What are expansion joints and why do bridges need expansion joints?
In simple words, an expansion joint prevents the buildup of resonant frequencies which can amplify the swinging motion of a construction piece such as a bridge.
An expansion joint is a metallic assembly used to absorb the expansion and contractions to provide safety to a construction material. An expansion joint absorbs vibrations and holds the parts together allowing movement during an earthquake or ground settlement.
In simple words, an expansion joint prevents the buildup of resonant frequencies which can amplify the swinging motion of a construction piece such as a bridge. Without a bridge expansion joint, a bridge is liable to collapse while endangering the lives of people on it. Expansion joints are also commonly found between buildings, sidewalks, railway tracks, pipes, ships, and other metallic or non-metallic structures.
When you go around driving a motorbike on a concrete bridge, you might have noticed the little gaps in between the road of a flyover. These gaps consist of bridge expansion joints which provides it flexibility and rigidness in the structure.
Expansion joints in between the bridges are designed to withstand the load of the heavy traffic allowing the structure to accommodate movement, shrinkage, and seasonal expansion and contraction while saving the concrete structure from collapsing. It is very important for an expansion joint to work properly as they are vital for life and brides as well.
Causes of joint failure
There are two main reasons for the expansion joint failure.
• Incorrect or improper installation and insufficient maintenance of the expansion joints renders the effective use of an expansion joint used in the bridge.
• secondly, the dirt and debris buildup around them can lead to the joints losing their ability to expand or contract with the structure, making them less effective and ultimately leading to collapse.
When an expansion joint loses its effectiveness, it reduces its flexibility resulting in cracking or crushing of the expansion joint material while compromising the operational reliability of the bridge.
The two types of expansion joints
Open joints: the open joints used in a bridge allows water, dirt, and debris to move freely through the joints. However, sometimes it can also lose its effectiveness because of dirt and debris buildup.
Closed joints: closed joints are prevented from dirt and debris or water from penetrating in it. It is made specifically for the size and movement properties of the intended joints.
Each of these joints is used for their specific applications and set parameters to ensure that it is able to ensure the effectiveness required by the expansion joints.