外套方钢管夹层混凝土加固方CFST柱压弯承载力计算方法

Calculation Method for the Compressionbending Capacity of Square Concretefilled Steel Tube (CFST) columns with Square Steel Jacket and Sandwich Concrete Reinforcement

摘要:

为研究外套方钢管夹层混凝土加固方钢管混凝土（CFST）柱的压弯承载力，进行3个原CFST柱和7个外套方钢管夹层混凝土加固方CFST柱（组合加固柱）试件的偏压试验，分析了试件的破坏形态和荷载—跨中挠度曲线。在试验基础上，通过纤维模型法对258个组合加固柱进行参数分析，分析了夹层混凝土强度、外套钢管厚度和屈服强度对组合加固柱N/N_u -M/M_u 曲线的影响。研究结果表明：原CFST柱和组合加固柱的破坏形态基本一致， 均为典型的弯曲型破坏，组合加固柱加固部分与原CFST柱变形协调良好；夹层混凝土强度的提高、外套钢管厚度和屈服强度的降低使试件N/N_u -M/M_u 曲线呈现外凸趋势；在这些因素当中，夹层混凝土强度对平衡点位置影响效果最显著，钢管厚度和屈服强度对平衡点位置影响不大。基于试验和数值模拟结果，提出了组合加固柱压弯承载力计算方法。通过公式得到的压弯承载力计算值与试验值、纤维模型法模拟值的误差均在10%以内，表明计算方法可准确预测外套方钢管夹层混凝土加固方CFST柱压弯承载力，为工程应用提供参考。

Abstract:

To investigate the compression-bending capacities of square concrete-filled steel tube (CFST) column reinforced with square steel jacket and sandwich concrete (composite reinforced columns), a series of eccentric compression tests were conducted on three original CFST columns and seven composite reinforced columns. The failure modes and load-midspan deflection curves of the specimens were analyzed. Based on the experiments, a parameter analysis was conducted on 258 composite reinforced columns using the fiber model method. The influence of the strength of the sandwich concrete, the thickness of the steel jacket, and the yield strength on the N/N_u-M/M_u curves of the composite reinforced columns was investigated. The research results indicated that the failure modes of the original CFST columns and composite reinforced columns were essentially consistent, both exhibiting typical bending-type failure. The deformation of the reinforced part of the composite columns coordinated well with the original CFST column. The increase in the strength of the sandwich concrete, and the decrease in the thickness of the steel jacket and yield strength caused the N/N_u-M/M_u curves to exhibit a convex trend. Among these factors, the strength of the sandwich concrete had the most significant effect on the equilibrium point position, while the thickness of the steel jacket and the yield strength had little impact on the equilibrium point position. Based on the experimental and numerical simulation results, a calculation method for the compression-bending capacities of the composite reinforced columns was proposed. The calculation results obtained from the formula showed an error within 10% when compared to the experimental and fiber model simulation results, indicating that the calculation method can accurately predict the compression-bending capacity of square steel jacket and sandwich concrete-reinforced square CFST columns, providing a reference for engineering applications.