A Threat and Vulnerability Risk Assessment Framework for Human-Induced Threats to Bridges over Navigable Waterways

Structural infrastructure plays a crucial role in contemporary urban environments by supporting essential public and commercial functions. As both newly developed and aging infrastructure systems expand, the need for effective monitoring and protection systems becomes increasingly critical. While most existing risk assessment frameworks primarily address natural hazards, human-induced threats—such as vessel collisions, terrorism, and cyberattacks—are often overlooked. This study introduces a threat and vulnerability risk assessment (TVRA) framework specifically designed to evaluate risks to bridge infrastructure spanning navigable waterways. The methodology employs a semiquantitative, weighted scoring system to assess asset importance, threat impacts, and vulnerabilities, thereby quantifying risk levels for asset–threat combinations. The framework was validated through a case study of the Delaware Memorial Bridge, demonstrating its practical applicability in real-world conditions. The TVRA framework is adaptable and scalable, enabling applications to a wide range of infrastructure systems and providing decision-makers, engineers, bridge owners, and government agencies with a structured tool for developing targeted protective measures and adaptive strategies to enhance resilience and safety against human-induced threats.