ABSTRACT The paper reports the analytical part of a development project into the design and fatigue performance of composite umbilicals, carried out under Work Package 2 of the "Umbilical - The Future" joint industry funded project A computer model of an electrohydraulical, symrnetrical umbilical subjected to various axial loads and bent around sheaves of different diameters has been developed This model entitled Gneg2 calculates the relative sliding between the cores and stresses due to the effects of bending, axial load and friction INTRODUCTION Over recent years, umbilicals have been increasingly used in many off-shore applications worldwide for subsea control, chemical Injection etc The failure of these components in a remote subsea installation can be extremely expensive both in lost production and rectification Unfortunately, insufficient knowledge of the complex behaviour of umbilicals has often led to defective design, manufacture, installation and operation A report from the Engineering Research Centre, dated July 1990, revealed a significant number of problems associated with unbilicals [3] It was concluded that some form of planned R&D was necessary if the industry was to improve umbilical reliability From 1985 to 1992 BP Norway Ltd, ABB Norsk Kabel and EFT, which is a part of the SINTEF Group. Norway, ran a project in order to achieve a better understanding of the behaviour of umbilicals and to try to reveal factors having a great influence on the life of umbilials It was decided, as a start, to concentrate on electrical umbilicals, both unarmoured and armoured, and to try to determine the stresses and the fatigue life of an axially loaded umbilical running back and forth over a sheave If this problem could be solved it was expected that more complex umbilicals and other types of bending problems could be included in later phases The theory developed, which was implemented in a computer program entitled Grieg was able to describe and calculate the internal movements and forces in all-electric umbilicals [l] and [2] However, there was a need to extend ths theory to the more common umbilical configurations containing both electrical cores and hydraulic hoses In 1993, when the R&D programme "Umbilicals - The Future" started, it was decided to continue the research work within a Work Package 2, called "Umbilical Modelling and Design" All results and expenence gained in the former project was made available to the new project This paper is the first of two papers which give a summary of work, description and results from both these projects The problems were attacked both analytically and experimentally simultaneously as the analysis required knowledge of parameters which have not previously been studied or quantified The analytical work, which will be presented in this paper, was based on several assumptions Some of these could be tested directly, others could only be tested indirectly by observing which assumptions and parameter values gave correspondence between calculation and test results Flgure 1 Investigated umbilicals (Available in full paper) Figure 1 shows the Investigated umbil~calsd unng the first project [I]

ABSTRACT The paper reports the experimental part of a development project on the design and fatigue performance of composite umbilicals, carried out under Work Package 2 of the "Umbilicals - The Future" joint industry funded project A series of tests have been carried out to improve the understanding of the internal behaviour of an umbilical, to verify the theoretical analysis and to gather physical data necessary for the development of an analytical theory for calculating internal stresses in an umbilical being bent over a sheave INTRODUCTION An analytical theory has been developed to describe the behaviour of a syrnmetrical electro-hydraulic umbilical and its internal electrical, mechanical and hydraulic components when it is forcibly bent around a sheave wheel This theory, which has been implemented in a computer program entitled Gneg2, is reported in Part 1 of this paper [l] The work has been carried out under Work Package 2 Umbilical Modelling and Design of the "Umbilical - The Future" joint industry funded project which was commenced in 1993 This paper describes a supporting programme of experimental work which was undertaken to provide essential input data for the Gneg2 program, and also to validate some key aspects of the theoretical analysis OBJECTIVES AND TYPES OF TESTING A number of experimental tests have been carried out in parallel with the development of the analytical theory described in Part 1 The man objectives for the experimental work were To improve the understanding of the internal behaviour of an umbilical as it is loaded and bent over a sheave To perform tests to verify and if necessary, modify the theoretical analysis as it was developed To gather necessary physical data that is used as inputs to the theoretical model Tests to improve the understanding of the internal behaviour of an umbilical and to verify analytical calculations include Measurement of the stiffness of hydraulic hoses under bending as well as in transverse, axial and shear loading Bend stiffness tests to measure the force required to bend the umbilical over a sheave with different axial loads on the umbilical Measurements to determine the strain in a core of an umbilical as it moves on a sheave for comparison with the results given by the analytical theory STIFFNESS OF HYDRAULIC HOSES Umbilicals often contain hydraulic hoses, which are usually so flexible that they will seldom be exposed to high stresses due to bending of the umbilical The behaviour of the hoses will, however, affect the pressure and the frictional forces between the other elements in the umbilical It is therefore necessary to know the stiffness characteristic of the hydraulic hoses in order to take the deflection under load Into consideration Test specimens Four different hoses were tested, two with outer diameters of 20 and 30 mm (called Poly20 and Poly30) and two with outer diameters of 23 and 36 mm (called ABB23 and ABB36) The hoses had the following data Table 1 Data of tested hoses (Available in full paper)