PSI - Issue 19

Sandro Citarelli et al. / Procedia Structural Integrity 19 (2019) 336–345 Sandro Citarelli, Markus Feldmann / Structural Integrity Procedia 00 (2019) 000 – 000

8

343

(∆ ) = max 0 [ ( 0 , ∆ ) (∆ ̂ ) ]

(5)

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1 0,2 0,4 0,6 0,8 1,0 0,

0,75 0,60 0,50 0,40

0,99 0,95

ML profile (R) [-]

confidence level [-]

50

55

60

65

70

75

 L [MPa]

Fig. 11. Exemplary ML profile and its confidence level (red) for the parameter ∆ of the investigated runway beams According to the procedure in (Pascual, F.G. and Meeker, W.Q., 1996), the parameter vector is defined as = ( 0 , ∆ ) and ∆ ̂ is the ML estimate of ∆ . Now, according to equation (5), for any ∆ it is examined when the so-called ML quotient (∆ ) becomes maximum by varying 0 4. Derivation of a new fatigue class

4.1. Fatigue evaluation for crane runway girders under investigation

The fatigue strength evaluation was performed using the aforementioned Maximum-Likelihood based statistical method, see section 3. This was initially done on the basis of the nominal stress concept according to (EN 1993-1-9, 2010) and (EN 1993-6, 2010) including all types of weld execution of investigated girders and excluding interactions with global bending stresses. Global effects were assessed afterwards, using notch effective stresses in combination with a more suitable damage hypothesis according to (Findley, W.N., 1959).

1000

100 stress range ∆σ [MPa] [log]

damaged runout

P = 50 % (164) P = 95 % (116) EC3-1-9 (71)

10

1,0E+04

1,0E+05

1,0E+06

1,0E+07

1,0E+08

1,0E+09

number of cycles N [-] [log]

Fig. 12. Nominal stress S-N-curve for the investigated runway beams