The U.S. infrastructure is facing critical challenges. Today’s engineering students need to be prepared to handle those challenges in their future careers. For example, highway bridge failures make headlines all too often. It’s essential for students to understand and apply National Bridge Inspection Standards (NBIS) as part of a comprehensive infrastructure rehabilitation and maintenance plan.
The level of detail in an inspection varies depending on what the intent is. With regard to new bridge structures, a great deal of time and effort is focused on geologic conditions, highway alignment orientation, and underpass crossing features. In a rehabilitation design, the inspecting engineer will spend time focusing on the existing structure elements in an effort to determine those that need simple maintenance and those that need extensive rehabilitation or replacement.
Maintenance inspections are conducted to rate a bridge structure and judge its condition and performance. Well-defined procedures for performing various tasks and qualified personnel are required to conduct specific types of NBIS inspections.
The principal intent of a maintenance inspection is to meet NBIS requirements, document the structure’s condition, provide input data for the bridge management system (BMS), and assist in the decision to maintain or rehabilitate the structure. There are 7 types of NBIS inspections:
1. Routine inspection: typically every 2 years (also called biennial inspections)
2. Underwater inspection: typically every 5 years
3. Fracture-critical member inspection: typically every 2 years
4. Damage inspection: unscheduled to deal with damages (as needed)
5. In-depth inspection: frequency determined by program manager
6. Special inspection: to inspect a known or expected structural problem; frequency determined by program manager
7. Initial inspection: when a bridge is newly built, or transferred from another agency
For NBIS inspections, the bridge owner should decide how detailed these inspections should be, based on individual bridge conditions and on previous inspection recommendations. It is important to remember that a highway bridge exists within a defined environment that is composed of many other features in addition to the bridge structure. A bridge inspection can fail if the inspector does not take into account important site features, such as drainage channels, wetland, embankments, utility lines, etc., and how they function within the confines of the bridge site.
This post is excerpted from Bridge Engineering: Design, Rehabilitation, and Maintenance of Modern Highway Bridges, Fourth Edition. For insight into a key topic relevant to all infrastructure projects, download this free white paper, Project Funding for Modern Highway Bridges.Tags: STEM learning, engineering education, AccessEngineering