Effect of carling-stiffener arrangement on the buckling and ultimate strength characteristics of a transverse bulkhead panel in FLNG: a nonlinear finite element investigation

Local carlings can modify elastic buckling restraint without governing the nonlinear load resistance of a stiffened bulkhead. Five arrangements in an FLNG transverse bulkhead were examined under a Design Load combining hydrostatic pressure and hull induced boundary deformation. The numerical basis was assessed using local shell sizes of 20, 50, 100 and 200 mm through linear, eigenvalue and nonlinear analyses. At 50 mm, the maximum linear displacement matched the 20 mm result at the reported precision, the first eigenvalue differed by 0.69 %, and the model used 17.2 % fewer elements. The nonlinear paths and broad deformation patterns were similar, although graphical sampling showed increasing displacement sensitivity at higher loading and local peak stress remained mesh dependent. These findings support 50 mm as a practical engineering balance for comparative panel response. Ultimate Strength was defined by the intersection of the elastic and plastic branches of each load displacement curve. Reducing three carlings to one lowered the elastic buckling factor by approximately 5.8 %, while the Ultimate Strength factor changed from 2.20 to 2.19; all five arrangements remained within 2.19 to 2.21 times Design Load. The results distinguish elastic modal restraint from nonlinear redistribution and support qualified examination of reduced carling details. Application remains specific to the investigated loading, imperfection assumptions and exclusion of welding residual stress; fabrication benefits require shop confirmation.