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Rp. Behavior of Steel Column of Sandwich Cross Section with Opening Under Concentric Loading pdf.

The development in the science of construction and the increase in the height of the buildings showed the need for structural members with higher bearing capacity with less dimensions. Concrete-filled double steel tubular columns (CFDST) are an example of this development in the past twenty years.
CFDST columns have many advantages, such as high bearing capacity (more elevated than those of reinforced concrete columns (RCC) as well as higher fire resistance),in this research, the following factors were taken into consideration: the type of concrete used in this type of column, normal concrete (NC) or plastic fiber concrete (PFC), the number of openings in one model, and whether these openings are from one side or two opposite sides. The researchers made (14) models, (seven) filled models with normal concrete and (seven) with plastic fiber concrete and compared the experimental results of (14) models with the results of similar finite element models obtained from the Abaqus software for accuracy. Columns models were tested using a central load, and the axial load was applied incrementally. The fourteen test samples were examined with different variables in the parametric study. The properties of normal concrete and plastic fiber concrete are necessary for the numerical analysis to provide working conditions similar to the laboratories.
Using PFC instead of NC resulted in a 17.80 percent increase in the column’s bearing capacity compared to NC, and the larger the number of opneings on one side, the lower the column’s bearing capacity, with a ratio ranging from 14.03 % to 19.23 %. Moreover, making opneings through opposite sides weakens the columns by 14.81% – 28.00%. When using the specified elements, the results were less than those in the experimental study, where the percentage ranged in the normal concrete models from 0-12.22%, while in the plastic fiber concrete 1.29%-10.52%.
The rate of difference between the results of laboratory models and numerical models in normal concrete was (-7.40 ), while in concrete models made of plastic fibers the rate was (-5.73) and therefore there was convergence between the two studies, so it is possible to rely on finite elements to form more complex models.