c. Accidental loads

This type refers to an extraordinary event that the structure needs to support, commonly produced by wind and earthquake loads. In some cases, a collision by a ship or a flood event may be considered.

In addition to physical loads, there are other factors that can affect the useful life of the bride, named environmental factors and described as follows:

### a. Humidity

This environmental factor affects the chemical composition of iron and steel materials, which in direct contact creates corrosion process and develops a material degradation.

#### b. Abrasive factors

These factors can affect the material composition due the chemicals reactions by air, water and soil exposures. Each material could have a specific chemical reaction and depends for the levels of exposure.

Dead, live and accidental loads affect the mechanical properties of the structure itself, which results are stresses and deformations. If a load exceeds the capacity of the material, some type of damage will occur, from permanent deformation to crack growth, and the structural element will require a repair.

The environmental factors are associated with the material degradation process, which can results in reduction of the effective inertia. All cases imply the reduction of material resistance and element sizes, developing a stress and strain increase, and therefore, a possible failure.

Proper maintenance avoids possible damages on the structural elements due any physical or environmental factors, and therefore, an increase of the structure expected life.

## **6. Degradation process: corrosion, wear and fatigue**

Since the physical and environmental factors are present in each structure, all materials may be subjected to alterations in their chemical composition, modifying the mechanical and physical properties, shortening the useful life of the structure and requesting any kind of repairmen. These factors with the alteration are listed in this section.

#### **6.1 Degradation due environmental factors: corrosion**

Structural steel and concrete reinforcing steel in presence of humidity will have the problem of corrosion, a chemical process involving an electrochemical reaction which occurs due the direct exposure to water, creating rusting and developing the material degradation process.

*Bridges: Structures and Materials, Ancient and Modern DOI: http://dx.doi.org/10.5772/intechopen.90718*

b. Live loads

c. Accidental loads

a. Humidity

b. Abrasive factors

therefore, a possible failure.

material degradation process.

expected life.

this section.

**112**

degradation.

ship or a flood event may be considered.

*Infrastructure Management and Construction*

and depends for the levels of exposure.

growth, and the structural element will require a repair.

**6. Degradation process: corrosion, wear and fatigue**

**6.1 Degradation due environmental factors: corrosion**

This type of loads refers to a generalized use of the bridge, this means the traffic flow and people walking, including braking, impact, collision and their dynamic loads. This category includes environmental factors such as rain and snow.

This type refers to an extraordinary event that the structure needs to support, commonly produced by wind and earthquake loads. In some cases, a collision by a

In addition to physical loads, there are other factors that can affect the useful life

This environmental factor affects the chemical composition of iron and steel materials, which in direct contact creates corrosion process and develops a material

These factors can affect the material composition due the chemicals reactions by air, water and soil exposures. Each material could have a specific chemical reaction

Dead, live and accidental loads affect the mechanical properties of the structure itself, which results are stresses and deformations. If a load exceeds the capacity of the material, some type of damage will occur, from permanent deformation to crack

The environmental factors are associated with the material degradation process, which can results in reduction of the effective inertia. All cases imply the reduction of material resistance and element sizes, developing a stress and strain increase, and

Proper maintenance avoids possible damages on the structural elements due any

Since the physical and environmental factors are present in each structure, all materials may be subjected to alterations in their chemical composition, modifying the mechanical and physical properties, shortening the useful life of the structure and requesting any kind of repairmen. These factors with the alteration are listed in

Structural steel and concrete reinforcing steel in presence of humidity will have the problem of corrosion, a chemical process involving an electrochemical reaction which occurs due the direct exposure to water, creating rusting and developing the

physical or environmental factors, and therefore, an increase of the structure

of the bride, named environmental factors and described as follows:

For reinforcing steel in concrete structures, the corrosion problem can be present when the rebar is exposed, oxidizing the area and develops structural problems.

**Figure 19** shows a damaged pier due corrosion of the reinforcement steel, losing the coating and reducing the cross-sectional area, which means a reduction of the mechanical capacity of the element.

On the other hand, if the structural steel is fully exposed to the environment without any humidity protection, the level of oxidation will be present on the entire element and will develop a generalized rusting reaction. **Figure 20** shows a structural steel bridge with all elements damaged by corrosion.
