Research Problem Statement and Background

This proposal is in response to New Jersey Department of Transportation RFP#2008-09 entitled “Seismic Design Recommendations”. Current Seismic design of new highway structures in New Jersey follows the requirements of Subsection 3.10 of the AASHTO LRFD Bridge Design Specifications. All bridges in New Jersey are considered as “essential” for seismic design and as “standard” for seismic retrofit. Highway bridges in New Jersey are seismically retrofitted according to “Seismic Retrofitting Manual for Highway Bridges” currently numbered as, FHWA-RD-94-052, May, 1995. However, because of the newly adopted “LRFD Guide Specifications for the Seismic Design of Highway Bridges” prepared by Roy Imbsen by the AASHTO Highway Subcommittee on Bridges* and Structures and the publication of 2006 Edition of the “Seismic Retrofitting Manual for Highway Structures: Part 1 – Bridges and Part 2 – Retaining Structures, Slopes, Culverts and Roadways” by the FHWA, it has become necessary to develop unified seismic design and retrofit recommendations for New Jersey bridges based on these documents. The main objective of the proposed research is to develop recommendations on adoption of these documents by NJDOT for seismic design and retrofit of highway bridges. The specific objectives of the proposed research are:

(i) Preparation of guidelines for seismic design of New Jersey bridges based on review and critical analysis of “LRFD Guide Specifications for the Seismic Design of Highway Bridges”.

(ii) Preparation of guidelines for retrofit of existing bridges based on review and critical analysis of “Seismic Retrofitting Manual for Highway Structures: Part 1 – Bridges and Part 2 – Retaining Structures, Slopes, Culverts and Roadways”.

(iii) Development of classification and importance categories for New Jersey bridges.

(iv) Recommendations on acceptable retrofit options and guidelines on the implementation of these retrofit options for New Jersey bridges.

(v) Development of computer models and examples illustrating applications of guidelines for the design of new bridges and retrofit of different types of bridges.

Seismically, New Jersey falls in central Appalachian seismic region. Several earthquakes of intensity V or greater on the Modified Mercalli Intensity scale have occurred in New Jersey since 1895. Figure 1 shows the seismic hazard map of New Jersey for 2% probability of exceedance in 50 years (2500 Years return period). It is observed that current seismic hazard levels in New Jersey vary from small hazards in Southern New Jersey to a moderate in Northern New Jersey and neighboring New York City. However, New Jersey ranks 10th in terms of Annualized Earthquake Loss (AEL) to building inventory because of high value building inventories, even though the seismic risk is relatively low [FEMA (366)].

Since the highway bridge network in New Jersey serves as a vital link in the transportation infrastructure in the NE region, the implications of seismic hazard to highway bridges in New Jersey are quite severe, even though New Jersey is a region of low seismicity. Hence, increasing the seismic resistance of highway bridges through detailed seismic design and retrofit planning is essential. This proposal offers to develop seismic design and retrofit guidelines specifically for New Jersey bridges through in-depth and critical review and analysis of all available documents and in particular the new guidelines by AASHTO and FHWA.