电力火灾后圆端形不锈钢管混凝土柱轴压性能研究

Axial Compressive Behavior of Round-Ended Concrete-Filled Stainless Steel Tubular Stub Columns After Electric Power Fire

进行了14根电力火灾后圆端形不锈钢管混凝土短柱的轴压试验,分析截面高宽比、受火时间和含钢率对其火灾后剩余承载力的影响。试验表明:该类短柱的破坏模态均为局部屈曲、焊缝开裂和混凝土被压碎;试件的剩余承载力随着受火时间或高宽比的增加而降低,受火120 min后该类试件的承载力降低了7.8%~13.9%。接着建立了有限元模型,该模型可很好地模拟实测结果。基于有限元模型开展了理论分析,结果表明初始荷载对该类组合柱的剩余承载力影响较小。参数分析表明当混凝土强度从30 MPa增加到90 MPa时,其强度折减系数降低了15.8%;当截面周长从1 228 mm增加到4 913 mm时,其强度折减系数提高了20.5%;当受火时间从0 min增加到180 min时,其强度折减系数降低了8%;但含钢率、高宽比和钢材强度对其强度折减的影响较小。最后给出了电力火灾后圆端形不锈钢管混凝土短柱的剩余承载力的设计方法。

Axial compressive tests of 14 round-ended concrete-filled stainless steel tubular(CFSST)stub columns after the electric power fire were carried out.Effects of the height-to-width ratio,fire exposure time,and steel ratio on the residual strength of the round-ended CFSST stub column after the fire were analyzed.The test shows that the failure modes of this type of short column are local buckling,weld cracking,and concrete crushing.With the increase in fire exposure time or height-to-width ratio,the residual strength of the specimen will decrease.The bearing capacity of the round-ended CFSST specimen was reduced by 7.8%-13.9%after 120 min of fire.The finite element(FE)model was then established,and the model can simulate the measured results well.A theoretical analysis based on the FE model was carried out,which shows that the initial load has a small effect on the residual strength of this compositecolumn. Parametric analysis shows that when the strength of concrete increases from 30 MPa to 90 MPa,the strengthreduction coefficient of column decreases by 15.8%. When the cross-sectional circumference increases from 1 228 mmto 4 913 mm,the strength reduction coefficient of column increases by 20.5%. When the fire exposure time increasesfrom 0 min to 180 min,the strength reduction coefficient of column is reduced by 8%. The strength reductioncoefficient of column is less affected by the steel ratio,height-to-width ratio,and steel strength. Finally,a designmethod for the residual strength of the CFSST stub column after the electric power fire was proposed.