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Bolt Group Calculator to AS 4100's banner
🔩

Bolt Group Calculator to AS 4100

This calculator analyses and checks each bolt in a bolt group for in-plane and of-of-plane loading. The bolt group is analysed using the Instantaneous Centre of Rotation (ICR) concept. The shear force, tension (pull-out) force and combined action in each bolt is then checked to validate the bolt group.
All calculations are performed in accordance with AS4100-2020.

Calculation

Assumptions

Bolt Properties



Bolt grade
:8.8



Tensioning spec
:S



Bolt type
:8.8/S



fuf
:830MPa


Bolt category



lj
:0 mm



kr
:1.0


Bolt splice



Threads?
:Included


Threads included or excluded



n
:1


Shear planes



μ
:0.3


Slip factor (for 8.8/TF bolts only)



Bolt Group Geometry

In-plane Loads

Out-of-plane Loads

Single Bolt Capacities

Bolt Group Check



V*f_max
:126.7kN



N*tf_max
:20.5kN


Bolt Group Analysis



ϕ
:0.8


Capacity factor



Minimum required bolt
:M24


Evaluation of each bolt in the bolt group is provided below:

0
0
105
0
SAFE
SAFE
2
0
50
62
0
SAFE
SAFE
SAFE
3
0
100
74
7
SAFE
SAFE
SAFE
4
0
150
127
20
SAFE
SAFE
5
50
0
88
0
SAFE
SAFE
SAFE
6
50
50
22
0
SAFE
SAFE
SAFE
SAFE
7
50
100
47
7
SAFE
SAFE
SAFE
SAFE
8
50
150
113
20
SAFE
SAFE
👉Note,

are the bolt coordinates from an origin point defined by the bottom left bolt and are in

. The design loads

are in

.

Explanation

Connections in building structures use a minimum of two bolts and often more than eight bolts. The bolts used in a connection form a bolt group. A bolt group may be acted on by loads and bending moments in the plane of the bolt group (in-plane) or at right angles to it (out-of-plane).
A typical connection with a bolt group is a beam to column bolted connection.
Beam to column connection


Bolt capacity

Bolts are required to be checked individually for shear and tensile loads, as well as with a combined action check.
The shear and tensile capacities of bolts are both based on the minimum tensile strength

rather than the yield strength.
Explore the toggles below for the bolt capacity equations to AS4100.

Bolts in shear

Bolts in tension

Bolts in combined shear and tension

It is common for textbooks to tabulate bolt capacities per bolt size. See the below toggle for such capacities taken from Australian Guidebook for Structural Engineers and the Steel Designers' Handbook.

Design capacity for Class 4.6 and 8.8 bolts

Analysis of bolt groups

Bolt groups are subjected to in-plane and out-of-plane loading. Loads on individual bolts are calculated by using a bolt group analysis.
Explore the toggles below for details on how to analysis bolt group based on loading type.

In-plane Loading

Out-of-plane Loading

In summary, the analysis of bolt groups follows these steps:
  1. The centroid of the bolt group is evaluated based on the inputted bolt group geometry.
  2. All applied loads
    
    are calculated as a concentrated resultant load
    
    at the centroid of the bolt group.
  3. The resultant loads are distributed to each bolt by calculating the shear force
    
    and tension force
    
    in each bolt, which is proportional to the distance from the bolt to the group centroid.
  4. The 'critical' bolt is considered to be the bolt furthest from the centroid, which is used for the design check on the overall bolt group.

References

  1. Australian Guidebook for Structural Engineers
  2. Steel Designers' Handbook
  3. Australian Standard AS 4100:2020

Related Resources

  1. Fillet Weld Group Calculator to AS 4100
  2. Steel Base Plate Designer to EC3
  1. Steel Baseplate Designer to AISC 360