Chances are that you either drive over or under a bridge on your way to work, the grocery store, or to meet up with friends. Bridges are structures that are built to carry traffic over natural features like waterways or valleys, and over infrastructure such as roadways or railroads. But have you ever thought about the safety standards that those bridges must meet in order for us to drive over them? Despite the public discourse on infrastructure needs and the upcoming ASCE Infrastructure Grade Report, most of us probably do not think about it much. Although for bridge inspectors, this is second nature. Here is an inside look into bridge inspections and the process that is taken to keep you safe.
And remember – BRIDGES ARE EVERYWHERE!
Who performs bridge inspections?
Bridge inspections are performed by a bridge inspection team, consisting of a Team Leader and at least one Team Member, with a background related to inspection meeting specific minimum qualified experience, training, and educational requirements. Certifications are held at a federal level with
states providing minimum qualifications on an individual basis. These certifications must be renewed with refresher and additional coursework to ensure the team has the latest knowledge needed to perform inspections based on current research and knowledge. It is the bridge inspector’s responsibility to understand the specific structural and safety elements of the bridge that they are inspecting and to assess the deficiencies of each element accordingly.
What is a bridge inspection?
There are multiple types of bridge inspections each serving their own purpose, but the most common is the Routine Bridge Inspection which typically occurs every other year. The purpose of a Routine Bridge Inspection is to determine the physical and functional condition of the structural components (e.g. beams) and safety components (e.g. guardrails) in addition to documenting items such as the pavement condition (i.e. potholes) and vertical clearances. Think of a Routine Bridge Inspection like going to the doctor for your yearly physical. You get a routine checkup just to make sure that you are healthy, and to monitor any existing conditions to see if they have declined since the previous visit. Routine Bridge Inspections replicate the same concept. If a bridge is in need of more frequent inspections due to condition or known components that need to be more closely tracked for changes a special or more frequent inspection schedule can be requested by the owner.
Common bridge materials include steel, concrete, and timber. Inspectors use visual techniques to inspect the bridge but also often use a hammer to audibly hear changes in material. Multiple senses are used by an inspector to determine the extents of any new or existing deficiencies from vision to sound to touch. Deficiencies are documented in a report form including both written descriptions, sketches, and photos. Not only are each individual defect documented but overall conditions are established to summaries for each portion of the structure.
During a bridge inspection, the team leader determines if the deficiencies are critical or non-critical findings. Non-critical findings may represent deficiencies that should be addressed and documented but are not required to be addressed immediately and do not pose a danger to the public. Critical findings require immediate notification of the bridge owner and result in rapid response to improve the condition of the structural or safety element. By performing inspections at routine intervals deficiencies can be tracked and changes noted to ensure the safe passage of all users both over and under the bridge.
What happens with all the documented conditions?
Bridge inspectors report their findings to bridge owners whether that is a state transportation department, state agency, municipality, or private owner. All Federal Highway Administration (FHWA)-defined bridges have the summarizing details relayed to the FHWA in the form of National Bridge Element (NBE) inspection quantities and updated Structural Inventory & Appraisal (SI&A) sheets. The NBE define the bridge elements and provide a breakdown of the defect types (what is found), quantities (how much), and condition states (how deteriorated). The SI&A sheets provide a high-level breakdown of the bridge information including overall condition ratings for the deck, superstructure, and substructure in addition to inventory data defining the structure itself such as bridge type, location, etc. Inspection reports and condition ratings allow decision makers and bridge owners to implement required preventative maintenance and repairs (i.e. cleaning or removal of debris and animal waste, drainage system improvements, joint replacements, and re-painting of beam) or flag that a bridge will need more significant rehabilitation or replacement.
Why are routine bridge inspections so important?
No matter your mode of transportation, bridge inspections are performed to make sure that you are safe. Due to the harsh environments with heavy salt use and minimal protection bridge conditions change frequently. Bridge inspections allow owners to track conditions, prioritize work, and ensure that the system continues to serve the public in a safe manner. Each inspection is a snapshot in time that assesses a bridge’s condition to maintain a safe, functional, and reliable infrastructure system. The inspection report produced by the bridge inspection team is also used for structural analysis of the structural components to determine their load carrying capacity relative to expected loading on the bridge. Whether the bridge is carrying routine trucks defined by FHWA and the owner or needs a special permit for unique loading expected, the inspection report will aid the engineer in determining if any deductions in the structural capacity of the bridge need to be taken or if conditions have changed (i.e. additional pavement creating additional load).
In summary, bridge inspection plays a key role in the management of our transportation infrastructure, and the findings of the inspection provide key input for the delegation of funds and prioritization of repair and replacement projects. Proactive measures, some very simple, can result from the inspections and easily extend the life of a structure by staving off the deterioration and formation of more severe deficiencies.
Green International Affiliates, Inc. (Green) is a leader in performing bridge and tunnel inspections throughout New England with a large (and growing!), experienced staff that has demonstrated a commitment to thorough and thoughtful investigations. We strive to provide our clients with quality and timely information to support them in their asset management efforts. For more information on bridge inspections or to have your questions answered, please contact us at info@greenintl.com.