Glossary · Steel structures
Profile perforation and bolts in slots
Factory slotted holes of a mounting C-profile; bolts go into the slots without drilling, and the maker confirms a slotted bolt’s resistance.
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Definition
The 41×41 mounting C-profile is made with perforation: a row of slotted holes along its axis. For example, the ПП.001 pattern has 30×11 mm slots at a 50 mm pitch on the back and also on the side walls. The perforation is there for fast assembly: an M10 bolt passes through a slot without drilling. So each part’s blank is cut so that the slots land under the node bolts.
Perforation matters for design twice. First, it reduces the section, which enters the effective properties. Second, a bolt in a slot behaves differently from one in a round hole. DSTU-N B EN 1993-1-3:2012 (Table 8.4) gives the bolt bearing resistance for round holes only:
Fb,Rd = 2,5 · αb · kt · fu · d · t / γM2A bolt in a slot is no stronger than one in a round hole. So if the node force exceeds Fb,Rd even for a round hole, the node fails. If it is below, that is not yet proof: for a bolt in a slot the resistance is confirmed by the profile maker’s data or by tests (EN 1993-1-3, section 9). Check the perforation dimensions on your actual profile: the maker’s table and the real profile sometimes differ.
What to know when ordering. Makers use different perforation patterns: the pitch, the slot size and whether the side walls are slotted all vary. Check the dimensions from the maker's table on the actual profile, since the pitch decides whether a truss node lands in a slot at a given angle. If a node does not land, there are two ways: change the tilt slightly, or drill a new hole, and then the node is no longer a 'factory' one. Solispec first looks for the nearest angle at which no drilling is needed and shows how far each truss or rail was shifted.
How Solispec applies it
When a perforated profile is chosen in the Solispec constructor, the engine puts every M10 bolt into a slot: it shifts the blanks, adjusts the truss angle so the triangle nodes land on the slot pitch, and moves rails to the nearest slot. For each node it computes Fb,Rd by Table 8.4 as a reference value and states that a slot needs maker data or tests.
Norms and clauses
- DSTU-N B EN 1993-1-3:2012, Table 8.4; section 9
Related terms
- Thin-walled cold-formed C-profileA bent steel section with thin walls that buckles locally before yielding; it is designed to DSTU-N B EN 1993-1-3:2012.
- Effective cross-sectionThe part of a thin-walled section that still carries compression after its walls buckle locally; computed per EN 1993-1-5 and EN 1993-1-3.
- Steel partial factors γM and γmFactors that divide the characteristic steel resistance: γ_M per Eurocode for C-profiles, γ_m per DBN V.2.6-198 for tubes.
- DSTU-N B EN 1993-1-3:2012: designing C-profiles for PV mountingNorms explained
Solispec’s calculation is preliminary: for a design it has to be checked by an engineer. The values and clauses follow the current editions of the norms on the date of the page.