Load testing to justify the planned use of a 3 tonne excavator on an LPS structure in Hammersmith.
Scope of Work
As an LPS structure additional load considerations needed to be considered due to the floors of the structure being constructed of precast, prestressed concrete panels.
Due to the small floor spans and uncertainty between the connections between two side panels. It could not be proved using calculations that the floors could take the load and load testing was required.
Bending Load: Following initial analysis the worst case bending moments were when the machine was operating on its toes. Therefore the load was placed at the end of the panel during testing.
Sheer Case: The load was to be applied at the edge of the panel and towards the support of the panel.
Critical Check: Calculations were made to determine the critical check and this was incorporated into the load testing.
Load Testing Configuration
To replicate the loading to the panel, a propping system was designed to utilise the weight of the floors above to jack from.
Within the propping system, two distinct sections were created to represent the two toes of the machine.
Simulating how the load would start at a given point and then work its way up the structure.
The load is then transferred up and into the slab taking a portion of the slab’s self-weight at various points to provide the load to push from onto the system.
Sheer Test Arrangement
Due to the proximity to the end of the slab a slightly different arrangement was used for the sheer test. An additional prop was added to take out the horizontal force being applied to the wall.
Testing Set Up
A section through the test set-up is shown below. It was detailed so that the engineer loading the structure and the engineer taking the readings could do this remotely from the adjacent bay.
The load was applied in increments with an engineer monitoring the load as it was applied.
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