Draw a roof truss on a grid, like in STAAD, or start from a ready shape. The tool works out the loads
to IS 875, analyses the truss, picks angle, channel or ISMB sections to IS 800, designs the bolts or welds, and then
designs the RCC beam or column the truss sits on to IS 456.
Draw the trussPick a ready shape and press Generate, or click on the grid to add nodes and members.
Set the supportsChoose the Support tool and click a node: first click pin, second roller, third removes it.
Fill in the buildingTruss spacing, height, roof sheet, wind speed and the RCC supporting it.
Press Analyse & designSections, bolts or welds, reactions and the RCC design appear below.
top chordbottom chordweb members▲ pin ●▲ roller
Start from a ready shape
Rise ≈ span/4 to span/6 for sheeted roofs. Panel length 1.2–2 m so that purlins sit on the nodes. For a flat truss, rise is the depth (span/10 to span/15).
Want a different shape entirely? These four are just a starting point — press Clear above, then use + Node and + Member to draw any truss you like, panel by panel.
Grid
Nodes snap to grid points. Change the spacing, then click on the grid to add nodes where you want them.
Choose Select and click a member to change its group, or a node to type exact coordinates.
Building
Truss spacing 3–6 m is usual. Height is from ground to the level where the truss sits. Live load follows IS 875 (Part 2): 0.75 kN/m², less 0.02 per degree of slope above 10°, not below 0.40.
Roof dead load
Weights from IS 875 (Part 1) or the sheet maker’s catalogue. The truss’s own weight is added automatically from the sections chosen.
Wind — IS 875 (Part 3):2015
Basic speed: Kolkata 50, Delhi 47, Mumbai 44, Chennai 50, Bengaluru 33 m/s. Sheds with large doors: 5–20% openings. Roof pressure coefficients are read from the IS 875 table for pitched roofs using your roof slope and height/width.
Steel
Double angles back-to-back are the usual choice for chords; single angles for webs. The bottom chord goes into compression when wind lifts the roof, so its sideways bracing matters. After the design runs, you can replace the suggested size of any group with your own choice in section 5 of the results.
Connections
Bolts are checked for shear and bearing (IS 800 Cl. 10.3); welds for throat stress (Cl. 10.5). The weld size is reduced automatically if it is too big for a thin leg.
What the truss sits on
On a beam: the trusses at the spacing above sit on a longitudinal beam, and the beam spans between columns.
For example a brick parapet on the beam. The beam is designed as simply supported between columns, which is on the safe side for sagging.
Columns are taken as fixed at the base and free to sway at the top, so the effective length is 2 × height (IS 456 Table 28). Foundations are not designed here.