Marlborough District Council Roading Assets - Activity Management Plan 2015 - 2018 SECTION 1 EXECUTIVE SUMMARY 1.6.4.2.7 Asset comparison to similar South Island Authorities (2011) Marlborough can be compared to other similar sized authorities in the South Island to consider the respective investment in the Bridge Assets, to gauge and generally compare, on the basis that an indication of comparative need could be identified. This information will not be used to determine the level of investment required, however, such comparison does bear a relationship to the level of service provided. Since 2011 when the above comparison was undertaken, the number of timber bridges in Marlborough has reduced from 85 to 82 at a total length of 875m. The renewals over this time have been of relatively short, low cost structures. Despite several restricted bridges being renewed since 2011 the overall number of restricted bridges in Marlborough has increased to 28 due to more bridges approaching end of life. 1.6.4.2.8 Remaining Useful Life A model has been developed to determine the remaining useful life (RUL) of a structure. The RUL of an asset is determined by taking the base life of a structural type, adjusting for external factors (using Technical Factors & F1), then subtracting the current age. The minimum RUL is 2 years. The calculated RUL values have been critically reviewed following inspections of all the structures and found to be practically representative. The base life for each structure type is taken as follows: Base Lives Life Ramm Type Foundations Beams Deck A C C C 100 B C C C 100 C C S C 95 D C S C 95 E C S S 90 F T S S 60 G S S S 50 H C S T 80 I C T T 70 J T S T 50 K T T T 50 Table 6.4.2.8a: Base life of bridge components The F1 factor is used to recognise that at the end of a service life that there is still a residual life left in the structure. The method of evaluating F1 is based on the 1996 NAMS manual section 4.6.5. Provided the asset is maintained and remains in reasonable condition, then as the asset becomes older its remaining life can be incrementally extended. Whilst not specifically catered for in the AVD Guidelines this factor is accepted in the industry as standard practice. The concept of technical factors are introduced in the AVD Guidelines to adjust the life of the asset to cater for design adequacy, usage, & other influences. The technical factors and percentage weightings adopted for bridge RUL are given in the table below: RATING % FACTOR 1 2 3 4 5 Design Standards 10 5 0 -5 -10 Construction Quality 10 0 -5 -15 -35 30 September 2014 Page 68 of Section 1