| Bridges located in cold regions are often threatened by spring ice platoons,and ice loads that are one of the loads in rivers and bays in cold regions must be considered as one of the loads.The ice impact force and ice-induced bridge vibration problems should be considered.Caused enough attention.The general specification for highway bridge design gives the formula for calculating the maximum ice pressure according to the Soviet standard formula.However,due to the different water quality,climatic conditions and river environment in different countries,the calculation results of ice pressure are not accurate.Moreover,only the static ice pressure is provided in the specification,and there is no corresponding regulation on the impact of the ice-cold impact force and its bridge vibration.The interaction mechanism between the drift ice and the bridge,the failure mode of the ice discharge,etc.are not clear,and the understanding is insufficient.It poses a serious safety hazard to the bridges built on the rivers in the cold regions.The work done in this paper is as follows:Firstly,the uniaxial unconfined compressive strength test of ice was carried out for the mechanical properties of the river ice in the Harbin section of Songhua River.The test was carried out using a 25-ton MTS tester produced by a US company.The test results show that the compressive strength of river ice is greatly affected by temperature and loading rate.From the test results,the compressive strength shows an increasing trend with the decrease of temperature.From the loading rate analysis,generally The compressive strength reaches a maximum at a loading rate of 1.0E-3.When the loading rate is less than 1.0E-3,the strength increases with the loading rate.When it exceeds 1.0E-3,the strength increases.As the loading rate increases,it shows a downward trend.The failure mode of the ice row with the loading rate was analyzed.When the loading rate was in the range of 1E-3 to 3E-3,the test showed the dual characteristics of ductile and brittle.When the loading rate exceeded 3E-3,it showed obvious brittle failure.The piece broke and broke.The current calculation of ice pressure calculation formulas in various countries was carried out,and the main factors affecting the impact force of drift ice were summarized.The calculation formula of the No.3 pier of Harbin Matsuura Bridge was calculated by the calculation formula of each country,and the calculation difference of the norm formula of each country was compared.Secondly,ANSYS/LS-DYNA is used to simulate the running ice-bridge pier collision simulation,and the finite element modeling strategy of the drift ice-bridge pier collision is introduced.The structural responses of rectangular piers,circular piers and elliptical piers under different ice thicKNesses and different ice speeds are analyzed respectively.The collision response is evaluated according to the impact force peak,energy distribution and acceleration curve.The shape of the appropriate pier is struck by the drifting ice,and some suggestions are given for the design of the icebreaker.Thirdly,in order to reduce the impact damage of the drift ice on the bridge,the development of the bridge anti-flow ice collision avoidance device was carried out.The design ideas of the anti-collision device are introduced,and the parameters are optimized,including the slope angle of the anti-collision device,the wave height,the elastic modulus of the energy-consuming buffer device,and the spring stiffness parameter of the return spring.Anti-collision device.Finally,the ice-crash collision analysis of the pier with the anti-collision device is carried out.Through the research on the collision response of the bridge before and after the anti-collision device,the damping energy consumption effect of the anti-collision device against the ice impact is evaluated.Based on the above research,the paper provides theoretical basis and engineering reference value for the design of anti-flow ice impact of bridges in cold regions. |
PDF Full Text Request