String Line Theory

 

  

 "As hangs a flexible cable, so, inverted, stand the touching pieces of an arch". 
Robert Hooke (1635-1703).

Robert Hooke observed that a cable hung with equal tensions is equivalent to an arch with equal compression points. 
 

 

 

 

 

Antoni Gaudi
In the 18^th century, Antoni Gaudi studied the nature of angles and curves throughout his life and incorporated this into his designs. Gaudi used a modelling system of threads which represented the structural elements, with small weights representative of the structural building weight.
   

The Sagrada Familia

 

 

 

 

 

 

 

 

The Sydney Harbour Bridge Example

 

 

 

 

 

 

 

 

Looking at the harbour bridge upside down, you can see the string line form. When weights are evenly distributed along the string line, it  forms the natural shape of an arch.