Dames & Moore And their subcontractor, Inca Engineers, have prepared this Manual of Practice for conducting bridge foundation-soil interaction analyses. The manual is intended to assist engineers in the Bridge Design office at the Washington State Department of Transportation (WSDOT) who perform dynamic analysis of bridge-foundation systems. The primary purpose of the manual is to present practical and accurate methods of estimating the foundation stiffness matrices for abutment or pier foundations supported on footings or piles. These matrices are needed for soil-structure interaction analysis to more accurately determine the seismic loads acting on the bridge superstructure and on the abutment and pier foundations.
This Manual of Practice consists of two volumes. Volume I presents five bridge example problems: 1. Coldwater Creek 2. Deadwater Slough 3. Ebey Slough 4. Northup Way 5. FHWA.
The first four examples are actual WSDOT bridges and the fifth example is a fictitious bridge that appeared in a 1991 FHWA course notebook on seismic design of highway bridges.
Volume II presents the input and output files of the SEISAB computer program for the dynamic soil-structure interaction analysis of bridges. The SEISAB computer program is currently used by WSDOT in the seismic design of Washington state bridges.
Dames & Moore recommends the FHWA and Novak methods to estimate bridge foundation stiffness matrices. These methodologies are presented in detail in the Coldwater Creek example problem in Volume I. In this example, the basic theory and relevant equations or inputs for implementing these methodologies are provided first and are immediately followed by their application to the Coldwater Creek bridge. The appropriate equations or inputs from the FHWA and Novak methodologies presented in the Coldwater Creek example problem are identified and applied in the other four bridge example problems.
Volume I also contains three appendices. The basis for the recommendation of the FHWA and Novak methods is provided in Appendix A, which is a reproduction of the 1992 Dames & Moore report to WSDOT on the evaluation of methods to estimate foundation stiffnesses. Appendix B consists of selected pages from the BMCOL 76 computer program user guide; this computer program, which computes the load-deflection and moment-rotation curves for single piles, is part of the FHWA methodology. Appendix C presents the method for transforming the foundation stiffness matrices from one coordinate system to another. This transformation process is important because the coordinate systems assumed in the FHWA and Novak methods are generally different and therefore are not necessarily the same as the SEISAB coordinate system. Coordinate transformations are also discussed in the ColdWater Creek example problem.