外包钢加固火灾后钢筋混凝土柱的试验研究

通过3根外包角钢加固的ISO834标准火灾作用后钢筋混凝土柱的受力性能试验以及3根未加固的ISO834标准火灾作用后钢筋混凝土柱和3 根常温下钢筋混凝土柱的对比试验,研究了火灾后钢筋混凝土柱的性能以及外包钢加固火灾后钢筋混凝土柱的有效性。试验结果表明:火灾后试件的刚度退化显著,在该文的试验参数和升温条件下,从开始加载到80%极限荷载的不同加载阶段,轴压柱的轴向刚度只有常温下轴向刚度的0.22~0.37,偏压柱的弯曲刚度只有常温下弯曲刚度的0.13~0.18;外包角钢加固对火灾后试件的刚度修复有一定的效果,不同荷载水平下,加固后轴压试件的轴向刚度与常温下试件刚度的比值在0.41~0.89 之间,偏压试件的弯曲刚度与常温下试件刚度的比值在0.33~0.91 之间。火灾后试件承载能力退化严重,在该文的试验参数和升温条件下,火灾后试件的承载力水平只有常温下的0.25~0.37;利用外包角钢对火灾后的试件进行加固,能将试件的承载力提高至试件未受火时大致相当的水平,加固后试件的承载力与未受火试件承载力的比值在0.97~1.06 之间,外包钢加固对火灾后试件承载能力的修复效果十分显著。

EXPERIMENTAL STUDY ON REINFORCED CONCRETE COLUMNS STRENGTHENED WITH EXTERNAL STEEL CLAD AFTER EXPOSURE TO FIRE

By the tests on three reinforced concrete columns strengthened with external steel clad after exposure to ISO834 standard fire and three reinforced concrete columns without strengthening after exposure to ISO834 standard fire as well as three reinforced concrete columns without exposure to fire,the mechanical properties of reinforced concrete columns after exposure to ISO834 standard fire as well as the strengthening effectiveness of external steel clad are experimentally studied.Test results shows that after exposed to fire,the rigidity and load bearing capacity of specimens are all declined sharply compared with that at normal temperature without exposure to fire.In various loading stages from the initial loading to 80% ultimate strength,the ratio of axial rigidity of concentric columns after exposure to fire and at normal temperature was ranged from 0.22 to 0.37,the ratio of flexural rigidity of eccentric columns after exposure to fire and at normal temperature was ranged from 0.14 to 0.18,and the ratio of the load bearing capacity of specimens after exposure to fire and at normal temperature was ranged from 0.25 to 0.37.But the rigidity and load bearing capacity can be increased to a certain extent when strengthened with external steel clad.The ratio of axial rigidity of concentric columns strengthened with external steel clad and at normal temperature was ranged from 0.41 to 0.89,the ratio of flexural rigidity of eccentric columns strengthened with external steel clad and at normal temperature was ranged from 0.33 to 0.91,and the ratio of the load bearing capacity of specimens strengthened with external steel clad and at normal temperature was ranged from 0.97 to 1.06.The strengthening effect of external steel clad on load bearing capacity of reinforced concrete columns after exposure to fire is remarkable.