Expansion Joints are important for the life of a bridge and need to be installed in the perfect way with proper maintenance in order to function properly. The major reasons for joint failure are improper installation and insufficient maintenance of the joint. In several cases, when dust, dirt, or other types of debris get accumulated in and around these joints, they lose their ability to contract and expand with the structure which makes them less effective. When this occurs, the reduced flexibility mainly results in distortion or cracking of the material of the joint which compromises the entire structural integrity of the bridge.
Bridge Expansion Joints must be able to –
- Protect the concrete edges from getting damaged by vehicle traffic
- Acting as a seal for preventing the foreign objects from entering the opening of the joint.
- Allow the contraction and expansion caused due to thermal cycles
- Allowing for the natural shrinkage and creep of concrete
Important Factors to look into
When you are using concrete as a building material, then there are various things that you need to consider. The strength and weight load of the concrete are important, but apart from this, another vital component is the effect of the environment on the material. Thermal cycles within the geographical area need to be also taken into consideration. With the changing of the seasons and the weather, the structure may expand and contract with the temperature. At times, this is overlooked and when these structures expand and contract, there can be several issues with the expansion joint system.
The cooling and heating cycles of concrete bridge decks may cause expansion and contraction respectively. If the contraction is much more than the tensile strength of the construction materials, cracking can happen. And inversely, when the expansion is restricted, distortion or crushing of the materials may happen. To prevent these types of failures, concrete bridge decks need joints to be fitted with materials which allow the structure to expand and contract without causing any damage to the structural integrity. These joints are called expansion joints and they may have several types.
The two major types of Expansion Joints
Open Joints – They allow debris and water to freely move through the joint but are often subjected to building up debris which can make them ineffective. These types of joints comprise –
- Finger joints
- Butt joints
- Sliding plane joints
Closed Joints – These joints prevent the debris and water from penetrating bust needs to be designed specifically for the movement and size properties of the intended joint. They comprise of the following joint types –
- Compression seals
- Poured joints
- Strip seals
- Asphalt plug joints
- Modular elastomeric joints
- Reinforced elastomeric joints
Each of these joint types comes with a specific application method and set of parameters that need to be followed for ensuring the effectiveness of the joint. Proper sizing of the joint along with an accurate assessment of the anticipated movement of the structure needs to be considered while selecting the proper type of joint for the intended project. Some additional things which need to be considered are climatic factors, manufacturer requirements, lane closure requirements, substrate preparation, physical properties, and limitations of the joint material.
Several bridges and roads in the west are fitted with expansion joints which are structurally deficient. The main reason for the failure ranges from the separation of the seal from the substrate, tearing, concrete deterioration, snow plow damage, accumulation of debris, and improper alignment of the sections of the deck. The major of these features can actually be attributed to improper installation or improper maintenance.
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