The BGCL site team at Test Bed 80 procured the services of specialist temporary works designers HPBW to develop an inventive solution to address issues affecting the stability of the structure in its temporary state. The main part of the building comprises of double skin concrete walls. These walls are relatively slender and sit eccentrically on a narrow foundation below. The structure does not become fully self-supporting until the inner and outer roof structures are constructed.
Original temporary works proposals involved eight metre long raking props/shoring being installed at 45 degrees to the building. Props were required every five metres along the external length of each wall. Considerable reinforced concrete foundations were required to transfer the loads into the ground. Internal ties were required to connect inner and outer walls. This proposal was extremely onerous on the contractor and was severely limiting due to the following reasons:
- Excessive temporary works hire charges.
- Excessive restriction and reduction in working space.
- Design, construction and removal of bespoke reinforced concrete foundations.
The solution: design and install temporary shear brackets every 900mm to provide restraint to inner walls, coupled with the installation of temporary ties every 1.5m between inner and outer walls, utilising tie holes, to restrain outer walls from inner. The advantages of this solution were:
- Removal of the requirement for a bespoke reinforced concrete foundation, reducing concrete use on site by 400m3 and requirement for muck to be removed from site. This provided environmental and financial savings.
- Removal of props frees up an additional 1600m2 of working room.
- Consolidation of construction programme, as the new method can run concurrently with existing planned works.
The project continues to progress at a good rate in part thanks to this innovative and effective solution.