**9. Preventing future bridge failures: inspection and maintenance**

Bridge inspection and maintenance are the two most important activities for an existing bridge to preserve its function and service life and to provide public safety. The American Society of Civil Engineers reports that one out of every nine bridges in the US structurally deficient. Age and deteriorated bridge conditions are a contributing factor to many recent bridge failures.

#### **9.1 Inspection**

As Silano and Henderson [7] states in his book "Bridge inspection and Rehabilitation" the primary purpose of bridge inspections is to ensure public safety. The secondary purpose is to preserve the remaining life of bridge structures through the early detection and addressing of deficiencies. Federal law governs the requirements of the Bridge Inspection Program. The United States Code (23 U.S.C. 151) requires the Secretary of Transportation, in consultation with State transportation departments, to establish national bridge inspection standards for the proper safety inspection and evaluation of all highway bridges. These requirements are spelled out in the Code of Federal Regulations (Part 650, Subpart C) and govern the National Bridge Inspection Standards (NBIS) through purpose, applicability, definition of terms, qualification of personnel, inspection frequencies, inspection procedures, inventory procedures, and supporting references. Federal Highway Administration (FHWA) has developed 23 Metrics for the Oversight of the National Bridge Inspection Program. These metrics are a risk-based assessment of the performance of state bridge inspection programs and compliance with the NBIS. Each year, bridge Inspection programs are audited by the FHWA for compliance on these metrics. And yet bridge failures still occur [7].

#### **9.2 Maintenance**

With proper inspection and identification of maintenance requirements to preserve the integrity of bridge structural members deterioration of bridge components to the point of failure can be prevented. Corrosion, one of the leading causes of section loss in steel members and concrete reinforcement, leads to strength degradation and increases the risk of failure. Timely maintenance can prevent bridge deterioration and potential failure. Lack of bridge maintenance is the most preventable of all bridge failure causes.

## **9.3 Non-destructive testing**

The use of non-destructive testing (NDT) on concrete and steel bridge components is useful in determining material condition. Of the many NDT methods available for the bridge inspector, visual inspection is one of the most effective. To test for voids and de-laminations in concrete the impact-echo method is effective in detecting substrate de-laminations. This method was applied with a small mobile impact machine to detect de-bonding of CFRP plates on the bridges in Macedonia [15]. NDT impact methods used in the periodic inspections of bridges provide significant data on the bridge condition [16].
