A previous paper (Henry, 1995a) introduced the technique of hardware compilation as the basis for developing highly flexible programmable hardware platforms for control applications such as sensor validation. This paper describes two PC-hosted architectures for sensor validation research. The first holds up to two FPGAs and supports a daughter board with application-specific circuitry. The second is based on the transputer TRAM standard, and consists of programmable hardware modules providing interfacing and low-level signal processing between the transputer and arbitrary I/O components. Three applications are described, based upon a thermocouple, a dissolved oxygen probe and a Coriolis mass flow meter.

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Offshore Structures are typically designed with a target end of field life between 20 and 30 years. Many offshore Structures remain in service while exceeding their designed life which requires robust methods for evaluating and maintaining target risk levels through regular sub-sea inspections. Risk based inspection plans are generated based on strength and fatigue analysis (typically S-N based fatigue assessment) which involves a number of uncertainties which are inherent to the fatigue process. These uncertainties inevitably lead to inconsistencies between analysis predictions and the outcome of underwater inspections. Although the inspection findings are acknowledged, there is generally not much effort made to make use of the inspection findings to optimise future inspection plans. This paper applies reliability updating methods to optimise inspection plans (inspection intervals) using fatigue reliability based on the results of in-service inspections. This methodology forms part of the work requested by ADMA-OPCO during the customisation of Atkins Fleet Management System (FMS) for the application to their Offshore Structures fleets. It has been reviewed and adopted by ADMA-OPCO to replace existing qualitative methods. The methodology works towards optimising their inspection efforts and cost to maintain acceptable target risk levels. The methodology is based on evaluation of the SN fatigue reliability since the SN Curves are implemented in the fatigue design methods outlined in International Standards. A probabilistic model for fracture-based reliability calculation is developed by calibration of initial crack size to match SN based fatigue reliability. This model enables utilisation of the Bayesian updating techniques which allow incorporation of the inspection results in the calculations. Environmental data from Umm Shaif Field (ADMA-OPCO) have been utilised in the calculations along with fatigue design SN Curves from the API RP 2A international standard. The calculations target the acceptance probability of failure levels of a critical component (hotspot) with a target design life of 30 years. In the event that no fatigue cracks are identified through in-service underwater inspections, the existing inspection plans can be revised utilising the developed methodology to optimise the inspection intervals, leading to cost saving and optimisation of the inspection plan. Major in-service inspection campaigns have been executed by ADMA-OPCO where no fatigue cracks were identified. Other operators within the region have also concurred that no fatigue cracks were observed during in-service inspection campaigns, which indicate that the methodology proves effective in optimising inspection costs within the region.

Present regional practices for performing a conventional offshore structural analysis erroneously considers strengthening proposed for any additional loads on existing structures to also support the already existing loads which mainly is due to the limitations of the linear analysis approach presently adopted. This method could lead to false perception of code compliance exposing strengthened structures to a higher failure risk. The paper introduces a more accurate approach for the assessment of the structure and the evaluation of the effectiveness of strengthening introduced at different stages through the structure’s lifetime. Through the course of this study, a comparison was carried out between the conventional linear strength analysis vis-a-vis the non-linear finite element analysis technique for a typical offsore structural Bridge. The work involved full simulation of a bridge supported by two offshore structures using the conventional method and assessing the results. Subsequently an integrated finite element model, with critical locations represented through 4-node shell elements was generated. A non-linear finite element analysis was adopted where stage-wise strengthening and load history was simulated. The structural assessment using the non-linear finite element analysis technique has demonstrated that the bridge did not comply with the structural strength requirements of ISO 19902 international standards in as-is condition. This was in contradiction to the conclusion and outcome of the previous design reports. The previous strengthening design had adopted the conventional linear design methods, ignoring the realistic effects of loading and strengthening stages throughout the history of the structure. Ignoring these effects had misled to the perception of effectiveness of the new combined sections, whereas accurate representation had demonstrated that only the new additional loading is distributed to the new combined section and the existing loading is resisted by original sections only. This behavior is applicable if the installation techniques did not include jacking systems to relieve the loading prior to strengthening. The results and conclusions of the study have given an insight to the limitation of the conventional linear structural analysis methods in capturing the accurate structural behavior. It also provided a demonstration of how an incompatible type of assessment may lead to incorrect perception of compliance.