1 Start a model

Every model begins in one of three ways. Pick what suits you, then continue with the same steps.

• Sample model. Choose an example in Sample model and press Load sample. The fastest way to see how everything works.
• Saved model. Models you saved earlier are listed in Saved model. Press Load saved. Saved models belong to the browser and site address that saved them.
• AutoCAD DXF. In Import from AutoCAD choose the DXF file, the drawing units and the layer, then press Import model. Only LINE and straight 2D polyline centre-lines are imported; supports, loads and sections are assigned in FaxinaX afterwards.

2 Build the model

1. Element properties. Choose the material and section type (steel database section, concrete rectangle, or manual properties) and the steel grade. Properties can be set per member, and each member can be a frame or an axial-only truss element.
2. Draw tools. Draw members on the canvas with snapping; nodes are created automatically. Existing nodes that lie on a member connect in the analysis. Add supports (fixed, pinned, roller), end releases, rotated restraints and spring supports.
3. Check the geometry. Use Node table and Member table to edit coordinates and connectivity, and Fit view, zoom and pan to inspect the drawing. Undo and Redo are available at any time.

Units are SI: metres, kN, kNm. Section areas are entered in m², inertia in m⁴, density in kg/m³.

3 Define loads

1. Load cases. Create named load cases under Define load case and choose the type (for example permanent, variable or self-weight). A self-weight case generates w = ρ × A × g for every member and shows the numerical values, so you can check them.
2. Add loads. Under Add load enter nodal forces and moments, uniform member loads or point member loads. Member ranges can be entered with short text such as 1to4.
3. Review in the load table. Load table lists every load by case. Edit values, targets or direction there, or press Remove to delete a load group.
4. Combinations. Under Define load combinations build combinations by hand or let FaxinaX generate ULS persistent/transient combinations.

Generate the wind load automatically (3D Structure)

FaxinaX can work out the wind pressure to EN 1991-1-4 and put it on the structure for you. The load is applied to cladding panels, which pass it to the frame members along their edges.

1. Define the cladding first. In Cladding enter the four corner nodes of each wall or roof panel in order round the panel, choose Two-way or One-way span, and press Add panel. Detect from members finds every rectangular panel formed by your members at once. Each panel needs members along its four edges, because the load can only reach the frame through members.
2. Create a wind load case. Under Define load case choose the type Wind (W). The button Wind load options… appears.
3. Choose how to define the load. Define manually closes the menu and lets you apply nodal, member or panel loads yourself. Generate automatic wind load opens the generator. A message tells you if no cladding exists yet.
4. Enter the wind inputs. Basic wind speed v_b,0, terrain category, directional, season and orography factors, c_sc_d and the internal-pressure coefficients c_pi. Use Wind load tab inputs copies what you last entered in the Wind load page.
5. Describe the building. Base level and height h, roof type (flat/duopitch, monopitch, hipped, multispan, vaulted, dome), pitch and ridge direction, parapet or eaves, and how the wall pressure varies with height (stepped strips, uniform at h, or continuous).
6. Choose the directions and cases. Tick the directions the wind blows towards (+X, −X, +Y, −Y) and the internal-pressure cases. One load case is made for every direction, internal pressure and roof case you tick.
7. Press OK · generate wind load. The cases appear in the load-case list with type Wind (W), the pressures are drawn on the panels (Wind pressure map under the canvas colours them), and a table shows the resultant force of each case and the pressure on each panel. Optionally, Rebuild automatic combinations adds the wind cases to the ULS combinations.

Check the resultant forces in the generated table against a quick hand estimate (q_p × projected area × c_f). If a panel receives no load, it is either covered floor slab (shells marked No wind) or its edge members are missing.

4 Run the analysis

1. Choose the Analysis type: static (displacements, reactions, internal forces), buckling (elastic critical load factor and buckling modes), modal (natural frequencies and mode shapes) or response spectrum (global X, SRSS or CQC). Moving vehicle load and Influence line are also available (see section 5).
2. Choose the Display result: a single load case or a combination.
3. Press Run analysis.
4. Read the Result check. A message appears after every run, even when it says 0 errors and 0 warnings. It reports a mechanism and its cause, huge displacements, isolated nodes or parts, deflection above span/50, suspicious units, the automatic self-weight notice, and whether the support reactions equal the applied loads (ΣFx, ΣFy, ΣM). Fix errors before trusting the numbers.

Buckling analysis

Buckling analysis answers the question by what factor must the loads be multiplied before the structure buckles? It is available in both the 2D Frame and the 3D Structure workspaces.

