North Shore Pumping Station Project

M2C evaluated the seismic stability of sections of the North Shore Pumping Station seismic design and retrofit project located in San Francisco, California. We provided a one-dimensional site response analysis using Fast Lagrangian Analysis of Continua (FLAC) to plot the free field spectral response and compare to the Target Spectra. Seven time histories were used in the 1D SHAKE and 1D FLAC site response analyses and comprised the following:

• Preparation of a 2D and 3D SSI FLAC model to model soil and structure interaction behavior during simulated shaking.

• Model Tunnel and pipelines into and surrounding the pumping station and study impact of tunnel and pipelines from surrounding pile and building foundations. Implement the 3-d liquefaction simulations and potential for buoyancy and design implications from the 3D SSI models. Comment on use of pile wall thickness and implementation of flexible couplings and strengthened deep foundations for pipelines and tunnels in models.

• Capture the 2D and 3D SSI model response at the free field as well as at the top of the structural wall and compare and calibrate the FLAC free field to the SHAKE, 1D FLAC results and target spectra used for structural design. The top of wall spectral response from 2D FLAC and any structural amplification relative to the target spectrum and free field will be evaluated and provided to the design team.

• Record acceleration, horizontal stresses and horizontal displacement histories along the perimeter of the irregular shape structure walls and document model performance. Estimate and provide racking displacements imposed on the structure both during simulated shaking as well as permanent deformation at the end of shaking resulting.

• Prepare a report summarizing the results of the findings. Additionally, provide electronic files (in MS Excel format) including the results of the study.