SHS Jointing, Flowdrill & Hollo-Bolt - Tata Steel

Corus Tubes library publication
The contents of this publication are current, when republished
it will be in the new Corus housestyle.

SHS Jointing
Flowdrill &
Hollo-Bolt

Flowdrill&Hollo-Bolt
Flowdrill &
Hollo-Bolt
Jointing
for Hollow Sections
Flowdrill and Hollo-Bolt give a choice of two
methods to produce bolted joints in
Hollow Sections. Both systems offer the
following benefits:
● They produce bolted joints of structural
capacity in Hot Finished Rectangular Hollow
Sections (HFRHS).
● They minimise the change in the fabrication
process by using connection details which
are standard in the construction industry.
● They reduce fabrication by removing the
need to weld plates or other fittings onto the
outside surface of the RHS.
● They simplify erection by using fully threaded
bolts -an increasing practice in the
construction industry.
● They maintain aesthetics by producing a
flush face on the RHS after fabrication.
Design Guidance
The design guidance produced in this
publication is for Flowdrill and Hollo-Bolt
systems with grade 8.8 bolts in conjunction with
Tubes and Pipes hot finished structural hollow
sections. The design guidance, for joints in
simple construction, result from Tubes & Pipes
initial research work undertaken in connection
with CIDECT (Ref. 1). The guidance
complements the information published by the
BCSA/SCI and is presented in a form
compatible with their publication “Joints in
Simple Construction” (Ref. 2).
Further test work is being undertaken to
establish design guidance for semi-rigid
joints.
Procedural checks are given for bearing, shear
and local bolt pull out of the RHS wall and for
the combined effect of the column axial load
and the structural integrity tensile load of
BS 5950 : Part 1.
The combined check for the column axial load
and the structural integrity tensile load
recognises that the flexibility of the RHS face
caused by the tensile load can, in the presence
of the column axial load, reduce the overall joint
capacity.

Hollo-Bolt
Fabrication and
Flowdrill
Construction
General detailing recommendations for beam
column connections, given in this
publication, are in accordance with the
BCSA/SCI publication -”Joints in Simple
Construction” (Ref. 2).
Both Flowdrill and Hollo-Bolt use fully threaded
bolts which allows standardisation of bolt
lengths throughout the construction. Where
beams are connected to adjacent faces of an
RHS column a check must be made with the
chosen bolt length to ensure that assembly is
possible (see Fig. 3 and 6) and the bolts do
not touch.
Both Flowdrill and Hollo-Bolt are suitable for use
with the two standard grades of Tubes & Pipes
SHS to BS EN10210-1 of S275J2H and
S355J2H (formerly BS4360 Gr43D and 50D
respectively).
At present, application of the Flowdrill process
is limited to RHS thicknesses up to and
including 12.5mm. For thicknesses of 16mm
and over, conventional drill and tap methods are
recommended, although due to the RHS
material strength being lower than that of the
grade 8.8 bolts, pull out strengths may be below
the bolt tension capacity.
Reference
1. Comité International pour le
Développment et l’Étude de la
Construction Tubulaire
UK Member
British Steel plc
Tubes & Pipes
PO Box 101
Corby
Northants NN17 5UA
2. Joints in Simple Construction
Volume 1 : Design methods
Volume 2 : Practical applications
Published jointly by:
BCSA SCI
4 Whitehall Court Silwood Park
Westminster Ascot
London Berks SL5 7QN
SW1A 2ES

