Summary.Traffic and wind excitation has been used to obtain the dynamic characteristics of the fust Bosporus suspension bddge. Structural symmetry and the absence of suspended side-spans allowed attettion to be focused on the main span and the Asian tower. For the main spa4 18 vertical and 20 lateral modes were obtained, including to$ional modes. For the tower, 12 vertical plane and lateral plane modes were abstracted, again ircluding torsion. All these modes lie in the range G1.1 Hz.A detailed comparison is given between tbese modes and corresponding calculated on€s, obtained by use of a three-dimensional finite element model which includes a geometdc stiffness matrix. Of particular interest is the validity of the theoretical model used for tbe box dec\ because of its subsequent use in respotse studies under aysnchronous seismic input.Cornparison with a more limited study made in 1973 shows that the bridge continues to behave as it was designed to behave, partiolarly with regard to the deck-towe! interface. From ltatuml frequency measurements of two hangers, the load which they carry was assessed.Introduction.

A key parameter for assessing the unburial behaviour of offshore pipelines, such as during upheaval buckling, is the soil uplift resistance. Despite much research on uplift response, two variables remain relatively unexplored: the effect of low relative density backfill and partially drained soil response. To address this shortcoming, an investigation into the plane-strain uplift resistance of pipe segments in saturated sand was carried out. The model tests, targeting drained and partially drained soil behaviour, demonstrate that soil state strongly influences the pipe–soil failure mechanism, and hence the mobilised uplift resistance. In very loose sand the normalised peak uplift resistance remained constant beyond a critical embedment depth, indicating a possible transition between different failure mechanisms. Faster rate tests result in positive excess pore pressures, which serve to further reduce the uplift resistance. Tests at varying uplift rates and densities identified a transition relative density between net contraction and dilation for a given embedment. These findings suggest that a minimum backfill density should be ensured prior to pipeline operation, to avoid the negative effects associated with contractive behaviour of loose soil.

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