Engineer's Book


Survey 08 – Iron Structure – 1892

Written By: Jean-Paul Cipria - Oct• 29•17

Ferme en Fer - La Construction Moderne 1892

Ferme en Fer – La Construction Moderne 1892 – [LCM-1892].

Before Tour Eiffel Building Vonstruction how did Engineers to Concept Iron Resistant Structures ? First Hand Drawings and Calculations ?


Created :2017-10-29 13:46:48. – Modified : 2018-12-01 17:59:52.


Complicated but Not Difficult - Bachelord Level

Bachelord Level – Not Difficult

Done ... Un Café ?

Done … Un Café ?

CAO Drawings

CAO Drawing

We report structural form measurements from document [LCM-1892] used in 1892. This is a short resume of a structural iron beams used to construct ans support a roof. We drew it by Autocad 2014 with polylines, points and some haches pattern from an original document described at the next paragraph.

Ferme en Fer - La Construction Moderne 1892

Fig. 1 – Ferme en Fer – La Construction Moderne 1892

Original Structural Form

Ferme en Fer-Structure

Ferme en Fer-Structure – Reference [LCM-1892]

Constant Lateral Pressure Arche ?

Matlab Calculation Result

Do it by Matlab and plot also small perpendicular directions from black curve (in red) in figure 2 below.

Ingénierie d'Architecture - Arche à Poussée Constante - Droites Orthogonales Locales. @J.P. Cipria - 31/01/2017.

Fig-2 : Ingénierie d’Architecture – Arche à Poussée Constante – Droites Orthogonales Locales.[CIPRIA-30-jan-2016]

We can see the black curve figure 2 up side down to recognize a constant pressure arche. Then in [LCM-1892] reference engineer made calculation as the same to approximate as the best they can such engineering curve in figure 1 iron structure.

Approximative Constant Lateral Pressure Curve

As we can see at the previous figure 3 we add a blue « chaînette » curve, by hands. We can see red iron curve structure surrounded the theoric « best » blue curve. We determined it by differential equations, known in 1892 by all engineers like Gustave Eiffel. Then in [LCM-1892] reference engineer presented this structural light obect with some small calculations on modern architecture newspaper.

Iron Structure - Lateral Constant Pressure Curve

Fig. 3 : Iron Structure – Lateral Constant Pressure Curve : The Theorical « Best » Curve » as defined constraints.

Technical Folder

Obviously they didn’t write or drew this blue « conceptual » curve. It is a hidden engineer small equation from 1992 to 2017. Fortunately all bachelors studied it but anybody seems to speak about it. Therefore is it a good pretender to understanding ? Yes it is !

Ferme en Fer-Dossier Technique-1892

Ferme en Fer-Dossier Technique-1892


Old and new engineers said all on  a primary school level in a master or doctoral newpapers !

« Principle in drawing are always the same : call, in each articulation point, the strengh equality for forces arriving at this point, … »

« Le principe de l’épure à tracer reste toujours le même : exprimer, en chaque point d’articulation, l’équilibre des forces qui concourent en ce point, c’est à dire l’équilibre des tensions ou compressions qui agissent sur les pièces assemblées … »

Then all primary school writings are described by « conservative … energies, strenghts, pressures, flux … » as the first and only (?) principle in physics ? Did they forget another one as important as the second principle ! Surely not ! They had to draw this famous curves before plot a structural iron form ! It is shame for simple bachelords convicted to remain in non-understanding level.

In such papers from 1982 to 2017 we have to verify if « épure » or structural forms had the right capacities to stand up but we can’t know HOW engineers constructed them !

Now after reading this article we can say : We understand it !\frac{x}{a})

That’s all folks ?

Surely not !


  • [LCM-1892] : La Construction Moderne – 11 mai 1892 – Page 383.
    Bibliothèque Historique de la Ville de Paris (BHVP).
  • [CIPRIA-30-jan-2016] : Jean-Paul Cipria – « Lateral Constant Pressure Curve. »
    « How do we optimize trajectories from distances or times constraints ? How do we maintain a constant lateral strenght on a bridge structure ? »

    Architecture 03 – Qu’est ce qu’un Brachistochrone et une Chaînette ?


Jean-Paul Cipria

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