外包UHPC钢管混凝土叠合中长柱偏压性能试验研究OA北大核心CSTPCD

To study the eccentric compression performance of UHPC-encased concrete-filled steel tube composite medium-long columns(referred to as'UC-CFST medium-long columns'),the eccentricity(0.52 and 1.04)and slenderness ratio(7.22-44.74)were selected as the main parameters,and a total of 18 UC-CFST medium-long column specimens were tested under eccentric compression loads,and the failure mode and eccentric compression performance index were obtained.The results reveal that with the increase of eccentricity and slenderness ratio,the failure mode of UC-CFST medium-long columns changes from material strength failure to instability failure,and the bearing capacity of specimens is significantly reduced.The specimens with a slenderness ratio less than or equal to 21.03 exhibit obvious material strength failure characteristics.The steel bars and steel tubes on the near load side of the small eccentric compression specimens first undergo compression yielding,while the UHPC outer layer in the tensile zone of the large eccentric compression specimens cracks,and the steel tubes yield in tension.When the peak load is reached,the UHPC in the compressive zone of the large and small eccentric compression specimens is crushed.The specimens with a slenderness ratio greater than 35.26 are subjected to elastic-plastic instability failure,while a specimen with a slenderness ratio between 21.03 and 35.26 is subjected to plastic instability failure.Finally,the applicability of the bending moment amplification factor method for concrete-encased CFST columns proposed in GB/T 51446-2021'Technical standard for concrete-filled steel tubular hybrid structures'to calculate the eccentric compression bearing capacity of UC-CFST medium-long columns is discussed.It is found that this method will significantly overestimate the eccentric compression bearing capacity of UC-CFST medium-long columns.Therefore,combined with the mechanical characteristics of UC-CFST medium-long columns,an improved moment amplification factor method which can be used to calculate the eccentric compression bearing capacity of UC-CFST medium-long columns is derived in this paper.The calculation results correspond well with the experimental results.