Vibration Analysis Study for the Lincoln Memorial

Hartman-Cox Architects

This study examines two sources of ground vibration at the Lincoln Memorial: ambient (or baseline) vibration and induced vibration. Ambient vibration is the general day-to-day environmental vibration caused by external sources, such as railroad, helicopter, and vehicular traffic. Induced vibration is vibration caused by specific construction equipment working in the vicinity of the Lincoln Memorial. We have analyzed the data and drafted guidelines for the use of equipment at the memorial. We recommend the following guidelines, not only for the scheduled restoration of the raised terrace, but also for future construction and maintenance activities at the memorial. • A maximum of five jackhammers or chipping hammers are permitted simultaneously on any side of the memorial. • No two 20- or 30-pound chipping hammers may be placed less than 10 feet apart, and 80 pound jack hammers must be a minimum of 20 feet apart. • Cranes must be equipped with a torque converter to minimize the amount of energy transferred to the ground and prevent high amplitude vibration impulses from reaching the structure. • Pumping mechanisms, i.e., grout pumps or concrete pumps, must be oriented so that the pump stroke is parallel to the side wall of the memorial closest to the pump. • Mechanical vibrating earth compactors are not permitted. We recommend additional testing during construction to monitor the initial and maximum levels of vibration induced in the memorial by specific pieces of equipment-both individually and in tandem-under actual working conditions. Due to operational differences (soil, engine and operator variations), the construction or maintenance equipment should be checked by field testing to verify the expected vibrations. We would analyze the initial data immediately and alert the Contracting Officer of any problems. The data from these tests should become part of the permanent record of the restoration and can be used in future projects. The maximum motions induced in the memorial during this study were from air traffic, both military and civilian. Unfortunately, not enough information could be gathered to definitively determine the effect the airplanes and helicopters are having on the memorial. We recommend further study be undertaken in this area to develop guidelines for air traffic in the vicinity of the Lincoln Memorial. The data suggests that the Lincoln Memorial does not rotate. Lack of rotation, however, is unusual for a structure of this size. A number of cracks observed in the skylight room indicate some form of movement within the structure, yet the ambient testing does not indicate the cracks. are due to rotation. We recommend further study which will be incorporated into a long-term monitoring system which is currently undo’ study in a separate report.

Vibration Analysis Study for the Lincoln Memorial

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