火灾与撞击联合作用下钢管混凝土柱力学性能研究

为研究火灾高温与撞击联合作用下钢管混凝土柱的力学性能，基于ABAQUS建立了高温作用下考虑轴力影响的钢管混凝土柱侧向撞击有限元模型。首先，对高温与撞击联合作用下考虑轴力影响的钢管混凝土柱的破坏模式与受力全过程进行了分析，探讨了高温下钢管混凝土柱的抗撞性能与工作机理；其次，重点研究了受火时间、材料强度、含钢率以及撞击能量对抗撞性能的影响，并给出了相关设计建议。研究结果表明:高温与撞击联合作用下，钢管混凝土柱主要发生受弯破坏；受火15 min后，构件抗撞性能明显降低。轴压力对构件抗撞性能产生不利影响，轴压比从0增加到0.2，受火60 min构件抗撞性能下降了7.8%；混凝土强度对高温下钢管混凝土柱抗撞性能有显著影响，受火90 min后，混凝土强度由30 MPa增加到50 MPa，构件抗撞性能提高约85%；外钢管强度与含钢率对高温下抗撞性能影响不大。

Mechanical behavior of concrete-filled steel tubular columns subjected to coupled fire and impact loading

To investigate the mechanical behavior of concrete-filled steel tubular (CFST) columns under coupled fire and impact loads, a finite element (FE) model was established with ABAQUS software to describe the impact resistance of axial-loaded CFST columns under elevated temperatures. The commonly used ISO 834 standard fire and rigid-body impact were employed to model the fire and impact loads, respectively. In the model, the static implicit and dynamic explicit analysis were coupled by using “Restart” and “Import” commands and the strain-rate effect was taken into account. The numerical model was validated by comparing the impact force time history curves obtained from relevant tests at different temperatures. Based on the validated FE models, the impact responses of axial-loaded CFST columns under coupled fire and impact loads were analyzed. Then, the influences of the fire duration, concrete and steel strength, steel ratio and impact energy on the mechanical behavior were investigated, and some design suggestions were proposed. The platform impact force and the maximum mid-span deflection were employed to quantitatively analyze the impact resistance of the CFST columns. The results show that the CFST column presents a flexural failure mode when it is exposed to coupled fire and impact loads. With the increase of fire duration, the proportion of energy consumption of the steel tube reduces. The impact resistance of the column decreases obviously when it is subjected to fire for a duration of 15 min. Axial compression load has an adverse influence on the impact performance. When the axial-load level increases from 0 to 0.2, the platform value of the impact force reduces by 7.8% at a fire duration of 60 min. The concrete strength has a significant effect on the impact resistance. When the cubic compressive strength of the concrete increases from 30 MPa to 50 MPa, the impact resistance is improved by approximately 85% when the fire lasts for 90 min. The steel ratio and steel strength have marginal influences on the impact resistance of the CFST columns at elevated temperatures.