Study On The Tuned Seismic Design For Continues Bridges By Taking Used Of Girder Mass And Mechanical Performance Of Bearing

Earthquakes are natural disasters that cannot be accurately predicted and avoided.In an earthquake,structural damage and collapse can cause huge losses.Bridges are throat projects of transportation networks.The seismic capacity of bridges has an important influence on the post-earthquake capacity of traffic networks.Continuous girder bridge is a relatively common girder bridge,because its force is even and reasonable,simple and beautiful shape and other advantages,has been widely used.It is of great significance to improve the seismic performance of continuous girder bridges to improve the post-earthquake capacity of the road network.However,in the isolation design of bridges,the selection of design parameters is more dependent on the experience of designers or repeated trials,lacking a clear theoretical basis,and can not fully play the role of isolation.A scientific and simple parameter design method for seismic isolation bearings is proposed.It is very important to improve the design efficiency of isolation and reduction of continuous beam bridges and the promotion of seismic isolation techniques.In view of the structural form of the continuous girder bridge,this paper proposes a tuned damping design method that uses the girder mass and bearing performance.In this method,the pier is considered as the main structure,the main beam is regarded as additional mass.The main beam and the support form a complete tunable power system by setting the tuned damper bearings,which can be tuned and damped according to the quality.The theory optimizes the seismic performance of continuous girder bridges to improve the damping efficiency of the bridge.In this paper,theoretical analysis and numerical simulation techniques are used to explore the design method of mass-tuned damping for continuous beam bridges.First of all,this paper simplifies the model of the continuous girder bridge and obtains the simplified mechanical model of the regular girder bridge.Secondly,in the light of the simple to complex ideas,tuning optimization studies are conducted under three conditions.First,the bridge pier damping is not considered and the harmonic loads are excited.The second is the consideration of the bridge pier damping and the harmonic load excitation.The third is the consideration of the bridge pier damping and random load excitation.All three methods use the minimization of the maximum bending moment at the bottom of the pier as the optimization goal,and the formulas for calculating the optimal frequency ratio and the optimal damping ratio are obtained.Then,using the above-obtained optimal frequency ratio and optimum damping ratio calculation formula to calculate the corresponding bearing parameters of each group of calculation examples,and the maximum bottom bending moment of each group of calculation examples is calculated by the finite element software;The three methods all have good damping effect;the calculation and analysis also show that the damping of the bridge pier has little effect on the tuning damping effect;compared with the simple harmonic excitation and the random excitation,the random excitation is more sensitive to frequency.For irregular continuous beam bridges,based on the principle of tuning damping,a method for mass distribution of superstructures is proposed,which expands the tuning damping method for regular bridges to irregular bridges.Examples show that this method effectively reduces the bending moment of high piers,makes the pier group bending moment more balanced,and realizes the collaborative force of piers and piers and the goal of seismic resistance of the system.