Study On Dynamic Characteristics Of Shallow Culvert Based On Acceleration Response Analysis

Culvert is an important part of highway transportation system,and its cost and quantity account for a relatively high proportion.Because the calculation and design of highway culverts have not been paid enough attention for a long time,most of them directly apply the design standards of small span bridges,which leads to some problems in the actual construction,use and maintenance of culverts.For example,there are longitudinal and transverse cracks in the culvert body,cracks in the culvert foundation and uneven settlement,cracks or inclination in the end wall and wing wall,etc.Especially in recent years,the frequent occurrence of culvert diseases and accidents has attracted widespread attention of the engineering community.These problems cause some losses,while the major ones cause delays in the progress of the project and affect the construction planning of the whole line.The culvert can be divided into open culvert and hidden culvert according to the thickness of fill(50 cm as the boundary).For the calculation of culvert stress,the earth pressure is mainly considered in high fill culvert,while the vehicle load is usually considered in low fill culvert,but it is usually regarded as static force.Even for shallow buried open culverts,they are simply regarded as simply supported beams,and the impact effect is considered by the calculation method of simply supported beams.In the current code,the overlying height of 50 cm is the limit to decide whether to consider the dynamic action,and this regulation is directly followed from the relevant code of arch bridge.In addition,there are many kinds of culverts,and the mechanical characteristics of different types of culverts vary greatly.It is obviously not enough to consider them with one method.Based on the above,this paper,referring to a large number of research and engineering examples,combines the basic theory of subgrade pavement and culvert stress,dynamic model test and ABAQUS numerical simulation method,carries out the response test of culvert based on culvert acceleration under two different modulus pavement conditions of rigid pavement and flexible pavement.The main work and achievements are as follows:(1)On the basis of plenty of theoretical research and engineering investigation,the force law of different pavement forms combined with foundation and culvert is discussed from static theory.The effect and transfer law of dynamic effect are further analyzed based on dynamic vehicle load,which lays a foundation for the following research scheme,which is dominated by model test and assisted by numerical simulation.(2)An ideal prototype test is designed according to several important factors considered in the dynamic response of culverts,such as pavement type,filling height and vehicle speed.According to the similarity theory,the similarity criterion that should be followed in the dynamic model test of conventional gravity field is deduced,the similarity scale of main parameters is determined,and the dynamic model test is designed.(3)Acceleration sensors are used to measure the vertical and horizontal vibration acceleration signals of culvert models under different working conditions.The relationship between the difference of acceleration waveforms between rigid pavement and flexible pavement and the law of dynamic action is further analyzed.It is concluded that the transverse vibration of culvert will be more affected when the load speed increases.The attenuation law of culvert acceleration with filling height under different pavement is studied.Combining with the seismic code,the safety threshold of 0.1g acceleration without considering the dynamic influence of vehicles on shallow buried culvert is established,and the corresponding limit filling height is obtained.The rigid pavement is 50 cm filling,the overlying height is 70 cm;the flexible pavement is 60 cm filling,and the overlying height is 80 cm.(4)Based on the prototype,a three-dimensional finite element dynamic model is established.The time history curves of vertical and horizontal acceleration of culvert under prototype working conditions are obtained by dynamic analysis step calculation,and compared with the model test results,the two laws are consistent,but the numerical values are slightly different.Therefore,it is believed that the results obtained from the model test are credible and have practical reference significance.