Seismic Design Considerations, Volume I: Technical Approaches and Results and Volume II: Appendices II - VIII

New Jersey Department of Transportation (NJDOT) has adopted “AASHTO Guide Specifications for LRFD Seismic Bridge Design” approved by the Highway Subcommittee on Bridges and Structures in 2007. The main objective of research presented in this report has been to resolve the following issues for an effective implementation of American Association of State Highway and Transportation Officials (AASHTO) Guide Specifications: (i) AASHTO Guide Specifications don’t provide any specific guidelines for classification and performance requirements for critical bridges. This issue is resolved by proposing performance requirements and classification criteria for critical bridges in New Jersey. (ii) Guide Specifications present displacement based approach, which is significantly different than the force-based approach in previous versions of seismic guidelines. Nine examples of reinforced concrete and steel bridges of different characteristics (spans, skew, etc.) illustrating the use of newly adopted seismic guide specifications have been developed for training of engineers in New Jersey. (iii) NJDOT maintains an extensive electronic database of soil boring logs for the State of New Jersey. A zip-code based soil site map for New Jersey has been developed by analyzing soil boring data and other available New Jersey soil information. This map can be used for a rapid seismic hazard evaluation for the entire state or for a network of bridges in the state. (iv) AASHTO Guide Specifications introduce seismic design categories based on local seismicity and soil properties. Using the seismic soil map and zip code based seismic spectra provided in the AAHSTO Guide Specifications, seismic design category maps for critical and standard bridges in New Jersey have been developed. A detailed analysis has also been carried out to develop liquefaction potential maps for the state of New Jersey. These maps can be used to determine the need for a detailed liquefaction analysis for a particular bridge site. A detailed guideline on developing site-specific spectra has also been developed, since AASHTO Guide Specifications recommend site-specific spectra for critical bridges. (v) Existing bridges in New Jersey are required to be retrofitted on the basis of the 2006 Edition of the “Seismic Retrofitting Manual for Highway Structures: Part 1 – Bridges”. Simplified guidelines for seismic retrofit of existing bridges, that are consistent with guidelines for the design of new bridges in AASHTO Guide Specifications, have been developed.