Study On Fatigue Life Of Orthotropic Steel Deck Based On Abaqus And Fe-safe

The orthotropic steel bridge deck used in bridge engineering is formed by welding the top plate and stiffening ribs.This structure has many welds,so there are many initial defects and large residual stresses.Therefore,under the cyclic action of the vehicle load,the weld is prone to fatigue failure.At present,the fatigue calculation methods for orthotropic steel bridge decks are mainly the nominal stress method and the hot spot stress method.The equivalent structural stress method derived from the concept of the hot spot stress method has been well applied in fatigue calculations in other fields,but it is less used in the field of bridge engineering.Therefore,considering that the orthotropic composite steel bridge deck is currently a research hotspot,this thesis uses the equivalent structural stress method and Fe-safe to analyze its fatigue performance.The content of this thesis is as follows:(1)This thesis summarizes the fatigue life calculation methods of orthotropic steel bridge decks,introduces the principle of equivalent structural stress method,and compares the above method conceptually.The results show that the advantages of the equivalent structural stress method are that it considers the combined effects of stress concentration,geometric size and load forms.It uses use only one main S-N curve for different structures.And it is not sensitive to the mesh size.(2)Based on Fe-safe/Verity and the theory mentioned above,this thesis establishes a process to calculate the fatigue life of weld and verifies it by the experimental data.The result show that the model is close to the experimental data so it is feasible.And the advantages of the theory mentioned above have been verified.(3)Based on the method mentioned above,a domestic medium-span steel box girder bridge is taken as an example to analyze the fatigue performance of the orthotropic steel bridge deck.The focus of the study is the influence of concrete bridge decks on structural fatigue performance and the changes in the correlation between structural parameters and fatigue performance.The results show that the concrete bridge deck greatly improves the fatigue resistance.Among the parameters,the thickness of the concrete layer and top slab have the greatest influence on the fatigue life of the weld toe,others have less influence.The correlation between some parameters and the fatigue resistance has changed after laying the concrete.(4)This thesis uses the element method to simulate the welding process and calculates the residual stress distribution.The influence of welding sequence on it is analyzed,and the fatigue life is calculated based on the function of Fe-safe considering it.The results show that the welding sequence has a great influence on it and it’s extreme value;when it changes the stress state of the structure,the calculated value of the fatigue life will change greatly.