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Trials conducted on the London Millennium Footbridge in 2000 monitored movements using three GPS receivers. After initial processing, the results gave plausible vertical and lateral (sideways) displacements, but also described implausible longitudinal movements along the axis of the bridge. Digital signal processing techniques applied to the data are reported. Due to the satellite constellation in the UK, a large void exists from the zenith to the horizon in a northerly direction. This lack of GPS satellites results in poor satellite geometry in the north-south direction, and hence poor north-south precision, explaining the unsatisfactory element of the Millennium Bridge results. More importantly a technique to overcome the issues is described. Notwithstanding this, the lateral vibration frequencies obtained from the GPS data agree extremely well with those found in the modal surveys carried out by Arup, even when displacement amplitudes are small.

Compression member buckling in association with joint instability was observed in several truss and model tests, involving certain types of prefabricated systems. It was also evident in a recent collapse. The paper presents an analytical procedure for evaluating the influence of the connection stiffness on the member elastic buckling load. The proposed model, which is suitable for implementation with the aid of spreadsheet calculations, is intended as an indication of the sensitivity of the system to joint instability and the need for rigorous stability and non-linear analysis. Some examples are presented, comparing results of the proposed method with analytical and numerical computations and with test results.