023 - Leonardo Bridge

023 – Leonardo Bridge

Construction of an arch  

Loadable bridge made of wooden plates

Introduction to:

Braiding, rigid components   

Material:  

  • Popsicle sticks = sticks for ice cream / thin plates made of wood.     
  • commercially available   

 Instructions:   

  •     Lay out two sticks as center supports in parallel. Clamp two more sticks as longitudinal beams over the first center beam and under the second center beam.   
  •     Clamp two more stems, mirrored to the last two, between the center beams.   
  •     Add a new center beam so that it clamps the longitudinal members between them with the nearest center beam.   
  •     Add two popsicle sticks lengthwise to reproduce the arrangement from 2.).  
  •     Step 3 and 4 applied again   
  •     Step 3 and 4 applied again  

Tips:  

  • The bridge can be extended further by adding new sections through steps 3 and 4.   
  • Water increases the frictional force of the wood and thus increases the stability of the structure, and simplifies its construction.  

Explanation:  

  • The type of arrangement causes a balance of forces at each connection of the popsicle sticks to each other.   
  • Through the point of support, the longitudinal beam exerts a supporting force FA perpendicular to its cross section. This force acts at the center of gravity S of the cross member.   
  • The supporting force can be split into a component FG perpendicular to the lower cross member and a component FZ parallel to the member.   
  • The weight force on the beam is compensated by its bearing force FT, thus preventing deflection or even breakage of the beam.   
  • The tensile force on the beam is compensated by the frictional force FR between the longitudinal and transverse beams, thus preventing any possible sliding apart of the beams.  
  • Both quantities are material-specific properties.   

Learning levels:   

Elementary school:  

Try out in teamwork, build (can be designed as a competition); simple understanding of construction, embedding in Leonardo da Vinci context possible.  

Secondary 1:  

Comparison: wet, dry stems → friction force as principle of self-supporting bridge; problem of maximum length with too many construction elements; build and compare different constructions, deepening self-supporting bridge possible.  

Secondary level 2:  

Drawing of forces on basic element of bridge (1 central beam), Trigonometric calculations of length, height, partial forces,  

Upper level:    

Generalization of the formulas for length, height to any number of construction elements, calculation of forces depending on the respective construction element, seminar paper, construction of a large Leonardo bridge made of wooden logs possible.