بررسی پارامتریک ظرفیت باربری محوری ستون های استوانه ای در حضور آسیب از نوع قرشدگی

The Presence of defects in the compressive structural members may reduce their load-carrying capacity to a large extent. These defects may be in the form of cracks, corrosion, perforation, or dents existing on the smooth surface of the member. In most cases, the impact of an external object is the main cause of these damages. For example, tubular sections of offshore platforms which are mostly under axial loads, may be damaged with the collision of supply vessels. Similarly, the columns of bridges and buildings, may be hit by heavy moving vehicles. The Existence of the mentioned defects in compressive members with circular cross-sections may cause premature failure of these structural elements due to local buckling followed by the memberchr('39')s overall instability. Hence, the effect of these damages on the buckling strength of tubular columns, and the effect of different influencing parameters should be studied in depth. This study presents a parametric investigation on the axial load-carrying capacity of cylindrical columns damaged by a spherical indenter. For this purpose, the numerical models were generated in general purpose finite element software "Abaqus" and verified against results of two axial compression tests on intact and damaged thin-walled cylinders. The studied parameters included depth of the damage, shell slenderness ratio, location of the damage, length of the axial member, and radius of the indenter object. The analysis results showed that, the depth of the damage, shell slenderness ratio, and the damage location were the parameters affecting the buckling capacity of the damaged cylinders under axial load. The increase in damage depth or shell slenderness ratio decreased the buckling load of the member. On the contrary, the buckled shape of the members with different damage depth values or shell slenderness ratios was almost identical. The post-buckling behavior of the studied specimens was affected by the shell slenderness ratio, the damage location, and the length of the compressive member. As the shell slenderness ratio or length of the member increased, the member strength in the post-buckling range experienced more rapid reduction. Also, as the damage became closer to the one of supporting ends, the buckling ring at the farther support vanished while the buckling ring at the closer support became more critical, resulting in an increased strength reduction. The radius of the indenter object had a negligible effect on the buckling capacity and post-buckling behavior of the specimens. For samples with the same damage depth and different radius of the indenter object, the damage profile difference was very small. This small difference vanished during the buckling process, and the final deformation profile for the samples became almost identical. Finally, a regression analysis was conducted on the results of analyses considering the effect of different parameters, and two predictive equations were proposed to determine the buckling and residual capacity of the studied members as functions of influencing parameters. The evaluations performed to estimate the accuracy of the proposed equations showed that they have good accuracy and provide reliable predictions for design re-checking of damaged cylindrical members subjected to axial compression.