Bolt Group Calculator to AS 4100

Verified by the CalcTree engineering team on August 8, 2024
﻿
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.
CalculationAssumptions
Bolt Properties
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, ﻿xi​,yi​ 
are the bolt coordinates from an origin point defined by the bottom left bolt and are in ﻿mm
. The design loads ﻿Vf∗​,Ntf∗​
 are in ﻿kN
.
ExplanationConnections 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 capacityBolts 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 ﻿fuf​
 rather than the yield strength.
Explore the toggles below for the bolt capacity equations to AS4100.
Bolts in shear
Bolts in tension
As per Cl 9.2.2.2 AS4100, the tension capacity of a bolt ﻿ϕNtf​
 is given by:
﻿
ϕNtf=ϕAsfuf\phi N_{tf}=\phi A_sf_{uf}ϕNtf​=ϕAs​fuf​
Where:
﻿﻿As​
 is the tensile stress area of the bolt
﻿﻿fuf​
 is the minimum tensile strength of the bolt
﻿
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
Tensile and shear (threaded and non-threaded) ULS capacities per bolt size for 4.6/S, 8.8/S, 8.8/TB and 8.8/TF, based on a single shear plane.
﻿
Exert from Australian Guidebook for Structural Engineers
﻿
Exert from Australian Guidebook for Structural Engineers
Tensile and shear (threaded and non-threaded) ULS capacities per bolt size for 4.6/S, 8.8/S, 8.8/TB and 8.8/TF, based on a single shear plane.
﻿
Exert from Steel Designers' Handbook
Analysis of bolt groupsBolt 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: 
The centroid of the bolt group is evaluated based on the inputted bolt group geometry.
All applied loads ﻿(Fx∗​, Fy∗​, Mz∗​, Vo∗​)
 are calculated as a concentrated resultant load ﻿(Fx∗​, Fy∗​, M1∗​, Mo∗​)
 at the centroid of the bolt group.
The resultant loads are distributed to each bolt by calculating the shear force ﻿Vf∗​
 and tension force ﻿Ntf∗​
 in each bolt, which is proportional to the distance from the bolt to the group centroid. 
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.
ReferencesAustralian Guidebook for Structural Engineers
Steel Designers' Handbook
Australian Standard AS 4100:2020
Related ResourcesFillet Weld Group Calculator to AS 4100
Steel Base Plate Designer to EC3
Steel Baseplate Designer to AISC 360

	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