Uboot

U-boot U-boot beton is a formwork made of recycled polypropylene, designed to create lightened intermediate slabs and raft foundations in reinforced concrete. The use of U-boot formworks permits to build specific mushroom slabs: the mushroom is part of the slab thickness. Thanks to the cone shaped foot, U-boot remains dip into the concrete casting. Thus, a grid of orthogonal beams, superiorly and inferiorly closed by plane slabs of different heights, is obtained without executing two distinct concrete castings; all that implies a remarkable saving of concrete and reinforcement. U-boot permits to build big spans slabs or slabs supporting high loads without beams. Light and easy to pose, thanks to U-boot modular formworks, the draftsman can change the geometrical parameters of the slab, in order to suit any kind of situation.

h

16

h

20

h

24

h

32

h

36

h

40

h

44

dali orm © T h o s e w h o i n v e n t e d I g l u’

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48

Le applicazioni U-boot is used in all applications that require a plate structural solution, along with concrete-savings and therefore weight-savings. In tower buildings, weight-saving at every floor reduces load on foundations. The fact of avoiding beams being out of the slab thickness, enables the reduction of height for each floor. Therefore, a higher number of floors can be built. By using U-boot beton, it is possible to build thick raft foundations with a reduced quantity of concrete (and weight). U-boot is the ideal solution to create slabs of big spans and/or with a high bearing capacity. In case of difficult access to the building site or restructuring, U-boot beton permits to build up the horizontal structures without using lifting and movement devices, because of its stackability, modularity, lightness and manageability. The U-boot system particularly fits structures that need significant open spaces, like bureaus,industrial and commercial buildings, and civil constructions as well. The system also allows a more irregular distribution of pillars, since beams are not necessary.

Advantages in short LIGHT - THIN - BIDIRECTIONAL [ Designedf or bidirectional slabs [ Decrease of concrete and weight up to 40% [ Reduced deformation (maximum stiffness loss 15%) [ Reduction of load on foundations [ Reduction of pillar section FLEXIBLE [ Spans up to 20 m [ Absence of beams between pillars [ Reduction of pillars number [ Possible use with prefabricated slabs (picture 3) [ No lifting and movement devices required, ideal for restructuring [ Possible creation of monodirectional slabs thanks to the “bridge” accessory ANTISEISMIC [ Reduced seismic mass [ Less dimensional limitations of elements [ Double inferior and superior slab OPEN SPACES More spacious rooms Bigger architectural freedom Easier change of use

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ECONOMIC [ Less concrete incidence, thickness being equal [ Less steel incidence [ Usable height saving on each floor, since avoiding beams being out of the slab thickness enables a higher number of floors, height being equal (tower buildings) [ Rapidity and easiness of pose (unique twophased casting) (picture 2) [ Possibility of big spans, load being equal (picture 5) [ Possibility of high bearing capacity, spans being equal [ Economical transport and easy stocking, since it is stackable [ Ready to smooth once the deck is taken off, the intrados is a plane surface which do not require false ceilings at an aesthetical level [ If a false ceiling is necessary, pose is made more rapidly SAFE [ Significant fire resistance (certification REI 180; concrete cover 3cm) [ Safety on building site (complete flat deck avoids plunking down)

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3

Posing

U-boot

U-boot beton formwork is an easy to use product. First, a flat and complete surface has to be prepared with a wooden deck or any other similar system. Then, the inferior steel reinforcement hasto be posed in the two orthogonal directions, as designed in the executive project; the lattices are finally posed in order to space out upper reinforcements. Afterwards, U-boots are laid down and connected by lateral flaps, respecting the required span between the lightening space. Thanks to the cone shaped feet, U-boots are raised above the slab intrados, and the concrete can thus be cast, filling the whole surface below the elements. If double elements are to be used (H32, H36, H40, H44, H48), it will be necessary to pre-emptively assemble the two parts, that will be delivered in different pallets at the building site. The reinforcement pose is to be completed by disposing the upper bending steel bars in two directions, the shear and punching reinforcement, where necessary. Due to the floating pressure exerted on U-boots, the concrete should be cast in two different phases: (picture 1) the first casting has to fill a thickness equal to the feet height. The final phase has to be done when the first concrete layer starts to set and becomes semi-solid. Casting proceeds each time from the previous starting point. While the casting proceeds, the concrete sets. Finally the casting has to be levelled up in a traditional way (picture 6). The U-boot system execution time will be accelerated by using new deck technologies which permit to disassemble within 2-4 days, or using the carpet reinforcement system, in order to reduce the steel bars posing time up to 4-6 times.

