受火后内配型钢圆钢管混凝土柱侧向撞击荷载作用下受力性能研究

Mechanical behavior of circular steel-reinforced concrete-filled steel tubular columns under lateral impact after exposure to fire

为研究火灾作用后内配型钢圆钢管混凝土(SRCFST)柱的抗撞击性能,利用有限元软件ABAQUS建立受火后柱的侧向撞击数值模型。在验证模型准确性的基础上,对受火后柱在侧向撞击作用下的受力机理进行分析,包括撞击响应全过程、截面内力发展和塑性变形;研究了受火时间、落锤与柱的质量比以及轴压比等关键因素对柱抗撞击性能的影响;并对比了受火后CFST和SRCFST柱的抗撞击能力。结果表明:受火后SRCFST柱表现出良好的抗撞击性能,与未受火时相比,受火1 h后的柱,由于抗弯刚度的损失导致柱跨中最大挠度增加17%,撞击力平台值降低12%;落锤与柱的质量比对撞击力时程曲线的形态影响显著,当质量比减小至3时,曲线的平台阶段逐渐消失;轴压比小于0.3时,轴力的存在会轻微提高撞击力平台值,当轴压比超过0.3时,柱的抗撞击性能明显降低;与受火后CFST柱相比,受火后SRCFST柱表现出更优的抗撞击性能,柱的跨中最大挠度平均可减小15%,撞击力平台值平均可提高22%。

To study the impact behavior of circular steel-reinforced concrete-filled steel tubular(SRCFST)columns after exposure to fire,a numerical model for the post-fire columns under lateral impact was developed using software ABAQUS.Based on the validated accuracy of the proposed model,the working mechanism of the post-fire columns under lateral impact was analyzed,including the impact response process,the development of sectional internal force and the plastic deformation.Moreover,the influences of key factors such as the fire time,the mass ratio of drop hammer to column and the axial load ratio on the impact resistance of the column were discussed in detail.In addition,the impact resistances of CFST and SRCFST columns after fire were also compared.The results show that the post-fire SRCFST column exhibits a good impact resistance.Comparing with the normal SRCFST column,the maximum mid-span deflection of the post-fire column with 1 h fire time increases by 17%,and the impact force platform value decreases by 12%due to the loss of flexural stiffness.The mass ratio of the drop hammer to the column has a significant influence on the shape of the time history curve of impact force,and the plateau stage of the curve gradually disappears when decreasing the mass ratio to below 3.The existence of axial load can slightly improve the impact force platform value when the axial compression ratio is less than 0.3.However,the impact resistance of the column significantly declines when the axial compression ratio increases to more than 0.3.Comparing the post-fire CFST columns,the SRCFST columns after fire shows a superior impact resistance with an average reduction of 15%in maximum mid-span deflection and an average improvement of 22%in impact force plateau value.