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The demand for electric resistance welded (ERW) pipe for deep-water installation has increased, which necessitates a higher degree of accuracy in evaluating the strength of pipe in order to satisfy the design limit state, otherwise referred to as the collapse performance. Since ovality and residual stress governs the collapse performance, an accurate evaluation of these factors is needed. An analytical approach using a three-dimensional finite element method was proposed to simulate the roll-forming and sizing processes in manufacturing ERW pipe. To simulate significant plastic deformation during manufacturing, a nonlinear material model that included the Bauschinger effect was incorporated. The manufacturing of ERW pipe made of API 5L X70 steel was simulated and analyzed for collapse performance. Controlling the ovality of the pipe significantly decreased the amount of pressure that would cause a collapse, whereas the effect of residual stress was minor. These two factors could be improved via the use of a proper sizing ratio.

Fatigue performance of full penetration groove-welded tube-to-end-plate connections was evaluated by parametric studies verified by laboratory testing of full-scale galvanized cantilevered highway sign and signal and high-level luminaire structures. In the absence of sufficient experimental basis, the fatigue resistance of this connection detail in the existing AASHTO specification is defined as Category E. Fatigue performance of tube-to-end-plate connections in thin-walled tubular structures is governed by secondary out-of-plane bending stress, the magnitude of which depends on relative stiffness of the tube and end plate. In some groove-welded connections, the backing ring is welded to the tube wall, adding more variability in fatigue performance of the connection. Twenty-three full-size specimens composed of five configurations of the groove-welded connections were fatigue-tested under constant amplitude loading simulating wind-induced aeroelastic oscillations, such as galloping and vortex shedding, that are typically experienced in service. Variation in six parameters of the connection geometry were considered: diameter of tube, thickness of tube, thickness of end plate, diameter of end plate opening, number of anchor bolts, and height of backing ring. The research results demonstrated that with a suitable combination of the geometric parameters, the constant amplitude fatigue threshold of the groove-welded tube-to-end-plate connections can exceed that of AASHTO Fatigue Category D for sections widely used in highway sign, luminaire, and traffic signal structures. The local stress-based approaches provided reasonable lower bound estimates of fatigue performance of the connection detail for different geometric configurations.