Bolted split sleeve grouted clamps may be used to repair and strengthen the members of steel jacketed platforms. Current design practice for these clamps is based upon the guidelines appropriate to grouted pile to sleeve connections. In the guidelines a factor of safety of 6 is recommended to be applied to the design bond strength for both static strength and long term effects such as fatigue.
To the authors knowledge, ho published results for the fatigue performance of bolted split sleeve grouted clamps exists. A series of experiments has been undertaken, therefore, to determine the fatigue performance of split sleeve clamps.
The paper discusses the experimental programme in which the behaviour of ten specimens has been investigated. Sinusoidal tension-compression axial loading has been applied to each clamp and the fatigue performance monitored. The applied load and the grout age were variables.
The results of the programme indicate that the margin of safety against fatigue may not be as great as expected. In fact, some results are close to the factored design loads. In view of the controlled nature of the laboratory experiments and the uncertainties associated with offshore grouting it is suggested that particular attention be paid to the fatigue performance of bolted grout filled clamps.
A frequent method of a repair or strengthening the members of a steel jacketed platform has been to use a split sleeve grouted joint or clamp. The joint is formed by bolting the two halves of a split sleeve around the member of concern and filling the annulus with grout. Shear connectors may be used to improve the bond between the steel and grout surfaces. There is no direct pre-stressing of this type of clamp apart from the local effect of the bolt forces. Figure 1 shows a typical split sleeve grouted clamp.
Grouted repairs provide a number of advantages when compared with other methods. The grout can easily accommodate geometrical imperfections and hence, it enables the repair to restore or enhance the member stiffness. Also, grouting techniques are well established in an offshore environment. For design purposes, it has been normal practice to use the guidelines appropriate to grouted pile to sleeve connections [Ref 1]. Not only must a split sleeve clamp be designed to provide adequate static strength, it must also provide the necessary fatigue performance. It is this latter requirement which is the subject of this paper.
An experimental programme has been undertaken in the Structures Laboratory of The City University to investigate the fatigue performance of a typical grout filled bolted connection. In the work to be reported only one type of connection has been examined and to the author's knowledge this is the first attempt to assess the fatigue strength of split sleeve bolted clamps. Figure 2 shows the general arrangement of the specimen which represents a typical repair.