Dynamic Response Analysis Of Long Span Continuous Rigid Frame Bridge With High Piers Under Debris Flow-structure Interaction

As a common geological disaster in highway engineering,debris flow occurs frequently,especially after earthquakes,heavy rains,and snowstorms,and its prone areas are mainly distributed in the mountainous areas of southwest my country.The method of erecting a bridge to cross the debris flow area is often one of the best choices for mountain road construction.Because the mountainous terrain is more diverse and the terrain is undulating,the bridge type of continuous rigid frame bridge with large span and high pier is often used,so it is inevitable that Encountered the problem of debris flow hitting the bridge.When the debris flow is serious,it will cause damage to the substructure or even overturning.In order to ensure sufficient reliability of bridges and other structures after the occurrence of debris flow,the research on the mechanical response of long-span high-pier continuous rigid frame bridges under the impact of debris flow has important theoretical significance and engineering application value.The details are as follows:(1)Firstly,the damage way and research status of debris flow to bridges are summarized,and the existing problems in the current research are pointed out.Then,the paper introduces the calculation method of velocity,impact force and other parameters,debris flow movement model and fluid and solid calculation theory.(2)Combining a continuous rigid frame bridge on an expressway in Yunnan as the actual engineering background,the paper uses Binghan model to simulate the slurry body under the guidance of the theory of two-way fluid solid coupling.The coupled analysis model of continuous rigid frame bridge is established by CFD software FLUENT.The distribution characteristics and movement rules of slurry in the basin are analyzed.On this basis,the changes in the load parameters such as the flow velocity and viscosity,the pier section form and the tie beam settings in the structural parameters are considered to the structure.The influence of mechanical response and damage characteristics.(3)Based on Hertz collision theory and the law of conservation of energy,the rigid body is used to simulate the block stone,and the LS-DYNA calculation in workbench is used to analyze the impact of the plate on the continuous rigid frame bridge with debris flow block stone.The influence of the initial impact velocity and volume mass in the physical properties of the block stone,the concrete strength in the bearing capacity of the structure and other factors on the dynamic response and damage of the structure is discussed.Finally,the dynamic response results of slurry and block stone to the structure are analyzed and compared.The main conclusions are as follows: the liquid phase slurry is the main factor to deform the structure,and the influence of the block stone is small;when the velocity is high,the impact force of a single solid block stone has exceeded the overall effect of the slurry.This paper studies the dynamic response of long-span high pier continuous rigid frame bridge under the interaction of debris flow and structure,and finally obtains the structural mechanical response and damage characteristics of continuous rigid frame bridge under the action of debris flow,and then puts forward corresponding security measures to reduce the risk of falling beam,overturning and even collapse of bridge under the impact of debris flow.It provides a reference for the design and construction of bridge structure in the prone area.