| Title of Invention | DOUBLE PRESTRESSED, COMPOSITE, ROOF-CEILING CONSTRUCTION WITH FLAT SOFFIT FOR LARGE SPAN INDUSTRIAL BUILDINGS |
|---|---|
| Abstract | The prestressed, roof-ceiling constructions with flat-soffit for constructing industrial large-span buildings are bearing plane-space, assembling pre-fabricated elements. They solve the problem of constructing flat-soffit, finished ceilings in large-span buildings whereby besides an aesthethic ceiling look; reduce the heating volume, ensure the ventilated and isolated loft space through which of all kind of installations can be guided. The construction comprise distinkted wide and thin concrete plate (1) with two-part upper, steel construction (2), interconnected by means of vertical elements (3). The construction is twice prestressed by two undepended methods. The soffit concrete plate is prestressed centrically in the mould (6) and after the plate (1) concrete is hardend , the upper steel construction (2) is prestressed by pushing apart, at the midspan, the steel separated halves (2) which are then connected. Prestressing of the soffit plate (1) is applied to eliminate or reduce cracks in its concrete while prestressing of the upper construction by pushing apart the steel separated halves (2) is used to control the deflections. |
| Full Text | TECHNICAL FIELD The present invention relates to Double prestressed, composite, roof-ceiling construction with flat soffit for large span industrial buildings and also to flat soffit roof ceiling construction for large span industrial buildings, which according to the international patent classification (IPC)covered under the group E04c,3/00 and 3/294. TECHNICAL PROBLEM The double prestressed, composite, roof-ceiling units, with flat-soffit ceilings are plane-space, bearing, pre-fabricated building elements for constructing industrial large-span buildings that solve several technical problems intending to achieve following: To construct flat-soffit ceilings in large span buildings, eliminating generally an unaesthetic view to the roof structure from the interior of the building, eliminating the useless space between sloping roof planes and reducing the unnecessary heated volume of the interior, to form a naturally ventilated space between ceiling and roof that saves the heating energy and enables installations to be guided invisibly through the shallow loft space, to solve the safety of works on height and to increase the speed of large span roofs constructing by use of large-panel but relative light elements. The solution of above mentioned technical problems is focused to solution of several constructive technical problems to ensure bearing capability, proper serviceability and durability of the construction preventing too large deflections and widths of cracks of the slender soffit-plate. The use of ordinary reinforced concrete soffit-plate would reduce the span of these slender constructions and would make the long term serviceability characteristics of the construction to become unreliable. Too large deflections of the reinforced concrete soffit plate could be decreased by applying stiffer upper beam or could be compensated by the counter-deflection in form but that would be only an uneconomical and unreliable manner to reduce deflections whereby the problem of cracks would remain unsolved. The reinforced-concrete soffit-plate applied to a large span undergoes a great amount of tension that causes cracks and their progress due to concrete creep and shrinkage whereby the magnitude of deflection increases interactively as the with of cracks increase. The initial cracks in soffit plate, due to combination of the large tension axial force and small-amount local bending moments concentrated locally at points where the upper construction is connected to the soffit plate, growing wider in time instead to distribute along the whole length of the soffit plate, what would be more desirable in reinforced concrete behavior. The problem is therefore focused to the proper prestressing method that can reliably and permanently counteract the large deflection and eliminate or reduce cracking of concrete in the high tensioned soffit plate, such a prestressing method that causes the upward deflection of the concrete soffit plate introducing the compression force into it. This problem can not be solved by the customary concrete prestressing method because of the specificity of these constructions whereby the centric prestressing force applied to the soffit plate gravity center, because of its small eccentricity to the gravity center of the overall cross section, can only affect cracks in soffit plate and practically does not affect deflections. The usual prestressing techniques introduce the compressive force into a beam or a concrete truss construction below the concrete cross-section gravity center that due to specific geometry causes upward deflection of the element, solving simultaneously both, the problem of deflections and problem of concrete cracking. The specific composite, roof-ceiling, flat-soffit construction (because its overall cross-section gravity center is placed at negligibly small eccentricity from the soffit-plate) can not be prestressed efficiently by usual prestressing method by introducing compressive force into concrete body to obtain the counter-deflection of the soffit-plate upwards and to close its cracks simultaneously. Introducing of such a prestressing force at the eccentricity below the gravity center of the overall cross section would require positioning of the tendon