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Civil-Comp Proceedings
ISSN 1759-3433 CCP: 79
PROCEEDINGS OF THE SEVENTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: B.H.V. Topping and C.A. Mota Soares
Paper 77
Fatigue Assessment of Bolted Bar Connections in Crane Structures M. Šraml+, J. Kramberger+, I. Potrc+, Z. Ren+ and J. Plešek*
+Faculty of Mechanical Engineering, University of Maribor, Slovenia
Full Bibliographic Reference for this paper
, "Fatigue Assessment of Bolted Bar Connections in Crane Structures", in B.H.V. Topping, C.A. Mota Soares, (Editors), "Proceedings of the Seventh International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 77, 2004. doi:10.4203/ccp.79.77
Keywords: contact problem, boundary non-linearity, fatigue life, high-strength steel, numerical calculations, strain-life method.
Summary
High level of material exploitation is often requested in optimization of crane
structures. One way to achieve this goal is by crane design modification. Other
possibility is to reduce the cranes structural member cross-sections by using high
strength steel. This results in lower material and production costs and appropriate
operational safety of the crane structures, which have to be designed to eliminate
every possibility of critical damage or even failure. Clear design guidelines are
needed in both cases to ensure that fatal fatigue failure of the crane structure is
avoided. The possibility of predicting operational strength of cranes, which are
exposed to variable amplitude loading in service, is therefore of a significant
importance.
This paper deals with the problem of service life evaluation of counterweight bar
bolted connection by means of computational analysis and experimental
testing [3,4,5].
The bolted joint fatigue is critical for a number of reasons: high
Computational analysis was done in two steps. First, a stress field in the bar end
connection is determined by solving the contact problem between the bolt,
connection plates and the bar by means of the finite element analysis [1]. The
computational analysis provides the stress concentration points in the bar end, which
are also the most critical failure points. Second, the fatigue analysis has been
performed, where the local strain-life method (
Experimental fatigue tests of high strength steel bars were carried out in a specially constructed hydraulic pulsation machine. Complete description of experimental testing of presented problem is given in [3,4]. The main drawbacks of experimental testing are high costs and time consumption, although this approach is the most reliable way of component verification that is subject to high stresses and a large number of load cycles.
Computational analyses and experimental observations have shown that the
connection hole in the bar end is the most critical location for crack initiation and
final failure (Figure 1). Comparison of results is given
in Table 1. Average number
of loading cycles to failure determined with experiments is approximately
References
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