Balliemore Burn

Balliemore Burn is a single span bridge carrying the B836 over Balliemore Burn located near Glen Lean on the Coral peninsula in the local authority of Argyll-Bute, Argyllshire, Scotland. The superstructure consists of 4 No. MY5 and 2 No. MYE5 pre-cast pre-tensioned beams composite with a reinforced concrete deck slab. The deck is integrally jointed with in-situ stitch to reinforced concrete abutments. The substructure comprises reinforced concrete abutments cantilevering from reinforced concrete spread foundations with precast reinforced concrete return walls flanking each abutment corner.

Scope of services

Nuttall Bowser undertook outline design and detailed design for a bridge replacement, of a partially failed and temporary closed bridge carrying a single carriageway, in accordance with Eurocode Standards. Nuttall Bowser provided full design package including design drawings, design calculations, specifications and as-built details for the integral bridge design and abutting retaining walls.  

Challenges

The original structure comprised a shorter span, of circa 8m, of reinforced concrete construction which had suffered undermining of the east abutment through river scour leading to structural damage of the deck and its support. The new bridge would require an increased span in order to enhance protection vs repeat scour whilst maintaining the existing minimum headroom to enable provision of an adequate hydraulic envelope beneath the structure. 

There was a client requirement to provide a relatively narrow deck to enable a cost efficient solution whilst also accommodating the original road curvature and safe walkway to one side as well as provision of services.

Value added

Nuttall Bowser developed an efficient integral pre-stressed that enabled an increased span length, with pad foundation design.  Working closely with our clients we developed details that reduced on-site in-situ concrete pours through provision of pre-cast pre-stressed concrete beams, second stage precast parapet up-stands to the edge beams and precast return walls flanking each end of the abutment.  

We recommended enhanced scour protection, through angled sheet piling, be provided to both the east (scoured side) and the west river edges to provide protection to the newly constructed abutments, and thus providing protection of investment for our end client and confidence of a serviceable life in line with the 125-year design life.

We worked collaboratively with Geo-Structural to specify a suitable concrete mix that both met the durability design requirements whilst also achieving practicality of concrete supply provision.