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

337

2

1. Introduction

Existing crane runway girders which are in use in the German metallurgical industry date mainly from the 1960s and 1970s. To this day, they have been continuously subjected to heavy service loads. Although their theoretical service life is generally far exceeded, they show almost no fatigue damage, which is strikingly contrary to the forecasts of today's regulations. Former crane runway girders were verified according to (DIN 120, 1936), (DIN 4132, 1981) or (TGL 13471, 1969). For a neuralgic fatigue detail, namely the introduction of the concentrated wheel load stresses into the K weld of full penetrated upper flange to web junctions, see detail 2 in Table. 8.10 of (EN 1993-1-9, 2010) and Fig. 1, the fatigue assessment could be carried out based on the fatigue limit D = 150 ∙ 0,85 = 127 MPa (which corresponds to  D for  = 0 and loading class B6). Compared to Δ = 52,3 MPa of the fatigue strength Δ = 71 MPa in (EN 1993-1-9, 2010) there are extreme discrepancies regarding the evaluation of this detail category with far-reaching economic consequences, see Table 1. The new regulation in Eurocode 3 is even more astonishing as no test results were used for justification (Kuhlmann, U. et al., 2015; Euler, M., 2017). Although older investigations exist which give clear indications of a better classification (Steinbach, G., 1988; Dittrich, W. and Ernst, L., 1973; Klöppel, K., 1966), extremely conservative considerations were made instead which lead to this problematic regulation. Recent test results on beams with fillet welds (Kuhlmann, U. et al., 2015; Euler, M., 2017) confirm this.

Fig. 1. Top flange to web junction of runway beams according to Eurocode 3-1-9, Tab. 8.10

For this reason, new investigations (Citarelli, S. and Feldmann, M., 2018) were carried out to evaluate the fatigue strength of top flange to web junctions under concentrated wheel loads for crane runway girders. In field investigations, crane runway girders from practice were examined, which were or still are installed in four German steel works and subjected to real loading conditions over decades, and whose load and transport history was precisely documented and comprehensible. The fatigue strengths thus determined were supported by additional FEM simulations using local stress concepts for the derivation of theoretic notch detail cases. The main results are summarized in the following chapters. Table 1. Comparison of fatigue classification for notch detail full penetrated web-to-flange-connection according to different standards EN 1993-1-9 FKM IIW-Doc. EN 13001-1 DIN 4132 Notch detail Nr. 2, Tab. 8.10 see IIW Nr. 431, Tab. {3.2}-1 Nr. 3.11, Tab. D.3 Nr. 153, Tab. 6 (B6,  = 0, St 37 / St 52)

 C [MPa]

71

80

90

112

200

1)

P 

95 % 1,645

95 % 1,645

95 % 1,645

97,7 %

90 % ( and  = 1,33)

1,995

1,282

2) [MPa]

92

104

117

154

245

 C,50%

Difference 3)

0 %

12,7 %

26,8 %

66,7 %

166 %

1) safety factor  = 1,33 has been excluded 2) s = 0,0688 acc. to (Stahlbau Handbuch, 1996) 3) related to EN 1993-1-9