Bridges

Asset Management Plan -Bridges

Bridges

Wagga Wagga City Council // Asset Management Plan // Bridges //

This Supporting Section should be read in conjunction with Council’s Asset Management Plan, the Asset Management Policy (which sets out Council's philosophy of asset management) and Council’s Asset Management Strategy (which provides Council with a clear direction and goal for managing the community's $1.185 billion (as at June 2010) worth of assets).

The condition of Council’s bridge assets has been audited as part of the asset inspection regime, rated against the bridge asset condition reference sheet and captured in Council’s electronic mapping system. The condition of all Council’s assets is rated from excellent to very poor. The colours on the following map indicate the condition of the asset, as detailed in the below table.

1 Excellent Dark Green

2 Good Green

3 Average Yellow

4 Poor Orange

5 Very Poor Red

1 Current Asset Base

Bridges


The following tables indicate the condition of the bridge network from excellent to very poor across the Wagga Wagga Local Government Area (LGA) for each bridge type.

Bridges Percent Area

Brick and Steel Bridge

Excellent 0 0% 0

Good 0 0% 0

Average 1 100% 225.4m2

Poor 0 0% 0

Very Poor 0 0% 0


ReinforcedConcrete and Steel Bridge

Excellent 1 1% 46.3m2

Good 11 77% 2,827.4m2

Average 3 22% 791.7m2

Poor 0 0% 0

Very Poor 0 0% 0


ReinforcedConcrete Bridge

Excellent 3 4% 335.3m2

Good 22 70% 6,501.8m2

Average 11 25% 2,290.7m2

Poor 1 1% 169.4m2

Very Poor 0 0% 0


Timber and ReinforcedConcrete Bridge

Excellent 0 0% 0

Good 2 24% 95.5m2

Average 3 54% 213.4m2

Poor 2 22% 85.3m2

Very Poor 0 0% 0


Timber Bridge Excellent 0 0% 0

Good 2 65% 173.3m2

Average 0 0% 0

Poor 0 0% 0

Very Poor 2 35% 95.1m2

Bridges



Bridge sized culverts

Excellent 4 3% 774m2

Good 65 63% 11,181 m2

Average 45 28% 5,001 m2

Poor 11 5% 850 m2

Very Poor 1 1% 74 m2

Size of the NetworkThe following table indicates how many bridges Council manages across the Wagga Wagga LGA.

Bridge Type Quantity Length (m) Area (m2)

Brick and Steel Bridge 1 18 255

Reinforced Concrete and Steel Bridge 15 643 3,665

Reinforced Concrete Bridge 37 1177 9,297

Timber and Reinforced Concrete Bridge 7 99 394

Timber Bridge 4 63 268

Bridge sized culverts 126 N/A 17,880

Total 190 1,999 31,760

Challenges of the NetworkSimilar to sealed and unsealed roads, the bridge network is spread across the entire Wagga Wagga LGA, with 72% being in the rural areas. The bridge network is ageing and this proposes management challenges in maintaining the structural integrity of the bridges and replacing the network. In the rural areas there is pressure for bridges to be wider to accommodate the increasing width of farm machinery.

The size and geographic spread of the network makes the inspection regime costly and time consuming. Due to the age of the network the findings of the structural inspections are often costly and require significant design and construction work.

Storm events typically present a significant challenge to bridges. They are generally located on waterways (creeks or rivers). When the water is flowing fast they may become a bottleneck for debris to become lodged. This limits the flow of water further creating more pressure on the bridge structure.

By nature of their design, it is a challenge to perform maintenance and renewal activities on the underside of the bridge, to the piers and underside of the deck. Machinery must be either driven down the waterway bank to access the bridge or sit on the bridge and reach down. There are risks either way.

Bridges


2 Condition Assessment

Condition Ratings Reference SheetThe condition of bridges is audited against a rating scale which ranges from excellent to very poor. This scale is used as the basis of all assessments of bridges by Council’s Surveillance Team. The rating scale forms the Condition Rating Reference Sheet below.

Bridges


Risk and Condition Ratings IndicatorsCouncil also uses Risk and Condition Rating Indicators to determine a prioritised works schedule for the maintenance, renewal and replacement of large asset categories. These indicators are used in addition to the Condition Ratings Reference Sheet to enable further analysis of the worst sections of the asset class.

The Indicators are used to develop an overall Works Schedule Priority Rating for each individual asset or section of an asset.

The first stage considers the risk the condition of the asset poses to the community based on road classification and estimated traffic volumes. The following table details the Risk Rating Indicators for the bridge network.

