Bridge expansion joints are bridge joints designed to make allowance for continuous traffic between bridge structures and as well to accommodate relative movement due to shrinkage, temperature variations on reinforcement and prestressed concrete, and other structures. They are basically designed to stop the bridge from moving or bending out of place during extreme conditions, and also to allow lateral movement that permits bearing replacement without necessarily dismantling the bridge expansion joint. There are different bridge expansion joint types, which are able to accommodate lateral movement from 30mm to 1,000mm (1.2 to 39.4 inches).
Bridge expansion joints are necessary to accommodate the thermal expansion and contraction of bridge materials caused by changes in temperature. While there are many different expansion joints, they all serve the same purpose. In this article, we’ll take a closer look at three of the most common types of expansion joints.
Types of Bridge Expansion Joints
The different bridge expansion joint types include the following:
- Small movement joints
- Medium movement joints
- Large movement joints
Small Movement Joints
These bridge expansion joint types have the capacity to accommodate movement up 50mm and they are categorized into four different categories as follows:
- Compression seal joints
- Sliding plate joints
- Poured sealant joints
- Asphaltic plug joints
Compression Seal Joints
A typical compression seal joint is designed to accommodate and cater to both horizontal and vertical movement up to 40mm and 3mm respectively. This bridge expansion joint type is made up of armored steel nosing at both ends of the joint gap perfectly anchored to the concrete deck with a performed chloroprene elastomer compressed into the joint gap by an adhesive girder.
Compression seal joints are highly recommended for simply supported spans and continuous spans right or skew moderately curved with horizontal movement, not more than 40mm.
Sliding Plate Joints
Sliding plate joints are slight movement joint types of bridge expansion joints with two plates of which one plate is fixed at one end and the other slides on top during expansion or contraction. The plates basically provide a low coefficient of friction surface to the bridge structure.
Sliding plates are commonly arranged in a sandwich form, comprising an upper slide plate and a lower slide plate. These bridge expansion joint types are commonly used for short and medium-span bridges and they are simple in structure and cost-effective.
Sliding plate joints are another popular type of bridge expansion joint type. They offer a high degree of flexibility and are resistant to damage from water and debris. However, they can be difficult to install and may require more maintenance than other types of expansion joints.
Poured Sealant Joints
Poured sealant joints are small movement joint types designed to minimize both infiltration of surface water and other incompressible material into the joint system of a bridge. They are also used to reduce the potential for dowel bar corrosion by reducing de-icing chemicals entering the bridge joints.
Asphaltic Plug Joints
Asphaltic plug joints are small movement bridge expansion joint types commonly known as general-purpose expansion devices for bridges with less than 50 mm total movement. These are bridge expansion joint types filled with asphalt material.
Medium Movement Joints
Medium movement joints are bridge expansion joint types with the capacity to accommodate total bridge movement between 45 mm to 130 mm. They are basically classified into two types:
- Strip Seal Joints
- Finger Plate Joints
Strip Seal Joints
Strip Seal Joints are medium movement bridge expansion joint types designed for sealing an elongated opening between two adjacent bridge slab sections by providing continuous support for vehicles crossing the bridge and as well allowing the desired temperature-responsive movement of the bridge slab sections. They are commonly made up of a single elastomeric neoprene rubber strip secured to the adjacent bridge sections on either side of the joint through heavy-duty edge beams under a specifically designed profile.
Strip Seal Expansion Joint systems are made up of elastomeric glands which are mechanically trapped between two steel edge members that provide a superior watertight sealing system. They are commonly designed to accommodate high vehicular traffic loads with movements ranging from 45 mm to 130 mm.
Finger Plate Joints
Finger joints are bridge expansion types often used for concrete bridge expansion joints. Finger joints allow for movement in one direction and provide support in the other direction. When used for bridges, finger joints are usually placed at the ends of the bridge deck where the deck meets the abutment or pier.
Finger joints are made up of a series of fingers that fit into each other. The fingers can be made from a variety of materials, but are typically made from metal or reinforced concrete. The number of fingers can vary but is typically between three and six. The fingers are interconnected with each other and are free to move relative to each other.
