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Both Pre-Northridge steel moment frame and non-ductile concrete buildings are ideal candidates for upgrades using fluid viscous dampers because they are inherently flexible structures permitting FVDs to dissipate large amounts of energy at relatively low force levels. Conventional retrofit methods are more costly, architecturally restrictive, and disruptive to building occupants.
With just a basic understanding of the building characteristic properties and an assumed configuration of the FVDs, Taylor Devices can provide a conceptual design and cost-estimate for an upgrade solution.
Retrofitting structures with FVDs is becoming the preferred solution for the following key reasons:
From one side of the Pacific Ocean to the other, major seismic events have shown the vulnerability of improperly detailed steel buildings. Many welded, steel, moment- frame buildings sustained significant damage in both Los Angeles, California and Kobe, Japan during the 1994 Northridge earthquake and the 1995 Kobe earthquake, respectively. This damage consisted of a brittle fracturing of the steel frames at the welded joints between the beams and columns due to the lack of suitable energy dissipation.
A few of the most severely damaged buildings could readily be observed to be out-of-plumb; however, many of the damaged buildings exhibited no outward signs of these fractures. The observed damage raised questions as to whether buildings in cities affected by other past earthquakes had also sustained similar undetected damage and were now weakened and potentially hazardous. In fact, some structures in the San Francisco Bay area have been discovered to have similar fracture damage most probably dating back to the 1989 Loma Prieta earthquake.
Seismic events like the 1964 Anchorage Alaska Earthquake and the 1971 San Fernando Earthquake laid bare the deficiencies of the existing building codes. Several concrete buildings collapsed, and many were damaged beyond repair. There were multiple reasons for the damage and collapses, but most can be attributed to non-ductile detailing of the columns, beams, and beam-column joints.
There are still thousands of pre-1980 non-ductile concrete buildings in high seismic regions in the U.S. and abroad. Several Southern California cities have recently adopted ordinances that require owners to assess the collapse potential of their older concrete buildings and retrofit these if the assessment deems this necessary. These cities include the City of Los Angeles, West Hollywood, and Santa Monica. San Francisco is currently deciding what to do about the non-ductile concrete building stock in the city.
To learn even more benefits, read our blog post outlining all the advantages of dampers.
