New Data on the Fatigue and Ultimate Limit State of Grouted Tubular Joints

Abstract

Abstract A Joint industry project (JIP) commenced in 1993'" to develop a design manual for tubular joints which are strengthened or repaired through chord grout-filling. This project has been funded by five oil companies and two regulatory bodies. The project has comprised the conduct of over 150 Stress Concentration Factor (SCF) and ultimate load tests on large scale as-welded and grounded tubular joints. Separate data capture studies, including capture of data on double-skin grout reinforced joints, have been conducted, together with studies on offshore deployment, to ensure that complete chord grout-filling is achieved for all practical scenarios. The primary reason for carrying out this project has been an industry-wide recognition that chord grout-tilling represents an extremely cost-effective and technically-efficient method to strengthen or repair tubular joints. Further, it has been Recognized that double-skin joints (e.g. pile through leg with anisettes grout-tilled) are often present in structures and the resulting enhanced strength and fatigue characteristics should be exploit+ to permit more efficient new platform designs or better estimation of joint performance for existing installations. Although API RP2A(?' permits the use of grouted joints, little guidance is provided, reflecting the lack of data and information in this area. This project has been carried out to generate a significant amount of new data/information, leading to the creation of a design manual for grouted, joint. Introduction Grout-tilling of chord members to enhance the static strength and fatigue endurance of tubular joints is recognized as perhaps the most cost-effective and technically efficient solution available for the strengthening, modification and repair of offshore ions. However, there are significant gaps in the data from the standpoint of present-day potential applications, i.e. the range of geometries, configurations, load cases and conditions for which chord grout-filling may be considered relevant and appropriate. Therefore, to generate new data applicable to appropriate strengthening or repair events, a test matrix was selected on the basis of likely strengthening and/or repair scenarios. To enable the measurement of Strain Concentration Factors (SNCFS) for all load types for each specimen, a specialized test rig was designed to facilitate loading in the four loading modes. A sophisticated test rig was designed to enable rapid execution of test measurements in all loading conditions without the need to remove or re-orientate each specimen. Review of Existing Guidance The provisions of major design codes on any aspect of grouted joints are limited. API RP2AC', HSE Guidance Notes('), NPD'4' and DNV(s' all state that capacity may be established by testing and/rrr analytical methods. The HSE Gui&nce Notes specifically allows the use of grout filling for joints on existing installations.