Study on the Vehicle Impact Resistance of UHPC Frame Structure
With the rapid development of the road system and the increase in vehicle velocity in China,the vehicle collision risk of the frame building located on the road sides is also increasing.Ultra-high performance concrete(UHPC)has been increasingly applied to frame structures to improve its service performance due to its ultra-high material fracture energy and tensile strength.The UHPC frame structure is also subject to high vehicle impact risk.In this paper,high-resolution vehicle collision models against the three-layer normal concrete(NC)and ultra-high performance concrete(UHPC)frame structures are established and Ansys/LS-DYNA is used to conduct nonlinear dynamic finite element analysis.The material parameters and the contact algorithm are verified against the previously reported drop-weight impact test of NC and UHPC beams.Based on the high-resolution vehicle collision model,the NC and UHPC frame structures are comprehensively compared in terms of three aspects,i.e.,the structural damage,the impact force characteristics and the energy dissipation mechanism.The main conclusions are as follows:(1)The anti-vehicle impact resistance of UHPC frame structure is much higher than that of NC frame structure.The damage of UHPC frame structure only exists in the impacted column,and the concrete in other parts is almost not affected.(2)Under the condition of high vehicle speed(80-120 km/h),the damage mode of NC column is severe punch shear damage accompanied by obvious plastic deformation,and the frame joints exhibit obvious tensile and shear damage.There is no tension area on the back of the UHPC column,which eventually develops into a punch shear failure through the section of the frame column.(3)The internal energy of concrete of NC column is higher than that of UHPC column,resulting in more serious damage of NC column than that of UHPC column.(4)When the vehicle bumper and engine impact the frame column,the first and second peaks of the impact force are produced,respectively.The peak impact force caused by the engine impact is much higher than that of bumper impact.The peak impact force of UHPC column is 22.6％higher than that of NC column on average,and the maximum impact force difference between UHPC column and NC column is 32.1％.The results of this paper are beneficial for the rational design of UHPC frame structure for impact resistance and ensure its safe and healthy operation.
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