Arches are among the most ancient and structurally efficient forms used in bridge construction. From early stone bridges to modern steel and concrete spans, the arch has proven its ability to safely transfer loads primarily through compressive forces, reducing bending stresses and material demand. Even in today’s era of cable-stayed and suspension bridges, arch bridges continue to be preferred for their strength, durability, and visual impact.
Understanding the different types of arches in bridges is crucial for proper design selection, as the arch form directly affects load behavior, span capability, foundation demand, and construction technique.
Structural Action of Arch Bridges
An arch bridge works by redirecting vertical loads from the deck into compressive thrusts along the curve of the arch. These forces are then transferred horizontally and vertically to the abutments. Because most construction materials perform better in compression than in tension, arches achieve high efficiency and long service life when correctly designed.
The classification of arches in bridges can be understood based on support conditions, shape, deck position, material, and structural system.
Classification Based on Support Conditions
Fixed Arch (Rigid Arch)
A fixed arch is one in which both ends are rigidly fixed into the abutments, preventing rotation as well as horizontal movement. This restraint introduces bending moments in addition to compressive forces.
Fixed arches are:
- Very stiff
- Suitable for short to medium spans
- Sensitive to temperature changes and settlement
They are commonly used in reinforced concrete urban bridges where foundation conditions are strong and stable.
Two-Hinged Arch
A two-hinged arch has hinges at the supports but no hinge at the crown. This allows rotation at the ends while restraining horizontal displacement.
Key advantages include:
- Reduced bending moments compared to fixed arches
- Better accommodation of temperature effects
- Greater structural flexibility
Two-hinged arches are widely used in modern concrete and steel bridges with medium spans.
Three-Hinged Arch
A three-hinged arch contains hinges at both supports and at the crown, making it statically determinate.
Important characteristics:
- No internal stress due to temperature change
- Unaffected by minor settlement
- Easy structural analysis
Although popular in earlier bridge designs, three-hinged arches are now less common due to maintenance issues at hinge locations.
Classification Based on Shape of the Arch
Circular Arch
The circular arch follows a constant-radius curve and is one of the oldest arch forms.
Key features include:
- Simple geometry
- Ease of construction
- Suitable for masonry structures
However, circular arches are not always structurally optimal for uniformly distributed loads.
Parabolic Arch
A parabolic arch closely matches the shape of bending moment diagrams for uniform loads, making it structurally ideal.
Engineering benefits include:
- Minimum bending stress
- Efficient force distribution
- High load capacity
Parabolic arches are commonly used in modern highway and railway bridges.
Elliptical Arch
Elliptical arches have a flatter profile than circular arches, offering both structural and architectural advantages.
Notable characteristics:
- Reduced rise-to-span ratio
- Improved headroom
- High aesthetic value
They are often selected for urban bridges and architectural landmarks.
Classification Based on Deck Position
Deck Arch Bridge
In a deck arch bridge, the roadway is placed above the arch rib, and the arch directly supports the deck.
Advantages include:
- Simple structural behavior
- Efficient load transfer
- Suitable for deep valleys and gorges
Deck arch bridges are widely used in mountainous terrain and highway crossings.
Through Arch Bridge
In a through arch bridge, the deck passes between the arch ribs, and loads are transmitted via hangers.
Key benefits:
- Efficient for longer spans
- Reduced deck thickness
- Better clearance below the bridge
Through arches are commonly used for river and railway crossings.
Semi-Through (Half-Through) Arch Bridge
A semi-through arch bridge places the deck approximately at mid-height of the arch.
This configuration:
- Combines features of deck and through arches
- Is useful where vertical clearance is limited
- Provides balanced load behavior
Semi-through arches are often adopted in urban and constrained locations.
Classification Based on Construction Material
Masonry Arch Bridges
Masonry arches are constructed from stone or brick and rely entirely on compression.
Their main features include:
- Exceptional durability
- Minimal maintenance
- Limited span length
Many historic masonry arch bridges remain in service today due to their robust construction.
Concrete Arch Bridges
Concrete arches, either reinforced or prestressed, dominate modern arch bridge construction.
Advantages include:
- High compressive strength
- Versatility in shape and span
- Long service life
Concrete arch bridges are extensively used in highways, railways, and metro systems.
Steel Arch Bridges
Steel arches provide excellent strength-to-weight efficiency, allowing longer spans with slender members.
Key characteristics:
- Lightweight compared to concrete
- Faster erection
- Ideal for long-span bridges
Steel arches are commonly used in through-arch and tied-arch configurations.
Special and Advanced Types of Arch Bridges
Tied Arch Bridge (Bowstring Arch)
In a tied arch bridge, the horizontal thrust of the arch is resisted by a tension tie, typically the deck itself.
Major advantages include:
- Reduced forces on foundations
- Suitable for weak soil conditions
- Capability to span long distances
Tied arches are frequently used in urban river crossings.
Network Arch Bridge
A network arch bridge uses multiple inclined hangers arranged in a crisscross pattern.
Key benefits:
- Increased stiffness
- Reduced deck bending
- Excellent fatigue resistance
This modern arch type is gaining popularity in steel bridge design.
Advantages of Using Arches in Bridges
Arch bridges offer several structural and functional advantages:
- Efficient compression-based load transfer
- Long lifespan with low maintenance
- Reduced material consumption
- High aesthetic appeal
- Proven performance over centuries
Limitations of Arch Bridges
Despite their benefits, arch bridges have certain limitations:
- Require strong abutments
- Construction complexity
- Higher initial cost in some cases
- Less suitable for very soft foundation soils
Careful site evaluation is essential before selecting an arch bridge system.
Selection Criteria for Choosing the Right Arch Type
The choice of arch type depends on:
- Span length
- Foundation strength
- Material availability
- Construction method
- Aesthetic requirements
- Economic feasibility
A well-selected arch form ensures structural safety, durability, and cost efficiency throughout the bridge’s lifecycle.
Conclusion
The different types of arches in bridges represent a rich combination of structural efficiency, engineering logic, and architectural elegance. From fixed and hinged arches to parabolic, tied, and network systems, each type serves a distinct purpose depending on site conditions and functional needs. With proper design and construction, arch bridges continue to be one of the most reliable and enduring solutions in bridge engineering, capable of serving society for generations.
