In recent years, consumer unmanned aerial system (UAS) technology has improved significantly with its use becoming widespread. Although an UAS is typically used by an individual for recreational purposes, an extremist can also acquire a UAS with relative ease for malice. These remote-controlled aerial vehicles are capable of carrying payloads that may be detrimental to critical infrastructures, and with the right expertise, a UAS can be a tool for delivering an improvised explosive device (IED) to places not typically accessible by an individual. Bridge owners are expressing concerns about UAS-borne IED (UBIED) threats against vulnerable components of bridges. If these critical components are compromised, the damage may lead to catastrophic failures. Proposed Research The objective of the proposed research is to assess and develop mitigation measures for bridge components identified by owners as vulnerable to UBIED attacks. The study will be conducted in phases where current (unmitigated) vulnerability to UAS threats will be assessed, mitigation concepts developed, and the most promising mitigation concept tested to demonstrate the protective capability. The study will be performed under the guidance of a Technical Advisory Group formed at the initiation of the project. Mitigation measures will be developed in stages for vulnerable bridge components, at the discretion of study participants, and subject to commitment of funds. Phase I will involve identification of critical bridge components for possible UAS threats along with an in-depth study of UAS capabilities. Bridge owners will be consulted to ascertain the full range of potentially vulnerable bridge designs/components to these threats. If necessary, initial mitigation schemes will be developed. Phase II will consist of numerical simulation with validation testing of the simulation models and select mitigation measures. Each subsequent phases will focus on specific designs/components (or class of components), and will involve extensive testing and validation of feasible protection measures. Depending on the component type, mitigations may consist of hardening, UAS access denial, or a combination thereof. Technical Advisory Group A technical advisory group (TAG) will be formed at the initiation of the study, with representatives from each project partner. The TAG will guide the research from its inception to approval of the final deliverables.

The objective of the proposed research is to assess and develop mitigation measures for bridge components identified by owners as vulnerable to UBIED attacks. The study will be conducted in phases where current (unmitigated) vulnerability to UAS threats will be assessed, mitigation concepts developed, and the most promising mitigation concept tested to demonstrate the protective capability.

Phase I Task 1: Bridge Component Vulnerability Several classes of potentially vulnerable bridge components to UAS threats have been identified. This task will conduct a more comprehensive study extending this list to further identify and prioritize others uniquely vulnerable to UAS threats. A component can be vulnerable to UBIED, in addition to other means of threat delivery. Previous work has already examined vehicle-borne IED (VBIED) threats and cutting threats, and it will be assumed these are effective against UAS threats. Task 2: UAS Capabilities The types of threats UAS proposes needs will be identified in order to develop mitigation and protection measures. This task will conduct in-depth study of UAS capabilities, focusing on threats they pose. Task 3: Mitigation Schemes Potential mitigation schemes as a means of protecting vulnerable components identified in Task 1, for the threats identified in Task 2 will be proposed. A detailed work plan will be developed for any analytical and experimental work to be conducted to validate the proposed protection systems. Task 4: Phase I Report The findings of the above tasks will be presented in a report. This report will form the backbone of subsequent phases to develop and validate mitigation schemes to protects bridges against UAS threats. Phase II The thrust of Phase II will be on numerical simulations with validation testing of the models and potential mitigation measures. High-fidelity numerical simulations will be used to study the effect of payloads on vulnerable bridge components and systems. Numerical models will be validated experimentally and used to assess the effectiveness of proposed mitigation schemes. A final mitigation concepts will be proposed and a technology demonstration at a larger scale will be conducted to show capabilities of the protective mitigation under subsequent phases, subject to availability of funds. Task 1: Validation through Numerical Simulations and Modeling Utilizing high fidelity computer programs, develop models of vulnerable components and mitigation schemes proposed under Phase 1. Validate and refine the proposed concepts through analysis. Task 2: Validation through Experimental Testing Validate the numeral models developed under task 1 for various bridge components and types to gain confidence in the models and the mitigation concepts. Because physical testing of every new concept envisioned is expensive and not feasible, having validated computational models will be of benefit not just for the mitigation concepts proposed in this study, but also for developing future concepts at a reasonable cost. Task 3: Technology Demonstration Plan Propose a technology demonstration plan to show protection capabilities of the final recommended concepts. Task 4: Phase II Report All work conducted in this phase will be presented in report. Phase III Phase III consists of carrying out technology demonstration of the mitigation schemes as proposed under Phase II – task 3 and the final report. This phase of work will be subject to availability of funds, and at the discretion of the sponsor, the TAG, and the performing organization, and may be addressed under a separate study or extension of this study, and are not included in the cost estimate given here.

Funding and General Information: The Federal Highway Administration will be leading this Pooled Fund effort and has committed partial funding for the project. Few states and transportation authorities have indicated their interest in joining the study. The funding level requested per partner is $50k per year for 2 years for Phases I & II. Facilities at the Army Corps of Engineers Research and Development Center (ERDC): The team at ERDC is uniquely equipped to perform the proposed research. They have the expertise, the clearance requirements for the sensitive research to be conducted, and the laboratory facilities and/or access to facilities to perform needed experimental work. The study will be performed through an Interagency Agreement between the Federal Highway Administration and the Army Corps of Engineers, and guided by participants of this Pooled Fund Study. Research Team: ERDC Research Team