COMMENTS ABOUT THE DESIGN
OF RUNWAY GIRDERS ACCORDNG
TO NEW EN STANDARDS
Helmuth Köber , Bogdan Ştefănescu & Şerban Dima
Steel Structures Department
Technical University of Civil Engineering Bucharest
The present paper is intended to illustrate some
particular aspects in using the new European
standard EN 1993-6: 2007 (Eurocode 3: Design of
steel structures – Part 6: Crane supporting
structures) and the other involved Eurocodes
regarding the design of runway beams for
travelling cranes. References are also made to the
Romanian and German design regulations in this
matter.
Two kind of simply supported runway girders were
analyzed to show these particular aspects:
- 9 meters span girders for two overhead travelling
cranes, having each a hoist load of 20 tons;
- 6 meters span girders for an underslung travelling
crane, having a 5 tons hoist load.
2
Two overhead traveling cranes:
- hoist load of 20tons HC2, S-class S4;
- 16.5m crane girder span;
- both traveling cranes are working together.
3
An underslung traveling crane:
- hoist load of 5tons, HC4, S-class S7;
- 6.0m girder span;
- a single crane is working on the girder.
4
STAS 10101/2A2-78, Actions due to the exploitation
process, Loads due to travelling cranes
Eurocode 1, EN 1991-3: Actions on structures, Part3:
Actions induced by cranes and machinery
• Maximum vertical wheel load, Qr,max
• Longitudinal forces caused by acceleration and
deceleration of the crane, HL
• Longitudinal buffer forces related to movements of
the crane, HB,1
• Transverse forces caused by acceleration and
deceleration of the hoist block, HT,3
• Transverse forces caused by skewing of the crane,
HS
5
Groups of loads according to STAS 10101/0-78 Actions for
Constructions. Classification of Actions. Groups of Actions
ΣniPi + ΣniCi + ngΣniVi
ni = 1,2 for vertical crane loads
ni = 1,3 for horizontal crane loads
ng = 1,0 for a single considered traveling crane
ng = 0,9 for two considered traveling cranes
Groups of loads according to EN 1990:2002 Basis of
Structural Design respectively CR0 – 2005 Basis of Design.
Basis of Structural Design for Construction
γQ,1 = 1,5
1,35ΣGj + 1,5Q1 + 1,05ΣΨ0,iQi
6
Dynamic factors
STAS 10101/2A -78
20tons traveling cranes (Hoisting Class HC2):
Ψ = 1,3 – 0,1 = 1,2 for vertical crane loads (two traveling cranes acting
together),
Respectively Ψ = 1,3 (for a single considered traveling crane)
α = 1,8 for horizontal crane loads
5tons traveling crane (Hoisting Class HC2):
Ψ = 1,5 for vertical crane loads (for a single considered traveling crane)
α = 2,2 for horizontal crane loads
7
Groups of loads considered as one characteristic crane action
(extracted from EN 1991 – 3:2006 table 2.2)
The self-weight of the crane Qc and the hoist load Qh are
8
amplified by different dynamic factors.
The greatest value of the bending moment on the
runway girder is generally obtained with group 1 of
loads.
For this group the self-weight of the crane Qc and
the hoist load Qh are amplified by different dynamic
factors (for Qc, respectively for Qh).
Most of travelling cranes producers offer only the
characteristic values for the relevant vertical wheel
loads, where the influences of Qc and Qh are not
separated. Following this, these producer’s values
cannot be used for the procedure recommended by
EN 1991 – 3:2006.
9
MAXIMUM VERTICAL WHEEL LOADS
Poduri 20tf - Apăsări maxime pe roată
200
26,48% for two 20t cranes
5,07% for one 20t crane
160
120
Ψ = 1,2
80
φ2 = 1,12 ; φ1 = 1,0
40
0
(kN)
STAS 10101
SR EN grup1
SR EN grup5
154.41
195.30
178.71
Pod 5tf - Apăsări maxime pe roată
75
γQ,1 = 1,5
ni = 1,2
60
45
Ψ = 1,5
φ2 = 1, 27 ; φ1 = 1,0
30
15
6,26% for one 5t crane
0
(kN)
STAS 10101
SR EN grup1
SR EN10grup5
62.39
58.73
48.82
VALUES OF THE DYNAMIC FACTOR φ5
The proper choice of the values for the dynamic
factor according to table 2.6 from EN could be
argued. There is a lack of information for choosing a
value between the limits given in that table (the limit
between smoothly and sudden changes of the
forces is not defined).
