Knostrop Footbridge – Innovative Design Solutions

<p>Knostrop Footbridge was designed and constructed as part of the Leeds Flood Alleviation Scheme. The project’s principle objective was to provide new walking and cycling routes along the River Aire, as well as creating a landmark gateway to the city. Given the intended purpose, budget, programme, and site constraints, a list of key aspirations was developed:</p><ul><li><p>Creation of a slender, flowing structure which “floats” over the water and encourages local use and interest.</p></li><li><p>Simplified construction through off-site fabrication and streamlined installation.</p></li><li><p>Mirroring the alignment of the soon to be constructed Knostrop Weir and utilising the weir walls for sub structure support, all whilst accommodating the construction lag between the weir and the bridge.</p></li><li><p>A durable, low maintenance structure is essential with the difficult access constraints of the weir.</p></li></ul><p>Achieving the above in combination required an innovative approach. Numerous potential solutions were developed, experimented with, and analysed, prior to finalising the design.</p><p>This iterative process allowed the bridge to develop into a unique, innovative, and recognisable design, and one which exceeded expectations to efficiently fulfil its purpose with minimal anticipated lifetime maintenance.</p><p>This paper presents the innovative design solutions adopted in overcoming the various challenges and achieving the design aspirations.</p>

Optimal Preventive Maintenance of Wind Turbine Components with Imperfect Continuous Condition Monitoring

Among the different maintenance techniques applied to wind turbine (WT) components, online condition monitoring is probably the most promising technique. The maintenance models based on online condition monitoring have been examined in many studies. However, no study has considered preventive maintenance models with incorporated probabilities of correct and incorrect decisions made during continuous condition monitoring. This article presents a mathematical model of preventive maintenance, with imperfect continuous condition monitoring of the WT components. For the first time, the article introduces generalized expressions for calculating the interval probabilities of false positive, true positive, false negative, and true negative when continuously monitoring the condition of a WT component. Mathematical equations that allow for calculating the expected cost of maintenance per unit of time and the average lifetime maintenance cost are derived for an arbitrary distribution of time to degradation failure. A numerical example of WT blades maintenance illustrates that preventive maintenance with online condition monitoring reduces the average lifetime maintenance cost by 11.8 times, as compared to corrective maintenance, and by at least 4.2 and 2.6 times, compared with predetermined preventive maintenance for low and high crack initiation rates, respectively.