PSI - Issue 10

N.G. Pnevmatikos et al. / Procedia Structural Integrity 10 (2018) 195–202 N.G. Pnevmatikos et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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The constant value logα in Eq.(1), for beam column connections ranges between 0.06 and 0.15, (higher values for less rigid connections). The slope constant of the fatigue curve, m, for welding connections ranges between 1.3 and 3.4. For low cycle fatigue considering only plastic rotation the value m=2 is the most representative. Parametric analyses were performed to calculate the damage index and the corresponding fatigue life for various values of m and the results obtained are shown in Fig.8.

Damage Index, DI

Damage Index, DI

Fatigue life (years)

Fatigue life (years)

Parameter,

Parameter, m (b) Fig. 8. Damage index vs parameter, m, (a), and fatigue life vs parameter m for low-cycle fatigue, (b), Loga=0.10. Parameter, m Parameter, m Param ter, m

(a)

Parameter, m

4. Conclusions

A fatigue analysis for steel moment resisting frame, subjected to earthquake load, was performed. It can be con cluded that several minor earthquakes aftershocks per year shorten the fatigue life of the structure. It was determined that for 50 small aftershocks (1/3 of Aigio earthquake) per year, in average, the fatigue life of structure is about 150 years. Furthermore, a low cycle fatigue model was applied and showed that one main earthquake can cause reduction in fatigue life due to inelastic deformation. It was estimated that a main earthquake event (twice that of Aigio earth quake) can influence significantly the fatigue life depending on the parameter, m, of the low cycle fatigue model. In general, fatigue due to earthquake should be taken into account in conjuction with fatigue due to other loads, such as traffic loads, since both load types reduce the life of a structure. ASTM Standard E1049-85, 2005. Standard practices for cycle counting in fatigue analysis. ASTM International, West Conshohocken, PA. BS7608, 1993. Code of Practice for Fatigue Design and Assessment of Steel Structures. Campbell, S.D., Richard, R.M., Partridge, J.E., 2008. Steel moment frame damage predictions using low-cycle fatigue, 14th World Conference Earthquake Engineering, Beijing, China. Castiglioni, C., Mouzakis, H., Carydis, P., 2007. Constant and variable amplitude cyclic behavior of welded steel beam-to-column connections. Journal of Earthquake Engineering 11, 876-902. Eurocode 3, EN1993-1-9. 1990. Design of steel structures, part 1-9 Fatigue. Koustomichali, N., 2012. Application of fatigue methods in structures subjected to earthquake actions, Master thesis, Greek Open University, Post-Graduate Program: Earthquake Engineering and Seismic Design of Structures, supervisor: Pnevmatikos N. Lassen, T., Reecho, N., 2006. Fatigue life analysis of welded structures. Flaws Hardcover. Plumier, A., Agatino, M.R., Castellani, A., Castiglioni, C.A., Chesi, C., 1998. Resistance of steel connections to low-cycle fatigue. 11th European Conference on Earthquake Engineering, Balkerma, Rotterdam. Suidan, M., Eubanks, R., 1973. Cumulative fatigue damage in seismic structures. Journal of the Structural Division 99(5), 923-943. Vayas, I., Sophokleous, A., Dinu, F., 2003. Fatigue analysis of moment resisting steel frames. Journal of Earthquake Engineering 7, 637-654. References