足尺钢框架结构中楼板火灾行为数值分析

NUMERICAL ANALYSIS OF FIRE BEHAVIOR OF CONCRETE SLABS IN FULL-SCALE STEEL-FRAME STRUCTURE

为研究受火跨位置和数量对结构中混凝土楼板火灾行为影响,基于Vulcan软件,采用厚板单元和梁柱杆单元,结合EC2材料高温本构模型,对钢框架结构中受火顶层楼板(角区格和中区格)和第二层楼板(四区格)的温度和变形进行数值模拟,分析了混凝土膨胀应变对火灾下结构中楼板受火区格变形的影响规律,考察了受火板格薄膜机理、裂缝分布和钢梁内力发展规律。结果表明:楼板温度和变形计算结果与试验结果总体吻合较好,且混凝土膨胀应变对结构中受火区格跨中变形有决定性影响,即膨胀应变取值较大时,计算变形较大;边界条件对受火板格薄膜机理和裂缝分布有决定性影响,且受火板格可分为环型、对边U型和对角U型三种薄膜机理;受火板格附近钢梁弯矩和轴力逐渐增加,且钢梁轴力增加幅度相对较大。

The influence of the position and quantity of fire span on the fire behavior of concrete floor in the structure is studied.Based on Vulcan software,using thick plate element and beam-column element,combined with EC2 material high temperature constitutive model,the temperature and deformation of fire top floor(corner and middle)and second floor(four)in a steel frame structure are simulated numerically.The influence of concrete expansion strain on the deformation of floor slab under fire is analyzed,and the membrane mechanism,crack distribution and internal force development of steel beam are investigated.The results show that:the predicted results of floor temperature and deformation are in a good agreement with the experimental results,and the concrete expansion strain has a decisive influence on the mid-span deformation of the fire zone in the structure,that is,when the expansion strain is larger,the predicted deformation is larger;the boundary conditions have a decisive influence on the membrane mechanism and crack distribution of the heated plate,and the heated plates have three kinds of membrane mechanisms:ring type,opposite-edge U type and diagonal U type.The bending moment and axial force of the steel beam near the heated grid gradually increase,and the increase of the axial force of the steel beam is relatively large.