Columns to remove, abnormal point loads to support?

During the modification of floor areas within existing buildings, the Architect will often ask the Engineer to remove vertical structural elements and replace them with transfer beams and grillages. To allow this, it is necessary to support the service loads of the structure, demolish the unwanted element and transfer the loads onto the replacement structure. Easily said but not so easy in practice.

Techniques

Using heavy duty props with load capacities of up to 1000 kN (100 tonne), in conjunction with fabricated structural steel beams of appropriate size, E P Rothwell & Sons Ltd can design and erect systems to carry the heaviest of loads.
Where necessary, foundations, either piled or pad, can be installed to support the temporary loads. Any special welding or fabrication work can be undertaken by our own engineers to suit the particular situation on site.
A variety of jacking devices is available to induce loads in the props. These can be installed, adjusted and monitored or simply installed for the client to use.
Work is undertaken by our own labour, all of whom have been trained in the handling of heavy equipment and working in the most difficult of site environments. They are all experienced in this type of work and bring many years of their varied experience to bear on every job that they work on.
The team allocated to each job will be carefully selected and sized to suit the required rate of progress and will arrive on site with all of the materials necessary to carry out the work with the minimum of supervision by the client. All tools and equipment will arrive with the team including all of the little but important items that would take an age to assemble if you were to do it from scratch.

Case Study

In refurbishing a retail unit in central London, the client had to remove a wall which lay directly in front of the new entrance and replace it with a smaller column positioned to minimise the obstruction. The wall carried a duct up through the building, which contained live services. The upper floors of the building remained in use, being occupied by a Law Practice - not the sort of tenant to let down!

RMD Megashors were designed in conjunction with the Structural Engineer to carry the weight of the building down into the basement raft slab. Hydraulic flat jacks were to be used to minimise movement of the structure and to ensure correct load transfer at the end of the job. The new structural steel was designed as part of the temporary works, with the protruding sections to be removed at the end of the job.

1) The shores were arranged in groups to support the grid of beams that converged on the original wall. Some required spreader beams in the basement and some could bear directly on the raft.

2) The new column and header beams were fabricated off site and erected within the temporary propping.

3) A confined working space within a main road shop meant access problems which meant that access had to be obtained through the back of the shop unit and down a normal staircase.

4) An interlinked set of control valves and gauges allowed full setting and monitoring of the loads within the structure throughout the job.