极地低温下GFRP管-混凝土短柱循环轴压性能

Cyclic Axial Compression Behavior of Concrete-Filled GFRP Tube Stub Columns at Arctic Low Temperatures

为了推广GFRP管-混凝土柱在极地基础设施建设中的应用,开展了14个GFRP管-混凝土短柱在极地低温环境下的轴压试验,主要研究参数为温度和GFRP管的径厚比.试验结果包括试验现象与破坏模式、荷载-应变曲线、塑性应变、刚度退化和耗能能力等.试验结果表明:所有试件破坏模式均为GFRP管环向撕裂,发生脆性破坏;单调加载下组合柱的荷载-应变曲线与循环加载下组合柱的荷载-应变曲线的包络线基本吻合,但循环荷载作用下组合柱的极限荷载和峰值应变略低于单调荷载作用下的组合柱;随着温度的降低,组合柱的极限荷载逐渐增大,峰值应变逐渐减小;循环荷载作用下,GFRP管-混凝土短柱的塑性应变与卸载点应变呈线性关系,且温度影响不大,混凝土强度是影响两者关系的主要因素;随着竖向应变的增大,GFRP管-混凝土短柱的刚度逐渐降低,且降低速率逐渐减小;GFRP管-混凝土短柱的等效黏滞阻尼系数逐渐增大,且增大速率逐渐降低.综合以上分析,采用“最远点”法确定GFRP管-混凝土短柱的名义屈服点,并提出了GFRP管-混凝土短柱在低温下的设计方法和设计流程,分别从强度、变形和GFRP管利用率3个角度来衡量试件设计的安全储备,为GFRP管-混凝土短柱在极地低温环境下的安全设计提供参考,保障其在极地和寒区环境的服役安全.

In order to promote the application of concrete-filled glass fiber-reinforced polymer(GFRP)tube(CFFT)stub columns in the infrastructure construction in the Arctic,a total of 14 axial compression experiment were carried out on CFFT stub columns at Arctic temperatures.The primary variables of interest were temperature(T)and the diameter-to-thickness ratio(D/t)of the GFRP tube.The results consist of experimental observations and analysis of the failure modes,load-strain curves,plastic strain,stiffness degradation,and energy dissipation capacity.The experimental results show that the failure mode for all specimens was the brittle failure of the GFRP tube via hoop rupture.Although the load-strain curves for the CFFT stub columns under monotonic loading are consistent with the envelopes of load-strain curves under cyclic loading,the ultimate load and peak strains of the composite columns under cyclic loading are slightly lower than those under monotonic loading.Furthermore,as the temperature decreased,the ultimate compressive load for the CFFT stub columns gradually increased,and the peak strain decreased.The plastic strain in the CFFT stub column was observed to vary linearly with the strain at the unloading point under cyclic loading.The temperature has little effect on this relationship,and concrete strength is the main influencing factor.The stiffness of CFFT stub columns decreases,and the equivalent viscous damping coefficient of CFFT stub columns gradually increases,each at a gradually decreasing rate with an increase in the vertical strain.Based on the above analysis,the“farthest point”method was used to determine the nominal yield point of the CFFT stub columns,and the design method and design process of CFFT stub columns at Arctic low temperatures were proposed,which consider safety reserve from three aspects of strength,deformation and GFRP tube utilization.The proposed design methods could provide a reference for the design of CFFT stub columns and ensure their service safety in the polar and cold regions.