Impact of Adjacent Construction on Existing Building

This paper presents a case study of a two-story unreinforced brick masonry building that was adversely impacted by construction activity associated with the development of an adjacent high-rise building. One longitudinal exterior wall of the URM building was located along the property line where the construction activity for the new building occurred. The new construction extended several levels below grade requiring support of excavation along the property line. The excavation was shored with a system of soldier beams cast in drilled shafts, raker beams, and lagging that also served as the formwork for the basement retaining walls of the new structure. However, the excavation activity disturbed the equilibrium of the URM building and caused settlement of its longitudinal exterior wall foundation, which resulted in cracking of the exterior walls, settlement of the floor slab-on-grade, and other distress to the URM building. The potential for damage to the URM building was mitigated to some extent because of a prior seismic retrofit, which tied the second floor and roof diaphragms to the building walls. Photographs taken during a pre-construction survey of the URM building confirmed that cracking of the URM building occurred after commencement of adjacent construction. Details of the investigation performed to determine the cause of distress to the URM building are described in this paper. The intensity of vibrations induced by shaft drilling and their attenuation with distance was also assessed through a desktop study to complement the findings. The measures adopted to remediate damage to the URM building with the added constraint of adjacent construction are also discussed in this paper.