Extensive high capacity hydraulic shoring equipment from Groundforce Shorco, the UK’s leading supplier of engineered shoring solutions has been used to support excavations during the multi-million pound redevelopment of Bristol’s Broadmead shopping centre.
The project forms part of Phase 1 of the Bristol City Centre Expansion project and involves the re-routing of Bond Street and the construction of a four-storey department store, a further 15 major stores and 100 additional shops set within the 15 hectare area.
Groundforce Shorco has provided temporary support to excavations on the main site. Poor ground conditions on the city centre site meant that a lot of the permanent works needed to be temporarily propped until floor slabs and beams were tied to them.
Groundforce Shorco was required to supply five of its 250 tonne capacity MP250 hydraulic struts to brace sheet piled retaining walls at the widest and deepest part of the excavation. These struts span 27 m. In addition, over 45No. raking props, were supplied in phases. These sloped down at varying angles to transfer lateral loads at capping beam level into the concrete base slab at ground level through purpose designed anchorages. These raking struts were used to support the perimeter retaining walls where direct horizontal bracing was not possible. The struts comprised both MP250 and MP125 (125 tonne capacity) hydraulic struts.
The design of the permanent works required the props to be connected at specific locations in order to transfer loads safely. This created awkward angles and fixing locations, says Neil Bleakley, design office manager at Groundforce Shorco. “This meant that each connection had to be individually designed, fabricated and constructed in order to comply with the stringent design criteria imposed.”
By using its high-capacity hydraulic struts, Groundforce Shorco was able to impose a positive load on the new capping beam via the in-built hydraulic jacking system.. This ensured minimal deflection of the new concrete structure and reduced the degree of ground movement as the building works progressed.
The complexity of the engineering demanded a significant design input from Groundforce Shorco. In the initial design stages Groundforce engineers advised on specific connection details required, with the result that a lot of awkward angles and resultant forces were eliminated from the structure.
Close liaison with the site team also enabled Groundforce Shorco to design and manufacture each of the angled bearing plates required to connect the struts on to the capping beam. Groundforce also supplied all necessary detailing and information required to enable the construction to commence on site without delay.
Groundforce Shorco began work on detailed design development in early 2006 but it was not until June that work on the temporary supports commenced on site.
The £500 million redevelopment project is due to open in autumn 2008.
