Bridge Projects
New Tacoma Narrows Bridge




The New Tacoma Narrows structure is a suspension bridge in the state of Washington where seismicity is very high.

EMI provided geotechnical and earthquake engineering for new bridge design under a design-build contract. EMI's role was to evaluate the performance of foundation options from the seismic performance point-of-view, and to perform soil-structure interaction analysis to support structural bridge design. Foundations evaluated included large-diameter piles and gravity caissons. Gravity caissons were ultimately selected for final design to support two main towers.

EMI performed pushover analyses using the finite-element method, and the solutions were implemented in the global structural bridge model to incorporate the deformation behavior of the caisson foundation including nonlinear soil stress-strain behavior and foundation uplift. EMI also developed a practical approach to estimate permanent deformation of the caisson resulting from an earthquake.