Flowdrill
Flowdrill
The
Process
Flowdrilling is basically a thermal drilling
process which makes a hole through the
wall of a structural hollow section without
the removal of metal normally associated
with a drilling process. The formed hole is
then threaded by the use of a roll thread
forming tool, leaving a threaded hole which
will accept a standard fully threaded bolt.
The Tools
The initial hole is made by a Flowdrill tool
consisting of a tungsten carbide bit held in a
Flowdrill Morsetaper collet adaptor (Fig. 1). The
tool can be used in a conventional drilling
machine or CNC machine as found in
fabricators works, provided it has adequate
horsepower and spindle speed.
1st stage
The tungsten carbide bit is brought into contact
with the RHS wall where it generates sufficient
heat to soften the steel. The bit is then
advanced through the wall and in so doing the
metal is redistributed (or flows) to form an
internal bush. As well as drilling the initial hole,
the tool is fitted with the means of removing any
surplus material which may arise on the outside
of the RHS section. The cycle time for
Flowdrilling is similar to that for conventional
drilling. However, if done on CNC machines the
feed rate can be slow at the beginning, rapidly
increasing as the material softens to improve
efficiency.
2nd stage
The 2nd and final stage is to tap the Flowdrill
bush. This is done by roll threading the bush
with a Coldform Flowtap. The complete cycle is
shown in Figure 2.
Fig. 2
Tool holder
Flowdrill data :
The Flowdrill system was developed by Flowdrill BV in Holland, and is available in the UK from
their agent - Robert Speck Ltd,. Little Ridge, Whittlebury Road, Silverstone, Northants NN12 8UD.
Tel: 01327 857307 Contact Mr Mike Carpenter.
Fig. 1
Collet
Flowdrill bit
1st Stage 2nd Stage

Drilling machine parameters :
Table 1 gives a guide to required machine
parameters for producing Flowdrill holes for
M12 to M24 bolts:
Note: The Flowdrill process is not suitable for
hand held or magnetic clamp type drilling
equipment when used in the sizes shown.
Max material
thickness
(mm)
Flowdrill detailing requirements.
See Fig. 3 and Table 3.
Note:
3
5
6
8
10
12
16
Table 2
● Flowdrilled joints used at
locations exposed to the
weather should not be
considered as water tight.
● Flowdrilling is not suitable
for use with pre-galvanised
materials.
Dimensions
(mm)
A 1
B 1
C 1
D 1
E 1 Minimum
Min Bolt Centres
M12
Short
Long
Long
Long
-
-
-
Flowdrill Length
M16
Short
Short
Long
Long
Long
-
-
Thread Size
M12
7
13
18
30
M20
Short
Short
Short
Long
Long
Long
-
Lb
tp
M24
Short
Short
Short
Long
Long
Long
-
tc
M16
10
17
20
40
Thread size
Flowdrill size
M/c spindle
speed rpm
M/c feed rate
Motor power
KW Min
Tapping speed
rpm
Table 3 (See Fig. 3 for nomenclature)
M12
10.9
1000-1500
2
250
M16
14.8
700-1100
Table 1
Drill length: The recommended length of
Flowdrill bits varies with the thread size and
thickness of material as given in Table 2.
Drill care: Flowdrills are made from tungsten
carbide. They are extremely hard but cannot
withstand shock loads. After drilling each hole,
FD KS paste should be applied to the Flowdrill
whilst it is still hot, so minimising oxidation and
preventing ‘build up’ on the surface.
Flat surface: the raised rim on the outer surface
of the RHS material caused during Flowdrilling
should be removed using Flowdrills with cutting
edges provided on the collar. One rotation of the
cutter is all that is required to remove the rim.
B 1
C 1
Width
Min bolt centres
Thread size/Bolt diameter
2.5
200
M20
18.7
600-1000
3.5
150
M24
22.5
500-800
0.1/0.15mm (0.004/0.006 inches) per rev
M20
12
22
26
Varies with overall bolt length (Lb) specified
C 1/2 + t c (for connection made to a single face or opposite faces)
B 1/2 + A 1 + D 1 + t c (for connection made to adlacent faces)
A 1
D 1
50
E 1
M24
15
25
29
60
5
100
Fig. 3
E 1

Hollo-Bolt
Hollo-Bolt
HOLLO-BOLT is a pre-assembled
three part fitting consisting of body,
cone and bolt.
The pre-assembled unit (Fig. 4) is
inserted through normal tolerance holes
in both the attatchment plate and the
RHS. As the bolt is tightened the cone is
drawn into the body, spreading the legs,
and forming a secure fixing. Once
installed only the Hollo-Bolt head and
collar are visible (Fig. 5).
The Hollo-Bolt
Location Flats
Body
Cone Knurling
Further information on
Hollo-Bolt is available from
Fig. 5
Fig. 4
Hexagon Head
Collar
Fixture
RHS
Cone
Legs
Central Bolt
Lindapter International
A Division of Victaulic plc.,
Lindsay House, Brackenbeck Road,
Bradford, West Yorkshire, Tel: 01274 521444
England, BD7 2NF Fax: 01274 521130