11
Longitudinal buffer forces related to
movements of the crane
Pod 20tf - Lovire pod în opritori
31.76
SR EN 1990
2,68 times bigger
for the 20t crane
11.84
STAS 10101
0
6
12
18
24
30
36
(kN)
Pod 5tf - Lovire pod în opritori
6.48
SR EN 1990
2,52 times bigger
2.57
STAS 10101
for the 5t crane
0.0
1.2
2.4
3.6
(kN)
4.8
12
6.0
7.2
Transverse forces caused by crab
acceleration or deceleration
EN 1991 – 3:2006
13
Transverse forces caused by crab
acceleration or deceleration
STAS 10101/2A -78
14
Transverse forces caused by crab
acceleration or deceleration
Poduri 20tf - Demarare/frânare cărucior
11% for variant 1
SR EN varianta1
12.78
78% for variant 2
SR EN varianta2
20.49
STAS 10101
11.50
0
4
8
12
16
20
24
(kN)
Pod 5tf - Demarare/frânare cărucior
SR EN varianta1
4.8
10% for variant 1
SR EN varianta2
5.01
12,6% for variant 2
STAS 10101
4.36
0
1
2
3
(kN)
4
515
6
CRANE TRANSVERSE SKEWING FORCES
STAS 10101/2A -78
EN 1991 – 3:2006
The horizontal forces HS,i,j,k, caused by crane
skewing, are acting as a single force (on a single
crane wheel) on each runway beam according to EN
1991. In the appropriate Romanian and German
code it is considered that the skewing of the crane
generates a couple of forces on each runway girder.
16
Forces used for the design of the runway girders
Two 20tons overhead traveling cranes
A single 5tons underslung traveling crane
17
The vertical wheel loads generated
by crane operations for lower
hoisting classes (HC1 and HC2)
were greater in the calculations
according
to
the
European
standard [5], compared to those
ones obtained with the Romanian
code [1]. For higher hoisting
classes (HC3 and HC4) bigger
values were obtained for the loads
given by the Romanian standard.
RUNWAY GIRDERS CROSS-SECTIONS
Two 20tons overhead traveling cranes acting together
+ 5,0%
according to
old Romanian
code design
19
RUNWAY GIRDERS CROSS-SECTIONS
A single 5tons underslung traveling crane
+ 5,0%
according to
old Romanian
code design
20
Effective loaded length leff
The limit between rigidly fixed and not rigidly
fixed connection is not clearly established. !
21
Local buckling checks of the web:
A frequent loading state of the webs of runway beams is when they are
simultaneously subjected to bending moment (My,Ed), shear force (Vz,Ed)
and transversal force (FEd). European codes do not specify an interaction
checking relation for this loading state and they do not make any
reference to such a relation. The Romanian code provides such an
interaction relation.
22
Checks against local web buckling for the 20tf
traveling cranes runway girder:
23
Recommended partial safety factors values γMf
for fatigue checks
The fatigue check requires the use of the partial safety
factors γMf given in table above, depending on concepts like
“low and high failure consequence”, “damage tolerant”24and
“safe life”, which are not clearly defined and delimited.
The cross-sections designed according to the new European standards were
checked according to the in charge Romanian codes in order to ensure an
objective comparison (to avoid the influence of the different load estimation
procedures) between the two sets of European and Romanian norms used for the
design of runway girders. The results are presented in the tables below.
General Conclusion
Based on our calculations the checks
according to the old Romanian code
are one the safe side in a range of
about 10% (excepting the fatigue
limit state checks which had no
influence on the designed crosssections). The European codes cover
the different design situations more
accurately.
THANK YOU VERY MUCH
FOR YOUR ATTENTION!!