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Lessons from Nonfailures

by Daniel A. Cuoco, (F.ASCE), Principal; LZA Technology, NY, NY,


Serial Information: Civil Engineering—ASCE, 1995, Vol. 65, Issue 10, Pg. 58-59


Document Type: Feature article

Abstract:

Two case histories are described in which building owners were told during rehabilitation projects that their structures were in serious trouble. In one case, the engineer told the owner that the building should be evacuated for safety purposes. The author's firm was asked to offer a second opinion and in both cases, found errors and oversights in the first engineer's investigation methodology and recommendations. In both cases, the buildings were found by the author's firm to have no serious structural problems. The author states that there is no way to know how many owners pay for costly retrofits that are not necessary because most owners do not want to spend what is probably far less money to get a second opinion. He also cautions engineers not to regard computer output as scripture. In one case, hand calculations showed errors in the computer results, due to mistakes in input. For one of the buildings, the first engineer performed an analysis based on the 1989 ACI codes rather than the 1979 code on which the building was designed and constructed. The latter code is much more stringent. For the other building, the first firm's analysis was based on working strength design, when ultimate strength design has been the method used by most structural engineers since 1971. The older working strength design is more conservative and give lower capacities. Other mistakes made by those investigating buildings were: improper testing, overconservative assumptions, and the no risk recommendation, one that relieved the engineer from any liability while exposing the building owner to great expense. The author notes that design engineers are used to new designs and are often unfamiliar with existing buildings. Hairline cracks in buildings of a certain age are not uncommon.

Subject Headings: Building design | Buildings | Owners | Standards and codes | Tensile strength | Structural strength | Rehabilitation

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