Demolished concrete lumps (DCLs) have been introduced as partial coarse aggregate replacements in concrete casting process. However, limited research works have been performed on sensitive behaviors of slenderness concrete filled steel tube (CFST) filled with fresh concrete (FC) and DCLs under axial compression. Based on the previous research work, orthogonal design method was employed to investigate further mechanical performance. Experimental studied involved 12 columns of CFST with diameter 159 mm and lengths 2000, 2200 and 2400 mm. The ratios of the diameter-to-thickness (D/t) were 79, 53 and 40, while replacement ratios of FC in DCLs were 0%, 20%, 40% and 60%, respectively. The results of experimental tests of the CFST filled with DCLs and FC indicated that ratio of slenderness have a greatest effect on the bearing capacity of slender column under axial compression, followed by the D/t ratio, and the weakest effect was observed for DCLs replacement. DCLs slightly affected the mechanical performances of slender CFST columns, so the ultimate bearing capacity of CFST can ignore the influence of replacement rate of DCLs. To calculate CFST slender column ultimate bearing capacity with DCLs, design codes AIJ, AISC, CE4, CECS 28: 2012, DL/T 5085-1999 were used to predicted ultimate bearing capacity, found that the code CECS 28:2012 was employed for the calculation of slender CFST DCLs filled column bearing capacity under axial compression being comparable accuracy.
In order to analyze the commuting behavior of residents more accurately, the quantitative family heterogeneity is integrated into commuting travel choice behavior analysis. Based on the data of residents' travel survey in Xi'an, MNL models with neglecting household heterogeneity and Multi-Level MNL models with household heterogeneity are established respectively, and the parameters are calibrated. The model calibration results show that 19% of the residents' commuting behavior selection is caused by household heterogeneity. Household heterogeneity cannot be ignored. Compared with the multi-layer MNL model, the MNL model overestimates the extent to which some explanatory variables affect the explanatory variables. At the same time, the analysis proves that having a car in the family is one of the key factors in inducing car travel. The transfer of bus and bicycle modes of transportation is highly accepted by commuters. We can increase the share of buses and reduce the use of cars by encouraging passengers to use bus and bicycle transfers.
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