John Muir Medical Center, Seismic Retrofits
In the event of an earthquake, hospitals must remain standing and should be functional, if possible. The poor performance of older hospitals observed following the 1994 Northridge earthquake forced the State of California to reassess seismic requirements for existing medical facilities. When the California State Senate passed Senate Bill (SB 1953), they required hospitals to evaluate the seismic resistance of their structures and report the findings to the Office of Statewide Health Planning and Development. The initial bill established a compliance timeline with a target date of 2030 to bring all existing buildings up to a satisfactory seismic performance level. SGH assisted John Muir Health with many compliance challenges, including the evaluation and retrofit design for multiple existing buildings at both the Walnut Creek and Concord Medical Centers.
Through multiple iterations of seismic evaluation, SGH helped John Muir Health identify that all of their buildings do not represent a significant threat to life, but we determined that a few structures required modification to achieve adequate anticipated seismic performance.
As part of our work, SGH evaluated an existing elevator/stair tower that is part of an existing building and adjacent to existing functional hospital buildings (Wings C and D). We developed an investigation and testing plan to collect information about the existing construction and performed a nonlinear time response analysis for the six-story, reinforced concrete structure. As engineer of record, SGH designed a seismic retrofit that utilized fiber-reinforced polymer strengthening and traditional retrofit techniques, including the addition of shotcrete walls, improved shear transfer, and reinforced concrete beam strengthening. We also performed a linear analysis of Wing C and Wing D to ascertain the effect of pounding between the tower and the adjacent buildings.