I have always liked the trusses. I remember when we were taught at the school the Cremona method to calculate them. It can not be said that it was the father party, but it was entertaining, and, according to one I was doing it, I could intuit (more or less) the composition and decomposition of the forces. It was as if the charges escaped by fleeing through the different bars, seeking their way, and neutralizing and balancing.
When I studied (eighties) the trusses were still the most economical and sensible solution to cover medium and large lights. It was unthinkable that industrial or agricultural warehouses did not have them. In addition, they could be made in sawtooth to form skylights, or give them different shapes that would adapt to the section that they wanted to give to the ship.
They were considered to be the best solution to save a span using the least amount of material possible. In many places they were called “air beams”, and I like that expression, because what works most in them is “the air”. That is, what is not steel or wood, but what is their distance, their separation, their song. That is, what does not cost money: the air.
But very soon the beams of uniform section beams (reinforced, all the more, in the recesses) began to become a hole. And, increasingly, they stopped “making a hole” to “fill the hole” and take it off the trusses. A beam of uniform section must be dimensioned for the most requested area, and, therefore, it maintains without necessity that same section where it is least needed.
It spends much more material than the truss, but now it is cheaper, because labor costs much more than the material, and the truss uses less material, yes, but it gives much more work. The truss has less kilos of steel than the portico, but each kilo costs a lot more money. It is logical, but I do not know what those ingenious and convoluted structures, but at the same time so intuitive, are in the doldrums.
The shape of the beam itself indicates its moment diagram. But it is a nuisance. On the one hand, the reinforcements at the top obstruct the placement of the straps or the covering material, and, on the other, reinforcing ends up being a can. It is much more practical to put a uniform beam. It uses a little more steel than strictly necessary, and to run. It is logical and, above all, comfortable, but we definitely lose that romantic and organic concept of structure, which no longer responds exactly to the demands and resolves them to the beast.
The calculation of a structure involves solving problems with as little material as possible, but now it is seen that killing flies by cannon is much more practical. A good example is when calculating a floor with a computer without restricting it; leaving him to his air. The computer seeks to solve the problem with as little material as possible, and we see that it uses bars of eight different diameters and that there are no two beams that have the same negative reinforcements. Conclusion: A real mess of assembly and control on site to save ten (or one hundred) kilos of steel.
We have to tell the program to use only three diameters, to equalize all the joists from one area to the worst, and not to get dizzy by five centimeters more in a bar of ten. (And let’s not say if we let him put a slab in. He gets a very complicated hodgepodge – but that faithfully represents the effort diagrams – until we tell him to use a base mesh and pull down the middle street).
All this is true, and I have always defended it: The works are a mess and a mess, and should be simplified as much as possible. A saving of material is an error when it involves complications, mistakes, inconveniences or delays in the work. The conclusion is that the design of the structure does not respond to the shape or the loads as much as we would like, for that of the integral, coherent architectural work … We think of the shells of mollusks or the horns of mammals. We think of the bones, which are formed in a wonderful way, depositing calcium molecule to molecule where it is most needed, and we would like the structures of the buildings to be a bit like that (not in the form, by God, but in the method or in the concept).
The conclusion is that in these times it is better to be a bit of a beast, to do the brute and to be free of finesse, and even structures that look more organic have a trap and go to cascoporro. Efficacy is more appreciated than elegance. (But we are not talking about strictly structural efficiency, but about effectiveness in the administration and organization of the work). Strength is more appreciated than skill and an elephant is worth more than a mouse.
(It was said that judo served so that a small person could beat a big one, but as soon as it became an “official” sport and records were made it was separated by pesos: One hundred kilos always wins one out of fifty). It is logical and understandable, but a little disappointing, that the form is not directed by the function or by the solicitation, but by the speed, by the simplification and by the money. On the other hand, the obligation of a structure is to solve, and not hinder or complicate; and in that sense, I say, it seems good to me. But I have a romantic nostalgia for when it was calculated by hand and “normal”, sharp and bending. Yes; also the torsores.
I get the feeling that the “fine and elegant structure” is quite out of place, and that the practical involves healing in health, spending three towns and letting go of nonsense and squeamishness.
José Ramón Hernández Correa
PhD Architect and author of Arquitectamos locos?
Toledo · july 2013
Nací en 1960. Arquitecto por la ETSAM, 1985. Doctor Arquitecto por la Universidad Politécnica, 1992. Soy, en el buen sentido de la palabra, bueno. Ahora estoy algo cansado, pero sigo atento y curioso.