Railway Bridge Orthotropic Plate U Rib And Beam Web Connection At The Fatigue Performance

In China, with the rapid development of high speed railway construction, orthotropic monolithic steel bridge deck has been getting more and more widely practical application because of its superior structure style. But fatigue failure tends to happen in orthotropic monolithic steel bridge deck because of the complex load distribution, structural forms'continuous development, stress concentration and welding flaws. Fatigue of orthotropic deck has always been the key point and the hot spot of railway steel bridges. On base of extensive collection and study of relevant information from home and abroad, experimental research was carried out on the fatigue performance of the U rib-to-diaphragm connection in orthotropic steel bridge deck. The results are as follows:1. Referring to the orthotropic monolithic steel deck structure style of Anqing Changjiang River Bridge, four full scale monolithic models of U rib-to-diaphragm connection were fabricated. The space finite element models on the four models were built and refined finite element analysis were carried out.2. The fatigue experiments were carried out on the four models and the results wree studyed. Results show that the U rib-to-diaphragm connection has good fatigue performance. The load and the deflection have positive linear relationship in each static load test after different load cycle times. The measured stress and the calculation value of linear elastic have a good agreement, and the order and position of the cracks' appearance agrees with the finite element analysis results.The deformation of diaphragm web in orthotropic steel bridge deck is mainly in-plane bending, and the out-of-plane bending deformation is small.3. The influence factors of fatigue performance in orthotropic steel bridge deck were studied. Results show that the fatigue performance of the U rib-to-diaphragm connection is influenced observably by the amplitude of fatigue load, but not influenced by the hole shape in the diaphragm under the U rib or the holes at the upper U rib-to-diaphragm connection. The holes at the upper U rib-to-diaphragm connection can relieve the stress concentration only. The influence of loading way on the fatigue performance is enormous. The steel rails should be avoided to be located on the deck right above U ribs.4. The fatigue performance of the U rib-to-diaphragm connection in orthotropic steel bridge deck was evaluated in the paper. The fatigue strength curve for the hole edge of the diaphragm web under U rib is 1g N+3.221gΔσ=13.333 and the allowable stress amplitude of 200 million times fatigue life is 155MPa. The hole edge of diaphragm web under U rib should be categorized into I fatigue type. The fatigue strength curve of the welding assembling position between diaphragm web and U rib is 1g N+2.821gΔσ=11.9624 and the allowable stress amplitude of 200 million times fatigue life is 101.8MPa. The welding assembling position between diaphragm web and U rib should be categorized intoⅦfatigue type.The research results of this thesis provide basis and reference for the fatigue design and the fatigue performance study of the orthotropic railway steel bridge deck.