THE INVENTION relates to 5 plane hollow reinforced concrete floors with two-dimensional structure and span in arbitrary direction.

The present floor structure is 1. art of a complete construction system developed for increased flexibility and large beamless span.

10 THE CONVENTIONAL TECHNIC

and the weakness of concrete floor structures is assumed well known.

Concrete floor structures have one fault.

The dead load is usually £-4 times as heavy as the useful carrying capacity, 15 This situation has coursed numerous attempts to make the construction less heavy, mostly through creating some kind of internal cavity space.

Yet, no one has ever succeeded finding a general solution of the problem.

To obtain static and practical relevanε a large number of conflicting conditions necessarily must be fulfilled at the same time, which is never £0 approximately achieved.

All serious previous attempts therefore have been related to the sirnpel one-dimensional structure (span in one direction) rather than the much more complex two-dimensional structure (span in arbitrary direction).

The two constructions have quite different static function and can not be £5 compared.

FLOORS WITH ONE-DIMENSIONAL STRUCTURE are since the 1950'es fully developed through the the prefabricated and prestressed hollow concrete element, where the hollow space profil are 30 made by monolitic concreting around steel pipes, wich are drawn out of the element after cementation leaving empty tubes inside the concrete.

The construction achieves maximum bearing strength corresponding to the concrete volume.

However, the construction can only be made as a prefabricated element, 35 and the bearing capacity exists only in one direction.

This weakness locks the whole building construction in a firm, rigid system because the construction widely must be adapted to the floor elements.

The building system suffers from the necessity of bearing walls o ⁿ beam= and offers no really flexibility. 0

£. Prior to the technics of today it was known embedding pipes of sheet metal and the like.

From DE £.116.473 (Hans Nyffeler apr.1970) it is suggested to convert the mentioned pipes to balls of lightweight materials (like a row of pearls), whereby shortning on the site of prefabricated pipes could be avoided. The ball lines are suggested made by boring holes through the middle of the balls and hang up the balls on a steel bar through the bore holes. The bar itself with the balls are to be hanged up in bent bars free of the reinforcement. The idea suffers from several serious faults, which make the concept quite unrealistic, f.ex. not all the mentioned materials can be converted, the perforated balls can not be made hollow without filling by concrete, a practical carrying out will be extraordinary difficult and doubtful1. It must be concluded, that the idea in theory is possible but in no way realistic.

In relation to two-dimensional structures the idea has no sense at all. It would be completely impossible pulling balls on crossed bars.

FLOORS WITH TWO-DIMENSIONAL STRUCTURE can not be used rationally in conventional compact design, especially in combination with supporting columns because of the high weight/thickness ratio.

If it is not wanted to provide the columns with capitals the feasibility is limited to small sections with side line about 3-5 .

This weakness binds the whole building construction in a very close structurel module, whereby also this system becomes rigid and without flexibility.

No tech ic known from the one-dimensional hollow structure can be transferred to a two-dimensional hollow structure.

THE PRESENT INVENTION

solves the general problems concernirig both improving shear conditions and making arbitrary flexible hollow space through a very simple technic. Hollow bodies (air bubbles) and reinforcement are integrated in a locked geometric and static unity by designing a geometric form which make the bubbles fit in the reinforcement mesh size, whereby the mutual position of the bubbles and their primary secure in horizontal direction is finally fixe

The top of the bubbles are secondary fixed through an upper walkable mesh. The vertical secure is provided through usual binding between the two mesh. Hereby is created an internal lattice work of steel and air ready for embedding in a monolitic concreting according to usual practice. 5 The invention also concerns the production technic regarding claim 4.

The system is at the same time untraditional and very simple, which is a consequence of two new ways of thinking,

First integrating reinforcement (instead of separating) with other 10 materials, which is the oposite of usual engineering teaching and practice. Second combining air and steel into an independent geometric and static unity, which is also a complete untraditionel and new construction.

The voids are provided through air bubbles, characterized by satisfying all 15 7 absolute technical conditions at the same time

1. simple incorporation and shape (feasibility)

≤. closed body (water-tightness)

3. strength (inflexibility of contact points)

4. reliable fixing (against trafic and concreting) £0 5. symmetry in body (£-axis or rotation)

6. symmetry in structure (£-axis or rotation)

7. no obstacles for continuous monolithic concreting

From these criteria is developed bubbles with shapes close to ellipsoid and £5 sphere. Regarding practic feasibility and transportation volume the bubbles are in additional developed as joint members includingvariaon possibilities.

Design by the present technic will replace 30-40% of the concrete with 30 air. The result is a two-dimensional plane hollow floor structure characterized by having less weight, higher strength and higher stiffness than all known floor structures and in fact with unlimited bearing capacity and flexibility, which of cource also results in a better economy. The technic results in unusual profits compared with traditional compact 5 floors, goes for less volume of materials is gained in concrete 40 - 50"/. plus in steel 30 - 40"A goes for higher strength is gained 100 - 150% goes for larger span is gained up to £00% 0

The technic is fit for both in situ works and prefabrication of elements. There might occur minor natural variations in system and carrying out f.ex. by prefabrica ion and prestressing the bubbles can be fixed at the form panel on distance pieces and the reinforcement can be concentrated in the concrete 5 ribs between the bubbles.

