Suspension Cable Tension vs. Tower Height


Suspension Cable Tension vs. Tower Height

Engineers had to balance the advantages and disadvantages of tower height and cable size in the final design of the Golden Gate Bridge. When completed in 1937, the Bridge had the tallest bridge towers in the world.

Making them considerably taller to reduce the tension (pulling) force in the cables would have been a more difficult and expensive design alternative.

This exhibit allows the visitor the opportunity to pull each of the ropes to find the relationship between tower height and cable tension. The more tension, the thicker (stronger) the cable must be.

Explore this Topic Further

Design Constraints

Engineers had to balance the advantages and disadvantages of tower height and cable size in the final design of the Bridge. Click image below for full size.

Suspension Cable Tension vs. Tower Height

Cable Tension

Cable Tension Spreadsheet (grade 6 through adult)
This Excel spreadsheet uses an approximation of the shape of the Golden Gate Bridge main cables to explore how the cable tension changes with tower height. When the user enters the tower height, the spreadsheet immediately calculates and plots the new cable shape and the maximum and minimum cable tension.

Feel the Forces of a Suspension Bridge from Scientific American (grades 3-8)
These simple experiments with people, straws and string help to understand concepts of tension and compression and the role of the main cables in a suspension bridge.

Clifton Suspension Bridge from pbslearningmedia.org (grades 3-12)
Using graphics, David Macaulay describes the forces at work on the cables of the Clifton Suspension Bridge. Includes background essay, discussion questions, and links to national standards. (2 minute video)

The Golden Gate Bridge (grades 9-12, College)
This chapter by Thalia Anagnos found in the textbook Statics by Sheri Sheppard and Benson Tongue (Wiley, 2007) provides a simplified analysis of the Golden Gate Bridge cable forces. It compares a simplified analysis with a more exact analysis.

Math

Equations of the Golden Gate Bridge Cables from Golden Gate Bridge, Highway and Transportation District (grades 8-12)
This web page gives the parameters of the hyperbola that models the shape of the main cable for the center span and for the parabola that models the side spans of the bridge.