| 摘要 |
A monitoring system and method for elongate subsea structures are disclosed. The structure monitoring apparatus comprises a strain gauge secured to the riser at a defined location which communicates signals indicative of actual strain values experienced by the riser information processing means to an information processing means in communication with a pre-compiled, theoretically determined, discretised bending moment variation matrix. After receiving and compiling sufficient data to form a profile of the bending moment variation occurring at the defined location or site of the monitoring apparatus, the information processing means interrogates the bending moment matrix, using the known bending moment variation profile at the site of the apparatus, along with the known location of the apparatus on the riser, to estimate the bending moment variations at various other locations along the length of the riser. In one embodiment, as the depth of the riser and thus the apparatus can vary due to subsea tidal, eddy and other effects, the information processing utilizes the bending moment variation matrix to create an envelope of possible bending moment variations at a particular point on the riser remote from the site of the monitoring apparatus by retrieving the multiple possible values of likely actual bending moment variation occurring at said particular point for many if not all possible depths. The maximum bending moment variation value in the envelope of values so determined is then selected as the likely actual bending moment variation value for the particular point. Finally, the bending moment variation values are translated into fatigue damage per cycle, for example using a Miner-Palmgren algorithm, and such values may then be aggregated to provide a total damage sustained at any location along the riser. |
