Costs and Benefits of Seismic Upgrading of Some Buildings in the Boston Area

We examine here the costs and benefits of reinforcing some existing buildings in Boston at the time of remodelling with significant change of use. The buildings of interest are the unreinforced masonry warehouses and the reinforced concrete manufacturing buildings that are remodelled into apartment or office buildings. Given some estimates of the Boston seismicity and of the performance of these buildings in earthquakes with and without additional reinforcement, we evaluate three possible levels of reinforcement that the Masssachusetts Seismic Advisory Committee could recommend as part of the building codes. For the unreinforced masonry buildings, the first upgrading level is the addition of floor and roof diaphragms, and the two subsequent levels involve addition of internal walls and reinforcement of the existing ones. For the reinforced concrete buildings, the first level involves increase of the shear walls' size, and higher upgrading levels involve addition of shear walls and increase of the columns' size. We introduce in our study the market effects of the additional costs. We conclude that only the first levels of reinforcement that we considered could be adopted as regulations, and that higher standards should be left to the choice of the buildings' occupants.