UHPC框架结构的抗车辆冲击性能研究

Study on the Vehicle Impact Resistance of UHPC Frame Structure

随着我国交通系统的发展及汽车车速的日益提升,坐落于道路两旁的框架建筑承受的车辆碰撞风险也与日俱增.超高性能混凝土(Ultra-High Performance Concrete, UHPC)由于其超高的材料断裂能以及抗拉能力逐渐被应用于框架结构中以提高其使用性能.UHPC框架结构同样承受较高的车辆撞击风险.本文建立了三维动力非线性的车辆-UHPC三层框架结构碰撞模型并采用Ansys/LS-DYNA进行求解.采用已发表的落锤撞击普通混凝土(Normal Concrete, NC)与超高性能混凝土(UHPC)梁试验对材料参数与接触算法的正确性进行了验证.基于三维动力非线性碰撞模型,从结构损伤、碰撞力特性及结构耗能机理三方面对NC及UHPC框架结构进行了全面对比.主要结论如下:(1) UHPC框架结构的抗车辆冲击性能远高于NC框架结构.UHPC框架结构的损伤仅存在于被撞柱,其他部位混凝土的使用性能几乎不受影响.(2)高车速条件下(80~120 km/h),NC柱的损伤分布为剧烈的冲切损伤并伴有明显的塑性变形,框架节点出现明显的受拉及受剪损伤;UHPC柱的背面始终不出现受拉区域,最终发展成贯通框架柱截面的冲剪破坏.(3) NC柱的混凝土内能均比UHPC柱的混凝土内能高,导致NC柱的损伤程度比UHPC柱严重.(4)当车辆保险杠撞击框架柱时,碰撞力产生第一个峰值;当车辆引擎与框架柱撞击时,碰撞力产生第二个峰值.引擎撞击产生的碰撞力峰值均远高于保险杠撞击.UHPC柱的碰撞力峰值平均比NC柱高22.6%,二者碰撞力峰值最大差异可达32.1%.本文研究结果有助于促进UHPC框架结构的抗冲击合理化设计,并保障其安全健康运营.

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 antivehicle 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.