Bridge Risk Rating Indicators- Based on Road Type

Weighting Road Type/Traffic Volume

1.3 Arterial Road or Highway

1.2 Sub Arterial/Regional Road

1.1 Collector/Distributor Road

1.0 Residential Road/Rural Road

The second stage of the process considers Condition Rating Indicators. The following indicators are considered for each bridge:

scouring

cracking

the condition of abutment (the approach)

the condition of piers and piles

the condition of guardrails

vegetation under guardrails

sediment in scuppers

signage

delineation and

condition of culvert cells

Bridges


The more deteriorated a bridge is, the higher the rating for the above indicators. Each section bridge is rated against the Condition Rating Indicators detailed in the below tables.

Score Cracking Scouring Abutment Condition

Vegetation under

Guardrail

Guardrail Condition

1 Isolated fine cracking

Less than 50cm

Good No cover Good

2 Some significantlarger cracking

Between 51cm and 1m

Average Moderate vegetation cover

Average

3 Widespread, large cracking

More than 1m

Poor Significant vegetation cover

Poor

Score Sedimentin

Scuppers

Signage Condition

Piers andPiles

Delineation Culvert Condition

1 Clear Good No visible signs of deterioration

Good Good

2 Partially blocked

Average Some cracking and deterioration

Average Average

3 Fully blocked

Poor Spalling, wood rot and splintering evident

Poor Poor

Bridges


The results of the Condition and Risk Rating Indicators are combined to give an individual asset or section of the asset a Works Schedule Priority Rating. For example a section of bridge could be rated as follows:

Bridge XYZ

Cracking (C) 1

Scouring (S) 3

Abutment condition (A) 2

Vegetation under Guardrail (V) 1

Guardrail condition (G) 3

Sediment in scuppers (SS) 3

Signage condition (SC) 2

Piers and piles (P) 1

Delineation (D) 2

Culvert Cells Condition (CC) 1

Road Type (RT) 1.1 (Collector)

Works Schedule Priority Rating Formula

(C +S+A+V+L+G+SC+P+D+CC)RT=

Works Schedule Priority Rating (1+3+2+1+3+3+2+1+2+1)1.1 = 19.9

The Work Schedule Priority Ratings for each bridge are then ranked from highest to lowest to produce prioritised schedule of works for maintenance, replacement and renewal of the network.

Intervention LevelsTo guide Council’s response to customer requests a set of reactive triggers has been developed for each asset category. These triggers are called intervention levels and include expected response times. The following tables detail the intervention levels and response times for maintenance of the bridge network.

Bridge Intervention Levels

Blockage Inspection within one week. Corrective action taken within one month.

Guardrails missing Corrective action taken within 1 week

Safety sign missing Corrective actions taken within 2 weeks

Damage Immediate inspection. Immediate corrective action.

Poor delineation Corrective action taken within 1 month.

Bridges


Condition Inspection RegimeThe condition and risk of the bridge network will be assessed simultaneously as part of the Condition Inspection Regime. This inspection will audit the condition of the section of bridge against the Condition Rating Reference Sheet and also assess the risk based on location and usage. The entire bridge network will be audited every year.

The inspections will be in the form of a GPS audit routine for all bridges in the Wagga Wagga LGA. The inspections will include:

pedestrian surfaces and railing barriers

guardrail protection barriers

vegetation under guardrails

road surface and expansion joins

abutments

sediment adjacent to abutment

scuppers

armouring on spill through abutment

scouring around bridge structure

underside of the bridge deck

abutments and piers and piles

the waterway and

vegetation and trees in the area of the abutments

Ad hoc inspections are conducted in response to customer requests, on a needs basis and where the asset degrades due to unforeseen or unusual circumstances, like a storm event. These inspections are done onsite by trained surveillance officers and the results are captured in Council’s electronic mapping system (ArcGIS).

A structural inspection regime will also be implemented across the bridge network in the Wagga Wagga LGA every 5 years for all bridge types except bridge sized culverts. This inspection will be in the form of a non-destructive structural audit.

Structural audits are carried out by specialist bridge engineers who perform a series of tests on each structure to determine its structural integrity. The outcome of these tests creates a set of actions to be completed on the bridge to ensure its ongoing structural integrity. These works are then carried out by Council staff or specialist contractors depending on the nature of the works. Each bridge should be structurally inspected every 5 years.

Bridges


Life cycle management details how Council plans to manage and operate the asset category at the agreed level of service while minimising life cycle coststhroughout the useful life of the asset.

For most local government assets there are four key phases to the life cycle, namely: acquisition, operation and maintenance, renewal, and disposal.

Costs occur in each phase of the asset life cycle. It is important to attributethese life cycle costs to each phase to allow for effective decision making about how the asset will be managed.