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To get up-to-date technical specifications, support material, new photos and case studies, browse our website www.daliform.com

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6

U-boot lightened slab scheme: note the lack of connection beams between pillars.

U-boot slabs do not need beams between pillars, a perimeter edge beam is enough. The orthogonal grid of beams transfers all stresses directly on pillars; around which it is enough to leave a massive area, called mushroom pillar, which is thick as the slab and variable in function of shear stresses. Table: U-boot slabs characteristics compared to massive slabs Square grid span

Slab thickness with overload 500 kg/m2

S2

Lightened slab inertia

Massive slabinertia

Equivalent height percentage loss

Lightened slab weight

cm

cm

cm4/m

cm4/m

%

kg/m2

kg/m2

% 29,09

S1

H U-boot

cm

Massive slab weight

Weight saving

7

26

5

16

5

124802

146467

5,196

460,9

650,0

8

30

7

16

7

203335

225000

3,319

560,9

750,0

25,21

9

34

5

24

5

249430

327533

8,680

563,3

850,0

33,73

10

36

10

16

10

367135

388800

1,893

710,9

900,0

21,01

11

38

7

24

7

379163

457267

6,052

663,3

950,0

30,18

12

42

5

32

5

426164

617400

11,624

671,8

1050,0

36,02

12

44

10

40

10

631763

709867

3,811

813,3

1100,0

26,06

12

46

7

32

7

619897

811133

8,573

771,8

1150,0

32,89

13

50

5

40

5

660882

1041667

14,073

774,2

1250,0

38,06

14

52

10

32

10

980497

1171733

5,766

921,8

1300,0

29,09

14

54

7

40

7

931415

1312200

10,797

874,2

1350,0

35,24

15

58

5

48

5

959465

1625933

16,123

876,6

1450,0

39,54

15

60

10

40

10

1419215

1800000

7,617

1024,2

1500,0

31,72

16

62

7

48

7

1319599

1986067

12,740

976,6

1550,0

36,99

18

68

10

48

10

1953799

2620267

20,439

1126,6

1700,0

33,73

IN DEPTH U-boot lightened slab scheme: note the lack of connection beams between pillars

Solid model deformed structure and stresses representation

Frame model non-deformed structure

Frame model representing bending stress

Shell model non-deformed structure

Shell model and bending stress representation

U-boot

Shell and solid model non-deformed structure

Raft foundation Among foundation different typologies, raft foundation is surely one of the most known and used, considering its evident technical advantages: high stiffness due to its static bidirectional behaviour, and thus load partition capacity on the ground; it also permits to absorb stresses coming from the building, with differential subsidences close to zero; easy and quick to carry out. If stresses increase or the ground bearing capacity decreases, the structure may require a thick raft foundation. This means having more concrete and more pressure on the ground; and therefore higher building costs. U-boot beton is a formwork made of recycled polypropylene, purposely designed to build lightened plate slabs and raft foundations. Once drowned into concrete, it creates an alveolar structure with two slabs of different thickness, joined by an orthogonal grid of beams of variable width, therefore building an ideal light structure for raft foundations. Statically, it can be seen as a grid of I beams which means having a rationalized masses distribution for the purpose of inertia, in order to get high stiffness with a minimum quantity of concrete. This perfect combination of lightness and stiffness permits, in particular cases, to avoid using foundation piles.

10.000 m2 raft foundation, thickness 68 cm, overloads 3.000 kg/m2. The project initially planned to use foundation piles.

U-boot or polystyrene? Polystyrene is a widely used material in the world of building, especially if associated to prefabricated slabs, because it is cheap and malleable. However, in the last few years, the technicalscientific community has been focusing on its numerous disadvantages. First of all, the fact that polystyrene releases toxic styrene monomers, at room temperature. Moreover, some studies carried out by the Polytechnic University of Milan highlight the fact that a slab lightened by means of polystyrene explodes after only 20 minutes, if exposed to fire load. This is partially due to the presence of warm air into the cavities which increases pressure, and partially due to styrene sublimation. That is the second problem. In order to avoid slabs explosions, prefabricated slabs producers recently planned some vents into the slab to maintain external pressure into cavities. But in this case, the styrene flows out from the cavity, and it is toxic. On the contrary, U-boot is made of polypropylene which is not toxic even if it burns. Moreover, the CSI laboratories carried out a fire test on a slab lightened by means of U-boot and with a 3 cm concrete cover, and the structure was certified REI 180 minutes. The certification is available on request. Finally, polystyrene is a material which needs huge volumes for transportation and stock on site; U-boot beton is designed to be stackable.

