Fatigue Behavior Of Orthotropic Steel Deck Considering Vehicle Bridge Coupling Vibration

With the progress of smelting technology and bridge construction technology in the world,steel bridge is undoubtedly playing an important role in contemporary bridge construction.With the extensive use of steel bridge,fatigue cracking problem is one of the most important factors that directly affect its use.Therefore,the study of static analysis,local vibration effect and fatigue performance of orthotropic steel bridge decks has extremely important theoretical significance and engineering value.Based on the research background of the special-shaped steel arch bridge of the Yellow River in Zhongwei,Ningxia,this paper uses theoretical analysis and numerical simulation to analyze the local stress effect,local vibration effect and fatigue performance of the structural details of the orthotropic steel bridge deck.The main contents of this article are as follows:(1)Static analysis of orthotropic steel bridge deckStructural characteristics of orthotropic steel bridge deck were analyzed to simplify the analytical model for orthotropic deck under local wheel loads.An elastic supported frame model was proposed to analyze local mechanical effects of orthotropic deck around the wheel load.After derivation of the elastic support stiffness and effective load density,a closed form solution for horizontal bending stress in the top plate of orthotropic deck was presented.Subsequently,the critical sensitive factor affecting the bending stress in bridge deck was discussed and identified.A box girder bridge was taken as an example to confirm the proposed theoretical solution for local stress under wheel load.The results show that the difference between the transverse stress value calculated by this method and the finite element results is no more than 10%,which indicates that this proposed method is accurate and can be applied in preliminary design of orthotropic steel bridge deck conveniently.It can also found that the bending stress in bridge deck increases with the thickness and height of U rib increasing,but decreases with plate roof thickness and diaphragm spacing increasing.The tensile stress in bridge deck is most significantly affected by the thickness of the roof,while is not sensitive to the changes of web angle and thickness of the U-rib.(2)Establish a vehicle-bridge coupled vibration model considering the contact area between the wheel and the bridge deckFirst,use the contact constraint method based on ANSYS to establish a threedimensional space vehicle model considering the wheel contact area,and verify the correctness of the vehicle model in the coupled vibration analysis of the vehicle bridge.Secondly,in order to simulate the actual bridge surface irregularities,this paper uses the harmonic superposition method to simulate the bridge irregularities samples.Finally,the vehicle model is used to study the vibration effect of the simply-supported girder bridge considering the unevenness of the road surface and the unevenness of the coaxial left and right rut roads are different.(3)Research on local vibration effect of orthotropic steel bridge deckThis paper first established a multi-scale vehicle-bridge coupled vibration finite element model for the local impact effect of steel box girder,mainly from the vehicle load,road roughness and driving speed to the local dynamic response of steel box girder based on orthotropic steel bridge deck influences.The local vibration and impact coefficients of steel box girder under different road roughness grades and different driving speeds are calculated.Through analysis,it is found that the heavier the vehicle load,the more obvious the local effect of the orthotropic steel bridge deck.The rougher the road surface,the more obvious the lateral local effect of the orthotropic steel bridge deck,the more intense the local vibration,and the greater the stress and local impact coefficient of the detailed structure.Although the vehicle speed does not show a direct and regular change with the lateral stress and local impact coefficient,in general,the higher the vehicle speed,the greater the local impact on the orthotropic steel bridge deck.(4)Fatigue performance evaluation of each detail structure of orthotropic steel bridge deckIn this paper,the S-N curve and Miner criterion are used to determine the fatigue performance at the junction of the longitudinal rib and the roof of the orthotropic steel bridge deck and the detailed structure of the junction between the longitudinal rib and the diaphragm from the influence factors such as the level of road surface roughness and vehicle speed.It was evaluated.Through research,it is found that the fatigue damage at each key point is dominated by low-stress cycles.The rougher the road surface,the greater the damage to the details of the orthotropic steel bridge deck.Although the fatigue damage of the vehicle speed and the details show a direct law,in general,the higher the speed,the more unfavorable the structure.Regardless of whether it is at different road grades or at different driving speeds,the coupling vibration effect of the vehicle bridge causes the greatest damage to the web at the junction of the longitudinal rib and the diaphragm.