February 11, 2010 § 1 Comment
Yesterday morning’s small earthquake woke people in Chicago up, but did no damage. While the city isn’t technically in a seismic zone, it’s not immune to the occasional tremble.
On the morning of Oct. 31, 1895, much of the midwest was shaken by a surprisingly violent earthquake. The next day, the Chicago Tribune reported that while many in masonry buildings had been shaken awake, those in the “lofty office buildings” hadn’t felt a thing:
“Night watchman W. C. Smith was on the thirteenth floor of the Reliance Building, no. 100 State street, at the time the earthquake should have alarmed him. He said last night: “I was on the thirteenth floor until 7:30. I was awake and walking about. I noticed nothing, and can find no one who did. The earthquake failed so far as this building is concerned.”
Further south, the Fisher building, under construction, also felt nothing:
“Of all structures which should have felt the shock, the lofty skeleton of the Fisher Building, now under construction on the northeast corner of Van Buren and Dearborn streets, seemed the most promising for a good story. Fourteen of its eighteen stories are under construction, and a forest of steel framework rises to a great height above the street level. Construction work goes on by night as well as by day.
“At 5 o’clock Foreman Arthur Hand had charge of a gang of thirty men working on the topmost floor of the structure. The earthquake came and went, but the workmen remained in blissful ignorance of the occurrence until the day men began to arrive with stories of earthquake shocks in all parts of town.
“Foreman A. D. Graham was on the framework of the fourteenth floor from 5 a.m. to 7 a.m. He was sure no shock had been felt, and thought the fact augured well for the solidity of construction work on the Fisher Building.”
This, of course, was a good sign that the new, moment-framed steel structures were resilient, but it also provides anecdotal evidence of their ductility, or ability to bend under load. Today, steel frames that give without breaking are preferred in seismic construction, particularly over brittle masonry structures. These two buildings, among the first to use self-braced frames to resist wind loading, seem at least anecdotally to have also protected against the “Great” Chicago Earthquake of 1895.
Quotes from “In the Lofty Office Buildings.” Chicago Daily Tribune, Nov. 1, 1895. 1, 6.