gravity center below the soffit-plate level that would ruin the flat soffit. Applying of centric prestressing that would introduce compressive force into the soffit plate gravity center, because of the small eccentricity, affect only cracks but it does not affect deflections at all. An additional technical problem at large span is stabilizing the upper slender beam against lateral buckling over the entire length that can cause instability and collapse of the entire construction. BACKGROUND OF THE INVENTION The present invention concerns to the specific composite, roof-ceiling constructions and there's no similar solution know. All the advantages given by the present Use of the plate-like, large-panel elements covering the big portion of the roof at once has many advantages compared to other custom constructing methods where primary and secondary girders are used. To achieve above mentioned advantages of these constructions at large spans the problem is focused to the constructive technical solution how to ensure bearing capability, the proper serviceability properties and durability of the construction. The problem is solved by double prestressing, by the combination of two independent prestressing methods, whereby the first one reduces deflections of the concrete soffit-plate and the other one eliminates or reduces its cracks due to high tension. The object of the present invention is to provide a double prestressed, composite, roof-ceiling construction with flat soffit for constructing industrial large span buildings comprising distinctly wide and thin concrete soffit-plate, the two-part upper steel construction, sloped or arch shaped, connected to the said soffit-plate by vertical elements , wherein the said soffit plate is prestressed centrically in the mould , and the said two-part upper steel construction, of priory separated halves, is prestressed by pushing apart, at the interrupt in the mid span towards ends, by the wedge, being subsequently interconnected. DESCRIPTION OF ACCOMPANYING DRAWINGS: Fig 1 illustrates on the simplified model the principle of the usual prestressing method by introducing compressive prestressing force under the cross section gravity center and shows developed internal forces. Fig 2 illustrates on the simplified model the principle of the prestressing method by introducing compressive prestressing force by pushing apart the upper construction above the cross-section gravity center and shows developed internal forces. Fig 3 illustrates on the simplified model additional centric prestressing into construction soffit plate and shows developed internal forces. Fig 4 is the lateral view of a real model showing necessary to illustrate prestressing methods and the constitutional parts. Fig 5 is the cross-section of the construction with its constitutive parts Fig 6 is the detail of the disconnected upper construction where the prestressing force is applied. Fig 7 presents the manner how the upper construction is prevented against buckling. DESCRIPTION OF THE PREFERED EMBODIMENT For better understanding of the technical problem that is solved by this invention, on the simplified model shown in Fig 1 and Fig 2 the custom prestressing method is compared to prestressing applied to composite flat-soffit roof ceiling constructions. By usual methods of prestressing beams or trusses as shown on Fig.l the compression force (Po) is introduced below the gravity center of the concrete cross-section (T) at the eccentricity (e), in the tensioned zone or out of it, pushing the beam ends towards the midspan producing in that way the negative bending moment (M=e x Po) which causes the upward beam deflection (u). By such prestressing the upward deflection reduces the downward deflection caused by applied external load whereby simultaneously, the applied compressive stress (NT) closes cracks in tensioned zone of the beam. This method is not applicable to specific, composite, roof-ceiling constructions which comprise the wide soffit-plate with low positioned concrete gravity center of the overall cross-section. The application of the weighty concrete soffit-plate for a lower part of the construction with light upper steel beam seems to be not logical decision because steel having usually stability problems undergoes thereby high compression and concrete that can bear only slight amount of tension is exposed to considerable tension. Nevertheless, this choice is the price that must be paid for achieving the flat soffit and its advantages. Because of such a load bearing, apparently not-logical, choice this prestressing will be more expensive then usual prestressing of concrete. Introducing the prestressing force (Po) below the gravity center of the cross-section would require descending of the tendons below the soffit plate level what would ruin the flat-soffit effect. The prestressing principle of the present invention, shown in Fig.2, presents a kind of inversion to the usual one. The upward-deflection (u) effect is obtained by pushing apart the upper beam separated in the middle, from midspan towards ends of the structure whereby the compressive prestressing force (Po) acts at the eccentricity (e) over the concrete gravity center (T) of the cross-section. In both compared methods, the negative bending moment (M=e x Po) was achieved to produce the upward deflection (u) of the soffit-plate. Since by usual prestressing the applied desirable compressive stress (NT) would be introduced in the soffit-plate, in case of the present prestressing manner, by pushing apart the upper