid: verify assumptions, equilibrium and design checks for the project before use.

Model Information

Use this tab for the five PDF title-block fields and project notes. The Output tab controls the positions of these fields on the A4 calculation sheet.

Node Coordinates

Generate a straight series

Enter the first node and its X/Y/Z coordinates. Use No. of Inc for the number of additional nodes, Node Inc for the node-number step, and X-inc / Y-inc / Z-inc for the coordinate steps in metres.

Enter Y in End / Inc to treat the three increment cells as the final coordinates instead. The generated nodes are spaced evenly up to that endpoint.

Copy a block — B

B1 copies the generated block starting at node 1. B1-5 copies all nodes produced by input lines 1 to 5, including nodes generated within those lines. The current row supplies the coordinate increments for each copy.

Leave Node Inc blank to number copies after the highest existing node. Enter a value to apply a specific node-number offset per copy.

Move a block — M

M1-4 moves the existing nodes generated by input lines 1 to 4 by the offsets entered in X-inc, Y-inc and Z-inc. Leave No. of Inc, Node Inc and End / Inc blank. Each node moves once, even if it appears on more than one referenced line; deleted nodes are skipped.

Generate a polar array — R

R1 rotates the nodes produced by input line 1. R1-4 rotates the nodes produced by lines 1 to 4. The R row's X/Y/Z coordinates define the rotation centre. No. of Inc is the number of additional copies.

For an R row, X-inc / Y-inc / Z-inc are angles in degrees about the corresponding global axis. For example, Y-inc = 45 with No. of Inc = 7 creates seven copies around the vertical Y axis.

Node Inc is the node-number offset per copy. For source nodes 1–4, an offset of 4 creates nodes 5–8, then 9–12, and so on. Choose an offset that avoids existing node numbers, or leave it blank for automatic numbering.

Enter Global in an R row's End / Inc cell to generate coordinates while retaining standard member-section and global support directions. Condense uses this setting for recognised rotational copies.

Condense imported definitions

After a DXF import, a Condense preview opens automatically when shorter definitions are available. Choose Nodes, Members or both, then Apply. Straight sequences, translated blocks and single-axis rotational blocks are recognised; irregular nodes remain explicit. Node numbers and member order are retained. Coordinates are checked within 0.000001 m. Undo restores the previous tables.

Automatic radial section alignment

Members joining consecutive nodes in the R source chain, and the matching segments in each rotated copy, automatically align their section depth (local Y) with the radius from the rotation axis. Beta adds a rotation to this alignment.

For a source chain 1-2-3-4, members 1–2, 2–3 and 3–4 and their rotated copies qualify. A connection between copies, such as 30–2, keeps the standard Beta orientation.

Automatic alignment requires a single rotation axis and a radial direction across the member. Compound rotations, conflicting R axes and members with no transverse radial direction keep the standard Beta orientation.

Delete or paste nodes

To remove a sequence, enter its first node, No. of Inc and Node Inc, then enter Delete in End / Inc. You can also paste a rectangular block of cells from Excel into the node grid.

Members

Define a node chain

1-2-3 creates members 1→2 and 2→3. Shorthand 1-2--6 expands to 1-2-3-4-5-6. Add a final node to close a chain: 1-5--29-1 expands through 1, 5, 9 … 29 and adds member 29→1.

Copy members

No. of extra and Node increment repeat the chain with an offset to every node number. B1-12 copies every member produced by member input lines 1 to 12. For example, No. of extra = 2 and Node increment = 20 produces copies at +20 and +40.

The DXF import Condense preview recognises chains and repeated member blocks. It preserves member order, section references, Beta, releases and active settings. Existing generators are left as entered.

Rigid links

Enter Rigid in the Section column for a weightless link with axial, bending and torsional stiffness set to 10 times the strongest defined member section. This is a very stiff frame member, so its end releases still apply.

Automatic radial alignment and Beta

A member joining consecutive nodes in an R generator's source chain, or the corresponding pair in any angular copy, automatically aligns its section depth (local Y) radially with that generator's axis. Beta is an additional rotation about the member.

For source chain 1-2-3-4, segments 1–2, 2–3 and 3–4 and their copies qualify. Connections between copies, such as 30–2, retain the standard Beta orientation. Click a member to see its alignment source in the status bar, or inspect its section in Properties.

Single-axis R commands about X, Y or Z are supported. If there is no unique rotation axis or transverse radial direction, the member keeps the standard Beta orientation.

End releases and Group

Releases normally apply to every segment. Entering P at both ends of 8-5-2 therefore pins both adjoining ends at node 5. Enter Y in Group to release only the two outside ends of the whole chain.

Use yz for a beam-style pin (releases My and Mz), or xyz to release torsion as well. P, PIN, PINN and PINNED are aliases for yz. Translational releases use codes such as UX, UY and UZ.

Axial-only members

Enter C for compression-only struts or T for tension-only ties. They are drawn as red/blue dashed members; inactive one-way members are grey dotted.

C and T members resist axial force only. They have no bending, shear or torsional stiffness. Member loads, including self-weight, are transferred to the two end nodes as equivalent joint forces, whether the member is active or inactive. This is a joint-load approximation; use ordinary frame members where bending from a load along the span matters.

Active

Leave blank to include a member row, or enter X to exclude it and all its generated copies. A node used only by excluded members, and supports at that node, are also excluded. This is separate from an inactive compression-only or tension-only member in an analysis result.

Copy and paste

Click-drag to select a rectangular range and press Ctrl+C to copy. Paste a rectangular block from Excel starting at the selected cell.

