AU763613B2 - Formwork attachment to frames for concrete walls - Google Patents

Description

Following on with the Steel Frames for concrete structures of Australian Patent Number 639522 (Appln. 69983/91) and after completing one house using this steel frame system for the walls. The advantages for sturdy wall structures are very apparent over basic brick and cavity concrete block being versatility of window and door design as well as being able to weld to external exposed surfaces and come out 25mm. or more to put water pipes and electrical cables in. The main draw-back of this method of building construction using metal Frames for concrete walls and structures is drilling and Tapping holes in the Formwork and hollow section Frames to hold the formwork to the steel hollow section Frames and then after pouring the concrete and when the concrete is set taking the boards or formwork off by unscrewing the bolts or screw and then cleaning the boards or formwork and then putting them up on higher positions or 15 unpoured positions of frames. This aspect of putting up formwork on frames and then taking formwork down for cleaning and re-application of release agent to be put up again in a different unpoured position is more time consuming than it should be and slows the pouring process down to the point that the frames system is not Economically viable against options like clay brick and concrete cavity block.

The aim of this invention is to speed up considerably the aspect of puLtting up and taking down formwork which is very time consuming and presently takes 8 or more hours to do up to 3 square meters of 150mm. thick wall to a point where 10 or more square meters of 150mm.

thick wall can be done by one person in 8 hours. This invention comprises thin steel or stainless steel sheet with 900 flaps, top and bottom being about 400mm. high for 150mm. thick wall pouring and flat face magnets being over 1,000 gauss on pole face holding sheet metal, steel formwork (with 900 flaps for strength) to metal 2 frames (Patent No. 639522) that form the concrete wall structure in the cast concrete with the magnets being attracted to the external exposed steel surfaces of the hollow section frames and thus squeezing and holding firmly the sheet metal formwork to the frames. When concrete is poured and set in formwork magnets are very quickly pulled off and sheet metal formwork comes straight off making the process of putting on and taking off formwork very rapid and thus making the frame system for concrete structures very much more streamlined and the Economic aim of up to 10m 2 of 150mm. thick 10 wall by a single person in 8 hours attainable. The 150mm. thick concrete walls have frame sizes of 750mm. by 750mm. with 20mm. by square hollow section steel of wall thickness of 1.6mm. inside this 750mm. by 750mm. diamension and this works well with concrete of compression strength of 15 MPa. (Mega Pascal pressure) to 25 MPa..

15 When mixing concrete in small batches it is best to go to 320 Kilograms of cement to every one cubic meter of concrete as water control becomes difficult with small batching as unexpected rain and varying moisture level in sand and. gravel make moisture control difficult which ultimately lowers the compression strength. The 750mm. by 20 750mm. diamension for frames for 150mm. thick walls works well to limits of -50C to 400C and only gives cracking above frame diamensions of 850mm. for 20mm. by 20mm. by 1.6mm. wall square hollow section when steel expansion stresses exceeds tensile strength of concrete.. Other wall size for 15Mpa. to 25MPa. compression strength concrete are as follows: Square Hollow Section 15mm. x 15mm. x 1.8mm.

wall for 600mm. x 600mm. x 115mm. concrete wall thickness Square Hollow Section 20 x 20mm. x 2.0mm. wall for 800 x 800mm. x 200mm. concrete wall thickness. Square Hollow Section 20 x x 2.0mm. wall for 850 x 850mm. x 2 50mm. concrete wall thickness.

-3 Square Hollow Section 20 x 20mm. x 2.0mm. wall for 850mm.x 850mm.

x 300mm. concrete wall thickness.

The sheet metal formwork (steel or stainless steel) for 150mm.

thick walls out of frames 750mm. by 750mm. (1.6mm. wall thickness) Hollow section steel is no more than 400mm. high with 20mm. 900 folds top and bottom with the sheet being 2.0mm. thick being steel or stainless steel so that Ferrite (Fe 3 0 4 magnets being 50mm. long by 19mm. wide and 6mm. thick and about 1200 gauss exert a attractive force of about 2.5 Kilograms through the pole face of 50mm. by 19mm.

so that the 400mm. sheet metal former over 750mm. by 750mm. frame have 8x magnets down each vertical frame segment and 15x magnets along each horizontal frame segment (if one is there)taking the holding capability of each S4aI to 80 kilograms whthout a horizontal frame segment and 155 kilograms of concrete with a horizontal frame .15 segment on each 56s4f. In each frame portion for 750mm. x 400mm. x 150mm. thickness there is about 100 Kilograms of concrete which is easily held by the 4x vertical frame segments of 400mm. high and 2x horizontal frame sections of 750mm. making 47x magnets even with adjacent 750mm. by 4.00mm. sections. If only 4x vertical frame seg- 20 ments of 400mm. high are available more powerful magnets must be used and must be about 2500 gauss for pole face sizes 50mm. by with a attractive force over pole face of 5 Kilograms weight attracted or in contact with steel.

