SEISMIC REHABILITATION OF ST. JOSEPH HALL AT SALEM MARITIME NATIONAL HISTORIC SITE, SALEM, MASSACHUSETTS

摘要

The National Park Service (NPS) retained URS Corporation to assist in the rehabilitation design of St. Joseph Hall for future use as a joint administrative and visitor center. The building is historic, and is a three-story building with unreinforced brick bearing walls that is planned to be used for general assembly. For both of these reasons, the NPS judged that the rehabilitation design should meet a minimum life safety performance level for an earthquake with a 10% probability of exceedance in 50 years. This level was selected to balance the need to protect the historic fabric of the building with the seismic retrofit requirements. This life safety performance objective was achieved at a reasonable estimated construction cost, without affecting the historic fabric of the building, and meeting the evaluation and design requirements of the U.S. Federal Emergency Management Agency (FEMA) guidelines. The existing building was found to have two specific deficiencies, each of which would prevent the building from meeting the life safety performance level of the FEMA guidelines. The first deficiency is the lack of shear strength for the five brick piers located at the building's south side. The evaluation found that these piers would be overstressed for both rocking shear and in-plane shear by the design ground motion. Each brick pier would fail, resulting in a partial collapse of the main exit of the building. The second deficiency is the lack of adequate connections between the roof and floor diaphragms to the perimeter bearing shear walls. Due to the absence of adequate connections, the building would not act as a predictable "box type" structure, and its behavior following a large earthquake would be unpredictable, and could lead to the loss of the exterior walls. This paper traces the evaluation of the existing building and the development of several strengthening schemes, and finally discusses the proposed strengthening scheme with structural details.