SUMMARYThe goal of existing building codes and standards for the evaluation and strengthening of existing buildings is to provide for safe buildings by prescribing loads and material properties and structural analysis methods for a broad spectrum of building heights, types and construction. Experience clearly shows that building codes and standards do not provide for the most economical, efficient and safe tall buildings because the codes are general and prescriptive in nature and do not allow the structural engineer the flexibility without significant difficulty to incorporate building-specific applicable experience, education and new technologies. Tall buildings are really a special class of buildings that have unique qualities and characteristics. The design of tall buildings has been recognized by the structural engineering profession to require more care and effort in both design and construction because of the need to meet safety and performance requirements. This recognition is based in part on the large number of people at risk in tall buildings and also the negative financial impact on the community and the building owner. To meet this need, an alternative procedure for Seismic Evaluation and Strengthening of Existing

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Following the Northridge Earthquake in 1994, the SAC project was initiated as a joint venture between Structural Engineers Association of California (SEAOC), Applied Technology Council (ATC), and Consortium of Universities for Research in Earthquake engineering (CUREe) to investigate the causes of widespread damage observed in the connections of steel moment frame buildings. The published results of these studies concentrated on local connection defects that potentially initiated the observed cracks. It was also considered that much of the observed connection damage was the result of yielding of the material in the connection region and the formation of plastic hinges. However, damage to some buildings could not be reconciled by the use of these failure mechanisms. This has led to a renewed interest in the effects of low‐cycle fatigue on the members and connections in steel buildings that are either elastic or have been driven into the weakly nonlinear range. The current paper is focused on the effect of low‐cycle fatigue in the connection damage observed in a 10‐storey steel building following the Northridge Earthquake. A comprehensive fatigue analysis procedure is developed based on the Palmgren–Miner method and S–N curves established for the high‐cycle fatigue range are extended to the low‐cycle region using the limited test results that are available. Fatigue analysis is performed at critical locations of a representative moment frame using the established procedure. Finally, the pattern of cumulative fatigue at critical connections and the observed damage are compared. Results of this analytical study indicate that the effect of low‐cycle fatigue may be significant in evaluating and predicting various types of connection damage similar to that observed in the steel moment frames following the Northridge Earthquake. Copyright © 2010 John Wiley & Sons, Ltd.

The seismic rehabilitation of steel buildings can be effectively done using viscous dampers. The dampers increase the energy loss without increasing the stiffness of the building and associated acceleration‐related earthquake damage. This paper discusses how a base‐isolated building used viscous dampers for seismic rehabilitation. Copyright © 2001 John Wiley & Sons, Ltd.

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