Recent Developments in the Design of Grouted Connections

Abstract

Summary A recently completed major research project on the structural behavior of grouted pile/sleeve connections covered static strength, the effect of cyclic movement during grout setting, long-term fatigue, calibration of measured strengths for different quality-control samples, and the investigation of connections removed after 13 years of service in the North Sea. Preliminary data from this project resulted in the issue of revised guidance notes by the U.K. Dept. of Energy and have been recognized in recent amendments to API RP 2A. This paper discusses unpublished test results, the provisions of the latest design codes in relation to the available data, and the implications for design. Results and discussions apply to all types of grouted connections and many types of structures, including pile/sleeve connections for fixed jackets and tension leg platforms and grouted connections used for repair of tubular structures. platforms and grouted connections used for repair of tubular structures. Introduction Grouted pile/sleeve connections are a critical element of offshore structures, especially for deeper-water fixed platforms and seabed templates where piles terminate below platforms and seabed templates where piles terminate below sea level and welding of the pile to the sleeve is not practical. Grouted connections are also used extensively practical. Grouted connections are also used extensively for repair and strengthening applications for both jacket members and joints. The piles may be distributed around the base of the structure (the so-called skirt-pile arrangement) or may be grouped (the cluster-pile arrangement) at the base of the main legs. In either case, the grouted connection between the pile and sleeve forms the primary load transfer between the structure and its foundation piles. These connections vary in length and size according to the structure and location. Recent designs are adopting shorter connections (generally 6 to 12 times the pile diameter in length) as test data on their strength and performance become available. The geometry of a typical connection based on a cluster design for a major North Sea platform is shown in Fig. 1. This paper outlines the results of a major research project undertaken with U.K. Dept. of Energy funding and project undertaken with U.K. Dept. of Energy funding and comments on the latest provisions of design codes that recognized this research effort. A complete discussion of the research program is given in Ref. 1.