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This paper provides an overview of an innovative new approach for the safety inspection of highway bridges. The National Bridge Inspection Standards (NBIS) mandate a uniform 24-month inspection interval for most highway bridges. The uniform intervals were based on engineering judgment at the time the NBIS was implemented in the 1970's and do not consider the typical performance characteristics of bridges with different designs, materials, exposure environments, or existing condition. A more rational approach to determining inspection frequency and scope would consider the structure type, age, condition, environment, and other characteristics of bridges. This paper will discuss reliability-based inspection practices that utilize a risk assessment framework to determine appropriate inspection frequency and scope. This approach utilizes engineering analysis of typical damage modes and deterioration mechanisms for different types of bridges, combined with the exposure environments and loading, to assess the inspection needs for a bridge. Under such an approach, inspection efforts are focused where deterioration and damage are most likely and where consequences of that damage are greatest. The approach is intended to improve the safety of bridges by optimizing the use of resources, focusing inspection efforts where inspection needs are greatest.

Ultra-high performance concrete (UHPC) is proposed as an innovative new material for the construction of highway bridge superstructures. UHPC mix designs typically include no aggregates larger than sand, and include steel fibers 0.2 mm in diameter and 13 mm in length. These steel fibers and special mix design increase the strength and toughness of the UHPC significantly relative to more traditional concretes. However, low water to cement ratios typically used result in difficult casting and curing conditions and as a result there is a need to evaluate strength and stiffness parameter of as-cast members. This research reports on the development of ultrasonic methods for monitoring the elastic properties of UHPC under a series of curing scenarios. Ultrasonic velocity measurements are used to estimate the bulk elastic modulus, shear modulus and Poisson’s ratio of UHPC and results are compared with traditional, destructive methods. Changes in ultrasonic velocities during curing and relationships to early-age strength of the materials are discussed. The application of ultrasonic testing for the evaluation of early-age material properties and for nondestructive, in-situ materials characterization are explored. The potential for the development of practical quality control techniques for the future implementation of UHPC is also discussed.