Amey's Mark Arndt says the repair to the broken member is down to the weather and whether other defects were identified.

Mr Arndt says conservative assumptions were made and the truss end links have pins at the bottom, which allows the swinging back and forward of the bridge.

If the pin becomes seized there is no way you could design any member for a fully locked pin, he says.

Mr Arndt says results from control load testing showed the pin was completely locked, that's why there was a very quick phase one repair to allow HGVs to get back over the bridge.

However the situation was not predictable, which is why HGVs still cannot cross. 

An independent technical expert has been taken on to advise MSPs during the inquiry, which will take evidence in January and February before reporting in March.

Amey's predecessor, the Forth Estuary Transport Authority, and Transport Minister Derek Mackay are also expected to be called before the committee.

The bridge was closed to all traffic on 4 December after a 20mm shear fault was discovered in a truss-end link, part of the structure which helps hold the carriageway up.

A temporary repair saw metal splints winched into place and used to clamp the metalwork together, with similar work done on other similar parts of the bridge as a precaution and monitoring devices installed.

Although it was re-opened to the majority of traffic ahead of schedule on 23 December, the repair put in place - estimated to have cost about £2m - was not deemed strong enough to allow HGVs to cross.

A permanent repair to allow vehicles weighing more than 7.5 tonnes is forecast to be complete by mid-February. HGVs account for 9% of traffic and 32% of the weight the bridge normally carries.

These vehicles have been diverted up the Forth Valley around Kincardine Bridge since the closure.

John Russell from Amey says the truss end link is probably the most inaccessible part of the bridge we have got.

Mr Russell says there were 23 inspections in that locus since 2001, with no defects discovered.

He says this is 51 year old bridge with a 60 year design.

Transport Scotland has commissioned Amey , externalto manage and maintain two iconic river crossings in the East of Scotland. 

Since June 2015 for five years it will manage and maintain the Forth Road Bridge and the Queensferry Crossing (currently under construction), as well as the associated approach roads. 

Image source, Amey

It delivers a range of services including engineering design, routine and winter maintenance as well as incident response to improve network reliability and journey times.  

Amey now manages and maintains every single vehicle crossing of the Forth river, including the Kincardine and Clackmannanshire bridges that it looks after as part of its Scottish Trunk Roads South East contract. 

And, indeed, through its examinations contract with Network Rail it also inspects and reports on the asset condition of the world-famous Forth Rail Bridge. 

Committee convener Jim Eadie asks about the tansfer of power from FETA to Amey.

Mr Eadie asks about the decision not to take forward £15m of repairs and is told by Transport Scotland that it was taken by FETA.

Amey's Mark Arndt details the maintenance of the Forth Road Bridge and explains it is a risk assessment based regime. 

Mr Arndt says the truss end links would have been examined on an annual basis.

He says Amey has a huge site presence 24/7 with 70 to 100 staff there all the time. 

The defect in the truss end link on the 1st of December this year.

A lorry driver has been charged after attempting to drive an articulated HGV over the Forth Road Bridge. 

Vehicles over 7.5 tonnes are currently banned from the bridge while damaged steel work is repaired. 

Image source, PA

Police Scotland said traffic had to be stopped heading northbound on the bridge on Tuesday morning to allow the HGV to be turned around. 

The bridge was closed to all vehicles for almost three weeks but reopened on 23 December. 

However, HGVs face a lengthy diversion until at least mid-February. 

Image source, Transport Scotland

Transport Scotland, external seeks to deliver a safe, efficient, cost-effective and sustainable transport system for the benefit of the people of Scotland, playing a key role in helping to achieve the Scottish government's purpose of increasing sustainable economic growth with opportunities for all of Scotland to flourish.   

Scott Lees from Transport Scotland gets us underway with an opening statement. 

Mr Lees goes into the detail of the repairs to the truss assembly. 

He says Transport Scotland believes the defect was unseen. 

Mr Lees says the decision to close the bridge set unprecedented challenges to the people on either side of the Forth and he thanks the patience of these people. 

He says the bridge will reopen to HGVs in mid-February. 

Traffic returned to the Forth Road Bridge on Wednesday 23 December after the completion of temporary repairs. 

The first cars were allowed back onto the crossing at 05:20 after engineers welded a splint onto damaged steelwork. 

Image source, Traffic Scotland

Heavy goods vehicles will remain banned until further work is carried out, with this scheduled for completion by "mid-February". 

The bridge was closed to all traffic on 4 December last year after a crack was discovered in a truss under the carriageway. 

Bridge operating company Amey said vehicles weighing over seven and a half tonnes are prevented from using the bridge until permanent repairs to a cracked steel truss are made. 

Infrastructure and Capital Investment Committee convener Jim Eadie gets the Forth Road Bridge inquiry underway.

The SNP MSP introduces the witnesses:

Wayne Hindshaw and Scott Lees from Transport Scotland, external

Mark Arndt and John Russell from Amey, external

Colin Clark from Fairhurst , external

Richard Hornby from Arup, external

The southbound carriageway of the Forth Road Bridge was closed as a safety precaution on Tuesday 1st December after a defect was discovered in the steelwork. 

Bridge operators Amey said the problem was found during a routine inspection. 

After a detailed assessment of the damage the bridge was closed because of structural faults on Friday 4th December. 

Image source, Forth Road Bridge

Originally Transport Minister Derek Mackay had said it would need at least three weeks to repair the bridge and safety was "paramount". 

The bridge re-opened to traffic on Wednesday the 23 December. 

Heavy goods vehicles remain banned until further work is carried out, with this scheduled for completion by "mid-February". 

MSPs are to begin an inquiry into the closure of the Forth Road Bridge this morning at 10am.

The bridge was closed for much of December after damaged steelwork was discovered. It remains closed to HGVs.

The Infrastructure and Capital Investment Committee, external is holding a "focused" inquiry into maintenance in recent years and the structural defect behind the closure.

The first session will take evidence from Transport Scotland and bridge operators Amey.

Good morning and welcome to Holyrood Live's coverage of the Scottish Parliament on 20 January 2016.

The Infrastructure and Capital Investment Committee begins its inquiry into the closure of the Forth Road Bridge from 10am.  

We’ll hear from Transport Scotland, Amey, Fairhurst and Arup this week, with the bridge still closed to HGVs and repairs ongoing.

Portfolio questions begins with infrastructure, investment and cities ministers in the hot seat. They will vacate said seat for culture, Europe and external affairs ministers.

Image source, Redfern

This section of portfolio questions will see a question about the impact of David Bowie on the culture of Scotland.

The Independent and Scottish Green group lead a debate, focusing on jobs in Scotland’s new economy.

Image source, PA

This follows the Scottish Green’s report which says that sustainable sectors in the new economy can employ significantly more people than currently work in fossil fuel industries.

Labour MSP David Stewart will lead a member’s debate calling for frontline fire and rescue services to be protected.