Fatigue Assessment of the Diaphragm-to-Rib Welded Connection in Orthotropic Steel Deck Using Effective Notch Stress Appr
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TECHNICAL ARTICLE—PEER-REVIEWED
Fatigue Assessment of the Diaphragm-to-Rib Welded Connection in Orthotropic Steel Deck Using Effective Notch Stress Approach Binhua Wang
Submitted: 4 August 2014 / in revised form: 19 October 2014 / Published online: 3 December 2014 Ó ASM International 2014
Abstract The effective notch stress approach to fatigue assessment of existing large-size specimens for diaphragmto-rib welded connection in orthotropic steel deck is investigated. Two kinds of specimens are designed. Specimen 1 has the form of circular arc transition; specimen 2 has the form of vertical transition. The first principal stress distribution at weld toe and weld root is calculated by the sub-model method of ANSYS software. By means of the maximum first principal stress analysis, it is possible to distinguish whether fatigue cracks will initiate at the weld toe or the weld root, which is agreed with the fatigue test results. Furthermore, the fatigue strength of specimen 1 and specimen 2 are evaluated by the effective notch stress approach according to fatigue tests. Finally, the factors affecting the stress intensity at the weld toe are studied. Keywords Effective notch stress Diaphragm-to-rib welded connection Fatigue assessment Weld toe Weld root
Introduction Due to the advantages of light weight and good economy, orthotropic steel decks have been widely used in the design of long-span steel bridges and also in deck replacement of existing bridges in many parts of the world. Its main structures are composed of welded longitudinal ribs, diaphragm plates and floorings. Therefore, the concentrated loads by vehicles have great influence on these welded B. Wang (&) Chang’an University, Xi’an 710064, Shaanxi Province, People’s Republic of China e-mail: [email protected]; [email protected]
structures [1]. For now, many early fatigue cracks of welded structures have been found in similar bridges [2–6]. For minimizing the restraint provided by the floor-beam web to rib rotation at the support due to unsymmetrical loads, the structures of cutout hole are designed and customarily widened to avoid the high stress at the bottom portion of the rib. However, there is a large number of welding joint’s cracks formed at the edge of cutout holes in practical engineering. The cracks are generated under the two kinds of stress conditions, namely, the condition of wheel load located at the top of diaphragm and the condition of wheel load located between diaphragms, which are shown in Fig. 1. Reference [7] has shown that the outof-plane moment stress caused by stress status is the main reason of causing cracks between longitudinal ribs and diaphragm plates. The code of AASHTO also details the classification of stress status . But it is not clear for stress status `. Therefore, for the sake of reducing the stress amplitudes and increasing the fatigue strength of this structure, it is important and crucial to design the reasonable detail structure. The nominal stress approach is generally adopted for the fatigue design and analy
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