Performance of axially restrained concrete encased steel composite columns at elevated temperatures
Performance of axially restrained concrete encased steel composite columns at elevated temperatures
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DOI：
10.1016/j.engstruct.2010.10.019
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发表时间：
2011
影响因子：
5.5
通讯作者：
B. Young;E. Ellobody
中科院分区：
文献类型：
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作者：
B. Young;E. Ellobody
研究了高温下轴心约束外包钢混凝土组合柱的受力性能。提出了一种有效的三维非线性有限元模型，用于分析两端铰轴压柱。在室温下，约束比为组合柱轴向刚度的20%~ 100%。通过高温下轴心约束外包钢混凝土组合柱的试验结果验证了有限元模型的正确性。研究的柱具有不同的横截面尺寸，不同的粗骨料和不同的负载率在火灾期间。有限元模型中考虑了钢筋、混凝土、纵、横向钢筋的非线性材料特性以及混凝土约束在常温和高温下的影响。还考虑了钢截面与混凝土、纵向和横向钢筋以及钢筋与混凝土之间的界面，以模拟粘结性能，并在柱变形期间保持不同部件的轮廓。初始的整体几何缺陷被仔细地包括在模型中。通过有限元模型计算了柱的时间-温度关系、破坏时的变形形态、时间-轴向位移关系、破坏模式和耐火极限，并与试验结果进行了比较。此外，影响轴向约束组合柱的耐火性能和行为的变量，包括不同的轴向约束比，不同的火灾期间的负载比，不同的粗骨料和不同的细长比进行了研究的参数研究。结果表明，轴向约束的组合柱在火灾中的行为不同的无约束列相比，因为典型的“失控”的失败是没有预测的有限元分析。从有限元分析得到的组合柱的耐火极限进行了比较，从欧洲规范4中得到的组合柱在高温下的设计值。结果表明，对于所有轴向约束外包钢混凝土组合柱，除了部分荷载和长细比较大的柱外，EC 4值基本上是保守的。
The structural performance of axially restrained concrete encased steel composite columns at elevated temperatures is investigated in this study. An efficient nonlinear 3-D finite element model was presented for the analysis of the pin-ended axially loaded columns. The restraint ratios varied from 20% to 100% of the axial stiffness of the composite columns at ambient temperature. The finite element model was verified against published test results on axially restrained concrete encased steel composite columns at elevated temperatures. The columns investigated had different cross-sectional dimensions, different coarse aggregates and different load ratios during fire. The nonlinear material properties of steel, concrete, longitudinal and transverse reinforcement bars as well as the effect of concrete confinement at ambient and elevated temperatures were considered in the finite element model. The interface between the steel section and concrete, the longitudinal and transverse reinforcement bars, and the reinforcement bars and concrete were also considered allowing the bond behaviour to be modelled and the different components to retain its profile during the deformation of the column. The initial overall geometric imperfection was carefully included in the model. The time–temperature relationships, deformed shapes at failure, time–axial displacement relationships, failure modes and fire resistances of the columns were evaluated by the finite element model and compared well against test results. Furthermore, the variables that influence the fire resistance and behaviour of the axially restrained composite columns comprising different axial restraint ratios, different load ratios during fire, different coarse aggregates and different slenderness ratios were investigated in a parametric study. It is shown that axially restrained composite columns behave differently in fire compared to the unrestrained columns since the typical “runaway” failure was not predicted from the finite element analysis. The fire resistances of the composite columns obtained from the finite element analysis were compared with the design values obtained from the Eurocode 4 for composite columns at elevated temperatures. It is shown that the EC4 is generally conservative for all the axially restrained concrete encased steel composite columns, except for some columns with higher load and slenderness ratios.