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Bridge assessments and overall condition score

  • 1.  Bridge assessments and overall condition score

    Posted 12 December 2018 00:08
    Hi,

    Just wondering how other Councils are using their bridge level 2 assessment data in developing a maintenance/capital works program.Our assessor uses the old VicRoads Bridge Inspection System software which calculates a BCN for each bridge.We are not convinced the BCN accurately reflects the condition of the bridge. I have looked at the way the NSW RTA assesses bridges into Good, Fair and Poor from the same type of assessment data which seems promising although I would like to classify it further into a score of 1 to 5.

    Can anyone provide some feedback on how you use condition data to develop your bridge programs?

    Thanks,

    John


  • 2.  RE: Bridge assessments and overall condition score

    Posted 12 December 2018 20:41
    Hi John,

    At City of Charles Sturt in Adelaide we use 1 -5 score (also matched the DPTI system).
    We then also run bridge maintenance against condition, functionality and risk to create our future maintenance planning.
    We created a matrix that is based on our condition data and the above paramaters

    Thanks
    Carmine
    Development Project Engineer
    City of Charles Sturt​


  • 3.  RE: Bridge assessments and overall condition score

    Posted 13 December 2018 17:25
    Hi Carmine,

    Is there any chance you could share the matrix you have developed?

    Thanks,

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    John van Nieuwkerk
    Strategic Systems Analyst
    Corangamite Shire Council
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  • 4.  RE: Bridge assessments and overall condition score

    Posted 12 December 2018 20:41
    ​John

    We follow the QLD DTMR Structures Inspection Manual which gives a 1-4 rating for components and 1-5 for the bridge as a whole. If a component was in condition state 5 then the whole bridge would automatically be a 5 and you would be closing or managing the bridge.

    We use the same scoring to condition rate footbridges, boardwalks and viewing platforms that don't require DTMR Level 2 assessments.

    The DTMR 1-5 rating lines up with the IPWEA ratings we use for all other asset classes and therefore is easy to explain to management and councilors.

    Daniel O'Hara
    Asset Management Engineer
    Moreton Bay Regional Council


  • 5.  RE: Bridge assessments and overall condition score

    Posted 13 December 2018 17:42
    Thanks Daniel.

    Do components have different levels of criticality? For example, does a condition state of 5 for railing make the bridge unsafe as it would for a condition state of 5 for say bridge decking?


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    John van Nieuwkerk
    Strategic Systems Analyst
    Corangamite Shire Council
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  • 6.  RE: Bridge assessments and overall condition score

    Posted 10 days ago
    We also follow the DTMR SIM guidelines and then apply a risk assessment methodology to rank the structures. This involved the incorporation of other factors list below to create a risk score to rank bridges with overall condition states
    • age of structure
    • environment where the bridge is located
    • AADT of road environment
    • detour length
    • road hierarchy
    • bridge replacement cost

    Regards,
    Carmen

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    Carmen Smith
    Engineer – Asset Performance and Monitoring

    PO Box 29 Gladstone Qld 4680
    Phone 07 4975 8236
    Email Carmen.Smith@gladstone.qld.gov.au | Website www.gladstone.qld.gov.au

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  • 7.  RE: Bridge assessments and overall condition score

    Posted 13 December 2018 21:14
    Edited by Charlette Newall 14 December 2018 00:45
    Hi John,

    In a previous role I held we ​used the VicRoads Bridge Inspection to assess our bridges and developed a BCN for each bridge. I found that the BCN provided a number but didn't reflect the condition of the bridge accurately enough to forward plan from. In the scenario where there where multiple girders in different conditions the fact that 1 may require immediate replacement was not identified in the BCN.
    Working with our bridge inspector we determined the best way to forward program the bridge works was to use the worst condition of each element to represent the component. For example a girder in condition 4 would mean the entire super structure of the bridge would be rated as a 4 (even though the surrounding girders may be in a condition 2). By doing this we were able to identify the bridges which needed more attention, and from that we could scope the required works and determine whether it was maintenance or capital work which needed to be undertaken.
    As for the condition 1-5, in practice any bridge which was closed to traffic due to deterioration and condition was considered a 5.

    For the renewal ranking criteria only the sub structure and the super structure conditions were used, along with other criteria such as Financial impact, grant funding approval, the importance of the bridge to the road network and any current load limit. To ensure we got the weighing of the criteria right I did some sensitivity analysis of the formula to see if the formulated answer reflected what we thought should be the priorities.


    Happy to discuss further.

    Thanks
    Charlette


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    Regards

    Charlette Newall
    Civil Assets Engineer
    Port Stephens Council
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  • 8.  RE: Bridge assessments and overall condition score

    Posted 10 days ago
    Thank you Charlette.

    Our bridge inspector rates the % of a component in conditions 1 to 4. E.g. a girder might be 20% condition 2, 30% condition 3 and 50% condition 4. Is that assessment what you refer to when you say "a girder in condition 4". The highest % for a component identifies the condition of that component?

    Thanks,

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    John van Nieuwkerk
    Strategic Systems Analyst
    Corangamite Shire Council
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  • 9.  RE: Bridge assessments and overall condition score

    Posted 10 days ago
    ​Hi John,

    Our bridge inspectors reports were per girder, he did not rate as a percentage of each girder, so the report would have

    Component Type: Super Structure
    Component:TGCG - Girder / Cross Girder
    Unit: Each
    Measure: eg 5 (quantity of girders)
    Then a column for each condition were the total adds to 5 eg 3 x condition 2 (60%) and 2 x condition 3 (40%).

    My comment regarding the condition 4 was for the renewal ranking criteria I developed to prioritise works. Both the condition of the super structure and the sub structure of the bridge had a 25% weighting for the priority for renewal. I found that if you took an average of all elements that make up the super structure and sub structure we were missing elements of each component which were potentially at risk of failure.
    For example if you have 5 girders 1 x condition 4 and 4 x condition 2 the average condition of the girders is 2.4. Then if you have timber bolting planks, and decking etc that are in condition 2 the average for the super structure will be even closer to 2. I felt that the average didn't really tell me much about the renewal needs of the structure and definitely didn't reflect the fact one of the girders is in condition 4 and needs replaced. So I decided to develop the priority list based on the worst condition of all elements within each component. So the condition for the component of super structure in this example would be a 4 and it would get the full 25% weighting for the renewal ranking criteria.

    Using that methodology the prioritised list could be developed (we had over 177 bridges (43 of which were timber) and major culverts).

    Once completed I could analyse the list and see what was driving each bridge to be on the list. Sometimes there would be a few elements that we could replace on a bridge rather than a full replacement of the structure. These elements would not have been identified as a priority if I had used the average condition of all elements of each component to develop the priority list. Other times I noticed things that were driving the bridge to be prioritised were things that don't effect the structure and can be easily fixed (such as paint work). In those cases I used the next worst element of the component and prioritised again.

    Hope that makes sense - it was just something I thought worked as we were trying to get on top of the timber bridges and keep them going rather than trying to fund full replacement all the time. Sometimes larger maintenance tasks were not being completed because of maintenance funding constraints - but prioritising this way meant we were identifying those tasks and could ensure funding was allocated for them.

    Happy to discuss, thanks

    ------------------------------
    Regards

    Charlette Newall
    Civil Assets Engineer
    Port Stephens Council
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  • 10.  RE: Bridge assessments and overall condition score

    Posted 8 days ago
    Thank you Charlette. Your detailed response is very helpful.

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    John van Nieuwkerk
    Strategic Systems Analyst
    Corangamite Shire Council
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