Structural Steel Fabrication and Erection

Steel factory buildings, steel hangars and terminals: where structural steel fits

Structural steel is the load-bearing system of choice where wide spans have to be crossed, erection time has to be cut and the weight of the structure has to come down. Factory and production buildings, aircraft hangars, airport terminals, stadium roofs, logistics warehouses and rolling mills are the building types where this need is most acute.

Unlike reinforced concrete, most of the load-bearing members are produced in the workshop, under controlled conditions. The site only erects. That distinction makes the schedule predictable and concentrates quality control at a single point.

What is an execution class (EXC), and how does it affect your project?

EN 1090-2 divides structural steel fabrication into four execution classes: from EXC1 to EXC4, the required level of inspection, weld examination and traceability increases. The class is set by assessing the consequence class, service category and production category of the structure together.

Most industrial buildings fall under EXC2, while structures carrying crane loads and subject to fatigue are generally EXC3. Because the execution class governs everything from the extent of non-destructive testing to welder qualifications, it needs to be settled at the quotation stage.

How does the fabrication process work?

The process begins with material acceptance: an EN 10204 3.1 inspection certificate is obtained for every batch and traceability is established piece by piece. Plasma or oxy-fuel cutting, drilling, assembly and welding follow. Welds are made under approved welding procedures (WPS) by qualified welders.

After fabrication come dimensional control, non-destructive testing and surface preparation. The coating system applied after Sa 2½ blast cleaning is selected according to the ISO 12944 corrosivity category of the structure's environment. A final inspection and a check of the piece list are carried out before dispatch.

Steel roof truss erection and tolerance control

Erection is an engineering task in its own right, separate from fabrication. Crane capacity and position, erection sequence, temporary stability members and working-at-height measures are all defined in advance in the erection plan.

In preloaded connections, bolts are tightened under EN 14399 by a defined torque or part-turn method. Column alignment, level and squareness tolerances are measured as erection proceeds; deviations are corrected before they accumulate.

Material selection: S235, S275, S355

The most common grades in structural steel are S235, S275 and S355 under EN 10025-2. The number gives the minimum yield strength of the material in N/mm². Because S355 offers higher strength, it allows a lighter section to be used for the same load.

The letters JR, J0 and J2 after the grade code indicate the temperature at which impact toughness is verified. In thick sections and at low service temperatures, this choice directly affects the risk of brittle fracture.