Figure 1 shows 8x magnets 3 on each vertical frame section 2a and 15x on each horizontal frame section 2b holding formwork 1 to frame sections 2a and 2b with 900 folds in sheet metal formwork 4a (bottom) and 4b (top) for strength. This pattern repeats for each 750 x 750mm.

section of frame and 32x magnets over each 4x vertical sections holds concrete in 150mm. cavity to 400mm. height at 2500 gauss over pole -4face of 50mm. by 20mm. and extra horizontal sections (2x on each side) 47x magnets holds concrete to 400mm. height with adjacent sections at cavity thickness (wall thickness) of 150mm. with magnets (47x) being only 1200 gauss over pole face of 50mm. by 19mm..

Ferrite (Fe30 4 is most inexpensive form of ceramic wide pole face magnet but is limited in strength and ceramic Ferroxdur 2 (Barium Ferrite BaFe 12 0 19 can be used which can go to 3500 gauss over a wide pole face and handle 400mm. high pours on 300mm. thick concrete walls with previously given frame sizes. The base horizontal frame section is needed and essential in terms of Fluid static height over base where pressure is highest and extra support is needed at base where magnets might give especially during vibration of concrete to settle concrete and get rid of gaseous cavities. One significant problem that continually needs to be considered and taken into 15 account is the problem that underneath surface of the Horizontal section of the steel Hollow.section frames where it is difficult for S concrete to flow to these underneath surfaces and a gap usually results inspite of fluid-static head exerting pressure during vibration usually varying amounts amounts of gap result. However with 20 good planning of where formwork is placed with a sizeable Fluidstatic head pressure this problem can be mostly overcome. Figure 2 shows the hollow section steel frames 1 with the previous pour 3 below the horizontal frame sections la with enough of gap for concrete to flow with a sizeable fluid-static head pressure with 2 the slope of the concrete during the pour. During vibration the slope angle 2 diminishing (concrete slope becomes more horizontal) and gaps 4 on underneath surface of horizontal Frame sections la results. Vibrator power and frequency is cut and concrete heaped at edges 2 and slow gentle vibration at slope region 2 helps alleviate gap problem 4 at concrete edges 2.

The high Fluid-static head pressure at the base of the formwork during vibration of concrete will cause the magnets to lift so security against this happening is required. Basically indents in the 20mm. fold of the 2mm. sheet metal every Ix centimeter means that a drilled and taped hole for a screw or bolt below fold on underside and above 900 fold on top side means tie wire around bolts which is twisted and tightened by pliers holds formwork against frame so shaking off does not occur. For formwork 2.4 meters long and .4 meters high over 3x frame sections of 750mm. by 400mm. high there are 2x ties below and 2x ties above and all that is required for each 2.4 meters formwork piece on each side of Frames. Figure 3a shows a 2.4 meter formwork span 1 over 3x frames with vertical sections of frames 2 with ties to formwork below 3a and 3b above 15 formwork which is only 4x drilled and taped holes per side instead of 8x per side when magnets were not used. Figure 3b shows a cut-away of Formwork sheet 1 over vertical Frame section 2. The drilled and taped hole holds screw 3 to which 1.6mm. steel tie wire 5 is wrapped and over 1 cm. spaced indents 4 in 900 fold at top and 20 bottom of form work sheet 1 with the tie wire tensioned and twisted by pliers. This guards against high fluid static-head pressures at base of formwork when concrete is vibrated during pouring operation. For this type of secondary fastening security approach which compliments the very fast application of magnets to sheet metal formwork various sizes apply: For 115mm. thick walls sheet metal is mm. thick with 15mm. 900 folds.

For 150mm. thick walls sheet metal is 2.00 mm. thick with 20mm. 900 fold. For 200mm. thick walls sheet metal is 2.5mm. thick with 900 fold. For 250mm. thick walls sheet metal is 3.00mm. thick 6 with 30mm, 900 fold. For 300mm. thick walls sheet metal is 3.00mm.

thick with 40mm. 900 fold.

