Further , more recent inspections had shown further excessive wear in the curved link plate support beams and in the hinges and feet of the link plates . This increases noise and play in the mechanism and wear surfaces , causes rapidly increasing damage to the joint with ultimate failure of the joint resulting .
There are also further joints in both carriageways of the approach viaducts comprising of interlocking combs ( or fingers ), and there are also corresponding joints in both foot / cycle ways . It was recommended , because their movement is less and they had suffered less wear and tear , that these joints continue to be monitored and inspected and their refurbishment or replacement might be carried out during other future closures .
The replacement or refurbishment of all the expansion joints was recognised as a maintenance priority ; the rate of wear was likely to rapidly increase .
In 2007 a feasibility study was commenced , and options to either repair , refurbish , or replace each type of the expansion joint were considered .
The works would cause major disruption to the road users so the timing of the works needed to be coordinated . Timing , periods of closure and economic impact were considered .
To allow traffic flow to continue during replacement work temporary ramps over the expansion joints were proposed . The ramps would be 80 m long with two lanes ; the headroom under them for working was a minimum of 1.8m . The existing bridge deck would have to be strengthened at each tower to accommodate these temporary structures .
Tenders were received for the replacement of the main expansion joints during 2008 . However , the cost of the temporary works pushed the prices out with the available budget at that time . At the same time , the Scottish Government announced the timescale for the building of a second bridge across the Forth .
In this situation , the main focus was to determine whether or not the replacement of the joints could be deferred until after the opening of the new bridge and the removal of the majority of the traffic off the existing bridge . A review of the project was commenced .
This included undertaking a Failure Mode and Effect Analysis ( FMEA ). It was seen as the best means of identifying the likelihood and consequences of the failure of the various components that make up the joints . During a weekend closure another inspection was carried out during which one sliding train was removed .
The review team concluded that it would be possible to delay the replacement of the joints subject to the following :
� Significant increase in inspection and monitoring level .
� Installation of the permanent access to aid inspection .
� Replacement of key components such as pins and springs . � Installation of temporary failsafe devices . � Annual revision of the decision .
These measures have made it possible to maintain operational safety levels for bridge users .
Figure 14 : Virtual reality model of ramps Figure 15 : Plate train being removed
1 / 2017