| With the continuous construction of urban roads and railways,the transition has become the most commonly used mode of the city at the intersection of railways and highways.Due to the constraints of existing routes and road planning,the underpass railway frame bridges often The existing railways have intersecting angles,and the force of the frame bridges becomes more and more complicated with the diversification of traffic conditions.Therefore,it is particularly important to analyze the stress of the skew frame bridges under different working conditions in the later operation stage.This paper takes the Ningbo Huancheng South Road overpass project as the background and builds the model through the finite element software ANSYS.The main results are as follows:(1)This paper mainly discusses the dynamic response of the skew frame bridge under the excitation load.The research shows that the acceleration peaks of the top and bottom plates of the frame bridge are basically M-shaped,and the maximum acceleration is concentrated in the mid-span position.The driving conditions and the speed change will not change the distribution of the peak acceleration of the frame bridge,but it will change.size.(2)The displacement of the roof of the bridge is W along the section,and the maximum displacement is distributed in the mid-span position;the displacement of the floor is M along the section,and the maximum displacement is distributed at the intersection of the floor and the vertical wall;the driving conditions and the speed change are not changed.The displacement distribution law of the frame bridge will be changed,but the displacement response of the frame bridge will increase with the increase of the vehicle speed,and the farther the frame bridge is from the train load position,the smaller the displacement response.(3)The dynamic stress peaks of the top and bottom plates of the frame bridge are distributed along the whole section,and the maximum value of each cross-span is mainly concentrated in the mid-span position,while the maximum stress at the end section is biased to the position of each obtuse angle;driving conditions and The vehicle speed does not change the stress distribution trend of the frame bridge.However,as the number of vehicles increases or the vehicle speed increases,the stress response of each section of the frame bridge increases,and the stress response of the roof section of the frame bridge is more affected by the driving conditions.(4)When the protective layer is not paved,the temperature at which the roof frame of the concrete frame bridge reaches the maximum is 14 pm;the temperature difference between the top surface of the sunny surface and the top and bottom of the unlayed ballast is large,and the temperature at the hole of the ballast and the shadow is laid.The difference is small;at different cross-section locations,the maximum principal stress of the concrete appears at thelocation of the male opening and the unrouted ballast.The protective layer has a significant influence on the corresponding time and the temperature of the roof when the concrete frame bridge reaches the maximum temperature;the pavement protective layer will reduce the main compressive stress of the concrete frame bridge by about 2 times.(5)Under the most unfavorable load during operation,the crack is most likely to occur on the roof of the frame bridge structure,and the reinforcement should be strengthened as needed.When the length of the frame bridge exceeds a certain range under the same external conditions,the change of the length has little effect on the magnitude of the first principal stress;the maximum tensile stress increases as the skew angle becomes smaller,and the stress concentration at the obtuse angle gradually increases,and Under different working conditions,the stress at the obtuse angle of the frame bridge is greater than the acute angle.In actual operation,attention should be paid to the maintenance of the frame bridge at the obtuse angle. |
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