V
tp
Drilling requirements:
Hollo-Bolt uses a plain drilled
hole which can be made on
site or in the fabrication shop
using all normal drilling
equipment. The finished hole
should have a tolerance of
-0.2mm to +1.0mm from the
nominal given in the data table
(Table 4).
tc
Material Options
Standard product is manufactured from mild
steel and is electro-zinc plated with the addition
of JS500 1000 hour saltspray corrosion
protection. The central fastener is a grade
8.8 bolt.
For special applications, the Hollo-Bolt is
available manufactured from 316 stainless steel,
with a grade A4-80 central bolt. This will not be a
stocked item, and would be manufactured to
order.
Installation
The only tools required to fit Hollo-Bolt are two
spanners - an open ended spanner to hold the
collar and a torque wrench to tighten the central
bolt. Alternatively a power operated electric
hand tool is in development.
Should the steelwork need to be adjusted,
the fixing can simply be removed and the
hole reused with another Hollo-Bolt.
Sealing Options
Width
X
Bolt
size
In certain applications, it may be necessary to
seal the Hollo-Bolt to prevent ingress of water or
other corrosive agents. For details of sealing
options available, please contact Lindapter.
Special Options (manufactured to order)
● Stainless steel
● Button head setscrew ● Socket head capscrew
● Countersunk setscrew/body ● Special body lengths
Y
M8
M10
M12
M16
M20
Bolt
length
(V)
W
mm
45
49
53
57
80
Fixing
thickness
(W)
Min Max
mm
3 22
3 22
3 25
3 28
3 34
Fig. 6
E 1
Bolt
centres
(X)
Min
mm
35
40
50
55
70
Internal
min. edge
distance
(Y)
mm
13
15
18
20
25
Edge
distance
(E1)
Min
mm
50-tp
55-tp
60-tp
65-tp
90-tp
Bolt
hole
dia.
(Dh )
mm
Table 4 (See Fig. 6 for nomenclature)
14
18
20
26
33
Across
flats
main
body
mm
19
24
30
36
46
Fig. 7
Tightening
torque
Nm
21
40
78
190
300

Design of
Joints in
Simple
Construction
Simple connections between Universal
beams and RHS columns can be made
using double angle web cleats or
flexible end plates.
The following procedural checks are
compatible with the BCSA/SCI rules for
Joints in Simple Construction (Ref. 2).
Length of cleat
I ≥ 0.6D
Cleat thickness, t p
t p = 8mm or 10mm
Notes
Double Angle Cleats Flexible End Plates
End projection t 1 , approx 10mm
Face of column Length of plate
I ≥ 0.6D
Face of column
D I
D I
g Bolt diameter, d g
Bolt diameter, d
Flowdrill hole diameter, D h
D h = d+2mm for d ≤ 24mm
D h = d+3mm for d > 24mm
For Hollo-Bolt D h see Table 4.
Plate thickness, t p
t p = 8mm or 10mm
● The cleats or end plates are generally positioned as close to the top flange
of the beam as possible to provide adequate positional restraint and a plate
length of at least 0.6D is usually adopted to give adequate torsional restraint
(BS 5950: Part 1, Table 9).
● Bolt gauge g: 90mm ≤ g ≤ 140mm, but g ≥ 0.3 x RHS face width B.
● Although it may be possible to satisfy the design requirements with t p < 8mm,
it is not recommended in practice because of the likelihood of weld
distortion during fabrication and damage during transportation.
● The plate thickness and gauge limitations apply equally to partial depth and
to full depth end plates.
If necessary, to comply with structural integrity requirements for a 75 kN tie force,
the connection must have at least 2 no. M20, Grade 8.8 bolts in tension with
/ ≥ 140mm, t ≥ 8mm and g ≤ 140mm.

