Loadsheaf user guide

Getting started: your first load ledger in two minutes

Loadsheaf opens with an example project. The left column is the Ledger: response channels, load cases and combinations. Select any item to edit it in the middle column, the Sheet. The right column shows Results, which recalculate in a background worker a moment after every edit.

• Pick a ready-made project from Examples, or press New for an empty one.
• Add a channel for each response you want to track, for example a column axial force (N) or a base moment (N*m).
• Add a case and choose its generator: direct forces, wind, snow, live load or seismic. Enter every parameter from your governing code and project documents, and record where each value came from in the Source note.
• Fill the case influence matrix: how much each channel responds to one newton of each generated force.
• Add combinations: each one lists cases with signed factors. Loadsheaf evaluates exactly the combinations you list.
• Read the Envelope tab for the largest and smallest value of each channel and the combination that produced it. Save the project as a file with Save, and export results with Export.

Loadsheaf ships no design-code tables or factors. Code factors and tables are USER-ENTERED: gust, exposure and pressure coefficients, snow factors, importance factors, seismic coefficients and exponents, live-load reduction parameters and combination factors all come from you. The examples use illustrative numbers that are not taken from any code.

The workspace: Ledger, Sheet and Results

The toolbar holds the project title, Examples, New, Open, Save, Export, Print, Undo and Redo, the display-unit switch (SI or US) and the run status with Cancel. The Workspace, Guide and Verify tabs switch views.

Ledger

Three lists: channels, cases and combinations. Each case shows its generator and its total generated force. Buttons add a new item to each list. Select an item to edit it; the Delete button on the Sheet removes it (Undo brings it back). Deleting a case also removes its terms from every combination; deleting a channel removes its row from every influence matrix.

Sheet

• Project: title, basis note, copyright and terms. These travel with saved files and exports.
• Channel: an identifier and a unit (N, N*m, Pa or m).
• Case: identifier, label, source note, generator parameters, and the influence matrix with one row per channel and one column per generated force.
• Combination: identifier, label, the source of its factors, and its terms (case and signed factor). A case may appear once per combination; enter its net factor.

Numbers are entered in SI units, shown beside every field. A field that does not hold a valid number is outlined and its last valid value is kept, so the model never contains a half-typed entry.

Results

• Loads: the step-by-step derivation for the selected case (dynamic pressure, net pressure, reduction ratio and its regime, base shear and level forces). Seismic cases show an elevation chart of level forces and story shears.
• Effects: tables of every case and every combination for every channel.
• Envelope: for each channel, the minimum and maximum over your combinations, with the governing combination, and a bar chart of all combinations for the channel you choose.
• Checks: sanity checks on your own model (seismic force sum equals base shear, base story shear equals base shear, overturning moment equals the sum of force times height), warnings such as unused cases or empty combinations, and the resource estimate of the run.

Charts always show their whole content in the panel and refit when the window or the data changes. When a chart has more items than fit legibly, it shows the most significant ones and says how many are in the table.

Load generators

Wind

The multiplier applies to both coefficients. If your governing method uses different velocity pressures for external and internal pressure, or a gust factor on only one of them, include that in the coefficients you enter, or make two cases. Positive pressure acts in the direction of your coefficient sign convention. An internal coefficient that already includes a gust effect must not be amplified again.

Live-load reduction

The reduction is applied only when the case is marked eligible, the area is not zero and the effective area is at least the minimum you enter. Otherwise the ratio is 1. The result panel names the regime: reduced, minimum (held at your lower bound), unreduced (the formula gives 1 or more), below-area, zero-area or ineligible. Eligibility is your decision: occupancy, number of floors supported and other exclusions are not checked.

Seismic distribution

Levels are listed bottom to top with strictly increasing heights. Weight is a force in newtons, not a mass. Each level is one generated force, so a seismic case needs one influence column per level; using only the base shear would lose its distribution. Period, spectrum, coefficient bounds, accidental torsion, directional combination and dynamic analysis are outside this model.

Influences, combinations and envelopes

Each influence entry is the channel response to one newton of that generated force, in channel units per newton. Supply influences from a suitable linear analysis or a reviewed hand calculation. Loadsheaf is not a structural solver; it multiplies and adds what you give it.

