Study On The Influence Of Local Scour Depth For The Dynamic Characteristics Of Structures And Anti Scour Measures

With the rapid development of economy,China's infrastructure construction is following up steadily,and the construction technology is also improving day by day.After years of disaster data statistics,it is found that local scour accounts for a large part of the causes of structural damage,so scholars at home and abroad pay more and more attention to the impact of local scour on the structure,and have done relevant research in this regard.The local scouring depth of the bridge pier foundation is an important parameter to determine the foundation burial depth and to ensure the operating safety of the bridge.As the local scour depth increases,the buried depth of the structural foundation decreases,leading to the stiffness change of the structure and affecting the safety and stability of the structure.This paper focuses on the pier foundation calculation method of the 11 different local scour depth formula in every dimension,general scour depth,the river bed and bed material on the depth of local scour.Moreover,this paper compares and analyzes the influence of four engineering examples,calculates the selecting phase for bridge pier local scour depth formula and analysis of the results.Then,the m method is used to calculate the stiffness matrix of the structure after each meter of erosion in the project and analyze its variation rule statistically based on the local erosion depth results of example 4.To further explore the influence of local scour depth on the structure,this paper uses ANSYS and UM software to conduct joint simulation calculations on the model of example 4 and summarizes the existing anti-scour measures.Research shows that:(1)Compared with the formulas for the local scouring depth of various piers in China,the calculation of HEC-18 and Bordakov formula for the single-pier bridge pier model is relatively simple,and the calculation result of HEC-18 is relatively safe.For the model of cap pier of complex pile group,the new formula of Chinese Academy of Railway Sciences takes more factors into consideration than the standard formula,and the result is more safer.(2)The stiffness along the bridge,in the transverse direction and around the vertical direction will decrease logarithmic-ally with the increase of scour depth,while in the vertical direction,the stiffness around the transverse direction and around the longitudinal direction will decrease linearly with the increase of scour depth.(3)With the increase of local scour depth,the overall vertical displacement,lateral displacement,vertical acceleration and lateral acceleration increase with different travel speeds;When the vehicle operation speed is higher,the vertical displacement,lateral displacement,vertical acceleration and lateral acceleration of the structure are more sensitive to local scour depth.The difference between the vertical displacement and the lateral displacement is of the order of magnitude,but the vertical acceleration is about four times of the lateral acceleration.In operation,attention should be paid to the control of the speed and flow of the vehicle on the structure.(4)According to the actual situation of the project to choose appropriate protection measures,it can reduce the local erosion depth,reduce the impact on the structure,as well as reduce the later maintenance and operation costs.