**2. Background**

The means and methods for bridge failure analysis used in this research paper involved a literature survey of papers that studied and analyzed the causes of bridge failures. Their papers address the types of bridge failures, their root causes, and events and processes that led up to their failures. In most all cases the cause of failure can be traced back to human error.

To provide a basis for the examining the six bridge failures presented in in this chapter a description of the seven bridge types is provided together with an outline of the basic components of a bridge structure, to include foundation, substructure, and superstructure. It is worthy to note that in the service life of a bridge deterioration can occur in any of these components to a degree that can increase the potential for a bridge structural failure. Deterioration is a process changing an object, in our case bridges, to a lower quality state in which a degraded condition can lead to structural failure. A steel bridge with structural beams in a rusted condition is an example of advanced deterioration.

For this chapter bridge failure analysis is the process to understand why structures, components, systems, methods, and processes fail. Failure analysis is a science to analyze how structural systems fail by determining the sources and causes of failure. The bridge failure analysis process includes structural analysis which incorporates the fields of mechanics, dynamics and failure theories. From a theoretical perspective, the primary goal of structural analysis is the computation of deformations resulting from internal and external forces and stresses. In practice, structural analysis reveals the structural performance of the engineering design and ensures the soundness of the structural integrity in design. Using an array of methods, to include nondestructive testing, the failure analysis process collects data on failed components for examination and analysis to determine the cause of failure. The objective of bridge failure analysis is to develop corrective actions and better structural designs with improved reliability to prevent bridge failure over its service life.

#### *Perspective Chapter: Bridge Deterioration and Failures DOI: http://dx.doi.org/10.5772/intechopen.109927*

The description of a bridge failure is presented in a paper by G. Zhang, et al.

"Bridge failure, is generally associated with serious economic and life losses is dedefined as the incapacity of a constructed bridge or its components to perform as specified in the design and construction requirements. Principal causes can be divided into internal causes and external causes or natural factors and human factors. Design error, construction mistakes, hydraulic, collision, and overload are the top 5 leading causes of bridge failures, resulting in more than 70% of the bridge failures. Causes of bridge failures are closely related to regional economy, structural type, type of use, material type, and service age. The failure rate is high for steel bridges, which is inseparable from excessive emphasis on structural strength and the lack of consideration on structural stability and fatigue in early years." [2].

The paper from Zhang makes an important point. The issue involves understanding the rate of fatigue in structural elements in both steel and reinforced concrete bridges and the impact on bridge performance relative to the weakest point(s) in the bridge structure. Not identifying through inspection and testing the weakest points in a bridge increases the risk of failure.

A description of four highway and two pedestrian bridge failures are presented in this paper. The failure analysis process used for each bridge looks at the bridge type and structure, its failure mode, the events leading up to the failure, and the factors contributing to its failure. Of all the factors contributing to a bridge failure the one common factor in all the failures is the role human errors played in the chain of events leading up to the bridge collapse. Stakeholders, designers, bridge engineers, inspectors, and maintainers are responsible for preventing bridge failures. Bridge failures are preventable.
