Frequently asked questions

iStruct2D is a 2D structural-analysis sketchpad for iPad — its tagline is “Sketch · Load · Analyse 2D structures.” You draw members by hand, add supports and loads, edit them interactively, then tap Analyse to see reactions, the deflected shape, and shear, bending and axial diagrams. It’s solved with the direct stiffness method, the same matrix approach used in professional analysis software.

Students learning statics and structural mechanics, educators demonstrating behaviour live in class, and engineers sketching a quick check on the go. It’s designed so reactions, internal forces and deflected shapes behave exactly as the theory predicts.

No. iStruct2D is in beta and is an educational / reference tool. The app itself states that “analysis results are for reference only — always apply your own engineering judgement before relying on them.” You remain responsible for your models, inputs and interpretation. It is not a substitute for a qualified structural engineer, accredited design software, or any building code. See the Terms & Conditions.

iStruct2D is free to download on the App Store. It’s currently a free public beta — connect on LinkedIn to be kept in the loop on future updates.

Pick the Member tool, then drag on the canvas from a start point to an end point and release. Endpoints near an existing node automatically join to it, so chained members share nodes and a connected structure forms as you go. Tap a finished member’s length label to type an exact length. The guide covers drawing in detail.

Tap anything to select it. A selection filter (All · Members · Nodes · Loads · Structures) keeps your taps precise. Tap a member to edit its length, x/y-length and angle; tap a node to edit its X/Y coordinates; with the Structures filter, tap and drag to move a whole connected structure. Tap the red ✕ on a selection frame to delete it.

In Settings ▸ General, enable Apple Pencil mode so only the Pencil draws and edits while your fingers pan and zoom. This lets you keep a tool selected while navigating. Pinch-to-zoom always works regardless of the mode.

Show grid displays the background grid (on by default) and Snap to grid aligns new members as you draw (off by default) — they’re independent. The Merge gap is how close two nodes must be to count as one; drawing within it joins structures, and Settings ▸ Data ▸ Merge cleans up duplicates.

Three: Pinned (restrains both translations, X and Y), Roller (restrains one translation perpendicular to its rolling surface — X if it faces left/right, Y if it faces up/down), and Fixed (restrains X, Y and rotation). Tap a support to rotate its orientation 90° at a time, then drag it onto a node; the snap ring turns green when a node is in range.

Three: a point load (PL) — a force at a point; a point moment (PM) — a concentrated moment that can be positive (counter-clockwise) or negative (clockwise); and a distributed load (UDL) with separate start and end magnitudes, so it can be uniform, triangular or trapezoidal. Drag a load onto a member to place it.

Select the point load and drag its circular handle; it snaps to horizontal/vertical within about 6°. For an exact value, tap the angle label and type the Angle to member or Global angle. The default 90° points perpendicular into the member.

A UDL set to Side A or Side B is perpendicular to the member and re-aligns automatically when the member rotates. A UDL set to Up, Down, Left or Right is locked to the world axes and stays in that global direction whatever the member’s angle.

Select the member to open its detail panel and use the Material and Section tabs. Pick from the library or add a new entry by name, then set the Elastic Modulus (E), Area (A) or Second Moment of Area (I). Materials and sections are shared globally, so editing one updates every member that uses it.

Force can be shown in N or kN, and length in mm or m — switch them with the two toggles under the tool dock. All internal calculations run in base units (N, mm), so switching units only changes the display and rescales load magnitudes; it never re-solves or corrupts your model. Elastic modulus is in N/mm² (MPa), area in mm² and second moment of area in mm⁴.

Tap the floating Analyse button. It shows a 0–100% progress ring while solving on a background thread, then becomes Re-analyze. A green “Analysis complete” banner confirms success. The app analyses each connected structure separately, so several beams, frames and trusses can share one workspace.

The structure is a mechanism or is under-restrained — it can’t be solved. The app advises: “add enough supports to fully restrain it, then analyze again.” Because each connected structure is solved on its own, the stable ones still solve and display while the unstable one is flagged with a red dashed overlay and an “Unstable” badge.

Your results are now out of date. A “Results are outdated — re-analyze” strip appears and the Analyse button pulses amber as Re-analyze. Tap it to solve again with the updated model; your previous results stay in memory until then.

After a successful analysis a bottom toolbar shows five independent toggles: Reactions, Deflection, Shear, Bending and Axial. Turn each on or off (you can stack several). Tap Summary for the governing critical values — max bending moment, shear, axial, deflection and reaction — plus the solve time. Try the interactive layer demo in the guide.

Drag the inspection scrubber along any member. A readout shows the layer code (M, V, N or δ), the value and the position, e.g. “M @ 0.5 m”. Tap the readout to pin a permanent marker; tap a pinned marker’s label to remove it. You can make the knob snap to sampled stations in Settings ▸ Analysis.

By default the app auto-blurs loads and supports behind the result diagrams to declutter the view. Use the Loads & supports menu to set each to Show, Blur or Hide, or turn off “Auto-blur loads & supports with results” in Settings ▸ Analysis.

It's available now on the App Store for iPad (iPadOS), currently in beta. Native macOS, visionOS, Android and Windows versions are in development. See the platforms overview.

They're on the roadmap but don't have public dates yet. The fastest way to hear first is to reach out on LinkedIn and let us know which platform you're waiting for.

Yes. The analysis runs entirely on your device — no account and no internet connection are needed to draw, solve or read results.

Open the App Store on your iPad and search for iStruct2D, or open the iStruct2D App Store listing and tap Get. It's free, and new builds arrive automatically as App Store updates.

The quickest way is to message the developer on LinkedIn, or use the Report a problem page — please include your device, iPadOS version and the app version so we can reproduce it.

The app needs no account and doesn't track you or show ads. Projects you create are stored locally on your device, and exported files are shared only when you choose to share them. If you've enabled “Share with App Developers” in your device settings, Apple provides the developer with standard crash and basic usage diagnostics under Apple's terms. Full detail is in the Privacy Policy.

Projects are saved locally on your device as .istruct2d files — there’s no cloud sync. In Settings ▸ Data, tap Share project file to export the .istruct2d file to back it up or send to another device. A bundled “Demo Examples · Frame, Beam & Truss” project ships pre-installed. Removing the app removes its locally stored projects.

You can undo and redo model edits — including unit changes — up to 60 steps with the top-right buttons. Deleting a project, however, is permanent: it removes the project from the device with no trash or undo. Resetting the workspace is also irreversible (though it’s undoable within the workspace history).

iStruct2D is independently designed, built and owned by Weng Chong LAO. The app is 100% owned by the developer.

iStruct2D was co-developed in collaboration with The University of Queensland, School of Civil Engineering. The collaboration informed the engineering and teaching design; ownership and copyright of the app remain 100% with the developer, Weng Chong LAO. See the ownership section of the Terms.

Reach out directly to the developer on LinkedIn — collaboration, partnership and licensing enquiries are all welcome.