Dynamic Response And Safety Evaluation Of Tied Arch Bridges Under Blasting Loads

With the continuous updating of blasting technology and the increase of its blasting accuracy and applicability,blasting operations have been widely used in various industries in social development,especially in civil engineering and mining engineering fields that have long become an indispensable part.On the other hand,while the blasting operation brings convenience,the vibration waves generated by the blasting also affect the surrounding rock masses and buildings,and the hidden safety hazards caused cannot be ignored.Tied arch bridge is a bridge type that combines the advantages of arch and beam.Compared with other bridge types,it is more in line with people's aesthetics.It plays an important role in urban construction,and the probability of being affected by blasting loads is increasing day by day.Taking the tied arch bridge as the research object,analyzing the internal force response characteristics of the main structure or components under the action of blasting vibration,and obtaining the safety evaluation method of the bridge structure under the action of blasting load,which is of great significance in engineering practice.Based on the natural seismic analysis theory,combined with the structural dynamic analysis theory,this paper uses a combination of field test and numerical analysis to discuss and study the response law and safety issues of a steel box tied arch bridge under blasting load.The research contents include:(1)The generation mechanism of the blasting vibration wave and the characteristics of the basic parameters of the vibration wave in the propagation process are discussed.At the same time,the blasting vibration wave and the natural seismic wave are compared,and the parameters that the blasting vibration wave has a greater impact on the building structure are obtained.The subsequent dynamic response analysis provides a theoretical basis.(2)By analyzing and studying the attenuation law of blasting vibration waves under different terrain and geological conditions,a quantitative formula for attenuation of the measured time history curve of blasting vibration waves is obtained to make it closer to the on-site vibration situation.(3)Taking Maotai No.3 Bridge project as the research background,combined with the time history analysis theory and structural dynamic analysis theory,the stress and displacement variation laws of main arch ring and main girder of steel box tied arch bridge under blasting load are analyzed and studied by using large-scale finite element software MIDAS civil,and the axial force,shear force-y,shear force-y of main arch ring of bridge under blasting load are obtained The maximum values of shear force-Z and bending moment-Z are at the arch foot,the maximum value of bending moment-y is at 1 / 4 span,the maximum values of transverse and vertical displacement are at the vault,and the maximum values of longitudinal displacement are at1 / 4 span and 3 / 4 span;The maximum values of axial force,shear force-y,shear force-z and bending moment-z of the main girder are at the arch foot,the maximum value of bending moment-y is at 1 / 4 span,and the maximum value of vertical displacement is at the mid span.(4)Under the action of blasting load,carry out local simulation analysis and research on the connection between the boom and the main beam,and obtain the accurate situation of the internal force(stress,displacement)change of each member at the boom by the dense grid division.The analysis results show that the maximum internal force occurs at the connection part of the boom,where the stress value is closer to the yield strength of the material,and corresponding protective measures need to be taken during the blasting process.(5)Analyze and evaluate the limitations of existing blasting safety evaluation standards for bridge evaluation,and combine the US bridge seismic evaluation method—capacity demand ratio with the failure characteristics of the bridge structure under blasting load,and establish the ability based on the blasting load.The bridge safety evaluation method based on the demand ratio method found that the internal force of the main arch ring and the main girder of the bridge is CDR>1,and the strength of the bridge itself meets the requirements of the blasting load strength.At the same time,it is found that the arch toe and the connection between the suspender and the main girder are two positions It is in a vulnerable part.