S-BT Threaded Fastener Specification

page78 Specifications
Universität Stuttgart
Institut für Konstruktion und Entwurf
Schwerpunkte: Stahlbau, Holzbau und Verbundbau
Prof. Dr.-Ing. Ulrike Kuhlmann
2017-06-30 S-BT Fatigue Page 39
9.2.6 Recommendation of a design S-N curve for BS 7608:2014
BS 7608:2014 includes 9 basic design S-N curves (B to W1) for direct stresses and two stand-
ard basic S-N curves (S1 and S2) for shear stresses, see
Table 7.1. The slope intersection for
direct stresses is again at 1
∙10
7
number of cycles. In general the slope varies between m = 3 to
4 as typical for welded details. The S-N curves for shear have a slope of m = 5. The S-N curves
in BS 7608 are in principle similar to those given in ABS:2014.
Based on the statistical evaluation of S-BT fatigue test data according to
Table 9.1 the fatigue
resistance of the Hilti S-BT fastening system can be well described by the design S-N curve of
Class S1, having a uniform slope of m = 5, see following
Table 9.6 and Figure 35. According to
the standard S-N curves for direct stresses given in BS 7608 the CAFL is set to N = 1
∙10
7
num-
ber of cycles.
Table 9.6. Details of basic S-N curves according to Table 18 of BS 7608:2014
Class C
o
log
10
C
o
m SD
Stand. Deviation
of log
10
N,
C
2
S
oc
(N=10
7
cyc.)
N/mm
2
S
ov
(N=5∙10
7
cyc.)
N/mm
2
B
2.343∙10
15
15.3697 4.0 0.1821
1.01∙10
15
100 67
C
1.082∙10
14
14.0344 3.0 0.2041
4.23∙10
13
78 49
D
3.988∙10
12
12.6008 3.0 0.2095
1.52∙10
12
53 31
E
3.2893∙10
12
12.5171 3.0 0.2509
1.04∙10
12
47 27
F
1.726∙10
12
12.2371 3.0 0.2183
6.32∙10
11
40 23
F2
1.231∙10
12
12.0902 3.0 0.2279
4.31∙10
11
35 21
G
5.656∙10
11
11.7526 3.0 0.1793
2.48∙10
11
29 17
G2
3.907∙10
11
11.5918 3.0 0.1952
1.59∙10
11
25 15
S1
5.902∙10
16
16.7710 5.0 0.2350
2.00∙10
16
46 (10
8
cyc.) 46 (10
8
cyc.)
S2
3.949∙10
16
16.5965 5.0 0.3900
6.55∙10
15
37 (10
8
cyc.) 37 (10
8
cyc.)
S-BT
5.902∙10
16
16.7710 5.0 0.2350
2.00∙10
16
74.2 52.5
Design S-N curve: log N = log
10
C
o
– 2 ∙

SD – m ∙

log

S
Universität Stuttgart
Institut für Konstruktion und Entwurf
Schwerpunkte: Stahlbau, Holzbau und Verbundbau
Prof. Dr.-Ing. Ulrike Kuhlmann
2017-06-30 S-BT Fatigue Page 46
10.2.7 BS 7608:2014
It is recommended to use the following S-N curve respectively stress category termed “S-BT”
given in Table 10.6 for the constructional detail “Steel base material with Hilti S-BT screw-in
threaded studs”.
Table 10.6. Recommendation of fatigue S-N curve and detail category according to BS 7608:2014
Product
form
Loca-
tion of
crack
Detail
Manufac-
turing re-
quirements
Special
requirements
Design
stress
area
Class Notes Sketch
Rolled
steel
plates
and
sections
At the
edge or
tip of the
pre-
drilled
hole
Hilti S-BT
screw-in
stainless
and car-
bon steel
threaded
studs with
pre-drilled
hole in
structural
steel base
material.
Installation,
static load-
ing and
spacing of
fasteners
only in
accordance
with the
require-
ments given
in [1] or [2].
Plate thick-
ness t  3mm.
Steel base
material up to
yield strength
355 MPa.
Net cross
section
S-BT
(S1)
Imperfect
fastener
installations
as e.g.
overwound
or pulled-out
fasteners
are covered.
Parameter of S-N curve for detail class S-BT
Class C
o
log
10
C
o
m SD
Stand. Deviation
of log
10
N
C
2
S
oc
(N=10
7
cyc.)
N/mm
2
S
ov
(N=5∙10
7
cyc.)
N/mm
2
S-BT
5.902∙10
16
16.7710 5.0 0.2350
2.00∙10
16
74.2 52.5
[1] Hilti S-BT screw-in threaded studs. Specification Binder, Edition 01/2017
[2] Hilti Direct Fastening Technology Manual. Edition 12/2016. S-BT product pages.
Stuttgart, June 30
th
, 2017
Prof. Dr.-Ing. Ulrike Kuhlmann
Universität Stuttgart
Institut für Konstruktion und Entwurf
Pfaffenwaldring 7
D-70569 Stuttgart
Prof. Dr.-Ing. Hans-Peter Günther
Ingenieurbüro für Stahlbau und Schweißtechnik
Nöllenstraße 7
D-70195 Stuttgart
BS7608:2014
ItisrecommendedtousethefollowingdesignS-Ncurverespectivelystress
categorytermed“S-BT”giveninTable8andFigure6fortheconstructional
detail“SteelbasematerialwithHiltiS-BTscrew-inthreadedstuds”.
Universität Stuttgart
Institut für Konstruktion und Entwurf
Schwerpunkte: Stahlbau, Holzbau und Verbundbau
Prof. Dr.-Ing. Ulrike Kuhlmann
2017-06-30 S-BT Fatigue Page 40
10
100
10000 100000 1000000 10000000
Number of cycles N [-]
Nominal stress range  [N/mm
2
]
300
200
100
400
50
500
B
10
70
20



t
Hilti S-BT
C
D
F2
F
BS 7608
S-N
curves
E
Hilti S-BT fastener
(correctly installed)
Hilti S-BT fastener
(installed and removed)
proposed design S-N curve
m =5
1
G
G2
S1
Figure 35. Comparison of Hilti S-BT fatigue test data with BS 7608:2014 fatigue curves
and new proposed fatigue curve for Hilti S-BT fastener
Figure6:ComparisonofHiltiS-BTfatiguetestdatawithBS7608:2014fatigue
curvesandnewproposedfatiguecurve“S-BT”forHiltiS-BTfastener
Table8:RecommendationoffatigueS-Ncurveanddetailcategoryacc.to
BS7608:2014