This property is a medium-sized, three-story (including basement) office block, of load-bearing masonry construction. The property is used as offices and the owner of the building wanted to achieve a more open plan environment. Therefore, the proposal was to remove four of the main internal load-bearing walls. As well as the walls, all three of the large chimney breasts were to be removed from ground floor to roof, whilst retaining the stacks above roof level.
We were tasked with providing a structural scheme to achieve the proposed internal alterations, allowing the contractor to provide an accurate fee proposal for the required works. Following confirmation of the scheme, we were tasked with providing a full set of structural calculations and construction drawings for submission to building control.
The primary problem faced was that all four walls and all three chimney breasts that needed to be removed ran in the same plane. North to South as you looked at the drawing. This meant that the majority of lateral restraint in this direction was lost by removing the walls.
To overcome this problem, we designed five steel stability frames, two two-storey and three three-storey frames, to be installed in place of the removed load-bearing walls. Wind, dead and imposed loads were calculated and applied to each individual frame to analyse the resulting shear forces, axial forces and moments. Based on these results we design the beams, post and connections and provided construction drawing and details. In order to pick up the remaining, large chimney stacks we specified steel plates welded to the top of the top beam.
During the design process, we liaised with contractor and architect to ensure we provided the safest, most efficient and economical solution.