SR99 Bored Tunnel-Assessment of Settlement Impacts ... - SCATnow

1.0 B&C Analysis MethodThe buildings have been evaluated using the methods prescribed by Boscardin &Cording [1989] (B&C) using a batch analysis tool developed in Microsoft Excel usingVisual Basic. The following is an outline of the steps taken within the analysis tool:1. Buildings are idealized as a rectangle. The approximate geometric centroid ofthe building has been located relative to the closest tunnel station (X) anddeparture offset normal to the tunnel (Y) as illustrated in Figure D-1.2. The building plan length (L), plan width (W), and rotation (θ) relative to thetunnel alignment are determined by the user and input into the tool. Thecoordinates of the four building corners are then determined from this data(See Figure D-1 for L, W, and θ).3. Additional building properties (building height, foundation depth, and wallstiffness) are input by the user. A description of these three inputs isprovided in the following sections.4. Each of the four building faces and the two building diagonals are dividedinto N segments and the vertical settlement (δ v ) and horizontal strain (ε h ) arein turn found at each end of each segment based upon settlement dataprovided by the geotechnical engineer. 15. Vertical displacement slope and curvature are found using numericaldifferentiation (5-point stencil method) of δ v .1 The second derivative of settlement described in step 5 may become erratic as the differencebetween segment end point settlements becomes small. To avoid this tendency a target segmentlength of 10 feet was selected. N was then found by dividing the horizontal length of the buildingface by 10 feet. N was further limited to at least 5 segments per face but no more than 20 segmentsper face.The Alaskan Way Viaduct & Seawall Replacement Program March 2010Proposed SR 99 Bored Tunnel - Assessment of Settlement Impacts to Buildings D-1Public Disclosure Request 11-0123 for Elizabeth Campbell - 2nd installment