Evaluation of Building Stiffness for Building Response Analysis to Excavation-Induced Ground Movements


A major element in the design and construction of tunnels and braced excavations in urban areas is the control of ground movements and protection of adjacent or overlying structures, which are often constructed with masonry and set on shallow foundations. Initial evaluation of potential building damage is obtained by assuming that building distortion is compliant with the imposed ground movements. Further investigations take into consideration the reduction in building distortion that occurs as a result of building stiffness. Presented in this paper are the results of numerical analyses for evaluating the equivalent bending and shear stiffness of masonry structures taking into account the anisotropy of the masonry units and the percentage of window openings. The distinct element code, UDEC, has been used to model each masonry block and the mortar between blocks for masonry walls in plane stress conditions. Parametric studies, conducted for a range of window opening percentage and brick/mortar joint stiffness, show that the equivalent shear stiffness for buildings with windows are low, typically in the range of 1/10–1/20 of the equivalent bending stiffness. Thus, for most masonry buildings, the shear deformation is dominant for a building subjected to excavation-induced ground movements. Equivalent bending and shear stiffness evaluated by the numerical analyses is compared with field data and analytical calculations, which may be available only for the case of no window openings.