Experimental and analytical investigation of fatigue life on trapezoidal longitudinal ribbed on steel bridge decks

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Yıldız Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Türkiye

Tezin Onay Tarihi: 2018

Tezin Dili: İngilizce

Öğrenci: MOHAMMED NAJEEB ABDULGHANI ABDULGHANI

Danışman: Fatih Alemdar

Özet:

Orthotropic decks were applied to the long span bridges after World War II due to several advantages, such as lightweight, high strength, few deck joints, durability, rapid construction, and life-cycle economy. In the past two decades, a lot of studies and investigations were carried out about fatigue problem. It was found that most of the fatigue cracks occurred at the welded connection details, such as the rib-to-deck plate, rib-to-diaphragm, and rib-to-diaphragm-to-deck plate (RDDP). These connections are sensitive to fatigue cracking due to high stress concentration and residual stress at welded connections.

This study includes one closed longitudinal rib which has trapezoidal cross-section. Laboratory tests will be carried out for the specimen including two types of tests which are static calibration and dynamic. In static calibration test, strain gages will be installed on the specimen and strain values will be obtained for all of the tests so as to compare the results of strain values obtaining by using finite element simulation (Abaqus Program) and hand calculations. Dynamic tests will be carried out to assess the fatigue life for specimen by observing the initiation of cracks and propagation by accounting in which a number of cycles the specimen will fail. Crack lengths will be measured versus a number of cycles until fatigue failure. The specimen will be classified according to S-N curve to determine in which category  lies to estimate its strength.

Also, this study includes two parametric studies for the same model by using finite element simulation (Abaqus Program). The first study includes the effect of using different lengths of connection pieces between the weld zones along the depth of longitudinal ribs on the behavior of displacements and stresses under applied loads. The second study includes the effect of different lengths of cracks in the weld zones on the behavior of stresses under applied loads.The stresses of the ribs will be evaluated due to applied loading using finite element analysis (FEA) and the results will be compared to each other.

Keywords: Orthotropic steel deck, crack initiation, fatigue life, finite element simulation, weld connection, strain gauge, static calibration test, dynamic fatigue test, S-N curve approach, stiffness.