Recent hurricanes have demonstrated the vulnerability of bridges to wave forces, storm surges, and storm-borne debris (coastal storm event hydrodynamic factors). Hurricane Ivan, in 2004, caused major damage to the I-10 Escambia Bay bridge in Florida. Permanent replacement of this bridge is still years away. Hurricane Katrina in 2005 caused extensive damage to a number of bridges in Louisiana, Mississippi, and Alabama. The potential for these storm events was not unexpected as scientists at the National Hurricane Center have been predicting a period of increased frequency and severity of tropical storm events. A functional transportation system is essential for both evacuation before an event, and for response and recovery after an event. Closures of critical routes can hurt response and recovery and can lead to hardships and economic losses. It is essential to address the increasing risk of hurricanes and other storm-related damages, and develop and implement solutions prior to the occurrence of these events. The seismic community and the wind hazards community have developed mitigation strategies to handle load-induced damages for the respective natural hazards. Years of research have gone into developing retrofit solutions for existing structures, and for improved designs of new structures. The result has been better understanding of important contributing factors and applicability of these mitigation strategies. Similarly, there is a need for a greater understanding of how coastal storm hydrodynamic factors can damage bridge structures. A systematic research approach leading to the development of strategies and options to reduce vulnerability of structures in coastal environments that parallels the seismic and wind programs needs to be undertaken. Initial steps would investigate the coastal force loadings and the applicability of bridge design options available for other hazards in a coastal hazard context. Subsequent work would refine and further develop appropriate strategies and methods. Ultimately, recommendations that include standard details and specification provisions would be provided. These recommendations to improve retrofit strategies, standards, and codes should ultimately reduce the risk and economic losses from future storm events. Project Description This project will develop guide specification language addressing wave loadings and potential solutions for retrofitting those bridges vulnerable to coastal storms borrowing from existing knowledge on hazard mitigation strategies and conducting analytical and limited experimental testing to validate these solutions for mitigating coastal storm event bridge damages. It is envisioned that the solutions developed will be risk based with retrofit options identified for varying intensity storms and wave heights, and with performance-based damage options that provide for solutions resulting in essentially no damage up to imminent collapse. Project results will provide retrofit options that allow owners to make investment decisions based on varying levels of acceptable risk versus anticipated performance. Some potential solutions borrowed from other fields may include venting, shear keys, tie downs, energy dissipation devices, or designing for continuity of spans or for uplift forces. However, these and any other recommendations envisioned would have to be validated for loads encountered by structures under this extreme event. The project must address concerns on how implementation of the new concepts may lead to changes in load path. The solutions should not lead to failures in other parts of the bridge where inspection is difficult or where repair or rebuilding may be delayed or more costly. The proposed recommendations must be practical in terms of workability and cost. These retrofit concepts will be presented ina handbook as a companion to the new wave loading guide specification.

The objective of this project is to develop retrofit strategies and options to mitigate damage to highway bridges subject to coastal storm hydrodynamic factors, and recommend improvements for bridges in coastal environments.

The scope of work consists of development of loading demands and retrofit solutions validated through analytical work and limited experimental testing in phase 2 to determine performance of bridges under varying wave height and loading conditions.

Suggested minimum contribution: $30,000 Urgency, Payoff Potential, and Implementation--Recent hurricanes and the resulting damages to highway bridges have illustrated the vulnerability of our highway bridges to coastal storm hydrodynamic factors and forces. There is an urgency to develop resilient structures and retrofit solutions to sustain the types of forces resulting from these events. With the 2006 hurricane season approaching, the need to develop and implement workable solutions is urgent. Currently there are no guidelines or standards available beyond increasing the low chord elevation, which may not be economically or technically feasible in many cases. The transportation system must be operational under any event as it is needed for evacuation and response and recovery. Most of our coastal regions are highly populated and the impact on communities from a bridge out of service can be tremendous. Many of the structures in these areas are lifelines making the need that more critical. The recommendations developed would ultimately reduce the risk and economic losses from future hurricanes. The solutions recommended and standards developed under this project will be available for immediate implementation by the States and other bridge owners, and for adoption into AASHTO specifications as appropriate. These unified efforts of a multidiscipline group are managed under a joint AASHTO/FHWA task force.