高温下钢筋混凝土异形柱的截面特性

Sectional Properties of Reinforced Concrete Columns with Special-Shaped Cross Section at Elevated Temperature

考察了高温下钢筋混凝土异形柱截面的温度场、广义中性轴位置、极限承载力、极强中心、N-M包络图和M-M包络图的特点,进一步揭示了异形柱的高温受力特性.研究表明:(1)常温下处于轴压状态的等肢T形柱和等肢L形柱,高温下会成为偏压柱;(2)当荷载不是作用在对称主轴上时,异形柱截面的广义中性轴的法线与弯矩作用平面之间的夹角随温度的升高而变化,最大夹角可达到29;°(3)方形柱截面的极强承载力与异形柱截面极强承载力之间的差值总体上随受火时间的增加而逐渐增大,180m in时前者可比后者平均大20%左右;(4)升温过程中等肢T形柱和等肢L形柱截面的极强中心在截面对称轴上发生偏移;(5)异形柱截面大、小偏压的界限偏心距总体上随受火时间的增加而减小.

With the cross section of special-shaped reinforced concrete column subjected to elevated temperature as the research object, this paper investigates the characteristics of its temperature field, the generalized neutral-axis position, the ultimate bearing capacity, the point position corresponding to the maximum bearing capacity as well as the N-M and M-M envelop diagrams, and reveals the bearing property of the column at elevated temperature. The results show that： （a） the axial compression columns with T-shaped and L-shaped cross sections at room temperature change to eccentric ones at elevated temperature; （b） when the load does not act on the symmetry axis, the angle between the normal of sectional generalized neutral axis and the plane exerted by a bending moment varies with the increase of temperature, and the maximum angle at elevated temperature reaching 29°; （c） the differences of ultimate bearing capacity between square and special-shaped cross sections increase with fire-exposure time, the former possibly being about 20% larger than the average of the later after being heated for 180min; （d） the points corresponding to the maximum bearing capacity of T-shaped and L-shaped cross sections with equal limb offset along the sectional symmetry axis during the heating process ; and （e） the limit eccentricity between large and small eccentric compressions of the special-shaped cross section mostly decreases with the increase in fire-exposure time.