Infrastructure Asset Management Assignment

Assignment Task

Brief

You are part of the team responsible for the asset management of a stock of similar metallic railway bridges owned by Network Rail on one of their main Routes. Figure 1 shows a cross-section of the type of bridge, which consists of two main girders and cross-beams in-between.

You are required to produce whole life maintenance planning for the next 105 years for this type of bridge using the LCAT tool provided. A number of the bridges in the route have been found to be corroded through their latest inspections and some appear to be uncorroded. On the corroded bridges the inspections have shown that there is 30% loss of flange thickness (both top and bottom) and web on both the cross-girders and main-girders.

Tasks

By using the LCAT tool, analyse the following maintenance regimes for typical bridges:

A do-minimum regime where only painting (re-coating) is applied on the bridge members (without any strengthening). Compare the whole-life costs resulting through using two different types of coatings separately, e. M27.4 and M21 for different element exposure levels (i.e when 10%, 50% or 90% of the element becomes exposed). Discussion should include reflection on the rate of strength loss over time and the remaining strength of the girders (in terms of % of nominal strength) at the end of the 105- year period for each case. Consider the main girders and cross-girders separately and discuss the differences in the results obtained between them. One set of analysis should be carried out for a corroded bridge and one set for an uncorroded bridge. Then, select one paint type and one type of member (i.e. main-girder or cross-girder) and compare the performance of a bridge in an industrial environment to the performance of a bridge in a rural environment. Compare the differences in the maintenance strategies obtained from the LCAT tool for the different scenarios analysed and comment on the results obtained between the different scenarios.

Repeat part (a) by carrying out strengthening interventions based on three different remaining relative strength limits (i.e. 99%, 95% and 90%). In this part, consider only a bridge located in an industrial environment and choose one paint type. Observe how the relative strengths reduce over time due to deterioration and comments on the relative criticality of each (i.e. buckling strength, shear strength and bending strength). You can assume that each strengthening intervention is carried out by increasing the element thickness by 1 mm. Consider both the main girder and the cross-girders and discuss the observations between the two types of.

The bridge owner would like to assess the cost of keeping the bridge in excellent condition. That means not allowing any of the relative strengths (i.e. local buckling, shear and bending) reducing to more than 98% of the nominal By analysing a number of difference maintenance strategies, combining re-coating (different paint types, different coverage percentages) and strengthening (different plate thicknesses in 0.5mm increments) interventions, propose an optimum intervention planning and estimate the optimum whole-life cost for it. Concentrate on the main girder only. You are not expected to carry out a full optimization; a reasonable number of different regimes you can attempt analysing is around 10-12. Discuss the results obtained from the different analyses carried out.

Data

• The discount factor can be assumed as 5%.
• The costs associated with the interventions are as follows:
• Re-coating by using M27.4 paint system = £8,000
• Re-coating by using M21 paint system = £14,000
• Each 1 mm of strengthening = £26,000
• Painting requires a two-night possession with an associated cost of £50,000.
• Strengthening requires five-day possession with an associated cost of £100,000/day.

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