Marlborough District Council Roading Assets - Activity Management Plan 2015 - 2018 SECTION 1 EXECUTIVE SUMMARY RATING % FACTOR 1 2 3 4 5 Material Quality 15 5 -5 -10 -25 Operational Stresses 10 5 0 -10 -15 Maintenance History 15 10 0 -10 -15 Working Environment 0 -5 -10 -15 -20 External Stresses 0 -5 -10 -15 -20 Table 6.4.2.8b: Technical Factors for RUL assessment. In ascribing values to the technical factors, each bridge is assessed individually by reference to the bridge database and applying knowledge of the asset. These values will be refined over time as the factors will be considered at each subsequent inspection and knowledge of the structures will improve. The results of this analysis provide a ranking of the bridges against each rather than a fixed indication of remaining life. The technical factors for this model are as follows: 1. Design Standards; for this AMP, estimation has been done using both the loading code at the time of construction and the age of the bridge. 2. Construction quality; this has simply been taken as an indication based on site inspections from very poor to exceptional. 3. Material quality; for this AMP this has been based on the age of the structure, with very poor being pre 1930 and exceptional being to 2009 current standards. 4. Operational stresses; this has been taken on the probability of heavy vehicles on the bridge, from footbridges with no heavy vehicles, through normal class 1 loads, forestry loading to quarry access loads and overweight routes. 5. Maintenance history; this is self-explanatory and was taken from the previous inspection sheets and goes from very poor for the off RAMM bridges to very good for the high visibility town or newer bridges. 6. Asset working environment; this has been taken as a history of either flooding or susceptibility to an earthquake movement. 7. External stresses; this has been taken as the potential to be loaded by an aggressive waterway with gravel or rafting debris, from normal low debris to very aggressive waterway and high debris load. The adjustment to working life is calculated by adopting the worst factor and adding a proportion of the remaining factors. The optimised depreciated replacement cost (ODRC) calculated on a straight-line basis, is simply the replacement cost multiplied by remaining life/useful life. The annualised depreciation is the ODRC divided by the remaining useful life. The structures evaluated as having less than or equal to two years remaining life are shown in Table 6.4.2.8c. The analysis on the bridges in this table includes weightings for both forestry and quarry access, either of these two factors obviously have a high impact on remaining life. Table 6.4.2.8c identifies several ‘all timber’ bridges (type K) which have a short base life (50 years) and are commonly approaching or over their useful life. Bridges with major timber components (type H, I, & J) have a slightly longer base life but are also highly represented on the above table due to approaching end of life. All bridges with aging timber components are a significant burden on maintenance budgets. The oldest bridge on the asset register, High Street West, is not included in Table 6.4.2.8c, even though in theory it has exceeded its useful life. The design loading from the era of construction is not generally adequate to accommodate the stresses imposed by modern vehicles, and the age of the reinforced concrete means it is likely to be deteriorated through the processes of carbonation and chloride ion ingress. However it is expected that the bridge can continue to be maintained for current operational requirements for the foreseeable future. 30 September 2014 Page 69 of Section 1