Strip Seal Bridge Expansion Joints – What are They?

Strip seal bridge expansion joints are a type of expansion joint used in bridges to accommodate movement and prevent damage to the bridge structure. Some key features of strip seal bridge joints are:

1. Design: They consist of two steel extrusions embedded in the bridge deck and approach slab, with an elastomeric seal that locks into a machined steel cavity.
2. Functionality: These joints are designed to be watertight, preventing rainwater and debris from penetrating the joint and causing damage.
3. Durability: They are resilient to harsh conditions, including freeze-thaw cycles, and are engineered for long-term durability.
4. Maintenance: Strip seal joints are relatively easy to install, check, maintain, and clean.

These joints are commonly used in bridges of moderate length and are often chosen for their effectiveness in sealing and durability.

Australian Bridge Products offer two styles of strip seal bridge expansion joint systems being BJXA Bridge Expansion Joint and BJXC Bridge Expansion Joint.

BJXA Expansion Joint is used in asphalt bridge decks and BJXC is installed into concrete bridge decks.

How do strip seal joints accommodate bridge movement?

Strip seal joints are designed to accommodate bridge movement in several ways:

1. Thermal Expansion and Contraction: These joints allow for the expansion and contraction of bridge components due to temperature changes. The elastomeric strip within the joint can stretch and compress, adapting to the bridge’s movements.
2. Traffic Loads: As vehicles pass over the bridge, the strip seal joints flex to absorb the dynamic loads, reducing stress on the bridge structure.
3. Seismic Activity: In areas prone to earthquakes, strip seal joints can accommodate the shifts and vibrations caused by seismic events, helping to maintain the bridge’s integrity.
4. Longitudinal and Transverse Movements: These joints are capable of handling movements in both the longitudinal (along the length of the bridge) and transverse (across the width of the bridge) directions.

By managing these various types of movements, strip seal joints play a crucial role in maintaining the structural health and longevity of bridges.

The mechanics behind how these joints work

The mechanics of strip seal bridge expansion joints involve several key components and processes:

1. Steel Extrusions: These are embedded in the bridge deck and approach slab. They provide a rigid framework that supports the joint and ensures it remains securely in place.
2. Elastomeric Seal: This is the flexible, rubber-like strip that fits into the steel extrusions. The seal is designed to stretch and compress, allowing it to accommodate the bridge’s movements. It locks into a machined cavity in the steel extrusions, ensuring a watertight seal.
3. Movement Accommodation: The elastomeric seal can expand and contract in response to temperature changes, traffic loads, and other forces. This flexibility helps to absorb and distribute stresses, preventing damage to the bridge structure.
4. Load Transfer: As vehicles pass over the joint, the elastomeric seal flexes to absorb the dynamic loads. This reduces the impact on the bridge deck and helps to prolong the lifespan of the structure.
5. Sealing Function: The watertight nature of the elastomeric seal prevents water and debris from entering the joint, which could otherwise cause corrosion or other damage to the bridge components.

By combining these elements, strip seal joints effectively manage the various movements and stresses that bridges experience, ensuring their durability and safety.