Posey and Webster Street Tubes

Seismic Evaluation & Retrofit Design

SC Solutions was responsible for assessing the Posey and Webster Street Immersed Tubes to determine the seismic response of the as-built tubes and several proposed retrofit configurations.  For each of these configurations nonlinear time history analyses with multiple support excitations were conducted and the structural integrity of each of the tubes was evaluated.

Nonlinear effects such as the representation of global geometric effects, joints between tube segments, and solid type analyses were also performed for several different cross-sections of the tube, and a 3D finite element model was produced to model the circular to rectangular transition segments.

The analytical team followed a unique approach during the evaluation of the global and local responses of these buried structures.  For the global model, the team carefully orchestrated a balance between the proper support spacing and mesh refinement of the model in order to create a simulation of continuously supported tubes using finite elements. 

For the local models, the proper construction sequence simulation was essential in determining the capacity envelopes for the tube components.  Studies were continuously conducted to determine the effects of variations in the soil properties on the tube structure.