Fatigue Damage Of Transversal Butt Weld On Marine Steel Tubular Piles During Installation

Steel pipe pile foundations have their own unique advantages such as high strength,light weight, high speed of construction, convenience in transportation and fabrication.Hence they are increasingly applied in large ocean engineering structures. Marinestructures are normally located in open waters which suffered more complicated naturalconditions, thus the fatigue strength design of steel pipe pile foundations is an importantconsideration in the structural design. Existing specifications only call for theconsideration of fatigue damage on marine steel piles caused by environmental loadsand operational loads. However, some scholars’ studies in recent years suggest thatmarine steel piles may suffer greater fatigue damage in driving process. Currentresearches on fatigue damage of transversal butt welds on marine steel piles duringpiling are not mature enough, so it is necessary to discuss it in depth to gain a furtherunderstanding on the mechanism of fatigue damage in steel pipe piles, and to facilitatethe development of basic scientific design of marine engineering structures, and theirconstruction and maintenance.This paper studys the S-N curve based method for fatigue evaluation on transversalbutt welds on marine steel pipe piles during pipling, and specifies how to calculate thehot-spot stresses at transversal butt weld on steel pipe piles during driving and themethod for cycle counting of the hot-spot stress time history. Subsequently, based on anexample of a large deep-water dock, this paper conducts a detailed analysis on theimpacts of seversal factors on pile driving fatigue damage, such as soil resistance duringpiling, the hammer efficiency, hammer cushion thickness, the stress concentration effectand so on. Then the author gives a number of suggestions on how to reduce fatiguedamgage during pile driving.Fracture mechanics visually describes the fatigue crack propagation process, givinga comprehensive reflection on the influence of material and load and other factors.However, no fracture mechanics based analysis of driving fatigue damage on steel pipepiles are found in literatures. This paper focus on the linear elastic fracture mechanicsbased analysis of driving fatigue damage at butt welds on steel pipe piles. Specifically,this paper studys the characteristics of marine steel pipe piles and selects a geometryfunction for stess intensity factor on circumferential surface cracks at butt welds.