Cantilever Bridge – Types, Advantages, Disadvantages

Cantilever bridges might seem familiar from city skylines and movies, showcasing their ability to bear heavy loads. Despite encountering them often, their specific name might elude you. These lengthy structures derive their name from the cantilevers used in their construction.

What is a Cantilever?

A cantilever is a structure fixed at one end while the other end extends horizontally into space. This projecting end plays a crucial role in supporting the entire bridge.

Working Mechanism of Cantilever Bridges

Cantilever bridges function by fixing the bottom part of each cantilever into the ground, providing stability. Simultaneously, the upper end supports the bridge itself. This unique design allows cantilever bridges to be erected worldwide, especially in situations where multiple supports are impractical.

Types of Cantilever Bridges

Cantilever bridges come in two main types: Balanced Cantilever Bridges and Continuous Cantilever Bridges.

1. Balanced Cantilever Bridges : Balanced cantilever bridges are chosen for constructing long-span bridges without the need for additional falsework. These bridges combine the advantages of both simply supported and continuous structures, requiring only one line of bearings over the piers.

2. Continuous Cantilever Bridges : Continuous cantilever bridges, resembling truss bridges, span across three or more supports without hinges or joints. These bridges are adept at maintaining bending moments and shear strength throughout the beam.

Advantages of Cantilever Bridges

Minimal Falsework : Unlike many other bridges, cantilever bridges require minimal falsework, reducing construction complexities.

Assembly Efficiency : The suspended bridge sections can be assembled separately and then elevated and attached between two cantilever spans.

Single-Sided Support : Only one side of each cantilever needs support, streamlining construction efforts.

Uniform Floor Formation : The bridge floor is easily formed into sections, ensuring uniformity and high quality.

Time Efficiency : Construction of multiple cantilever spans can commence simultaneously from all its columns, saving time.

Uninterrupted Navigation : Passage under the bridge remains unaffected during the construction process.

Thermal Resistance : Cantilever bridges can withstand thermal expansion and floor speed better than other bridge types.

Flexible Design : The absence of supporting piers provides flexibility in designing the highway supported by the bridge.

Suitability for Challenging Terrains : Ideal for flood-prone areas and deep rocky valleys where falsework might pose challenges.

Disadvantages of Cantilever Bridges

Structural Heaviness : Cantilever bridges require a heavier structure to ensure stability, balancing compressive and tensile forces.

Tension During Construction : High tension levels, known as negative moments, are experienced during the construction of cantilever bridges.

Climate Limitations : Construction in extreme climate conditions is challenging due to the absence of multiple seasons.

Advanced Analysis Required : Preventing future fatigue failure demands advanced analysis of elements and welds.

Construction and Maintenance Challenges : Large-scale structures pose challenges in both construction and maintenance.

Need for Stronger Support : Larger and stronger support columns are necessary to withstand the bridge load.

Earthquake Sensitivity : Cantilever beams are unsuitable for earthquake-prone areas or regions with low-rock stability.

Some Facts: Top 10 Longest Cantilever Bridges in the World