Cables are geometrically nonlinear, pinned, tension-only members. Their property reference must point to a row in Cable Props, normally created with the Cable Properties Helper. Installed pretension is an element initial force, so it remains present in every load case and is not multiplied by ordinary load-combination factors.

Support Conditions

Fixity

Leave Active blank to include a support row, or enter X to exclude it and all its generated copies. A support on a node still used by permanent members must be switched off here explicitly.

Uppercase letters restrain translation (X, Y, Z); lowercase letters restrain rotation (x, y, z). XYZ = pin, XYZxyz = fixed, Y = vertical roller, and YZ = roller free in X. At nodes created by an R row, the support axes follow that radial generator: X is radial, Y follows the rotation axis, and Z is tangential. At other nodes, they are the global axes.

Spring supports

Enter a numerical stiffness in any X/Y/Z/x/y/z spring cell to make that direction an elastic spring support. The same radial axes apply at R-generated nodes. Leave Fixity blank for a row containing only springs.

Gap / one-way restraint

Leave blank for restraint in both directions. For Y, enter + for bearing/downforce-only support (no reaction in the negative direction), or − for uplift/hold-down-only support. X/Z use the same sign convention in their support axes, including the radial axes at R-generated nodes.

Generate supports

Node accepts a single number, list, range or B-row reference such as B1-3. Use No. extra and Node inc. to repeat supports: node = 1, No. = 4, Inc. = 5 creates supports at 1, 6, 11, 16 and 21.

Properties

In the 3D view, click any member to highlight its section as a blue prism and show the orange mid-length cross-section cut face with local axes. Click a Member Props row to preview every member assigned to that section.

Izz = major/strong bending inertia for local BMD-z (normal horizontal beam under gravity). Iyy = minor/weak bending inertia for local BMD-y. Optional Ksy/Ksz are transverse shear rigidities (kN) in local Y/Z; blank or zero omits shear deformation. Aw is additional area used for self-weight only, not axial or bending stiffness. The lattice helper assumes one pin-jointed diagonal per panel acting in both tension and compression. Buckling, joint slip, verticals, gussets and out-of-plane bracing are excluded; model members individually where these effects matter. E, G, A, I and J may be entered in engineering notation such as 200E3, 6E3, 120E6 or 1.5E6.

Cable axial stiffness can be calculated as EA = Jb or entered independently. The represented fabric width is the tributary width carried by one cable line; installed pretension is defined separately in the Cables table under Members.

Loadings

Nodal Loads

Positive moments follow the right-hand rule. Use No. extra and Node inc. to repeat the same forces and moments at additional nodes. For example, Node = 2, No. extra = 3 and Node inc. = 5 applies the load at nodes 2, 7, 12 and 17. Automatic self-weight is generated as analysis case SWT. SWT is calculated from section density and applied as global Y member UDLs. Inclined members use their actual member length, so they carry their true weight. SWT is analysed in results and combinations, but is not drawn as load arrows on the canvas.

Member Loads

Enter a member or node chain such as 1-2-3. Direction may be global X, global Y, global Z, local y, or local z. For a multi-member chain, a variable UDL is now tapered continuously from w start at the first chain node to w end at the last chain node, rather than restarting on every member. Uniform loads remain uniform on each member. These rows are saved with the model, shown on the frame, and included in the analysis.

Member Point Loads

Enter a member or node chain such as 1-2-3. The same point load is then applied to each member in that chain. Direction may be global X, global Y, global Z, local y, or local z to the member. These rows are saved with the model, shown on the frame, and included in the analysis.

Cable UDL Loads

Applies load-case pressure to cables having the same node chain. Strip width and fabric stiffness come from the cable property; pretension comes from the Cables table. The nonlinear compatibility solution uses EA = Jb and applies the resulting cable end actions to the frame.

Load Combinations

Use case names from the loads tables, including automatic SWT. Case names are not case-sensitive. If any translational support action is one-way, combinations are re-solved directly with the combined load vector because support contact/lift-off is non-linear.

Stages

Stage structures

Mark optional members X in the Members table. In Stages, enter X against the load cases and combinations where those members are absent. Blank keeps all members. Both ULS and SLS use the chosen structure; the factors in Loadings are unchanged.

Analysis stops if a combination contains cases with different structure settings, or its setting differs from those cases. Support rows marked X remain excluded in every stage.

Grid

Grid markers are drawn on the XZ plan at Y = 0. Set the origin as an X,Z coordinate pair in metres, for example 0,0. X increases along positive X and Z grid numbers increase along positive Z. The origin is marked on both rectangular and polar grids. Enter one spacing per interval, separated by commas; a single spacing repeats evenly. Enter one custom label per interval; separate labels with commas when they use multiple characters. The origin line is left unlabelled.

Extends each grid line beyond the outer crossing grid lines by this distance at both ends.

Member Forces

The frame-member table shows forces and moments at both ends of each regular member for the selected load case or combination. Line identifies the row in the Members table that defines the member. Property is its section property reference; the Property control in Visibility filters both member-force tables and the canvas.

N is axial force, Vy and Vz are shear forces, T is torsion, and My and Mz are bending moments. The numbers 1 and 2 identify the member ends.

Select a member in either table or on the canvas to locate it. Use the diagram buttons to display results on the model. The AFD cut-off in Visibility greys smaller axial-force diagrams and hides their labels without changing the calculated results. Click a column heading to sort its table independently; click again to reverse the order.

One-way members

Tension-only (T) and compression-only (C) members are listed separately when present. N rep is their representative axial force in kN; zero means inactive for the selected case. Active ties are blue dashed, active struts red dashed and inactive members grey dotted.