GLI APPROFONDIMENTI

U-boot

Boroli La Brunella wine cellar - Castiglione Falletto (CN) - Architectural project Arch. Guido Boroli - Structural Project Carosso & Daliform - Spans 7.5mx5m - Overloads 3000 kg/m2 - surface 400 m2

Nola Interport - Nola (NA) - Architectural project: Renzo Piano Building Workshop - Structural project : Favero&Milan En - Spans 10mx10m - Overloads700 kg/m2

Direction center Treviso 2 - Treviso (TV) - Architectonic project Arch. Mario Botta - Structural project Studio Vitaliani - span 10mx10m - overload 600 kg/m2 - Surface 500 000 m2

U-boot - Data sheet Elements for project specification Supply of recycled plastic U-boot elements, with a truncated pyramid shape and a lower base 52x52 cm. U-boot is composed of feet, lateral flaps and upper tips used as spacers, in order to create an alveolar void in concrete massive slabs. Elements are to be posed on site on a predisposed deck, or in factory on a pre-cast slab. Elements height: 16, 20, 24, 32, 36, 40, 44, 48 cm; feet of 0, 5, 7, 10cm; flaps of 12, 14, 16 ,18, 20 cm.

Parameters and consumption table Formwork

Base B cm

Height H

Feet P

cm

cm 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10 0-5-7-10

u-16

52x52

16

u-20

52x52

20

u-24

52x52

24

u-32

52x52

32

u-36

52x52

36

u-40

52x52

40

u-44

52x52

44

u-48

52x52

48

Spacers d cm 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 0 0 0 0 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5 0 e 1,5

Beam width

Beam interax

U-boot incidence

cm 12 14 16 18 20 12 14 16 18 20 12 14 16 18 20 12 14 16 18 20 12 14 16 18 20 12 14 16 18 20 12 14 16 18 20 12 14 16 18 20

cm 64 66 68 70 72 64 66 68 70 72 64 66 68 70 72 64 66 68 70 72 64 66 68 70 72 64 66 68 70 72 64 66 68 70 72 64 66 68 70 72

pz/mq 2,44 2,30 2,16 2,04 1,93 2,44 2,30 2,16 2,04 1,93 2,44 2,30 2,16 2,04 1,93 2,44 2,30 2,16 2,04 1,93 2,44 2,30 2,16 2,04 1,93 2,44 2,30 2,16 2,04 1,93 2,44 2,30 2,16 2,04 1,93 2,44 2,30 2,16 2,04 1,93

Concrete saving

mc/pz 0,031 0,031 0,031 0,031 0,031 0,039 0,039 0,039 0,039 0,039 0,047 0,047 0,047 0,047 0,047 0,062 0,062 0,062 0,062 0,062 0,070 0,070 0,070 0,070 0,070 0,078 0,078 0,078 0,078 0,078 0,086 0,086 0,086 0,086 0,086 0,094 0,094 0,094 0,094 0,094

Concrete consumption

mc/mq 0,076 0,071 0,067 0,063 0,060 0,095 0,090 0,084 0,079 0,075 0,115 0,108 0,102 0,096 0,091 0,151 0,142 0,134 0,127 0,120 0,171 0,161 0,151 0,143 0,135 0,190 0,179 0,169 0,159 0,150 0,210 0,198 0,186 0,175 0,166 0,229 0,216 0,203 0,192 0,181

B

B

52

d

B

d H

H p d p

Certification On customer request, Daliform provides load tests on formworks and reinforced plates, certified by the University of Padova

mc/mq 0,084 0,089 0,093 0,097 0,100 0,105 0,110 0,116 0,121 0,125 0,125 0,132 0,138 0,144 0,149 0,169 0,178 0,186 0,193 0,200 0,189 0,199 0,209 0,217 0,225 0,210 0,221 0,231 0,241 0,250 0,230 0,242 0,254 0,265 0,274 0,251 0,264 0,277 0,288 0,299