A combination is a list of cases and signed factors. Opposite wind directions, alternative dead-load factors and mutually exclusive actions each need their own combination. Loadsheaf does not generate combinations, add missing patterns or decide which actions may act together. A combination with no terms is an explicit zero state.

The envelope evaluates only the combinations you list. It keeps the signed minimum and maximum of each channel and the combination that produced each one; on an exact tie the first combination in the list wins. With no combinations the envelope is shown as unavailable rather than zero. Extremes of different channels can come from different combinations, so they are not one simultaneous state. No PASS/FAIL structural verdict is produced.

Units and sign conventions

All inputs and saved files are SI. The display switch changes only how results are shown: SI shows kN, kN·m, kPa and mm; US shows kip, kip·ft, psf and ft, converted with the exact international foot, pound and standard gravity of NIST SP 811 Appendix B. Switching units never changes the model or the saved file.

Signs follow your own convention. Wind and direct forces are signed; snow, live and seismic generated forces are non-negative, and a negative combination factor reverses a case. Seismic heights are measured up from a common base.

Files and exports

Save writes a .loadsheaf.json file: format version 1, SI units, title, copyright, terms, basis, channels, cases with their generators, sources and influences, and combinations. Open accepts only that format and refuses unknown fields, wrong versions, non-numeric values or an altered notice, without changing your current project. Files are limited to 2 MiB. Your work is also kept automatically in this browser and restored when you come back.

• CSV: a rectangular table of metadata, every case and combination effect and the envelope, made in the gated worker. Numbers keep full precision; text that could be read as a spreadsheet formula is neutralised.
• SVG and PNG: the chart in the active Results tab.
• Print: a report of the project, effects and envelope, ready to save as PDF from the browser.

Every export carries the line "Made with Loadsheaf · simulations4all.com" and the professional-use notice.

Keyboard shortcuts

Limitations and troubleshooting

A project may hold up to 128 cases, 256 channels, 256 generated forces per case, 1024 combinations with up to 32 terms each, 16 snow factors and 4,000,000 multiply-add terms, with an estimated memory of at most 64 MiB. CSV exports are limited to 32,768 rows. These are browser budgets, not design-code limits. Non-zero inputs must lie between 1e-50 and 1e50 in magnitude.

Loadsheaf does not look up wind speeds, snow loads or seismic hazard, does not select coefficients, does not handle drifting, sliding or unbalanced snow, roof zones, gust algorithms, spectra or modal analysis, and does not analyse a structure. It does not decide whether a combination set is complete.

How we verify this tool

The Verify tab runs the same reference catalogue as the automated tests, in your browser: 119 ready cases (88 verification, 31 validation) and 2 pending a legitimate source. Each case states what is checked, the independent reference, the computed value, the difference, the tolerance and PASS or FAIL. Run all checks produces a summary badge and a printable report.

• 68 verification cases compare with independent methods that share no code or algebra with the engine: exact rational arithmetic, a numerical work integral for dynamic pressure, inverse construction of the live-load ratio, free-body equilibrium of story cuts and moments, and signed unit-force parcels for combinations and envelopes. 20 more recompute the engine's own algebra at 40-digit precision; they are labelled same-formula and guard arithmetic and regime branches, not the formulas themselves.
• Validation cases compare with the printed results of an openly published worked example (a university senior-thesis portfolio): two equivalent-lateral-force vertical distributions with non-integer exponents, and wind pressures and story forces. The code factors used in that example stay in the example; they are not shipped as defaults.
• Snow and live-load reduction have no openly published worked example in hand yet. Those rows are marked PENDING SOURCE, carry no number and are never counted as passes.
• The automated suite also runs seeded random comparisons, scale sweeps, edge values, file round trips, CSV consumer checks, resource limits and worker cancellation.

Compared with other tools

Commercial load-generation packages typically add hazard maps and site lookups, built-in coefficient catalogues for specific codes, prescribed combination sets, complex roof and building geometry, and links to structural analysis. Loadsheaf has none of these. Its strengths are transparency and portability: every number is visible and traceable to the value you entered, results run privately in your browser, combinations and envelopes are explicit, the reference checks run in front of you, and projects are open JSON files.

Professional use

For education and preliminary design only. Results must be checked by a qualified professional. Not a substitute for code-compliant design or licensed engineering judgement. No certification, code compliance or regulatory acceptance is claimed.