The ceramic magnets tend to chip and brake and so metal jackets with small handles are required. The jackets are of .5mm. rolled stainless steel sheet and the handle is 5mm. diameter stainless steel rod weld tacked to top of jacket. Figure 4 is of the metal jacket with rod handle. The .5mm. (Stainless Steel sheet) metal jacket 1 has side folds la which cover top and end folds lb that covers ends with a flattened part 2a of 5mm. stainless steel rod 2 that is weld tacked to top of metal jacket 3 with top part of rod 2b bent in a being the handle: This system makes the application of formwork considerably easier and faster for walls. Corners require special attention. This is nothing more than a steel block with a vertical hole to where the 15 sheet metal forms meet at the corner a pair of over-laping steel blocks with vertical holes so that a steel rod goes through holes to fasten corners. Figure 5 shows the corners for formwork metal sheets la and Ib with a pair of metal blocks (about 12mm. x 12mm.) with 2a on sheet la and 2b on sheet Ib with a steel rod 4 up to 20 diameter through holes 3a in 2a and 3b in 2b to fasten corners.

Two or more blocks can be on end of .each formwork sheet so that 2 or more rods go through 2x or more over-lapping pairs of blocks for extra strength at corners.

In terms of costs the Frames e*ected on site with joins in frames being small welds and the re-inforcement layers joined by welding adjoining spans in two or more positions and this works out at about $40.00 per square meter for 150mm. thick walls erected, joined, painted and ready for pouring concrete. The concrete in small batch mixes can be reduced to cost about $15.00 per square meter with -7- 320 Kilograms of cement in each cubic meter of concrete with labour for pouring concrete and sheet metal formwork application and retrieval being about $15.00 per square meter making the cost by 1999 Australian standards $70.00 per square meter for concrete walls being comparable to cavity concrete block and more versatile in terms of windows and Doors than cavity concrete block as well as being able to come out for water pipes and electrical cables etc..

It is much stronger than clay brick and plaster board and plaster board can go directly onto externally exposed surfaces of frames or a further insulation gap for plaster board can added and system o is much stronger than brick with wood interior which has a fire potential whereas this system has no fire hazzard.

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Claims (5)

1. A system of appying.sheet metal formwork to steel square hollow section frames that support Formwork on external sides of.two opposing.frames separated and joined by spacing rods so that frames remain in concrete and frames support formwork dur- ing pouring of concrete.where wide pole face permanent magnets hold sheet metal formwork to externally exposed steel face on ext- ernal surface of steel..hollow section frames on each side of frames by a large number of individually strong permanent magnets so that sheet metal formwork on outside.surface of steel hollow section frames is suitably of certain height usually not more than 400mm. high with 90° folds at top and bottom for increased strength acc- ross frames of steel hollow section which form the structure for concrete to be poured into with overlaps accross frame segments and formwork being held by permanent magnets that give significant strength and rigidity to the sheet metal formwork.during pouring.

2. The system of applying sheet metal formwork to .steel square hollow section frames that support Formwork as claomed in claim 1 with use of some steel wire ties on top and bottom of sheet metal formwork where drilled and taped holes secure screws or bolts beloW and above sheet metal formwork on each externalside of steel hollow section frames around which tie wire is wrapped which goes around two indents in the 900 folds of sheet metal formwork about Ix centimeter apart and is twisted and tensioned with pliers to give security against magnets failing to hold sheet/metal form- work over external surfaces of steel hollow section frames during vibration of poured concrete where high fluid-static pressure heads exist particularly at base of concrete pour covered by sheet metal formwork. 9

3. The system of applying sheet metal formwork to steel square hollow section frames that support Formwork.as claimed in claim 1 where ceramic magnets..are held in thin sheet metal stainless steel jacket folded at top and at ends so magnet block can slip into jacket with ends folded up and flattened stainless steel rod weld tacked-to top of metal jacket and remainder of stainless steel rod which forms a acts as a handle to magnet in stainless steel sheet metal jacket o magnet in jacket can be put onto and pulled off from metal formwork over external surface of. steel square holl- ow section frames.

4. The system of applying sheet metal formwork to steel square hollow section frames that support Formwork as claimed in claim 1 where sheet metal formwork has metal blocks attached on ends with a vertical hole in blocks for concrete:wall corners containing steel square hollow section.frames that have 90 .corners of sheet metal formwork over wall corners so that blocks. that over-lap and a steel rod goes through the steel block's vertical holes on ends of metal formwork thus securing corner and this pair of blocks with steel rod through corner blocks fastens corner of formwork for corner of concrete wall being constructed where concrete is poured between metal. sheets of formwork so greater.sturdiness at corners is achieved during pouring and vibration of concrete with two or more over-lapping block pairs per corner.of contacting sheet metal formwork.

5. A system of applying sheet metal formwork to steel square holl- ow section frames that support Formwork with steel square hollow section frames, magnets, sheet metal Formwork and metal jackets for ceramic magnets and end blocks on sheet metal Formwork as herein described with reference to accompanying drawings. 10 GEORGE ANTHONY CONTOLEON APPLI CANT 7TH. OF JUNE,2003. DATE