Research On Hydrodynamic Characteristics For Elevated Floating Gate Bridge

Applying elevated floating gate bridge is an important safeguard means for the rapid delivery of personnel and the transportation of logistic materials to overcome the cross-water barrier in the war.The analysis of the loading capacity of the bridge is an important step.Although the test is the best way to check the traffic capacity of the pontoon,the dynamic performance of the elevated floating gate bridge is often analyzed by the finite element software because of the large cost and long time.Combined with the special hydro-logical conditions of the Yangtze River and the "Regulations of the railway bridge repair",a collapsed bridge using pontoons instead of the collapsed ones is the background of this paper.The stability,hydrodynamic characteristics and motion response of the elevated floating bridge is carried out by the numerical simulation and can provide some reference for the design and checking of the railway pontoon.Firstly,the design of the 1 500 t pontoon is carried out.Based on the numerical simulation of SESAM software,the stability characteristics of beam and pier under three kinds of bearing restraints are compared and analyzed,the optimal form of bearing restraint is obtained;according to the actual length of the gate bridge,the influence of the different pier spacing on the stability of the structure is found;the influence of the different positions of the load on the stability of the gate bridge is studied,and the most unfavorable loading position is obtained,they are the basis of the subsequent calculation and analysis;the influence of different wind speed on the overturning moment of the structure is compared,and checking whether the whole system on the six-stage wind load can meet the stability standard.Secondly,the calculation theory of hydrodynamics and motion response of the elevated floating gate structure is analyzed,and they are studied under wave research;according to the hydrodynamic calculation results of the gate bridge under the amplitude wave,change rules of the added mass,radiation damping,first-order wave force and second-order steady drift force in different water depth and incident angles are obtained.Finally,the design wave method based on spectral analysis is applied for long-term forecast of the wave loads of the floating structure,determination of the representative section wave load is the key.Based on the calculated load transfer function by the regular wave,by giving the wave propagation pattern,the transcendental probability level and the reproduction period,and explaining the calculation of the wave load control parameters based on long-term wave prediction method,a certain degree of beyond the probability level of wave load and the wave parameters are obtained,and the structural response under the unit amplitude is achieved.At the same time,the actual amplitudes and phase angles of the results are combined to get the actual stress,and the strength of the beam is calculated in accordance with the "railway bridge specification".Finally,the internal force calculation is carried out in different spacing of piers,and the reasonable pier is obtained.