Direct Answer
A structural truss is a triangulated framework of steel members (chords, diagonals, and verticals) that spans long distances with high structural efficiency. Trusses are fabricated by cutting and profiling each member to length, assembling on a precision jig that maintains the design geometry, and welding or bolting the joints. Welded trusses are fabricated in the shop; bolted trusses may be assembled and trial-erected in the shop before final shipping.
Full Explanation
Truss components: (1) Top chord — the compression member along the top. (2) Bottom chord — the tension member along the bottom. (3) Verticals — members connecting top and bottom chord. (4) Diagonals — inclined members carrying shear. Materials: W-shapes, HSS, or angles depending on load and aesthetics. Fabrication sequence: (1) Cut all members to length. (2) Profile any HSS-to-HSS connections. (3) Build a steel jig on the shop floor at the correct geometry (including camber if required). (4) Set chord members in the jig. (5) Fit and tack-weld all web members. (6) Inspect geometry before final welding. (7) Complete final welding in a balanced sequence to control distortion. (8) Inspect and measure final geometry against drawing tolerances.
What This Means for Your Shop
Truss fabrication is among the most skill-intensive work in a structural steel shop. Geometry errors discovered after final welding are expensive to correct — heat straightening a truss panel with multiple welds is a day-long process. Invest in jig accuracy upfront.
Common Mistakes
Welding trusses without a precision jig and relying on tack welds to hold geometry. Final welding shrinkage will distort an untrestrained truss — the finished product will not match the drawing geometry.
Recommended Process
For each truss type, build a steel jig that sets every node location precisely. Verify jig dimensions with a measuring tape and/or total station before loading members. Inspect geometry after tacking and before final welding — corrections at the tack stage are fast; corrections after final welding are slow.