基于升降温全过程的PEC柱耐火性能指标研究

发布时间：2018-03-20 19:04

  本文选题：PEC柱　切入点：升降温　出处：《苏州科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：自然火灾包含升温和降温两个阶段,其中降温段对结构的耐火性能有很大影响。目前构件的耐火极限大多基于标准升温条件,与实际结构经历火灾的过程存在一定差异。试验和分析表明PEC柱在降温段也可能产生破坏。当外界温度场处于降温阶段时,由于混凝土材料的热惰性,导致结构内部温度场较外部出现温度滞后的现象,结构内部可能在继续升温,使得结构在火灾降温段的承载能力进一步降低,最终可能导致结构在降温段发生破坏。为全面分析PEC柱在升降温全过程的耐火性能,本文基于火灾全过程分析,重点对降温段可能的破坏进行了研究,主要的研究工作如下:(1)应用ABAQUS软件建立了考虑火灾升降温全过程的局部填充混凝土(Partially Encased Concrete,简称PEC)柱耐火性能分析有限元模型,并采用已有的高温下及高温后柱的试验数据验证了模型的正确性。(2)考虑降温段材料属性较升温段有所恢复的特点,分别计算了钢材和混凝土在升温段和降温段的材料属性。(3)定义场变量,编写能够实现材料不同温度阶段的材料属性的自动识别和转换的子程序,实现升降温全过程的计算过程。(4)定义并分析了自然火灾下的耐火性能指标(duration of the heating phase,简称DHP),利用验证后的模型分析了PEC柱在全过程火灾下可能出现的延迟破坏现象。(5)分别考虑荷载比、截面尺寸、长细比、混凝土强度、截面配筋率等五个因素对PEC柱DHP值的影响:火灾荷载比和截面长细比对PEC柱的耐火性能影响较大;截面尺寸对DHP的影响变现为两个过程:当荷载比较小时,DHP随截面尺寸的增大而增大,当荷载比较大时,截面尺寸对DHP的影响变小,DHP不随截面尺寸产生明显的变化;混凝土强度和截面配筋率对耐火性能的影响不大。并以计算的数据为基础拟合出包含这些因素的DHP实用计算公式。
[Abstract]:The natural fire includes two stages of heating and cooling, in which the cooling section has a great influence on the fire resistance of the structure. At present, the fire resistance limit of the components is mostly based on the standard heating conditions. The test and analysis show that the PEC column may also be damaged in the cooling section. When the external temperature field is in the cooling stage, due to the thermal inertia of the concrete material, As a result of the phenomenon that the temperature field inside the structure lags behind the external temperature field, the internal temperature field of the structure may continue to heat up, which further reduces the bearing capacity of the structure in the fire cooling section. In order to comprehensively analyze the fire resistance of PEC columns in the whole process of rising and cooling, based on the analysis of the whole process of fire, the possible damage of the cooling section is studied in this paper. The main research work is as follows: (1) using ABAQUS software, a finite element model for analyzing the fire resistance of partially filled Encased reinforced concrete columns considering the whole process of fire rising and cooling is established. The validity of the model is verified by the existing experimental data at high temperature and the post column at high temperature. The field variables are defined by calculating the material properties of steel and concrete in the heating and cooling stages, respectively, and a subroutine that can realize the automatic identification and conversion of the material properties at different temperature stages is written. This paper defines and analyzes the duration of the heating phase under natural fire, and analyzes the possible delay damage of PEC column under the whole process of fire by using the verified model. Take into account the load ratio, The influence of five factors, such as section size, aspect ratio, concrete strength and section reinforcement ratio, on the DHP value of PEC column is as follows: the fire load ratio and section length ratio have great influence on the fire resistance of PEC column; The effect of cross section size on DHP is realized in two processes: when the load ratio is small, it increases with the increase of cross section size, and when the load is large, the effect of section size on DHP does not change obviously with section size; The concrete strength and section reinforcement ratio have little effect on the fire resistance. Based on the calculated data, the practical DHP formula containing these factors is fitted.
【学位授予单位】：苏州科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU398.9
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本文编号：1640404