1. Set Analysis type to Buckling analysis. The buckling options appear in Analysis options.
2. Choose the Load case or combination that loads the structure. Use the compressive load you care about, usually the governing ULS combination or the gravity load.
3. Set the number of modes (the lowest few are usually enough) and the elements per member. Several elements per member are needed so that the bowing of a member between its ends is captured. Four per member is a good start; use more for slender members or when the mode looks angular.
4. Press Run analysis. FaxinaX solves a linear static analysis for the chosen loads, takes the axial forces, and solves the buckling eigenproblem.
5. Read the result table: each mode has a load factor λ. The lowest, λ_cr, is the critical one. Display result shows the mode shape, normalised to a maximum displacement of 1 m, so only the shape is meaningful, not the size.

• λ_cr > 1 means the applied load is below the elastic critical load; the critical load is λ_cr times the applied load. EN 1993-1-1 allows a first-order analysis when λ_cr ≥ 10 for elastic analysis.
• Check with Euler. For a pin-ended column P_cr = π²EI/L². Compare it with λ_cr × P for a single column before trusting a large model.
• Limits. The analysis is linear (bifurcation of a perfect structure, no imperfections, no material yielding). Shells add stiffness but no geometric stiffness in 3D. Use λ_cr to find buckling lengths and to decide whether second-order effects matter, not as a design resistance.

5 Read the results

• Diagrams. N, V and M draw axial force, shear and bending moment with signed values. Deformed shows the deflected shape; the Force and Shape sliders scale the drawing.
• Normalize. When the real values are tiny, Normalize scales the deformed shape and diagrams so they stay visible.
• Contours. The Contour list colours members by displacement or force. Values prints numbers on the model.
• Numbers. Reactions shows support reactions, Member max/min the extreme values per member, and the node and member tables list displacements and actions.
• Switch between cases and combinations in Display result at any time; cached results are kept until the model changes.

Moving vehicle load and influence lines

For bridges, crane runways and any structure crossed by a vehicle, FaxinaX steps a vehicle along a route and records the response at every position. The same run also solves the influence line, so you see both on the model canvas.

1. Make a load case for the moving load and open Moving vehicle load above the canvas. The panel with Route, Vehicle and Load steps opens.
2. Route. Press Auto route to follow the members, or press Draw route on canvas, click the route points (in 3D, in Plan view at the route elevation) and press Finish route. Points can also be typed as X, Y (2D) or X, Y, Z (3D), one per line.
3. Vehicle. Choose a preset (two-axle truck, single point load, EN 1991-2 LM1 tandems for lanes 1 to 3, HL-93 design truck) or Custom and type the axles as offset behind the front axle (m) and downward load (kN).
4. Load steps. Set the travel step; a smaller step is more accurate but slower. The tolerance defines how close to a member the vehicle must be to load it. Leave Receiving members blank to load every member below the route.
5. Run. In Analysis options tick the moving load case together with the other load cases, set Analysis type to Moving vehicle load and press Run moving vehicle load. Choose Influence line to solve only the unit-load influence line.
6. Play the result. Use Step, Play vehicle, the speed and Loop controls. Canvas result selects what is drawn: vehicle loads, deformed shape, reactions, or the N, V, M (and T, M_y, M_z in 3D) diagrams at the current step.
7. Read the influence line. Under Influence line / response history on canvas choose a Response (support reaction, node displacement, or member force at a station), the node or member and the station. The curve is drawn along the route: its ordinate at a point is the response caused by a unit load at that point.
8. Export. Download all step results (JSON) saves every step for post-processing.

Use the influence line to place the load where it is worst: positive areas are loaded for the maximum, negative areas for the minimum. The vehicle results are characteristic and quasi-static; apply dynamic and lane factors from your design code afterwards. Shell interiors and deck distribution are excluded.

6 Check steel members (Eurocode 3)

1. Run a static analysis first, then open the Steel check tab.
2. Press Define inputs and enter the member numbers (for example 1to3, 19). Choose the checks, buckling lengths, and the lateral-torsional buckling input: define brace points, critical length or Mcr.
3. With brace points, FaxinaX reads the bending-moment diagram of each braced segment and selects the loading case and equivalent moment factor for you. The selection is shown so you can review it.
4. Set the deflection limit. It is measured relative to the line between the two member ends.
5. Assign the ULS and SLS combinations to the members and run the check. Review the interaction factors and press Utilization to colour the model by maximum utilization ratio.

7 Check RC members (Eurocode 2)

The RC check designs the reinforcement for concrete beams, columns, slabs and walls in the 3D Structure workspace, to EN 1992-1-1:2023. Run a static analysis first.

1. Give members a concrete section. In Element properties choose Concrete rectangle, the concrete class and the width and depth. Slabs and walls are shell elements with a thickness.
2. Open the RC design tab. Choose Results to design for (factored combinations are recommended), the concrete grade, f_yk, the cover, the link diameter and the main bar diameter. Partial factors γ_C, γ_S, γ_V and k_tc can be edited for the National Annex.
3. Per member. Select a member and choose Design as beam or column (automatic: vertical = column), the effective-length factors k_y and k_z and the creep ratio φ_ef for columns.
4. Shells. Choose whether shells are slabs, walls or automatic (horizontal = slab, vertical = wall).
5. Press Run RC design. The RC design results appear below the canvas.
6. Punching shear. Fill in the top-steel ratio (blank = from the RC design), any load inside the perimeter and the column overhang, then press Run punching check. Every concrete column that ends at a slab is checked at the control perimeter.

