For all of their importance, suspension bridges are relatively under-represented in counterterrorism research. Physical modeling in this area has mainly been conducted on buildings, protective structures, and girder and truss bridges. Because of the latter, modeling the behavior of suspension bridge plate and truss elements would require only a small departure from established analytical models. Modeling the behavior of multi-cell towers, main cables, and main cable-suspender rope interaction--although done on actual vulnerability assessments--is less firmly established in experience. Part of this deficiency is being addressed in an FHWA-led pooled fund study on steel multi-cell towers being conducted by the Eastern Research and Development Center of the Army Corps of Engineers. Physical testing, however, employs specimens built specifically for the study, that is, specimens constructed with modern steel alloys and bolted or welded connections. The specimens, because they are new, are also in pristine condition at the time of testing. A useful extension of this test program would encompass early 20th Century alloys, riveted connections, gusset plates, built-up cross-sections, and the uneven effects of corrosion.

o Verify and calibrate analytical predictions of the behavior of multi-cell steel towers, main cables, and main cable-suspender rope interaction on steel suspension bridges for specified attack methods. o Verify and calibrate analytical predictions of the behavior of currently-used and proposed retrofits for these structural elements.

The scope of work consists of the verification of blast loading and structural response phenomena, previously identified by analytical modeling, and further refined on scaled specimens. It shall further consist of the development of retrofit solutions validated through analytical work and experimental testing to determine performance of retrofit elements on bridges constructed with early-to-mid 20th Century materials and subjected to decades of environmental and traffic loading. The study will consist of physical, full-scale testing of steel suspension bridge elements, their connections, and, where practical, assembled groups of bridge elements, subjected to simulated attack. Attack methods include the use of vehicle bombs or other standoff charges; hand-emplaced breaching charges, cutting charges, and mechanical cutting. Direct impact by airplane, vessel, or truck is beyond the scope of this study. The proposed program is based on the availability of a particular suspension bridge to be demolished, the Waldo-Hancock Bridge, near Bucksport, Maine, and the availability of a test facility where full-scale explosive demolition testing may be conducted in a secure environment. The main testing phases of the study will be conducted in two parts: 1) A limited on-site study, followed by removal of the structure; 2) A more extensive off-site study. The earliest phase of the study will consist of the overall study design, obtaining information on existing loads, stresses, strains, and displacements, design of the on-site study, coordination with the demolition and salvage operation and of transportation of structural elements to the off-site study location, and design of the off-site study. The on-Site study will consist mainly of a Suspender Cutting Charge study; Dynamic Effects on Stiffening Truss and Main Cables, Main Cable Shear study, and Dynamic Effects of Stiffening Truss Demolition on the Towers and Main Cable. Note that any or all of the testing in this phase may be reconfigured for the off-site phase or eliminated altogether for any of the following reasons: environmental impact, worker safety, security, physical impediments in the existing structure, interference with the demolition schedule, or cost. The off-site study will consist of a continuation of the Suspender Cutting Charge study, a Tower Section Standoff Attack study, a Main Cable Standoff Attack study, and a Main Cable Cutting Attack study. If sections of main cable remain, a fire heat transmission study will also be conducted off-site. After the behavior of the unprotected structure has been calibrated, the behavior of several retrofits will be studied in the Off-site phase. These will include: Main cable wrapping; Tower plate thickening; Internal tower reinforcement; Suspender replacement materials; Energy-absorbing suspender sockets; and any other retrofit identified as suitable for inclusion in this study. Delineation of Tasks--The project will consist of the following tasks: Part A--Bridge Baseline Study and Overall Study Design Task 1-Bridge Baseline Information Task 2-Design On-Site Study Task 3-Planning for Post-Demolition Salvage, Storage, and Transportation Task 4-Design Off-Site Study Part B--On-site Vulnerability Testing Conduct the following tests, subject to restraints imposed by the site or structure: Task 5-Main Cable Task 6-Suspenders Part C--Removal and Transport of Specimens Task 7-Identify Sections for the Off-Site Study Task 8-Section Storage and Removal Task 9-Effects of Stiffening Truss Demolition on the Towers and Main Cable Part D--Off-site vulnerability and countermeasure testing Task 10-Main Cables and Suspenders Task 11-Trusses Task 12-Tower Sections Part E--Analysis and Reporting Task 13-Analysis Task 14-Draft and Final Reports

Suggested minimum contribution: $30,000 per year See the attached proposal for the full description of the proposed study.