Coupling Analysis Of Safety Influencing Factors Of Trestle Ultra-High Steel Pipe Pile Under Complex Construction Environment

In order to facilitate the operation of personnel passage and material equipment transportation in the construction process of the main structure of the bridge across the river,trestle has become an indispensable temporary structure and even a key factor to guarantee the construction schedule and construction cost.At present,there are many studies on stress analysis and calculation methods of trestle ultra-high steel pipe piles,but few studies on safety influencing factors in construction,especially under the coupling effect of geometric initial defects,water flow load,wind load,ship traveling wave and other construction adverse environmental factors,which have not been reported yet.Aiming at the problem that the deviation of steel pipe pile is not convenient for the construction personnel to calculate directly,a simplified calculation method for the deviation of steel pipe pile is established by considering the geometrical initial defects,wind load and water flow load.Aiming at the problem that ship traveling wave may lead to excessive shaking of trestle bridge,considering the ship traveling wave and geometrical initial defects of steel pipe pile,the dynamic response of steel pipe pile under different ship types,water levels and ship speeds is studied by simplifying the fluid-solid coupling effect with additional mass and additional damping ratio,and the measures to control excessive shaking of steel pipe pile are proposed.It provides technical support for the construction of similar trestle super high steel pipe pile..The main research contents and conclusions of this paper are as follows:(1)The influencing factors and rules of deviation of trestle ultra-high steel pipe pile are analyzed.This paper analyzes the factors that may cause the deviation of ultra-high steel pipe pile on trestle bridge at the construction site,deduces the deviation formula of ultra-high steel pipe pile under wind load and water flow load,and studies the amplitude and influence rule of the deviation of steel pipe pile under different loads.The results show that the water flow load has the greatest influence on steel pipe pile construction.(2)Considering the coupling effect of geometric initial defects,wind load and water flow load,the simplified theoretical calculation formula of deflection of steel pipe pile was established by theoretical derivation.In order to facilitate theoretical derivation,the geometric initial defects were represented by displacement function,the wind load was simplified as concentrated force on the top of the steel pipe pile,and the water flow load was simplified by using the inverted triangle model.The simplified calculation formula for the deflection of the top of the steel pipe pile was derived by solving the equilibrium differential equation that was included in the nonlinear equation.On this basis,the influence of geometrical initial defects,the height of steel pipe pile and the ratio of axial pressure and the height of water level on the deviation of steel pipe pile is analyzed,and the results show that the above factors have great influence on the deviation of steel pipe pile of trestle bridge,and the geometrical nonlinearity has obvious influence on the deviation of steel pipe pile.(3)On the basis of considering the geometrical initial defect,the influence law of ship traveling wave on the displacement response of steel pipe pile is studied,and the measures to eliminate the excessive shaking of trestle are put forward.The overall finite element model of the trestle was established,and the influence of water on structural frequency and vibration suppression was considered by the additional mass method and the additional damping method respectively,and the resonance mechanism and amplitude of the trestle under different ship types,water levels and ship speeds were analyzed.The results show that the mechanism of excessive displacement of trestle caused by passenger ship is resonance reaction,and the large barge has a large traveling wave load.It is recommended that the speed limit of small and medium-sized passenger ships should be15 km/h to prevent resonance,while the speed limit of large barges should be 10 km/h to reduce the wave load.