Local shear and bearing capacity of the
RHS column wall and bolts.
Basic Requirement
For Shear
Q_ 2
≤ Pv Pv = local shear capacity of
RHS column wall
= smaller of 0.6pyc Av and
0.5 Usc Avnet Av = [g/2 + (n -1) p = et] tc with [et ≤ 5 d]
Avnet = Av- n d tc n = number of rows of bolts
p = bolt pitch
d = nominal bolt diameter (or
hole diameter in RHS
columns for Hollo-Bolt)
g = bolt gauge width
tc = RHS column wall
thickness
pyc = design strength of RHS
colunm wall (S275 = 275
N/mm2 : S355 =
355 N/mm2) Usc = ultimate tensile strength
of RHS column wall
For bearing
Q_ 2
≤ Pbsc Pbsc = bearing capacity of the RHS
column wall per bolt = d tc pbsc pbsc = bearing strength of the RHS
column wall (S275 =
460 N/mm2 : S355 = 550 N/mm2) Bolt diameter
-
-
M12
M16
M20
M24
Flowdrill
kN
-
-
31.6
58.9
91.9
132
Bolt diameter
M8
M10
M12
M16
M20
-
Flowdrill
kN
12
25
38
75
100
-
e t
Q
t c
n rows
of bolts
Bolt Check (Table 5)
Critical sections
The single shear capacity for Flowdrill and
Hollo-Bolt can be taken as follows:-
g
Q/2 Q/2
p
p
p

Bolt
diameter
mm
M16
M20
M24
Bolt
diameter
mm
M16
M20
M24
5
46
70
80
Structural integrity-local bolt pull-out
of RHS colmn wall.
Note: This check is only needed if it is
necessary to comply with structural
integrity requirements.
Basic Requirement
Tie force ≤∑Local bolts pull-out
resistances
∑ Local bolt pull-out resistances
= 2 n Pp(si) The local bolt pull-out design resistance
in kN of a grade 8.8 bolt in a flowdrilled
hole or a Hollo-Bolt should be taken from
the following tables which are based on
test results:
Flowdrill normal design strength (P p(n) kN
RHS column wall thickness t c mm
Grade S275 (Grade 43) Grade S355 (Grade 50)
6.3
60
85
101
8
95
122
10
70
97
134
12.5
110
159
5
59
102
103
6.3
130
Flowdrill structural integrity design strength (P p(si) kN
5
30
46
53
RHS column wall thickness t c mm
70
110
8-12.5
159
Grade S275 (Grade 43) Grade S355 (Grade 50)
6.3
40
56
67
8
63
81
Bolt
diameter
mm
M8
M10
M12
M16
M20
10
46
65
89
Table 6
Table 7
12.5
73
106
5
39
68
68
6.3
86
Hollo-Bolt design strengths
Normal design
strength (P p(n) )
kN
16
26
38
70
110
Table 8
46
73
8-12.5
106
Structural integrity
design strength (P p(si) )
kN
10
17
25
46
73
n rows of
bolts (critical
bolts are
those in
the column)
Note:
Tie force
1. The tension capacity of Grade 8.8 bolts for
normal design and for structural integrity
design is shown in the shaded areas.
2. The pull-out resistances for structural
integrity Pp(si) are less than those for normal
design because the design method
presented here for structural integrity leads
to thinner cleats or end plates than for
normal design methods, based on BS 5950:
Part 1, and, as a result, will lead to higher
prying forces. This has been taken into
account in the quoted resistances.

Structural integrity - tie force
capacity of RHS column wall in the
presence of axial compression in the
column.
Note: This check is only needed if it is
necessary to comply with structural
integrity requirements.
Basic Requirement
Tie force ≤ Tying capacity of RHS column
wall
Tying capacity of RHS column wall
8 m u
= (� 1+ 1.5 (1 - � 1) 0.5 (1 - � 1) 0.5)
(1 - � 1)
M u = moment capacity of RHS
column wall per unit length
p yc t c 2
=
4
p yc = design strength of the RHS column
(S275 = 275 N/mm 2 : S355 = 355 N/mm 2)
tc = thickness of RHS column wall
�1 n
= (n - 1)p - d
2
(B - 3tc )
� 1
� 1
=
=
g
(B - 3t c )
d
(B - 3t c )
B = overall width of RHS column
wall to which the connection is
made.
d = bolt diameter (or hole diameter
in RHS column for Hollo-Bolt)
g = bolt gauge width
n = number of rows of bolts
p = bolt pitch
p
Yield lines
(n-1)p
Bolt holes
deducted
B
g
Tie force
(applied at
bolt positions)
t c
1.5 t c

British Steel
Tubes & Pipes
PO Box 101, Weldon Road,
Corby, Northants, NN17 5UA
Tel: 01536 402121
Fax: 01536 404111
British Steel plc Registered Office: 9 Albert Embankment, London, SE1 7SN Reg. in England No: 2280000
TD 384.12E.95