12 STORY ADDITION ON TOP OF EXISTING 15 STORY BUILDING

SGI provided Structural Engineering Services for 12-story steel structure addition on  top of an existing 15-story occupied commercial building in midtown New York City.  The new 12 story addition of 45,000 SF building is supported only by two concrete  towers within the light wells of the existing building and is supported by new foundations   independent of the existing building. Vertical post-tensioning and rock anchors are used  to control the horizontal movement of the building.