Maintenance Prioritisation (VFM) 5 – Scheme Option Analysis and Selection (Tier 3) - Completing a scheme

BridgeStation Knowledge Base > BridgeStation Web Edition > Modules
This will explain how to begin a scheme option analysis. Once you have you structure selected Step 2 will ask you to detail various Structure Details.  
 
 
Most data, where they exist, at Step 2a of the wizard will be automatically inserted into their fields. If this data either doesn’t exist, or is incorrect, you can change it here. Any changes, however, will not be affecting the permanently recorded data stored in Bridgestation, but they will only be taken into account for the calculations carried out in this analysis. Therefore, it is strongly recommended, that you change your recorded data, if required.

Step 2a: Review Basic Structure Details

Dimensions and Primary Material

Fill in all the Dimension fields in this section and use the drop-down menu to select the Primary Deck Material. 
 

Traffic details on Route Supported

Use the drop-down menu to select the type of Route Supported (over the bridge). Then complete the following data if applicable:
  • Avg Speed Over (mph): the Average Speed of the Vehicles over the structure.
  • AADT Over: the Annual Average Daily Traffic over the structure.
  • AADT Buses Over: the Annual Average Daily Traffic for buses over the structure.
  • AADT HGV Over: the Annual Average Daily Traffic for HGVs over the structure.
 
If the structure: i) carries no vehicular traffic (e.g.: a footbridge), then leave these fields blank. ii) is closed to vehicles, then fill in the vehicles it was carrying when it was open (or make a realistic assessment).
 

Traffic Details on Obstacle Crossed

Use the drop-down menu to select the type of Obstacle Crossed (under the bridge).
Type the following data if applicable:
  • Avg Speed Under (mph): the Average Speed of the Vehicles under the structure.
  • AADT Under: the Annual Average Daily Traffic under the structure.
  • For structures that don’t cross any vehicular traffic (e.g.: bridges over rail, water, land etc), leave the fields above blank but make sure you select the relevant Obstacle Crossed.
 

Parapet Details

The relevant Parapet Details will be filled in automatically if they are recorded in your element inventory.
  • Parapet Length (m): the length of the bridge parapet in metres.
  • Highway Alignment: use the drop-down menu to select the alignment of the highway over the structure.
  • Parapet Type: use the drop-down menu to select the type of parapet of the structure.
  • Other Factor: The drop down reveals all the options. These are local geometrical and carriageway characteristics of the parapet relating to the distance of the parapet from the carriageway, the existence of a concrete step barrier, trief curb, or arrester bed in front of the carriageway. Pick the first applicable option from top to bottom. For example, if the parapet is less than 1.0m away from the carriageway and there is also a trief curb installed in front of it, select the option with “Trief Curb”.
Click Next (Diversion Details) to proceed to the next step

Step 2b : Update Diversion Details Due to Failure event

One of the purposes of this module is to determine what is the risk of a structure in the event of a failure event. It is, therefore, reasonable to assume that following the failure of the bridge, there will be diversions in place to redirect the traffic that would otherwise use it. In this step we capture this information.
 

Copy from previous year:

For consistency, if the structure has been analysed in the past (say, for the previous year), then you can press this button and the figures previously used will be copied into the relevant fields of this step.
Structure is currently closed: Tick this box if you have closed your structure to all vehicular traffic.
 

Diversion Over & Diversion Under:

  • Length (m): Insert the length of the diversion in the event of a failure.
  • Average Speed (mph):  Enter the average speed of the vehicles on diversion. This figure could come from a traffic survey or a realistic estimate based on the AADT and speed limit. For example: It is reasonable to assume that by diverting 50,000 vehicles per day from an A-Road on a local B-Road with a speed limit of 30mph, the average speed of the vehicles on diversion would drop considerable to, say, 10mph.
  • Duration (days): Make a judgement of the duration that the diversions will be in place. As an example, for the diversion over, this would obviously be a judgement on the time it takes to repair/replace the bridge after the failure event.  For the diversion under, this could be a judgement on the time it takes to clear or make safe the road underneath.
 
Click Next (Existing Diversion) to proceed to the next step: 

Step 2c : Update Any Existing Diversion/Speed Restrictions

If a bridge is currently closed, or the movement over it is restricted in any way, the users are not receiving the full benefit of the structure. All vehicular restrictions are recorded in this step. These could be:
1. Diversions of all vehicles, if you have indicated on the previous step that the structure is closed to all traffic.
2. Diversions of certain vehicles due to loading, height or width restrictions.
3. Signed speed restrictions.
4. Speed restrictions resulting from lane closures.
 

Diversion Over & Diversion Under

  • Vehicles on Diversion: Insert the number of vehicles that are currently on diversion. If the structure is closed then this figure should be the same as AADT Over (or Under) in Step 2a.
  • Length (m): the length of the diversion that is currently in effect.
  • Average Speed (mph):  Similar to Step 2b, enter the average speed of the vehicles that are currently on diversion. This figure could come from a traffic survey or a realistic estimate based on the AADT and speed limit. For example: It is reasonable to assume that for a diversion of 50,000 vehicles per day from an A-Road on a local B-Road with a speed limit of 30mph, the average speed of the vehicles on diversion would drop considerable to, say, 10mph.
 
Article ID: 293, , Modified: 12/19/2018 at 11:40 AM

Was this article helpful?

Share this article