Research On The Anti-collision Performance Of UHPC Precast Segmental Concrete Barrier

With the rapid development of prefabricated bridges and the demand of assembly transformation of anti-collision barriers of bridges in service,this paper proposes a new type of precast segmental concrete barriers assembled by ultra-high performance concrete(UHPC).Combined with a pilot project,this paper introduces the structure and construction technology of the segment assembled barrier and carries out the force behavior research and parameter analysis of UHPC segmental anti-collision barrier under quasi-static actions and impact actions,as well as the safety evaluation under vehicle impacts.The main research contents and achievements are as follows:(1)Analysis of the influence of the lower boundary of the barrier on the impact force of truck collisions.By comparing the impact force of truck collision in three cases of direct consolidation,flange plate connection and integral box girder connection,the influence of the lower boundary condition of the barrier on the impact force of the truck collision is revealed.The results show that: when the lower boundary of barrier is the flange plate and the box girder,the time history curve of impact forces is basically same,while the lower boundary of barrier is direct consolidation,the number of peaks of impact forces decreases and the peak value increases.(2)Analysis of the influence of UHPC vertical connection on the dynamic shear resistance of segment assembled barrier.Taking UHPC vertical connection as the research object,without considering the longitudinal connection,the difference of ultimate bearing capacity and dynamic shear performance of segmental assembled barrier under two kinds of vertical connection is compared and analyzed and carried out parameter analysis and structural optimization for the advantageous vertical connection form.The results show that: when the vertical connection has an extended transition section,the ultimate bearing capacity and dynamic shear performance of the barrier are better than ordinary ones.Among them,the length of UHPC extended transition section and the transverse reinforcement are sensitive parameters.The top displacement value of the barrier decreases with the increase of the transverse reinforcement ratio,but the decreasing degree gradually declines;the damage of flange plate first decreases significantly with the increase of transverse reinforcement ratio,and then slowly increases.When the length of UHPC extended transition section covered the cantilever length of the flange plate,the damage of the top of the flange plate is significantly reduced.(3)Analysis of the influence of UHPC longitudinal connection on the dynamic shear resistance of segment assembled barrier.Based on the optimized UHPC vertical connection structure,the research object is vertical connection and longitudinal connection with UHPC.The influence of UHPC longitudinal connection method on ultimate bearing capacity and dynamic shear performance of the segmented barrier is analyzed,and parameters of its structure are analyzed.The results show that: the ultimate bearing capacity of the barrier segment and the longitudinal connection under quasistatic action is basically same;under the impact,the segmental assembled barrier has a failure with larger inverted trapezoidal yield than the ordinary barrier;the deformation of the barriers spliced by vertical connections at different collision heights and speeds are both smaller than that of ordinary barriers;in order to ensure that the longitudinal connection strength of UHPC is greater than that of the barrier,the length of its longitudinal structure needs to overlap with the longitudinal steel bars of the barrier to a certain extent.(4)Safety performance evaluation of UHPC segment assembled barrier under vehicle impacts.In this paper,numerical simulation analysis of the oblique impact segment assembled barrier of minibus and truck are carried out.Combined with relevant specifications at home and abroad,and taking the ordinary barriers as a reference,the safety performance of the segment assembled barrier is evaluated through the maximum dynamic displacement and guidance of the barrier,vehicle acceleration and other parameters.The results show that the maximum dynamic displacement of the segment barrier under the oblique impact of minibus and truck is less than that of the ordinary barrier,and the barrier has a good guidance to the vehicle,and the vehicle acceleration meets the specification requirements.