Investigation of Explosive Collapse Process and Mechanism of Girder Bridges with Double-column Piers
This study combined theoretical analysis and experimental research to investigate the collapse patterns and damage characteristics of girder bridges with double-column piers under blasting demolition.A theoretical formula for the collapse demolition of bridges was derived,and the collapse motion of the main girder during the blasting demolition process was analyzed.Several finite element models were established to conduct a comparative analysis of the span-by-span collapse blasting scheme with and without torsion effect.The movement and damage characteristics of the collapsed bridge were studied.A parametric analysis was also conducted to investigate the effects of blasting delay on the extent of damage to the bridge during its collapse.The results indicate that the proposed method for determining the limits in blasting delay is practical and feasible.The upper limit for the blasting delay allows for controlling over the entire collapse process,whereas the lower limit prevents adverse effects derived from cumulative collapse vibrations.During the span-by-span collapse process of the blasting demolition,the main girder collides with the ground multiple times.The conversion of kinetic energy to internal energy primarily occurs during the first two collisions,accounting for over 70％of the total energy.In a comparison of the span-by-span collapse-blasting schemes,the scheme that incorporates the torsion effect optimizes the demolition sequence of the pier columns to control the collapse posture of the main girder.The impact of the collapse is used to generate torsional and shearing forces on the main girder,thereby increasing the extent of collision damage and improving demolition efficiency.Within the range of detonation delay limits,an increase of delay time leads to greater damage to the bottom of the main girder.
bridge engineeringblasting demolitionexperimental studyconcrete double-column pierblasting delaycollapse process
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