Safeguarding History

by Scott W. Harper, (A.M.ASCE), Pres.; Metrum Corp., Lakewood, CO,
Merton Weichman, (M.ASCE), Pres.; SDG Inc., Lakewood, CO,

Serial Information: Civil Engineering—ASCE, 1991, Vol. 61, Issue 5, Pg. 46-49

Document Type: Feature article

Abstract: Even monolithic marble monuments, such as the Thomas Jefferson Memorial, fall prey to materials deterioration. Now, sensitive instrumentation systems can document and analyze even the slightest change in such complex structures and ensure that restoration programs are on target. Thousands of tourists mill through the Jefferson Memorial in Washington, D.C. each day, unaware that small sensors will help engineers to eventually restore the monument before the cracking problem becomes serious and costly. This monitoring system is only a portion of a larger, ongoing study of the Jefferson and Lincoln Memorials commissioned by the National Park Service in 1988. Structural engineering and instrument consultants, SDG Inc./Metrum Corp., both of Lakewood, Colo. are undertaking the electronic monitoring of the monuments cracks and joints. The 48-year-old memorial shows signs of minor cracking in the limestone inner dome at the vertical ribs between coffers, in the marble columns and capitals, and in the concrete main-floor slab. Thermal expansion and contraction are causing minor problems both in the substructure under the entrance steps and at the interface between the masonry ring wall that supports the annular concrete roof slab.

Subject Headings: Cracking | Deterioration | Marble | Monitoring | Monuments | Probe instruments | Restoration |

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