ABSTRACT:

A series of static and dynamic tests were carried out on grouted connections as used in grouted pile/sleeve connections offshore. The grout had a C-S-A expansion agent which generated prestress up to 8 MPa radially by the elastic confinement due to hoop stiffness of the tubes, and longitudinal prestress due to function restraint of the tubes. Plain pile-sleeve surfaces with shot blasted finish gave reliable results with a coefficient of function about 1.0. 20,000 cycles m the range 17-93% of ultimate (slip) strength and 2 million cycles with a load range 30% of ultimate did not produce visible damage. The addition of welded bead shear keys to already prestressed grouted connections did not significantly increase capacity.

INTRODUCTION

The technology of grouted tubulars has been pioneered by the offshore oil industry. The traditional application of these connections has been in forming "structural" connections between steel piles and the Jacket structures. The steel piles protrude for a certain length above the sea bed and are then grouted to sleeves. These sleeves either skirt- the main legs or are positioned around the base of the jacket. More recently grouted connections have also been adopted in repair and strengthening of tubulars. The advantages of grouted connections over other alternatives include the ability to accommodate high geometrical tolerances, relatively low level of construction skill and preparation, relatively low cost and rapid installation time, with good quality results readily achievable. Axial loads are transferred between the concentric tubulars through shear m the grout annulus. In strengthening and repair, this would, however, require underwater welding of the shear keys and shear key connections have been shown to have reduced fatigue strength compared to plain pipe connections loaded with the same ratio of dynamic load to ultimate capacity (Tebbett and BIllington 1985).

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