Custom Fabricated Steel Portal Frame Knee Joint with Haunch & Bolted End Plate Connections for Industrial Steel Buildings

Target Keywords

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Brief Description

Heavy-duty welded steel portal frame knee joint with integrated haunch bracket and bolted end plate connections. Designed to transfer moment and shear between column and rafter in single-story industrial steel frame buildings.

Detailed Description

This portal frame knee joint is the critical moment-resisting connection between the vertical column and the inclined rafter in single-story steel frame structures - warehouses, factories, hangars, and commercial sheds. Fabricated from Q355B structural steel plate, the knee assembly features a haunch (deepened bracket section) that increases the section depth at the joint to resist the peak bending moment that occurs at the column-rafter intersection. The assembly includes bolted end plate connections on both the column side (10 × M20-M30 bolts in 2×5 pattern) and the rafter side (5 × bolts), enabling rapid on-site bolted assembly without field welding. Vertical stiffener plates are full-penetration welded inside the web to prevent local buckling under combined axial compression and bending. All welds are executed to AWS D1.1 / ISO 3834-2 and undergo UT/MT inspection. The joint is shot-blasted to SA 2.5 and coated with 60-80μm epoxy zinc-rich primer. Hot-dip galvanizing is available for corrosive environments. We provide complete connection design calculations per AISC 360 / Eurocode 3, including moment-rotation characteristics and bolt group capacity verification, as part of our free engineering service. Each knee joint is match-marked and shipped with its matched bolt kit and an erection drawing.

Product Attributes

Product Selling Points

Engineered haunch design: Haunch depth and length are calculated specifically for your frame span, column height, and roof pitch - not a generic template - ensuring optimal moment resistance without overdesign

Bolt group capacity verified: Every bolted connection is checked for shear, bearing, tension (including prying action), and combined loading per AISC 360 Chapter J or EC3 Part 1-8

Match-drilled end plates: Column-side and rafter-side end plates are drilled as matched pairs in the shop, guaranteeing 100% bolt alignment during site erection

Stiffener placement optimized: Web stiffener spacing and thickness are determined by FEA or code-based web crippling/buckling checks - not rule-of-thumb spacing

Full traceability: Each knee joint is tagged with heat numbers, weld maps, NDT reports, and coating inspection records - a complete digital quality package

Site-ready delivery: Lifting lugs pre-welded, match marks stamped, bolt kit included, erection drawing in the crate - your erector starts work immediately

Company Advantages

20+ years of steel structure fabrication for industrial and commercial projects across 30+ countries, with portal frames as our core specialty

In-house 20,000 sqm production facility with CNC plasma cutting, robotic welding cells, and automated shot blasting lines

Dedicated structural engineering team performs connection design for every knee joint - moment, shear, bolt group, and stiffener adequacy all calculated per your governing code

AWS/ISO certified welders; every full-penetration weld is UT tested and documented with a traceable inspection report

End-to-end project support: we review your portal frame GA drawings, propose connection optimizations, and deliver shop drawings for approval before fabrication

Integrated logistics: steel cradles, VCI wrap, and container or break-bulk shipping per component size

Flexible MOQ from 1 ton; trial orders welcome with full engineering support

Frequently Asked Questions (FAQ)

Q1: What is the purpose of the haunch at the knee joint?

A: The haunch (deepened section at the knee) increases the section depth at the point of maximum bending moment - where the rafter meets the column. By increasing the lever arm between flange forces, it significantly boosts moment resistance without requiring a heavier rafter section along its full length. Our engineers size the haunch for your specific span, loading, and frame geometry.

Q2: Do you design the bolted connections or do we need to provide the connection design?

A: We design all bolted connections as part of our standard service. For each knee joint, we calculate bolt shear, bearing, tension (with prying), and combined forces per AISC 360 or EC3. We also check end plate bending and stiffener adequacy. The calculation package is submitted with shop drawings for your approval.

Q3: What is the difference between a rigid (moment-resisting) knee and a pinned knee?

A: A rigid knee transfers both moment and shear between column and rafter - this is typical for portal frames, where frame stability relies on the continuity at the eaves. A pinned knee transfers only shear (no moment). We fabricate rigid knee joints by default for portal frames; pinned connections are available if your structural system specifies them.

Q4: Can you also fabricate the columns and rafters to go with the knee joints?

A: Yes. Most of our portal frame projects are supplied as complete kits: columns with base plates, rafters with apex connections, knee joints, purlins, and bracing. This ensures all connections are factory-matched and eliminates interface issues between different suppliers. We can supply the frame only, or the complete steel package including cladding rails and ancillaries.

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