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CROSS Safety Report

Failure of pile load test arrangement

Report ID: 484 Published: 1 January 2015 Region: CROSS-UK

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Overview

A pile was being load-tested, for confirmation of design pile loads for the foundations of a road bridge, when the web of the deep steel beam used in the testing arrangement buckled.

Key Learning Outcomes

For construction professionals:

  • It is good practice to have a load test arrangement designed and assessed by a suitably qualified engineer to ensure the members can accommodate the test load

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In 1985, a 12m long 600mm diameter pile was being load-tested for confirmation of design pile loads for the foundations of a road bridge. The testing arrangement was a deep steel beam with a tension pile at each end and a load cell in the centre pushing against the pile (Figure 1). At around 1.5 x working load (105t), the beam web buckled, and the load dropped back to an approximate working load of 76t. 

Image
Figure 1: pile test arrangement

The pile contractor unloaded the pile, welded some stiffeners in and reloaded satisfactorily to 1.5 x working load for 48 hours. Analysis of the beam to BS449, showed the web as being close to buckling at 105t, with fbc=179N/mm2 and fe (fbc+fb+fq) =194N/mm2 at midspan, cf 230N/mm2 max. 

The pile contractor had just taken over the sub-contract from the previous contractor, who had gone into administration. Hopefully this failure would not be dealt with in this manner these days!

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