Bridge of Cally - Cantilever Drop Scaffold

Project Background

Bridge of Cally is a small village in Perth and Kinross, Scotland. It sits at the junction of three glens, Glenshee, Strathardle and Glenericht and is centred round the bridge over the River Ardle.

Following a period of heavy rainfall, the bridge drainage was overwhelmed resulting in extensive parapet damage resulting in a lane closure due to the road deck also being partially undermined. 

Our customer was appointed as the Principal Contractor with HAKI Access Solutions sub-contacted to provide specialist scaffolding and rope access services. 

Client Initial Specified Work Scope

Our customer required a suspended scaffolding solution to allow the damaged abutment wall to be rebuilt in stages following the parapet and wall collapse. 

The access solution had to provide access to the full work face while not imposing any loadings within the stipulated loadings exclusion zone around the collapsed area. Furthermore, the scaffolding had to be located within the existing lane closure while avoiding the overhead services.

Our Solution

The initial response was to deploy an industrial rope access team to clear the site of debris, vegetation and to install temporary props where safe to do so to minimise the risk of further collapse while the scaffolding was designed and checked. Upon site clearance the access solution and repair scheme could be finalised. 

Our access solution was designed in-house by our specialist design team and given an additional independent Cat 3 temporary works check due to its complex nature.

A pair of HAKI Universal system scaffold towers were erected with circa 8,000Kg of concrete kentledge per tower required to provide the necessary support for the cantilevered structure with 750mm HAKI beams needling out from the towers. The towers were sited approx. 14m apart to ensure all ground loadings from the scaffolding would be a safe distance from the collapsed parapet and undermined road deck.

The towers were joined by a 18m run of HAKI 750 beams from which a HAKI Universal Aluminium scaffold was suspended from to provide access to the masonry contractor. 

 

Safety & Commercial Benefits

The deployment of a rope access team following the collapse allowed the site to be quickly cleared and assessed for the necessary repairs. 

Our choice to recommend a cantilever dropped scaffold was the quickest and safest way on this specific site to provide the necessary access with the alternative of erecting from the riverbed quickly ruled out due to the fluctuating water levels presenting a major stability risk for the ground works necessary to support such a scaffold along with the environmental impact. 

While lane closures are unavoidably disruptive to road users, the bridge remained open for the duration of the repairs with minimal closures required for the erection of the scaffolding only. 

The design was also able to be repurposed for a later scope of drainage upgrades on both sides of the structure to future-proof the bridge against future storm events and ensure its resilience.