摘要
利用SAFIR程序开展了约束混凝土梁的升降温全过程轴力分析,考察了轴向约束刚度比、截面宽度、全截面配筋率、升温时间等参数对ISO 834标准升降温作用下约束混凝土梁的轴力影响规律,并与单调升温时的相应规律进行了对比;通过对288种工况的计算分析,给出了该类构件轴力比的实用计算方法。研究结果表明:对于轴向和转动约束梁,无论是单调升温还是先升温后降温,轴力比总体都呈现出先逐渐增大而后平缓变化,然后以较大速率降低的趋势,主要区别在于先升温后降温时平缓段的持续时间比单调升温时更长;对于先升温后降温的轴向和转动约束梁,转动约束刚度比、截面高度、梁跨度和荷载比对轴力比影响很小,而轴向约束刚度比和全截面配筋率越大或截面宽度越小,轴力比峰值就越大;考虑到实际工程情况,可近似忽略混凝土保护层厚度变化对轴向和转动约束梁轴力比的影响。
Using the program SAFIR, the influences of some parameters, including axial restraint stiffness ratio, section width, reinforcement ratio, and heating time, etc. on axial forces in restrained concrete beams exposed to ISO 834 standard fire with cooling phase, which compared with those fire without cooling phase were analyzed. Based on the simulation results of 288 cases, a practical calculation method for axial forces in restrained concrete beams subjected to fire with cooling phase was proposed. The results show that for axially-and-rotationally restrained beams in fire with or without cooling phase, the axial force ratio increases gradually first, then varies gently, and finally decreases quickly, but the gentle variation stage related to fire with cooling phase is longer than that without cooling phase; the influences of rotational restraint stiffness ratio, section height, beam span and load ratio on the axial force ratio of axially-and-rotationally restrained beams subjected to fire with cooling phase are limited, while the peak value of the axial force ratio increases with increasing of the axial restraint stiffness ratio and reinforcement ratio or with decreasing of section width; and the effect of concrete cover on the axially-and-rotationally restrained beams can be neglected approximately.
出处
《建筑科学与工程学报》
CAS
2010年第1期12-20,共9页
Journal of Architecture and Civil Engineering
基金
"十一五"国家科技支撑计划项目(2006BAJ03A03-12)
国家自然科学基金重点项目(50738005)
教育部科学技术研究重点项目(108106)
教育部高等学校博士学科点专项科研基金项目(20060561014)
亚热带建筑科学国家重点实验室重点研究项目(2008ZA10)
关键词
钢筋混凝土
约束梁
轴力
升温段
降温段
reinforced concrete
restrained beam
axial force
heating phase
axial force ratio of cooling phase
