Experimental Study on Axial Compression Behavior of Phosphogypsum-Filled Thin-Walled Square Steel Tube Stub Columns
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摘要: 提出了一种新型的冷弯薄壁型钢墙架柱——磷石膏填充薄壁方钢管短柱,它是由磷石膏填充到薄壁方钢管中形成的组合构件,满足冷弯薄壁型钢结构“轻质”的特点。在构件中,核心磷石膏的支撑作用可延缓薄壁方钢管的局部屈曲,钢管的约束作用可提升核心磷石膏的强度,从而充分发挥两种材料的力学性能,提升构件的轴压承载力。为了探究磷石膏填充薄壁方钢管短柱的轴压性能,以薄壁方钢管内是否填充磷石膏、磷石膏水灰比、空心率、薄壁方钢管壁厚为试验参数,设计并制作了3个空钢管试件与24个磷石膏填充薄壁方钢管短柱试件,对其开展轴压试验,研究了磷石膏填充薄壁方钢管短柱的力学性能,分析了各试件的破坏模式,荷载-变形曲线、荷载-应变曲线及轴压承载力。研究结果表明:空钢管试件呈局部屈曲破坏模式,填充试件呈腰鼓型破坏模式,核心磷石膏的支撑作用不仅可延缓薄壁钢管的局部屈曲,而且可改变试件的破坏模式,与空钢管试件相比,填充试件的轴压承载力提升了65.52%;试件空心率的变化对试件承载力的影响较为显著,这是由于含水率对磷石膏自身强度影响较大,改变试件空心率的大小会导致磷石膏含水率出现差异进而影响试件的承载力;填充磷石膏水灰比降低时,试件的轴压承载力得到一定程度提升,当磷石膏的水灰比由0.9下降到0.8、0.7时,试件的承载力分别提升了6.36%、12.42%;增加薄壁钢管壁厚,可显著提升试件的轴压性能,当钢管壁厚由0.85 mm增加到1.48,1.93 mm时,试件的轴压承载力分别提升了115.36%,176.55%,提升效果明显。基于叠加理论推导了空钢管试件与填充试件的轴压承载力计算公式,结果表明:所推导的计算公式有较好的计算精度,可较为准确地预测试件的轴压承载力。基于上述研究结果,磷石膏填充薄壁方钢管短柱具有良好的轴压力学性能,其应用前景广阔,该类构件的研发也可为磷石膏的综合应用提供一条切实可行的路径。Abstract: A new type of cold-formed thin-walled steel wall stud called phosphogypsum-filled thin-walled square steel tube(PFST) stud was proposed in this paper. The stud consists of a square steel tube and phosphogypsum inside, which meets the characteristics of lightweight. In this kind of stud, the supporting effect of the core phosphogypsum can delay the local buckling of the thin-walled square steel tube, and the restraint effect of the thin-walled square steel tube can improve the strength of the core phosphogypsum. Hence, the mechanical properties of the two materials can be fully developed and the axial bearing capacity of the stud can be effectively improved. To study the axial compression performance of PFST studs, 3 hollow steel tubes(HST) and 24 PFST studs were designed and fabricated with consideration of the section with or without phosphogypsum, water-solid ratio, hollow ratio and wall thickness of steel tube. Through axial loading tests, the failure mode, load-deformation curve, load-strain curve, and bearing capacity were analyzed. The test results indicated that the hollow steel tube stud presented a failure mode of local buckling. For the studs filled with phosphogypsum, the “drum shape” failure mode was observed. It is evidenced that the phosphogypsum can delay the local buckling of the steel tube, and change the failure mode of the stud. Compared with the hollow studs, the axial bearing capacity of the studs filled with phosphogypsum increased by 65.52%. The hollowness ratio has a significant impact on the bearing capacity of the stud, due to the fact that the water content of phosphogypsum varies with the hollowness ratio, which finally affects the strength of the infill material. The axial bearing capacity of the stud improved with decrease of water-solid ratio of phosphogypsum. When the water-solid ratio decreased from 0.9 to 0.8 and 0.7, the bearing capacity increased by 6.36% and 12.42%, respectively. Increasing the thickness of the steel tube can significantly improve the axial compression performance of the stud. When the thickness increased from 0.85 mm to 1.48 mm and 1.93 mm, the axial bearing capacity of the stud increased by 115.36% and 176.55%, respectively. Based on the superposition theory, the axial bearing capacity calculations of the HST and PFST studs were deduced. The results showed that the calculated formula has good accuracy, which can accurately predict the axial bearing capacity of the stud. In conclusion, the PFST stud has good mechanical properties and broad, wide application prospects. This kind of stud can also provide a feasible path for applying phosphogypsum.
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