考虑有效混凝土强度的中空夹层钢管混凝土短柱轴压性能研究

STUDY ON AXIAL COMPRESSIVE BEHAVIOR OF CONCRETE-FILLED DOUBLE SKIN STEEL TUBULAR SHORT COLUMNS CONSIDERING EFFECTIVE CONCRETE STRENGTH

随着混凝土强度的提高,因为混凝土的脆性导致其强度折减而降低利用效率。然而,现存的中空夹层钢管混凝土(CFDST)柱数值分析模型并没有考虑混凝土强度的折减效应,导致这些模型在分析高强度混凝土填充CFDST柱的性能时出现较大的离散性,从而影响实际工程设计。为了更加有效和准确地分析CFDST柱的力学性能,建立了考虑有效混凝土强度的CFDST轴压短柱纤维单元分析模型,同时,一个考虑混凝土脆性对混凝土强度影响的强度折减系数被引入在该模型中。进一步,通过对比笔者前期试验结果和收集的试验数据,以及现有的纤维单元分析模型,验证了该文提出的纤维单元分析模型具有较高的预测精度。基于验证的纤维单元分析模型,研究了各柱的参数对CFDST柱轴压性能的影响,结果发现:混凝土强度、空心率、外钢管屈服强度和外(内)钢管径厚比影响CFDST柱的承载力和延性,而内钢管屈服强度仅影响CFDST柱的承载力而对延性几乎没有影响。最后,基于试验和数值分析结果,提出了CFDST柱轴压承载力计算公式,并与试验和数值结果吻合较好。

With the improvement of concrete strength,its utilization efficiency is reduced due to the strength reduction caused by the brittleness of concrete.However,existing numerical analysis models of concrete-filled double-skin steel tubular(CFDST)columns did not consider the reduction effect of concrete strength,which leads to large discreteness in performance analysis of CFDST columns filled with higher strength concrete,thus affecting the actual engineering design.In order to analyze the mechanical properties of CFDST columns more effectively and accurately,the fiber element analysis model of axially loaded CFDST short columns considering the effective concrete strength was established.Meanwhile,a strength reduction coefficient considering the effect of concrete brittleness on the concrete strength was introduced into this model.Further,by comparing the author’s previous test results and collected test data,as well as the existing fiber element analysis models,it was found that the proposed fiber element analysis model has a higher prediction accuracy.Based on the verified fiber element analysis model,the effects of column parameters on the axial compression performance of CFDST columns were studied.The results show that:the concrete strength,hollow ratio,yield strength of outer steel tube and diameterto-thickness ratio of outer(inner)steel tube affect the carrying capacity and ductility of CFDST columns,while the yield strength of inner steel tube only affects the carrying capacity of CFDST columns and has little effect on the column’s ductility.Finally,based on the experimental and numerical results,a formula for calculating the axial carrying capacity of CFDST columns was proposed,which is in good agreement with the experimental and numerical results.