The life cycle costs of assets include:

initial capital investment

operation and maintenance

refurbishment and renewal

administration, overheads and taxes

depreciation

capital use rate charges or rate of return and

disposal of the asset at the end of its useful life

The initial capital or investment cost of a new asset is a significant cost and often dominates the decision as to whether to acquire the asset or expand the infrastructure network. However, it is important to include all the costs associated with each phase of the asset life cycle, including ongoing operation and maintenance, future renewal and disposal.

3 Life Cycle Management

Bridges


Target Maintenance EventsThe following table details the target maintenance events associated with the bridge network annually.

Bridge Network Target Maintenance Events

Event Target Maintenance Events per Year

Visual inspection Twice per year

Structural testing Once every 5 years

Minor maintenance Once per year

Vegetation control 4 times per year

Painting Once every 5 years

NB minor maintenance includes – cleaning scuppers, cleaning and sediment removal from abutment, cleaning of expansion joints and general removal ofdebris.

RenewalA detailed work plan for the renewal of the bridge network is developed annually to support this Asset Management Plan. This renewal program is prioritised based on condition and risk.

DisposalCurrently, Council includes the cost to dispose of an asset in the unit rate of that asset type. As Council moves towards strategic asset management this cost will be captured separately. The Asset Management Plan will be updated to reflect this change as it occurs across the asset types.

Bridges


The Asset Management Plan for 2011 has been developed based on data collation, research outcomes and the results of Council’s internal stakeholder engagement process.

The next stage of the process is to ask the community to identify which asset condition is satisfactory to them. This will begin with an extensive community consultation process. The consultation will be in the form of a community survey which will be conducted online, at community gatherings, through focus groups and stakeholder meetings. The survey will use new technology, be based on images and a simple selection process. The outcomes of the consultation will form the foundation for true community engagement to occur in relation to the management of infrastructure across the Wagga Wagga LGA, in particular the development of agreed levels of service, supported by Council and the community.

As Council gathers data from the community about the level of service for each asset category the outcomes will be integrated into the Asset Management Plan.

Until the outcomes of the community engagement are known Council will provide costings to achieve an average condition for each asset category and use this as the satisfactory level of service.

4 Level of Service

Bridges


Current LiabilityThe following graph details the proportion of the bridge network in each condition.

*The increase in the number of bridges included in this graph from 2008/09 to 2009/10 is due to changes in the way the condition rating data is categorised. In 2009/10 the condition ratings of bridge sized culverts were included in the bridge category.

Council’s current liability in relation to the infrastructure network is the sum of all asset units which have a condition rating of poor and very poor. The current liability of the bridge network is estimated to be $2,537,350 (in 2010 dollars). The following table provides the details of the bridge network current liability.

Asset Condition Amount Estimated Cost in 2010 dollars

4 – Poor 2,067m2 $2,427,985

5 – Very Poor 95.1m2 $109,365

Total Current Liability 2,162m2 $2,537,350

5 Financial Considerations

Bridges


Project Annual Maintenance Costs For Council to achieve the intervention levels as detailed in Section 2 of this Asset Management Plan and the target maintenance events as detailed in Section 3, the projected annual maintenance budget for the bridge network is estimated to be $700,038 (in 2010 dollars). This estimate was developed by Council’s Asset Management Planning and Program Integration Teams in 2010. It is a first principle estimate and is expected to vary as Council improves its asset management process and strategies. The following table provides further details of the maintenance costs associated with maintaining the bridge network each year:

Bridge Network Projected Annual Maintenance Costs

Event Projected Annual Maintenance Costs

Bridge visual inspections $48,092

Bridge structural testing $80,000

Minor bridge maintenance $409,325

Vegetation control $69,426

Delineation $21,959

Sign maintenance $6,000

Guardrail maintenance $10,240

Painting $54,996

Required Increase to Annual Maintenance Budget perAdditional UnitAs the asset base increases it is important to ensure that the annual maintenance budget also increases. The annual maintenance budget for the bridge network should increase by $9.22 per additional square metre of bridge.

Bridges


There are some generic assumptions made in the management of assets in Wagga Wagga City Council, these are found in the Asset Management Plan. In addition, the following assumptions have been made in relation to the bridges network:

Culverts which are longer than 6m are considered to be bridge sized culverts and are included in this Section of the Asset Management Plan.

Bridge sized culverts are condition rated in line with the Bridges Condition Rating Reference Sheet and the Culvert Condition Rating Reference Sheet.

The bridge sized culvert condition ratings were included in the bridge network data for the first time in 2009/10.

6 Assumptions

Bridges

Documents

Transcript of Bridges