S-BT Threaded Fastener Specification

Specifications page 71
S-BT Screw-in threaded studs
5.7 Effect of S-BT threaded stud fastenings on the
fatigue strength of base material structural steel
ReportNo.2017-38XbyProf.U.KuhlmannanProf.H.-P.Güntherfromthe
UniversityofStuttgart:Fatigueclassicationoftheconstructionaldetail“Structural
steelbasematerialwithHiltiS-BTscrew-inthreadedstuds”,(2017)[4]
ReportNo.5214011585/e,No.5214013022/e_corr.and5214014601/eSwiss
FederalLaboratoriesforMaterialsScienceandTechnology(2016and2017)[1],[2],
and[3]
General comments
WhenusingHiltiS-BTfastenersinstalledintostructuralsteelelementsthatare
subjectedtocyclicloading,theeffectofthefasteneronthefatiguestrengthofthe
steelbasematerialhastobeconsidered.Hiltihascompletedacomprehensive
fatiguetestprograminordertoclassifytheconstructionaldetail“Structuralsteel
basematerialwithHiltiS-BTscrew-inthreadedstuds”incompliancewithdifferent
fatiguecodesandstandards,namelyEN1993-1-9[5],AWSD1.1/D1.1M[6],ABS
[7],BV[8],DNVGL-RP-C203[9]andBS7608[10].Acorrespondingevaluationwas
madebyProf.U.KuhlmannandProf.H.-P.GüntherfromtheUniversityofStuttgart
(ReportNo.2017-38X,[4]).
Test Concept
9differenttestserieswerecarriedoutvaryingthefollowingparameterswhichcan
inuencethefatigueresistance:
•5differentplatethickness’(t=3,4,6,8and20mm),
•2differentstressratios(R=+0.1and+0.3),
•2differentinstallationconditions(correctlyinstalledandfastenerremoved),
•2differentfastenermaterials(stainlesssteelandcarbonsteel)
ThesteelbasematerialwasconservativelychosentogradeS235JRacc.to
EN10025-2,beingawarethathigherstrengthandnegrainsteelshowingeneral
betterfatigueresistancefornon-weldeddetails.
page 43
• The partial safety factors for fatigue actions as well as fatigue resistance have
to be considered according to fatigue design provisions (for example:
Eurocode 4 or AISC-LRFD) in agreement with the statistical evaluation of N
k
.
• If global safety concepts are applied, the global factors of safety have to be
taken in agreement with the statistical evaluation of N
k
meeting the conditions
of the used design standard.
This summary is intended to be representative of the test(s) carried out. It is not intended to be a full and complete test report.
5.6 Effect of S-BT threaded stud fastenings on the fatigue
strength of the base material structural steel
Report No. 2017-38X by Prof. U. Kuhlmann an Prof. H.-P. Günther from the
University of Stuttgart: Fatigue classification of the constructional detail
“Structural steel base material with Hilti S-BT screw-in threaded studs”,
(2017) [4]
Report No. 5214011585/e, No. 5214013022/e_corr. and 5214014601/e
Swiss Federal Laboratories for Materials Science and Technology (2016 and
2017) [1], [2], and [3]
General comments
When using Hilti S-BT fasteners installed into structural steel elements that are
subjected to cyclic loading, the effect of the fastener on the fatigue strength of
the steel base material has to be considered. Hilti has completed a
comprehensive fatigue test program in order to classify the constructional
detail “Structural steel base material with Hilti S-BT screw-in threaded studs” in
compliance with different fatigue codes and standards, namely EN 1993-1-9
[5], AWS D1.1/D1.1M [6], ABS [7], BV [8], DNVGL-RP-C203 [9] and BS 7608
[10]. A corresponding evaluation was made by Prof. U. Kuhlmann and Prof.
H.-P. Günther from the University of Stuttgart (Report No. 2017-38X, [4]).
Test Concept
9 different test series were carried out varying the following parameters which
can influence the fatigue resistance:
• 5 different plate thickness’ (t = 3, 4, 6, 8 and 20 mm),
• 2 different stress ratios (R = +0.1 and +0.3),
• 2 different installation conditions (correctly installed and fastener removed),
• 2 different fastener materials (stainless steel and carbon steel)
The steel base material was conservatively chosen to grade S235JR acc. to
EN 10025-2, being aware that higher strength and fine grain steel show in
general better fatigue resistance for non-welded details.
Table 1: Overview of the test program
Shape and dimension of the test
specimen
Loading condition of test specimens
Hilti S-BT fastening system under
cyclic loading
Table1:Overviewofthetestprogram
Base material
S-BT fastener
fatigue
loading
F
t
HiltiS-BTfasteningsystemunder
cycling loading
Universität Stuttgart
Institut für Konstruktion und Entwurf
Schwerpunkte: Stahlbau, Holzbau und Verbundbau
Prof. Dr.-Ing. Ulrike Kuhlmann
2017-06-30 S-BT Fatigue Page 7
3.2 Conventions
The following conventions, shown in Figure 3, were adopted for the individual test series.
235-08-01-ci
Stress ratio:
01  R = +0.1
03  R = +0.3
Installation condition:
ci  correctly installed
io  installed and overwound
ip  installed and pulled-out
Plate thickness
03  t = 3mm
04  t = 4mm
06  t = 6mm
08  t = 8mm
20  t = 20mm
Steel base grade:
235  S235JR+N
Figure 3. Conventions and abbreviations used for test series
4 Test specimens
4.1 Type and dimensions
Figure 4 shows the general shape and dimension of the test specimens used for the fatigue
tests.
On each specimen two fasteners were installed. The overall length of the specimens was fixed
to 580mm. Details about the dimensions of the single test specimens are given in the test re-
ports [4] to [6].
In all cases the rolling direction of the steel plate was parallel to the length of the specimen.
150
R97
Hilti S-BT
fastener
50
580
65
100
150 100 65 25 25
t
t
Figure 4. Standard test specimen with geometry
Shape and dimension of the test
specimen
Universität Stuttgart
Institut für Konstruktion und Entwurf
Schwerpunkte: Stahlbau, Holzbau und Verbundbau
Prof. Dr.-Ing. Ulrike Kuhlmann
2017-06-30 S-BT Fatigue Page 12
Figure 7. Test facility of type SCHENCK 630 kN at
EMPA, [5]
Figure 8. Lateral operating grips for load introduc-
tion, [5]
5.3 Loading conditions
All tests were carried out with a pulsating force F at a constant stress ratio R depending on the
tests series either R  +0.1 or R  +0.3, whereby the dynamic loading over time formed a sine
curve, see Figure 9. The stress ratio was limited to R  +0.3 as mild steel grades S235 does
not allow much higher ratio in order to prevent yielding at upper load F
max
.
R =
tension
F
t
F
min
F
max
R = +0.1R = +0.3
F
max
F
min
F
m
F
a

F
Figure 9. Loading condition of test specimens
Depending on the maximum loading force F
max
, the test frequencies achieved were in the range
of 6 to 16 Hz.
The tests were run without interruption until a through-going crack or a total fracture occurred.
The number of load cycles from the crack initiation to a total fracture was observed to be negli-
gibly small in relation to the total number of cycles.
Loading condition of test specimens