Research On Anti-explosion Performance Of Prefabricated Concrete Box Girder

With the deepening of reform and opening up and the comprehensive construction of"One Belt,One Road",the cooperation between China and the international comm unity has become more and more extensive.However,opportunities and challenges co exist,with an increasing number of bombings caused by chance,terrorist attacks and war around the world,and bridges,which are vital for sustaining national livelihoods,are at increasing risk of explosion.The main elements of the study are as follows:(1)To determine the applicability of different software,numerical simulation of b last shock waves using LS-DYNA and AUTODYN was studied.In addition,verify th e relia-bility of the numerical simulation by comparison with the empirical equations.(2)Based on the general diagram of the bridge superstructure posted by the Mini stry of Transportation and Communications,a three-dimensional solid model of the cas t-in-place and prefabricated prestressed reinforced concrete box girders under explosive load was established,and the advantages and disadvantages of the explosion resistanc e of the box girders of the two systems under the action of different explosion positi ons were compared and analyzed.(3)To study the influence of different parameters on the dynamic response and d amage of the prefabricated box girder by changing the high span ratio,number of pie ces,concrete strength and proportional distance of explosive load of the box girder.(4)To establish the prefabricated box girder damage assessment standard,change the peak overpressure and impulse size of the explosive load,and obtain the pressure-toimpulse(P-I)curve of the prefabricated box girder damage assessment through a lar ge number of trial simulations.The main conclusions are as follows:(1)In the explosive equivalent of 227kg of explosives,the explosive load of 1m height,even if the explosion location is different,the box girder web can effectively s low down and limit the lateral extension of the bridge opening,and reduce the deflect ion of the main beam.The weak part of cast-in-place box girder is the wing edge,th e weak part of explosion resistance of prefabricated assembled box girder is directly a bove the box chamber.The strength and duration of the overall power response of pr efabricated assembled box girder is greater than that of cast-in-place box girder;the e nergy consumption capacity of prefabricated assembled box girder is better than that o f cast-in-place box girder.(2)When the explosion is located above the center of the bridge,only change th e explosive equivalent,so that the proportion of distance from 0.21m/kg^1/3 to 0.085m/kg^1/3 gradually reduced.Prefabricated assembled box girder local damage would be ch anged from bending damage mode to shear damage mode,while the cross-bridge will occur to the box chamber,box chamber wing edge,and wet joints of the three mutu al separations.(3)The increase in span diameter of the prefabricated assembled box girder will reduce the cross-bridge damage to the range,but the local damage will aggravate.An d increase the relative displacement between the box girder sections,but also increase the contact energy consumption of the main beam.The increase in beam height will aggravate the damage to the exploding surface,the back exploding surface damage re duction,a large beam height will make the local damage pattern from bending damag e to shear damage;prefabricated assembled box girder high span ratio will increase th e cross-bridge damage to the expansion of the range.(4)With the prefabricated assembled box girder bridge deck and box girder secti on width ratio increases,the main beam cross-bridge damage to a smaller range,away from the damage at the burst heart to reduce the extent,but near the burst heart of the local damage will increase.The increase in concrete strength will reduce the dama ge and deflection of the main beam's onrushing surface and significantly increase the contact energy consumption of the main beam,but increasing concrete strength above C50 is not obvious to improve the main beam's explosion resistance,but will increase the explosion load on the onrushing surface.(5)Fitting P-I damage curves can well predict the damage of prefabricated assem bled box girder.The overpressure limits for moderate damage,severe damage and coll apse derived from the fitting curves are 2.036MPa,2.575MPa and 3.038MPa respectiv ely,and the corresponding impulse limits are 3.334MPa·ms,9.092 MPa·ms and 11.05MPa·ms respectively.