رفتار اتصال های لوله‌یی x شکل مقاوم شده با حلقه خارجی تحت بار محوری فشاری

در پژوهش حاضر، اثر سخت‌کننده‌ی حلقوی خارجی در مقاومت نهایی اتصال‌های لوله‌یی x شکل تحت بار فشاری مطالعه شده است. برای این هدف، ابتدا مدل عددی ساخته و دقت آن با نتایج آزمایشگاهی مقایسه شده است. سپس، 117 مدل المان محدود جهت بررسی پارامتریک مشخصات هندسی اتصال و سخت‌کننده‌ی حلقوی ساخته شدند. در مدل‌های عددی مذکور، اثر غیرخطی هندسه و مصالح لحاظ شده است. همچنین، جوش متصل‌کننده‌ی اعضاء فرعی به عضو اصلی مدل‌سازی شده است. نتایج نشان داده است که سخت‌کننده‌ی حلقوی خارجی می‌تواند مقاومت نهایی اتصال را تا %367 افزایش دهد.علی‌رغم اثر محسوس سخت‌کننده در مقاومت نهایی اتصال، تاکنون هیچ رابطه‌یی جهت محاسبه‌ی مقاومت نهایی اتصال‌های x شکل با سخت‌کننده‌ی حلقوی خارجی استخراج نشده است؛ بنابراین، پس از انجام مطالعات پارامتریک در پژوهش حاضر، فرمول تحلیلی برای محاسبه‌ی مقاومت نهایی اتصال‌های سخت شده تحت بار فشاری ارائه شده است.

behavior of tubular xjoints retrofitted with external ring subjected to compressive loading

tubular structures are made of hollow steel members with circular crosssections and connecting them is one of the major challenges in their design. so far, some techniques to improve the performance of tubular connections have been proposed. most of these methods (e.g., internal ring, doubler plate) can only be used for structures during the design, but there are only a few techniques (e.g., external ring, frp) which can be applied during both fabrication and service. this paper investigates the ultimate strength of circular hollow section (chs) xconnections stiffened with external ring subjected to axially compressive load. the solid186 in ansys was used to establish the finite element (fe) models. in these models, both geometric and material nonlinearity were considered. moreover, the welds joining the chord and brace members were modeled. the validation of the fe model with several experimental data indicated that the proposed fe model can accurately predict the static behavior of the ringstiffened xjoints under compression. in the next step, 117 fe models were created and analyzed to evaluate the effect of the connection geometry and external ring size on the static capacity through a parametric study. results indicated that the external ring can considerably increase the initial stiffness. moreover, the ultimate strength of the ringreinforced xjoints under brace compression can be up to 367% to that of the strength of the corresponding unreinforced joint. despite these significant differences between the ultimate strength of unstiffened and ringstiffened xconnections under compressive load, the investigations on this type of stiffened joints have been limited to only three xjoint tests. also, no design equation is available to determine the ultimate strength of xconnections stiffened with the external ring. hence, the parametric study was followed by the nonlinear regression analysis to propose a theoretical equation for the static design of xconnection stiffened with the external ring in compressive load.