This research looked into the influence of negative skin friction on timber piles in Amsterdam. Tensile load tests were performed on new, instrumented timber piles at Overamstel in Amsterdam. The negative skin friction calculated from the test data was compared to the negative skin friction from NEN 9997-1 for a single pile. The test results came close to the values from NEN 9997-1. A reduction of the factor required for timber piles when calculating negative skin friction using NEN 9997-1 seems necessary, but further studies are needed.

Alpha factors were derived from the test data, and comparison to the alpha factors from compression load tests confirmed the influence of tapering on the timber piles.

The research also confirmed the suitability of fibre optic sensors for pile load tests on timber piles.