http://yetl.yabesh.ir/yetl1/handle/yetl/19048 2026-08-25T19:56:56Z http://yetl.yabesh.ir/yetl1/handle/yetl/4316901 Corrected Stress Concentration Factor for Hi/Lo at the Root of a Pipe Girth Weld Peek, Ralf Abstract. The stress concentration factor (SCF) for a hotspot at the root of a pipe girth weld due to high–low misalignment offset (hi/lo) is used in fatigue and fracture assessments, since some such offset is inevitable due to fabrication and welding alignment tolerances. Where the hi/lo is not already accounted for by the SN fatigue resistance curve used, an SCF is needed. Following established practice, the SCF is determined to account for bending stresses across the wall thickness of the pipe, but does not account for stress concentrations arising from the reentrant corners that can arise at both the root and the cap of the girth welds. This SCF arises from a linear distribution of stress across the wall thickness, which is statically equivalent (in terms of membrane force and bending moment) to the actual stress distribution. A simple approximation to determine this SCF using the line of tension from axisymmetric shell theory and considering the actual details of the geometry at the girth weld leads to the same result as in the Recommended Practice DNV-RP-F108 at the cap, but at the root, the value of SCF-1 is found to be more than double that from DNV-RP-F108. The result is confirmed by axisymmetric finite element analysis. 2026-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4316890 Experimental Investigation of Dynamic Characteristics of OC-3 SPAR Platform Subjected to Aero-Hydrodynamic Loading Rony, J. S.; Arya, Thomas; Sashank, R.; Srineash, V. K.; Behera, Manasa Ranjan Abstract. This study presents insights gained from wave flume experiments conducted to investigate the hydrodynamic responses of a SPAR floating offshore wind turbine (FOWT) platform supporting a 5 MW wind turbine under combined wind and wave loading conditions. The significance of this work lays in the methodology in which a FOWT model was subjected to regular and irregular waves under aerodynamic loading introduced as rotor thrust force for below-rated and rated wind speeds to determine platform-level dynamics. First, free decay tests were conducted to obtain the natural periods and damping ratios of the SPAR FOWT system. Furthermore, the wave elevations, displacements, rotations, and rotor thrust were measured under the influence of varying regular, irregular waves, and thrust forces. Response amplitude operators (RAOs), statistical and spectral analyses, were carried out to determine the response behavior of the SPAR FOWT under aero-hydrodynamic loading. It could be noted that the surge was affected by the rotor thrust force. A coupled surge–pitch phenomenon was observed during the wind–wave interaction on the platform, especially for higher wave periods. The rotor thrust influence on heave was negligible. However, the aerodynamic damping resulted in reduced pitch responses. The rotor thrust exhibited noticeable fluctuations under wave conditions, highlighting the clear coupling between platform motions and aerodynamic loading and became more pronounced with increasing wave heights, primarily due to the amplified platform responses under larger waves. These observations highlight the importance of including aerodynamic loading effects in understanding the dynamics of FOWT and suggest that the proposed aero-hydrodynamic framework could be a robust design approach for effective FOWT analysis. 2026-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4316886 Liner Wrinkling and Buckling of Girth-Welded Lined Pipe Under Monotonic and Cyclic Bending: Effect of Triple Point Imperfections Naous, Emile; Kyriakides, Stelios Abstract. It is well recognized that girth welds of carbon steel pipe lined with a thin layer of a corrosion-resistant alloy constitute a weakness. Plastic bending to levels such as those imposed by reel-lay installation leads to stress concentration due to the mismatch of properties between the carrier steel, the liner alloy, and the weld. Furthermore, the constraint of the weld causes a local periodic separation of the liner from the carrier, which triggers wrinkling and subsequently large-amplitude buckles (Yuan and Kyriakides, 2015, “Liner Wrinkling and Collapse of Girth-Welded Bi-Material Pipe Under Bending,” Appl. Ocean Res., 50, pp. 209–216. 10.1016/j.apor.2015.01.018). The present analysis shows that replacing the contact stress of manufacture by a low level of constant internal pressure does not alter the induced disturbance or its consequences under bending, and that the growth of liner separation accelerates when the liner achieves a moment maximum (critical curvature). In addition, the presence of small geometric imperfections in the neighborhood of the weld was shown to reduce the curvature at which the stability of the liner becomes critical. Cyclic bending causes progressive accumulation of liner separation adjacent to the girth weld. The evolution of events as the number of cycles, N, increases is similar to that of monotonic bending, with N replacing curvature. The rate of growth of liner separation depends on the amplitude of the imperfection, the internal pressure, and the curvature of the bending cycle. It was observed that, when the liner separation reaches the level at which the instability becomes critical under monotonic bending, its rate of growth per cycle accelerates. Thus, monitoring liner separation during cycling can guide design. 2026-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4316871 Impact of Sea-Bed Trench on the Deflection of a Floating Ice Sheet Due to a Moving Load Kumar Nehra, Mahesh; Bora, Swaroop Nandan Abstract. The steady-state response of an ice sheet floating above a trench-shaped sea-bed and subjected to a concentrated load moving at a constant speed is investigated. The fluid domain is divided into three virtual regions corresponding to the geometry of the sea-bed, and the required matching conditions between two adjacent regions are provided. To ensure the structural continuity of the ice sheet, conditions on deflection, slope, shear force, and bending moment are imposed at the virtual boundaries on the upper surface, together with appropriate matching conditions at the instantaneous position of the moving load. The dispersion relation of flexural gravity waves is used to study the phase speed and group speed in shallow and deep water regimes, providing insight into their dispersive properties. The analysis is based on a plane-wave approximation, which is deemed appropriate for the present parameter regime where the propagating-mode effects dominate. The ice deflection is described in a piecewise analytical form across various regions by solving the governing equations using standard ordinary differential equation techniques in a moving coordinate framework. The steady-state deflection profile of the ice sheet is then obtained, highlighting the combined influence of the sea-bed geometry, trench depth, and load speed on the wave propagation. The results further demonstrate that increasing trench depth leads to a reduction in the ice sheet deflection by weakening the ice–water interaction, whereas higher load speeds intensify wave generation and amplify the dynamic response of the ice sheet, particularly within the critical speed range. 2026-01-01T00:00:00Z