Experimental study on cold-formed steel lipped channel medium-long columns strengthened longitudinally by steel strips or steel bars

Abstract

Based on the existing methods of reinforcing cold-formed steel lipped channel column, this paper proposed that reinforced the cold-formed steel lipped channel column longitudinally with steel strips or steel bars for the first time. In order to study the influence of section forms and initial stress ratio on axial compression behavior of columns, a series of pin-pin ends axial compression tests were conducted. The experiment specimens contained 20 concentrically loaded specimens with two cross-section shapes, four initial stress ratios, respectively. It was shown that when reinforcing column longitudinally with the reinforcement, under axial compression, the ultimate bearing capacity of the specimens could significantly increase with little change in the quantity of steel. Moreover, the reinforcing effect of the column decreased linearly with an increase in the initial stress ratio (β) of the load-strengthened specimens. Here, unloading or partial unloading reinforcement was recommended, and the initial stress ratio should be lower than 0.3. Finally, the experimental results were compared with the calculation results for the axial bearing capacities of the column based on the current Chinese standard (GB50018-2002) and North American standard (AISI). It indicated that for the section prone to local-global interactive buckling, the result calculated by GB50018-2002 is more accurate, but has a large deviation in calculating the section prone to distortional buckling. Results of direct strength method of AISI are the opposite to the result of GB50018-2002.