火灾后十字形型钢混凝土柱双向偏心受压力学性能试验研究

Experimental study on the mechanical properties of cruciform steel reinforced concrete column with two-dimensional eccentric compression after fire

探究双向偏心荷载对火灾后十字形型钢混凝土柱的影响,对火灾后1h的十字柱进行静力荷载试验。通过对极限承载力、试件的破坏形态、异形柱的侧向位移和混凝土与槽钢之间的粘结滑移的分析,讨论十字柱在不同试验偏心距下的力学行为。试验表明:①十字柱的破坏均经历了弹性阶段、带裂缝工作阶段和破坏阶段;②槽钢和混凝土之间的粘结滑移量很小,型钢和混凝土能够继续共同工作;③当沿着45°荷载角进行加载试验时,十字柱会发生双向弯曲;④偏心距的增大使中性轴的位置由受拉区向受压区移动,但中性轴的位置始终与弯矩作用面相互垂直;⑤平截面假定在十字形型钢混凝土异形柱截面依然适用;⑥当荷载角为45°时异形柱界限偏心距e为190mm。

Four cross-special-shaped steel reinforced concrete columns with different loading methods are tested to explore eccentricities effects in the compression behavior. Columns are exposed to fire for 1 hour. The experimental data is analyzed in terms of damage mode,bearing capacity,loading-displacement curve and bonding-slip curve.The study show that: ①there are three stages in destruction process: elastic stage,working with cracks stage and destruction stage;②the bond-slip between the concrete and channel is small,revealing that channel and concrete can still work together;③when the load angle of 45 °,the cruciform column will be two-way bending;④as the eccentricity increasing,the location of neutral axle shift from the tensile area to the compressed area,however,the position of the neutral axis is still perpendicular to winding surface;⑤ plane cross-section assumption still suits cross-section of the cruciform steel reinforced concrete columns;⑥when loading at 45°,the limit of the eccentricity is about 190 mm.