U.S.G.S. Vibration Inspection – Lincoln and Jefferson Monuments

King, K; Carver, D

Lincoln and Jefferson Monuments are under the care and protection of the National Park Service. Each monument is unique and requires special protection, maintenance and restoration. The National Park Service is now involved in restoration on the monuments (memorials). They are using the restoration program as an opportunity to assess the probable causes of degradation of the monuments and methods of mitigation of those problems. One of the potential problems to the monuments is the increased amount of induced vibrations. Road building activities, maintenance operations, public activities, and increased traffic from the heavier and larger modem vehicles (road, air, rail) have changed the vibration environment of many historic structures. The present vibration environment can put a strain on historic structures which was not known or planned for during the original construction. The National Park Service requested a vibration inspection and a general vibration sampling of the two monuments; and, specifically a vibration inspection of the raised terrace area of the Lincoln Monument and the volutes on the top of the columns at Jefferson Monument. The basic objective is to make a sampling and a preliminary evaluation of the vibration environment of the unique and irreplaceable structures. The use of site-specific empirical data rather than structural models to detail vibration parameters of a specific structure, result in better resolution and accuracy. Accomplishment of these objectives included vibration sampling and preliminary determination of a number of parameters. The most important of these include: (1) the frequency or frequencies at which the structures are most sensitive, (2) the amount and type of vibratory energy induced into the monuments by the general traffic (particle-velocities and spectra), and (3) the possible amplification of that energy by the structure. The objectives are limited by the scope of this project. The scope encompassed a limited visual inspection and vibration sampling. The discussion, therefore, will give only the more general conclusions.

U.S.G.S. Vibration Inspection – Lincoln and Jefferson Monuments

Series

Collections