Description

Description

Once a bridge is opened for use, management begins and carries on for the life of the bridge. Hence, the bridge must be regularly inspected and maintained for the benefit of its users.

There are three levels of inspection:

1. General inspection:

1. Usual inspection of representative parts of a structure.
2. Carried out nor more than two years after last general or principal inspection.

2. Principal inspection:

1. It involves close examination of all inspectable parts of the bridge structure and adjacent earthworks.
2. The interval between principal inspections would normally exceed six years.

3. Special inspection:

This inspection occurs for special cases such as:

A standard format for inspection reports must be maintained and should include recommendations for remedial measures. The information collected in a bridge inspection reports is sent to the highways agency. Here the data is fed into the agency’s database such that it can gain an overall picture of the state of the bridge and calculate an estimate of likely future expenditure.

Not all the components of a bridge is deteriorate at the same rate. For instance, the concrete sub and superstructure should not need replacing during 120 year design life. A little minor maintenance should suffice.

Bridges are key elements of the infrastructure  because of their strategic location and the dangerous consequences when they fail or when their capacity is impaired. The fundamental justification for a bridge inspection programme lies in the assurance of safety. Timely and economic planning and programming of remedial and preventive maintenance and repair work, or even bridge replacement with the minimum interruption to traffic are dependent upon detailed bridge inspection. It is particularly necessary in case of old bridges not designed to modern loading standards and also whose materials of construction have deteriorated as a result of weathering. Inspection is aimed at identifying and quantifying deterioration, which may be caused by applied loads and factors such as deadload, liveload, wind load and physical/chemical influences exerted by the environment. Apart from inspection of bridge damage caused by unpredictable natural phenomena or collision by vehicles or vessels, inspection is also needed to identify or follow up the effect of any built-in imperfections. Inspection can also help to increase life of older bridges. For example, there are certain types of deterioration which appear early in the life of a bridge and which, if not recorded and repaired promptly, can lead to considerable reduction in the length of service life of the bridge.

Purpose of bridge inspection

Specific purposes of bridge inspection can be identified as detailed below:

1. To know whether the bridge is structurally safe, and to decide the course of action to make it safe.

2. To identify actual and potential sources of trouble at the earliest possible stage.

3. To record systematically and periodically the state of the structure.

4. To impose speed restriction on the bridge if the condition/ situation warrants the same till the repair/ rehabilitation of the bridge is carried out.

5. To determine and report whether major rehabilitation of the bridge is necessary to cope with the natural environment and the traffic passing over the bridge.

6. To provide a feedback of information to designers and construction engineers on those features which give maintenance problems

Planning the inspection

 Careful planning is essential for a well-organized, complete and efficient inspection. The bridges over water are inspected at times of low water, generally after the monsoon. Bridges requiring high climbing should be inspected during seasons when winds or extreme temperatures are not prevalent. Bridges suspected of having trouble on account of thermal movement should be inspected during temperature extremes. The bridges are inspected starting from foundations and ending with superstructures. Planning for inspection must include the following essential steps:

1. Decide the number of bridges to be inspected on a particular day.

2. Go through the previous inspection reports of those bridges before starting the inspection.

3. Try to have plans and other details of important bridges.

 4. Plan any special inspection equipments, staging etc. required in advance.

5. Don’t rush through the inspection just for completion sake. Remember that you are inspecting the bridge only once in a year.