US 2655846 A
Description (OCR text may contain errors)
Oct. 20,- 1953 E. FREYSSINET H LARGE SIZED CONCRETE AREA ADAPTED FOR AIRPLANE RUNWAYS AND THE LIKE Filed Sept. 23, 1948 a: I A.
W g f lnvenTor Eugene Freya-finer I wuim, M, GM: *1! wwim/i Patented Oct. 20, 1953 LARGE SIZED CONCRETE AREA ADAPTED FOR AIRPLANE RUNWAYS' AND THE LIKE Eugene Freyssinet, Neuilly-sur-Seine, France Application September 23, 1948, Serial No. 50,814 In France August 14, 1945 1 Claim. (o1. 94-8) This application is a continuation-in-part of my pendin application, Serial No. 650,814.
The object of my invention is the .production of large plane concrete surfaces adapted to carry heavy, concentrated loads, such surfaces consistingbasically of large slabs each individually prestressed in two directions, and bearing on a foundation over the whole area. The slabs are also as free as possible to slide upon their bearing area.
Another object of my invention is to avoid, as far as possible, the breaking up of these slabs due to variations of temperature and humidity.
A further object is to obtain highly resistant areas with a thickness of concrete which is much less than that used as present.
For the production of a pavement according to my invention I use slabs whose ratio of minimum linear dimension to thickness is not less than 200:1, the thickness being between cm. and cm. (6"-10"). In practice each slab is of a roughly square shape with sides of the order of 100 yards in length.
I arrange these slabs on the ground on a foundation which gives rise to the least possible friction, and, if the margins are to be subjected to loading, I support them on especially strong separate foundations. This latter foundation is indispensible particularly at the joints between two slabs; thus the foundation is the support for the expansion joint between two slabs.
The margins of the slabs rest on their foundations just as in the case of the central part, in such a way as to ensure the maximum ability to slide. The simplest way of achievin this object is to provide a thin layer of some plastic or viscous fibrous material such as bitumen-impregnated paper or felt, between the slab and the foundation. Preferably this layer of plastic material should lie, in the center of the slab, on a thin bed of sand properly levelled and spread out over the foundation soil.
For the individual prestressing of each slab, I use by choice a square mesh network of reinforcing rods in tension, whose ends are anchored in the edges of the slab. However, in some cases I induce a compression in the slab in at least one direction parallel to its surface by means of thrust against two abutments running parallel to and touching two opposite edges of the slab. This compression can be obtained by wedging, or, preferably, by some pneumatic or hydraulic system contained in at least one of the joints between the slab and the abutments.
The attached drawings show diagrammatically certain embodiments of the invention.
I Figure 1 is a diagrammatic plan view of a concrete area according to the invention;
Figure 2 is a large-scale diagrammatic plan view of a part of this area, and
Figure 3 is a view on line III-III of Figure 2.
The slabs A, B, C, shown in Figure l, have a square-mesh network of reinforcing rods 22-23 which are inclined with respect to the sides of the slabs in opposite directions. These slabs are disposed in end-to-end relationship with their adjacent end sides slightly spaced apart to provide fora gap D. The end portions of the slabs rest on a concrete foundation [3.
The concrete foundation I3 is prestressed 1ongitudinally by means of reinforcing rods M which are anchored in the usual Way at its ends. It carries the two edges of the slabs through a sandwich layer ll of some plastic or viscous material. The layers II are extensions of those which cover the sand-bed i5 placed on the ground surface to carry the central part of the slabs. Thus, the slabs can slide freely on their foundations as well as on the ground between these foundations.
The space H between two slabs is filled with some material relatively plastic, for example soft wood blocks impregnated with pitch, and with the grain running vertically.
As illustrated moreclearly in Figures 2 and 3 in which adjacent end portions of two successive slabs F and G are shown, the reinforcing rods 22 are bent, in the vicinity of the space II, as at 22a and then extend parallel to the rods 23.
The reinforcing rods l8 consist of cables covered in such a way as to prevent bond with the concrete, for example being in tubes III or covered with .paper or bituminous paint.
In the region [8a the wires forming the cables are spread out in the form of a cylinder with a vertical axis in such a way as to give each wire of the cable a good bearing on the concrete and to avoid local shear effect.
The reinforcing rods (or cables) 22 and 23 are subjected, after the concrete has set, to considerable tensile stress, for instance, by means of jacks acting on their free ends which protrude from the concrete structure. This tensionin action can be performed since the rods are not directly embedded Within concrete, but are surrounded by a sheath Ill. At their ends, the various wires or strands 9 of the rods (or cables) 22 -23 are flared out in conical formation, against the wall of a frusto-conical end recess 19a in a block l9.
been described, the ground is trimmed and lev- V elled, then the foundations 13 are laid, and then the layer of sand I5 is spread onthe ground be-' tween those foundations. The sand and the foundations are then covered with the plastic or viscous layer ll upon which the slabs are cast individually after placing the reinforcing rods.
It should be noted that tensioning the rein-- forcing rods after the setting of the concretecan be elfected by allowing the tensioning apparatus to'bear directly on the concrete of the slabs themselves. V @The sliding bed upon which each slab bears over its entire surface allows relative movements between the slab and the ground. These movements are of two types, an initial sliding due to the elastic contraction of the concrete at the time of prestressing, and secondly, slidin in servicedue to the effect of variations of temperature and humidity.
Having thus described the invention, what is claimed as new and desired to be secured by LettersPatent is:
A -concrete pavement of large area capable of v carrying concentrated loads and. in particular an air-strip for heavy aircraft, consisting of at least one rectangular slab, a primary series of parallel tensioned reinforcing rods embedded in said slab equally spaced, inclined to one side of rectangle, and a second series of parallel tensioned reinforcing rods embedded in said slabs, equally spaced and crossing the first series, the reinforcing rods of each set which approach the end edges of the slab being curved in the neighborhood of these latter edges and extended in a direction parallel to the other set, the ends of all rods beinganchored on the opposite side edges of the slab.
References can in the file of this patent UNITED STATES PATENTS 2,338,785 Sommerfeld Jan. 11, 1944