Massive Resistance

by James S. Bailey, Vice Pres. & Proj. Engr.; E. W. Allen Assoc., 16 Exchange Place, Salt Lake City, UT 84111,
Edmund W. Allen, (M.ASCE), Pres. & Founder; E.W. Allen Assoc., 16 Exchange Place, Salt Lake City, UT 84111,


Serial Information: Civil Engineering—ASCE, 1988, Vol. 58, Issue 9, Pg. 52-55


Document Type: Feature article

Abstract:

The recently completed structural reinforcement of the 95 year old landmark Salt Lake City & County building, and its 250 ft high central clocktower, is believed to be the first historic structure in the world to be retrofitted against possible seismic damage using a base isolation system. Installation of a matrix of some 477 base isolation devices between the base of the structure's masonry walls and concrete footings, permits transfer of vertical loads while isolating the building from horizontal components of seismic forces. For the isolators to work properly, however, the structure's foundation walls also had to be isolated from the ground horizontally. A moat excavated around the structure's perimeter permits the building to move horizontally, relative to the ground, in the event of an earthquake. In addition to isolating the structure from its foundation and the surrounding ground, the seismic retrofitting project also included strengthening the two structures internally: and anchoring all masonry walls to existing floors as well as newly installed structural plywood diaphragms and shear walls.

Subject Headings: Base isolation | Shear walls | Seismic tests | Walls | Vertical loads | Structure reinforcement | Structural strength

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