Finger Plate Joints are simply supported or cantilevered steel tooth expansion joints designed to accommodate movements ranging from 40mm to over 130mm. They consist of steel finger plates, anchor bolts, CR sheets, and pairs of other independent components. These bridge expansion joint types create an effective seal at the joint opening that prevents water and deleterious materials from contacting the bridge steel support girders and the bearings. The orientation of the fingers is always in the direction of vehicular travel, to minimize noise and as well improve drivers’ comfort.
One advantage of finger joints is that they allow for thermal expansion and contraction without significant deformation. This is due to the fact that the fingers can slide past each other as the temperature changes. Finger joints also have a high load-bearing capacity and can resist large amounts of shear force.
Disadvantages of finger joints include the fact that they can be difficult to seal properly, which can lead to water infiltration and corrosion. In addition, if not designed properly, finger joints can become clogged with debris, which can cause the joint to fail.
Large Movement Joints
Large movement joints are bridge expansion joint types with the capacity to accommodate total movement above 130 mm. There are basically two types of Large Movement Joints which include the following:
- Modular Elastomeric Seal Joints
- Bolt-Down Panel Joints
Modular Elastomeric Seal Joints
These types of bridge expansion joints are designed to provide adequate vehicular load transfer and to resist water from extensive expansion joint movements and openings. They are made up of multiple components in order to accommodate larger movements compared to other types of expansion joints.
Modular Elastomeric Expansion Joints are designed specifically in consideration of the necessary movement capacity and field applicability which can accommodate total motion above 130mm.
If you’re looking to expand your bridge, a modular bridge expansion joint is a great option. These joints are easy to install and can be adjusted to accommodate different expansion needs. Plus, they’re durable and low maintenance, so you can enjoy your expanded bridge for years to come.
Bolt-Down Panel Joints
Bolt-Down Panel Joints are expansion joints that are fabricated in different width sizes relative to the entire allowable movement range that have the capacity to accommodate movement exceeding 130mm.
How to Install Bridge Expansion Joint
Installing a bridge expansion joint is a crucial part of maintaining the structural integrity of a bridge. Though the installation process can vary depending on the type of joint being installed, there are some general tips that can help make the process go more smoothly.
First, it is important to make sure that the area where the joint will be installed is clean and free of debris. Any dirt or debris could potentially interfere with the joint’s sealant and cause problems down the road.
Next, the joint should be positioned in its desired location and secured in place. Once the joint is in position, it is time to apply the sealant. The sealant should be applied evenly around the perimeter of the joint to ensure a proper seal.
After the sealant has been applied, the joint should be left to cure for the recommended amount of time before being put into use. Following these simple tips can help ensure that your bridge expansion joint is installed correctly and will provide years of trouble-free service.
There are many different types of bridge expansion joints to choose from, and the best one for your project will depend on a variety of factors. Be sure to consult with a professional before making your final decision, as they will be able to advise you on the best type of joint for your particular needs. Thanks for reading!
FAQs on bridge expansion joint types
What is the maximum length for an expansion joint?
There is no definitive answer to this question as it depends on a number of factors, such as the type of bridge, the material used, the climate, and the amount of traffic that the bridge will be subject to. However, expansion joints are typically designed to accommodate movement of up to 2 inches.
Why expansion joints are provided in bridges?
Expansion joints are provided in bridges to allow for the expansion and contraction of the bridge deck due to temperature changes. Without expansion joints, the stress on the bridge deck from thermal expansion and contraction could cause the deck to crack or even collapse. Expansion joints also help to absorb vibration from traffic, which would otherwise damage the bridge deck.
Do all bridges have expansion joints?
No, all bridges don’t have expansion joints. However, most bridges do have them. They are particularly important on longer spans, or where the bridge is subject to a lot of movements, such as from traffic or temperature changes. Expansion joints allow the bridge to expand and contract without damaging the structure. This helps to prevent the bridge from cracking or breaking.