Primary Framing
Bolted End-Plate Moment Connections in PEB
Definition: A bolted end-plate connection joins two frame members through a thick steel plate welded to each member end, bolted together with high-strength bolts. In pre-engineered buildings it forms the knee, ridge and rafter splice joints that make the frame moment-resisting.
Key facts
- Used at knees, ridges, rafter splices and some column splices.
- Bolts are high-strength structural bolts installed snug-tight or pretensioned as specified.
- End-plate thickness and bolt layout are designed for each connection.
- Column web stiffeners and doubler plates may be required at the knee.
- Accurate shop fit and squareness are essential for good bearing.
Role in the structure
At the knee, the end-plate connection transfers the rafter bending moment, shear and axial force into the column. The tension flange pulls on the bolts nearest to it, while the compression flange bears through the plates. Stiffeners distribute these forces into the column web. Because all welding is done in the shop, field work is limited to bolting.
How does an end-plate connection resist moment?
The bending moment is resolved into a tension force in one flange and a compression force in the other. Bolts near the tension flange carry the tension; the plates bear against each other near the compression flange.
The end plate must be thick and stiff enough that it does not bend excessively under bolt tension. The engineer checks plate bending, bolt tension and shear, welds and the column panel zone according to the governing code.
Snug-tight or pretensioned bolts?
Some end-plate connections may be designed with snug-tight bolts, while others require pretensioning, for example where loads reverse, fatigue applies, or seismic provisions call for it. The design drawings state the requirement for each joint.
Pretensioning methods include turn-of-nut, calibrated wrench, direct tension indicators and tension-control bolts. The method, and the inspection that goes with it, should be agreed before erection.
Why does fabrication accuracy matter for end plates?
If an end plate is not square to the member, the plates will not meet evenly and the frame geometry will be wrong. Welding heat can also distort thin plates.
Shop procedures therefore control fit-up, welding sequence and flatness, and fabricators check plate squareness before coating.
Materials & coatings
- Structural steel plate for end plates and stiffeners.
- High-strength structural bolts, nuts and washers to recognized ASTM, CSA, AS or EN product standards.
- Galvanized bolt assemblies where the frame is galvanized.
- Complete-penetration or fillet welds as designed.
Design considerations
- Moment, shear and axial forces from all load combinations.
- Bolt grade, diameter, number and arrangement.
- End-plate thickness and need for extended plates.
- Column web stiffeners and panel zone capacity.
- Bolt installation class: snug-tight or pretensioned.
- Seismic detailing where applicable.
Fabrication
- Cut and drill end plates to template.
- Weld plates to members using qualified procedures and welders.
- Check plate flatness and squareness.
- Mask faying surfaces if the joint is slip-critical.
Erection
- Bring plates into firm contact before tightening.
- Install bolts in a pattern that draws plates together evenly.
- Pretension bolts by the specified method where required.
- Do not ream or enlarge holes without engineer approval.
Inspection & quality
- Verify bolt grade markings and assembly components.
- Check plate contact and gaps.
- Inspect pretension by the agreed method.
- Review weld inspection records from the shop.
What to include in your RFQ
- Governing steel and bolting standards.
- Bolt finish to match frame coating.
- Inspection level and third-party inspection needs.
- Seismic design category or equivalent, if applicable.
3D model & IFC of this component
Rotate the model, isolate the component and download its IFC4 file for your BIM coordination model.
IFC entity: IfcPlate + IfcMechanicalFastener. Illustrative geometry for coordination and learning. Final member sizes come from the project design.
Frequently Asked Questions
Why not weld frame joints on site?
Shop welding is more controlled and faster. Bolted end plates allow quick, reliable site assembly without field welding inspection.
Can I replace a bolt with a different grade?
No. Use only the bolt grade and assembly specified on the drawings, from a traceable supply.
Can pretensioned bolts be reused?
Bolts that have been fully pretensioned should generally not be reused. Follow the bolting standard and engineer instructions.
Engineering content is general guidance. Every World Steel building is designed by qualified engineers to the code and loads of the project.
