Useful tips to make structural Design of Steel Fin Plate Connection

The purpose of connections is to allow smooth fabrication and easy erection. It is considered as the prime component in developing economical steel work. To attach open section steel beams to SHS column, the fin plate or tab arrangement is most effective.

The fin plate connection is recommended for construction industry because of simple erection process, and non-existence of shared bolts in two sided connections. It compromises of a length of plate that is welded to the supporting member (i.e. column or primary beam), and the supported member screwed to the fin plate. Mechanically, fin plates procure their rotational strength from shear deformation of the bolts, and hole distortion in the fin plate and/or the beam web.

Practical Understandings and Approved Geometry

With 10mm thick fin plate in S275 steel, 8mm fillet weld to the supporting member can result in protecting the chances for weld failure (CSI, 2011). Fin plates are categorized as short or long as follows;

Short tp/zp ≥ 0.15
Long tp/zp < 0.15

Where zp denotes the distance among the face of the support and the first line of bolts. In the case of short fin plates, erection on site is generally more complicated, but when long fin plates are applied, precaution should be taken to resist lateral torsional buckling, particularly when the beam is laterally unrestrained.

With adherence to SCI (2011), the points given below should be considered at the time of detailing the joint:

(1) Full strength fillet welds are arranged
(2) The fin plate is placed adjacent the top flange to allow positional restraint
(3) The depth of the fin plate should be minimum 0.6 times the supported beam depth to allow the beam with sufficient torsional restraint

(4) The density of the fin plate or the beam web is ≤ 0.50d (for S275 steel)
(5) Property class 8.8 bolts non-preloaded are utilized
(6) All end and edge distances on the plate and the beam web should be minimum 2d

Solved Example: A secondary beam UKB 305 x 165 x 40 is supported on a primary beam of UKB 533 x 210 x 101 containing an ultimate shear force of 100.25 kN. A fin plate connection for this joint will be designed with grade 8.8 non preloaded bolts.

Preliminary Considerations
As the depth of beam is under 610mm, the fin plate size is taken as 100 x 10mm
Gap gh = 10mm
Bolt rows = 3
Length of plate = 0.6 × 303.4 = 182.04mm (provide plate length = 220mm)

To learn the detail design process for fin plate connection, go through the following article structville.com