Reading the RC results

• Beams. Bottom and top bars (for example 3Ø16), side bars when needed, the links with spacing, V_Ed against V_Rd,c and V_Rd,max, torsion, and the governing check.
• Columns. Longitudinal bars and ties, the N–M interaction ratio including second-order effects, and slenderness λ against its limit.
• Slabs and walls. Required steel in mm²/m on each face and each direction, with a bar suggestion, and the governing check.
• Ratio and status. The ratio is demand divided by resistance; PASS is ≤ 1.00. A red note explains any failure, for example a section that is too small or a column that is too slender.

Download the RC design report

After the design has run, press Download RC design report (PDF) under the results. Enter the author name when asked. The report contains the design basis and material data, a summary table with utilisation bars, one block per beam or column with a to-scale section sketch showing the bars and links, the reinforcement, the shear and torsion checks and the ratio of every check, the slab and wall table, the punching results, and the engineering-review statement. Run the design again after any change to the model: the report always shows the last run.

The bar arrangement is the lightest practical layout that satisfies the checks for the envelope of the selected results. Detailing (anchorage, laps, curtailment, serviceability and durability) must be completed by the designer.

8 Fire design (Eurocode)

The Fire design tab checks steel members to EN 1993-1-2 and concrete members to EN 1992-1-2, using the fire load combination of EN 1990 §6.4.3.3. It works in the 3D Structure workspace.

1. Create the fire combinations. Set the combination factor ψ for the variable load (ψ_1,1 or ψ_2,1) and for wind, then press Create fire combinations. All partial factors are 1.0: ΣG_k + ψ_1,1Q_k,1 + Σψ_2,iQ_k,i. The accidental fire action itself is the heating, not a load.
2. Run the analysis with the fire combinations ticked. Use a static analysis.
3. Fire exposure. Choose the temperature–time curve (Standard fire ISO 834, External fire or Hydrocarbon fire) and the required resistance R (for example R60).
4. Steel members. Choose Unprotected or Board / spray (box) protection and give the conductivity λ, density ρ, specific heat and thickness of the protection. Choose 4 sides or 3 sides exposed (slab on top) and whether the member is statically indeterminate.
5. Concrete members. Give the cover to links and the bar diameters, whether beams are simply supported or continuous, whether slabs are one-way or two-way, the column exposure, the column reinforcement ratio and the load level μ_fi (blank = calculated).
6. Press Run fire design.

Reading the fire results

• Steel. The steel temperature at time R, the critical temperature of the member, the reduced resistance and the interaction ratio of the member in fire (flexural buckling, lateral-torsional buckling, N–M interaction). The chart shows the gas and steel temperature against time, so you can see when the critical temperature is reached.
• Concrete. The tabulated-data method (EN 1992-1-2 §5): the minimum section width and axis distance required for the fire class are compared with the section you have. FaxinaX reports the highest fire class passed (R30 to R240). If a validity condition fails, for example l_0,fi above 3 m for a column, the table does not apply and the result says so.
• Load level. The load in fire is lower than the load at normal temperature. The ratio μ₀ = E_fi,d/R_fi,d,0 controls the critical temperature of steel and the table to use for concrete columns.

Fire design is the third check after ULS design: size the members for normal temperature first, then verify the fire class. If a steel member fails, add protection or enlarge the section; if a concrete member fails, increase the axis distance (cover plus half the bar diameter) or the section width.

9 Reports, export and saving

• FEA results PDF. Press Export FEA results to PDF above the canvas, choose the sections and results, and enter the author name. The report contains assumptions, loads, results, diagrams, contours and a section that lists the model check errors, warnings and equilibrium check.
• Steel design PDF. After a design check, use the steel report button in the Steel check tab.
• RC design PDF. After Run RC design, press Download RC design report (PDF) in the RC design results.
• Exchange files. Use Export in the top bar for Robot Structural Analysis RTD, SAP2000 S2K or AutoCAD DXF.
• Save. Press Save model (or Ctrl+S) to keep the model in this browser.

10 Tips and good practice

• Ctrl+Z and Ctrl+Y undo and redo, Ctrl+S saves, Esc clears the selection or cancels an unfinished drawing action.
• If the result check reports a mechanism, read the cause it gives: add supports, remove releases, or reconnect isolated parts.
• Always compare a few results with a hand calculation. FaxinaX is an engineering aid; a qualified engineer must review the model and the results before they are used in design or construction.
• Use Send feedback to tell the developer about problems, ideas and your experience.