The invention and carrying out is more in detail explained in the following text referring to the drawings showing examples of the primary design with bubbles placed in the reinforcement mesh, and where the variation possibilities indicated in fig.6-13 are referring to the same floor 10 thickness, and where in principle fig.1 shows a plane view of floor structure with bubbles and supported on columns,

fig.£ shows a vertical profile of the same floor structure, 15 fig.3 shows components of the variable bubble,

fig.4 shows the lock between the components,

£0 fig.5 shows a joint bubble,

fig.6 shows a plane view of floor section with bubbles of ball shape placed in every second mesh and fixed in top by binders,

£5 fig.7 shows a vertical profile of the same section,

fig.S shows a plane view of floor section with bubbles of ball shape placed in every third mesh and fixed in top with walkable net,

30 fig. shows a vertical profile of the same section,

fig.10 shows a plane view of floor section with bubbles of ellipsoid shap standing in every second mesh,

35 fig.11 shows a vertical profile of the same section,

fig.1£ shows a plane view of floor section with bubbles of ellipsoid shap lying in every second mesh,

40 fig.13 shows a vertical profile of the same section.

There exist no substantial difference between carrying out prefabricating and in situ work, why the last will be described.

Two-way reinforcement (1) is layed out in the form (16) in quite usual way, fig.6-13, and anchored to the buttorn (16). Then the bubbles (3) are layed directly on the reinforcement (1) in every second mesh (£).

The tops of the bubbles (3) are in the same way connected through an upper walkable net (IE). As an alternative to the upper atress the bubbles can be tied by binders pricked into predetermined "eyes" (15) in the bubbles (3

The two steel nets (1,1£) and the bubbles (3) between thern now form a stabi inflexible system in horizontal direction. The top net (1£) is locked to th bottom net (1) by usual binding wires (13).

Now is completed a three-dimensional stable lattice of steel (I, IE) and air

(3), ready for concreting in usual way.

If wanted, the vertical binding can be carried out suitable loose, then the uplift pressure will lift the bubbles and secure full concreting of both mesh and bubbles, but the lattice it self is so elastic that complete embedding must be expected in any case.

The finished floor structure appears as a cross web construction with plane upper and underside (a three-dimensional concrete lattice).

It shall be pointed out that the work is no more time-consuming than a usual floor construction with double reinforcement.

In the following is given some calculations to illustrate the advantages of the bubble floor (o) compared with a traditional compact floor (m) .

SAME THICKNESS

3£ CM COMPACT FLOOR ctr. 3£ CM BUBBLE FLOOR

Calculations are based on same statical condition in the two floors : same effective thickness h,e same pressure zone = £05- af h,e same moment depth = 90% - h,e h,e is set = h÷3 cm

1. DIRECT PROFIT IN BEARING CAPACITY

With same support the load on o-floor can rise (10,6 - θ,0) 3/4 £,0 kN/mE to 1,5 + £,0 ^~ or 100 * £,0/1,5 130 %

PROFIT IN FREE SPAN

10,6 A, m

B,0 A-o

1,33 * A, m/A, o

1.33 * A.rπ

If based on shear force same result.

In both cases an 33% increase of space area (κl6% in every direction).

B. SAME BEARING CAPACITY

1. IF COMPACT FLOOR SHOULD GAIN SAME CAPACITY AS BUBBLE FLOOR

bearing load p-o = the thickness must rise from 3£ cm to corresponding to an increase of or an extra dead load

10

Ex : thickness judged 46 cm permanent load working load

15 design load q,m for load M,m/M,o q,m / q,o for floor M,m/M,o (h,rn/h,o) ^■ h,m/h,o h,m 32 * 1,45

£0

IF BUBBLE FLOOR SHOULD BE REDUCED TO SAME CAPACITY AS COMPACT FLOOR

working load p-m the thickness could sink with 6 cm from 3£ crn to

£5 corresponding to a reduction or a total load reduction 7,7 - 4,£ corresponding to

Ex : thickness judged 6,£4 * 2/3

30 permanent load working load

design load q-o = load M,o/M,m K q,o / q,rπ = 7,1/10,6 floor M,o/M,m ~ (h,o/h,m) * h,o/h,m h-o = 3£ * 0,θ£

0

SAME WEIGTH

3£ CM BUBBLE FLOOR ctr. £1 CM COMPACT FLOOR

Loads dead load (both) g floor finish g light partitions g

10 working load p

design load q g+l,3p

1. GAIN IN BENDING STRENGTH

15 for load M, =_ M,o q k 1 q A for floor M,o/M,m (h,o/h,m) • (£9 / ιa) ^« £,6

£0 The bending strength for bubble floor is 160% higher than the strength for compact floor.

£. GAIN IN SHEAR STRENGTH

The shear strength will also be increased with more than 100%. but depends besides the thickness also of the width of supporting area.

GAIN IN FREE SPAN

30 for area M, o/M,m q A,o / q A,m £,6 A,o/A,m £,6

Free span area of bubble floor is 160% larger than free area of compact floor, or 60% in every direction.