Numerical Simulation Of Bridge Structure Blasting Demolition

With the rapid development of urbanization and reconstruction in China,the bridges built in the early days have been unable to meet the rapid development of transportation in terms of traffic functions,load levels,and safe operations.Demolition technology has become an urgent need for the city to re-plan the construction of wealthy people.Blasting demolition at this time has been widely used because of its own superiority.However,the theoretical research on blasting demolition in our country is relatively backward.Safety accidents caused by blasting demolition have occurred from time to time.Therefore,it is particularly important that the use of numerical simulation techniques to predict the collapse condition of blasting demolition in advance to ensure the safety of personal economic and property.The main work of this paper is as follows:Firstly,it summarizes the application situations of blasting demolition of urban viaducts,lists some domestic examples of demolition blasting of bridges,and briefly outlines the development of demolition blasting at home and abroad,and then introduces the research contents and methods of this paper.Then the collapse theory of reinforced concrete structures was studied;the destabilization mode and mechanics model of the demolition were briefly introduced;followed by the introduction of the finite element model of blasting demolition of urban viaducts;and finally,by the method of spiral holes,the reinforced concrete of bridge piers has been designed two different blasting schemes,namely,millisecond blasting and simultaneous blasting.The finite element software ANSYS/LS-DYNA is used to establish the separate joint node model of the pier,which reproduces the collapse of the pier from force to instability.Then the reinforced concrete and concrete elements of the piers under the two blasting schemes were compared and analyzed by the stress curves,displacement curves and velocity curves.It was found that under the same conditions,the stress of the bridge piers demolished under the same conditions was smaller than that of the simultaneous initiation,and at the same time,the trajectories are not the same under two schemes.The range of the millisecond blasting burst is small,which shows that under the premise of satisfying the instability of bridge piers,the use of millisecond blasting is more advantageous;finally,the finite element model of the continuous beam bridge is established,and the collapse process of the continuous beam bridge is analyzed.In addition,the analysis of the velocity curves of the ground points at the time of continuous bridge collapse and the comparison of the vertical velocity curves with empirical formulas shows that the contact-to-ground vibration velocity in the transverse direction is greater than the allowable velocity value of the empirical formula,and the collapsed contact area may cause damage to the surrounding structure,so the necessary measure should be given.Through the above studies,it can be seen that the use of numerical simulation technology can effectively guide the blasting demolition of the bridge,making the demolition technology more scientific and more secure and it has guiding significance for engineering practice.