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

2

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.

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Two overhead traveling cranes: - hoist load of 20tons HC2, S-class S4; - 16.5m crane girder span; - both traveling cranes are working together.

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An underslung traveling crane: - hoist load of 5tons, HC4, S-class S7; - 6.0m girder span; - a single crane is working on the girder.

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• 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

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

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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

1,35ΣGj + 1,5Q1 + 1,05ΣΨ0,iQi γQ,1 = 1,5

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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

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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

amplified by different dynamic factors.

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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.

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MAXIMUM VERTICAL WHEEL LOADS

Poduri 20tf - Apăsări maxime pe roată

0

40

80

120

160

200

(kN) 154.41 195.30 178.71

STAS 10101 SR EN grup1 SR EN grup5Pod 5tf - Apăsări maxime pe roată

0

15

30

45

60

75

(kN) 62.39 58.73 48.82

STAS 10101 SR EN grup1 SR EN grup5

26,48% for two 20t cranes

5,07% for one 20t crane

6,26% for one 5t crane

γQ,1 = 1,5 ni = 1,2

Ψ = 1,2 φ2 = 1,12 ; φ1 = 1,0

Ψ = 1,5 φ2 = 1, 27 ; φ1 = 1,0

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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).

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Longitudinal buffer forces related to movements of the crane

Pod 20tf - Lovire pod în opritori

11.84

31.76

0 6 12 18 24 30 36

STAS 10101

SR EN 1990

(kN)

Pod 5tf - Lovire pod în opritori

2.57

6.48

0.0 1.2 2.4 3.6 4.8 6.0 7.2

STAS 10101

SR EN 1990

(kN)

2,52 times bigger

for the 5t crane

2,68 times bigger

for the 20t crane

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Transverse forces caused by crab acceleration or deceleration

EN 1991 – 3:2006

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Transverse forces caused by crab acceleration or deceleration

STAS 10101/2A -78

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Transverse forces caused by crab acceleration or deceleration

Poduri 20tf - Demarare/frânare cărucior

11.50

20.49

12.78

0 4 8 12 16 20 24

STAS 10101

SR EN varianta2

SR EN varianta1

(kN)

Pod 5tf - Demarare/frânare cărucior

4.36

5.01

4.8

0 1 2 3 4 5 6

STAS 10101

SR EN varianta2

SR EN varianta1

(kN)

11% for variant 1

78% for variant 2

10% for variant 1

12,6% for variant 2

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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.

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Forces used for the design of the runway girders

Two 20tons overhead traveling cranes

A single 5tons underslung traveling crane

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.

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RUNWAY GIRDERS CROSS-SECTIONS

Two 20tons overhead traveling cranes acting together

+ 5,0% according to

old Romanian

code design

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RUNWAY GIRDERS CROSS-SECTIONS

A single 5tons underslung traveling crane

+ 5,0% according to

old Romanian

code design

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Effective loaded length leff

The limit between rigidly fixed and not rigidly

fixed connection is not clearly established. !

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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.

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Checks against local web buckling for the 20tf

traveling cranes runway girder:

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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” and

“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.

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 cross-sections). The European codes cover the different design situations more accurately.

General Conclusion

THANK YOU VERY MUCH

FOR YOUR ATTENTION!!