Ultimate strength of hollow concrete-filled steel tube with lateral opening under axial and uniaxial loads

A concrete-Filled Steel Tube (CFST) is a section composed of concrete and steel together. This type of column has the advantages of both concrete and steel together, and this is what makes this type of column preferred in many construction places that enjoy privacy in terms of implementation and loads placed on them. Where these types of columns are much among the advantages are high strength, fire resistance, and hardness. This type of column has been interesting to many researchers, as it is considered one of the most important elements conceivable in advanced concrete. During this research 12, hollow CFST models with a square cross-section with two layers of steel were studied. Each layer of steel tube has a thickness of 2 mm, the outer and inner steel layer dimensions were (101.6 * 101.6) mm and (50.8 * 50.8) mm respectively. Nine specimens contained a lateral circle service opening which had a diameter (50.8) mm. The space between the two layers was filled with Self-Compacted Concrete (SCC), as this concrete has a lot of wading that makes this concrete suitable for such types of composite columns. Narrow areas that are difficult for normal concrete to reach and the inability to use the manual vibrator during pouring. During this research, two variables' parameters were studied, the first parameter represented by changing the location of the lateral hole under various applied loads to study the effect of the lateral hole under different applied loads (axial and uniaxial load with e/h = 0, 1 and 2) where loads applied at a distance (0, 101.6, and 203.2) mm, respectively, from the center of the column. The second variable is the change in the location of the transverse open during the longitudinal section to know the effect of the difference in the location of the lateral hole on the ultimate strength. Therefore, three lateral hole locations were studied as follows (25, 33.4, and 50) mm, respectively from the bottom length of the column. The presence of lateral hole through the longitudinal section of the columns led to a decrease in the amount of ultimate strength of column where a decrease of models (e/h=0) by (7.22,11.11,15) %, models (e/h=1) was (3.7,18.51,33.34) % and models (e/h=2) was (11.6,16.6,23.3) %. It was noticed decrease in the ultimate strength of the model increase when the location of the lateral hole approaches the center of the column length.