Design Considerations for Arch Bridges

May 19, 2021
BLOG BRIDGE INSIGHT

Design Considerations for Arch Bridges

 

 

Table of Contents:

 

1. Arch Bridge  Definition and Classification

2. Design Considerations of Arch Bridges

3. Vortex Shedding

4. Buckling of Arch Rib

5. FEM Analysis


 

Arch Bridge Definition and Classifications

 

An arch bridge is usually defined as a vertically curved and axially compressed structural member spanning an opening and providing support for the moving loads above the opening. The deck can be supported or hung from this main structure, and depending on the position of the arch relative to the deck, arch bridges can be classified as deck arch, through arch, and half-through arch bridges as shown below:

 

Deck Arch BridgeFigure 1. Deck Arch Bridge
 
 
Through Arch BridgeFigure 2. Through Arch Bridge
 
Half-Through Arch BridgeFigure 3. Half-Through Arch Bridge

 

Design Considerations for Arch Bridges

 

There are many factors that affect the design of an arch bridge. In general, these factors are related to function, cost, safety, aesthetics, traffic demand capacity, foundation conditions, erection procedure, clearance requirements, and so on. General design recommendations focus mainly on the arch-to-span ratio, the arch and deck slenderness, and the number of hangers or piers.

 

Rise-to-Span Ratio

 

The rise-to-span ratio for arches may vary widely because an arch can be very shallow or, at the other extreme, could be a half-circle. Most arches would have rise-to-span ratios within the range of 1:4.5 to 1:6.

There are typical spans used for different types of materials. Below are some:

 

  • Filled spandrel masonry arch bridges are suitable for spans < 20 m.
  • Spans of masonry arch bridges range from a few meters to 146 m.
  • Concrete arch bridges are suitable for spans ranging from 35 m to 200 m, though there are some bridges with spans well over 200 m.
  • Steel and CFST (Concrete Filled Steel Tube) arch bridges have a larger capacity than the ones mentioned above, allowing larger spans because of the higher material strength.

 

Vortex Shedding

 

Vortex shedding should be taken into consideration when designing an arch bridge. There are times when an arch is identified that is having problems with hanger vibrations especially those with I-section hangers. These vibration issues are usually solved by connecting the hangers as shown below, reducing the length of the hangers, and changing their natural frequency.

 

Horizontal Cable Connecting Hangers
Figure 4. Horizontal Cable Connecting Hangers (The Bridge Engineering Handbook by Wai-Fah Chen and Lian Duan)

 

Buckling of Arch Rib

 

Since the curved rib of the arch bridge is subject to a high axial force, the chance of a failure due to buckling of the rib must be taken into consideration when designing an arch bridge.

 


 

FEM Analysis

 

With the development of computer technology and its applications to structural analysis, various challenging arch shapes have turned up in practice that previously may have been imagined but were impossible to design. MIDAS has played a major role in the infrastructure of the world and midas Civil has been used to design some of the most beautiful arch bridges in the world.

 

As an example, look at some of the midas Civil project applications below:

Arch Bridge (Taipei, Taiwan)Figure 5. Arch Bridge (Taipei, Taiwan)

 

Steel Arch Bridge (Nanning, China)Figure 6. Steel Arch Bridge (Nanning, China)
 
 
Laguna Espanola Bridge, ArubaFigure 7. Laguna Española Bridge, Aruba
 
 

 

 

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About the Author
Edgar De Los Santos | Senior Engineer | MIDASoft Inc.

Edgar is a Senior Engineer at MIDASoft Inc. experienced in numerical modeling and bridge design and has over 8+ years of experience. Edgar has participated in designs of Prestressed Girder Bridges and Segmental Bridges. Edgar pursued his Civil Engineering Degree from the New Jersey Institute of Technology (NJIT) and is currently pursuing a Master's Degree in Civil Engineering at the Universidad del Norte in Barranquilla, Colombia.

 

 

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