beam towards The upper construction (2) separated at middle span symmetrically at two equal parts, is placed to the mould (6) for concreting the soffit plate (1) standing on vertical elements (3). The steel tendons are prestressed at the mould (4), being previously conducted through holes (5) at the ends of bars (3) and the soffit plate (1) is then concreted. After concrete is hardened, fastened by the steam curing process, tendons (4) are released from the mould (6). Thus, the first prestressing step is over. At the interrupt of the steel construction (2) into the prepared detail, that lessens the stress concentration ) the steel wedge (7) is positioned and the driving device (8) for pushing the wedge is prepared. Driving the wedge into the gap between two separated parts of upper beam ait interrupt, both separated parts of upper construction (2) are prestressed whereby the introduced force is controlled by measuring the upward deflection of the soffit plate (l)at the midspan and measuring the wedge driving force through the manometer pressure on the driving device (8). From results of these two measurements the introduced force can be calculated reliably. The double prestressed, composite, roof-ceiling constructions with flat soffit are intended for constructing large-span industrial buildings and similar large span buildings. Due to their specific solutions there are many advantages when compared to some custom constructing systems such as: These plate-like large elements solve at once both roof and the ceiling with finished soffit. An aesthetic soffit closes the useless space between sloping roof girders and reduces the heated volume of the interior that saves the heating energy. The naturally ventilated space between ceiling and roof is formed that enables all kinds of installations to be guided invisibly through the shallow loft space, instead of being guided through its interior that interferes the interior of the building and is more expensive. Use of the plate-like, large panel elements that cover the big portion of the roof at once has many advantages compared to many custom constructing methods where primary and secondary girders are used. An aesthetic soffit closes the useless space between sloping roof girders reducing the heated volume of the interior that saves the heating energy. The safety of works on height during constructing is ensured after the soffit plates are assembled whereby the thermo-insulation can be placed on the wide flat plane, working in standing position is enabled without need to climb the girders. The low costs of these constructions are due to fact that the roof-ceiling plates that comprise finally finished soffit are the bearing construction simultaneously, with low material spend. The prestressing pushing-apart method is cheep, the large panel roof-ceiling construction that is quickly assembled covers big portion of the roof at once and the surface to volume ratio of these elements is suitable for quick concrete hardening by steam that enables rapid production. Due to above mentioned advantages of the flat soffit on which arbitrary deep thermo-insulation can be placed, to the closed, shallow , naturally ventilated loft space theseconstructions are suitable for buildings with fine, climatized interiors such as fine industries, big markets, sport and similar buildings. We Claim: 1. The double prestressed, composite, roof-ceiling construction with flat soffit for large span industrial buildings comprising distinctly wide and thin concrete soffit-plate (1), the two-part upper steel construction (2), sloped or arch shaped, connected to the said soffit-plate (1) by vertical elements (3), characterized in that the said soffit plate is prestressed centrically in the mould (6), and the said two-part upper steel construction (2), the separated halves, is prestressed by pushing apart, at the interrupt in the mid span towards ends, by the wedge (7), which subsequently gets positioned therein. 2. The double prestressed, composite, roof-ceiling construction with flat soffit for large span industrial buildings as claimed in claim 1, wherein centric prestressing of the soffit plate (1) is applied to reduce cracks in its concrete. 3. The double prestressed, composite, roof-ceiling construction with flat soffit for large span industrial buildings as claimed in claim 1, wherein prestressing by pushing apart at the interrupt in the midspan of the said two-part upper construction (2) is applied to control deflections of the soffit plate (1) 4. The double prestressed, composite, roof-ceiling construction with flat soffit for large span industrial buildings as claimed in claim 1 wherein connections between concrete plate (1) and the upper steel construction (2) is achieved through vertical elements (3), provided with holes (5) at their bottom ends whereby prestressing strands (4),passing between the two reinforcing mesh layers, are conducted through said holes anchoring in that way said vertical elements (3) into the soffit-plate concrete (1). 5. The double prestressed, composite, roof-ceiling construction with flat soffit for large span industrial buildings as claimed in previous claims, wherein the compressed upper construction (2) is prevented against lateral buckling by connecting elements (9) anchored to the concrete soffit-plate (1). 6. The double prestressed, composite, roof-ceiling construction with flat soffit for large span industrial buildings, substantially as described herein before and with reference to the accompanying drawings. |
|---|
00305-delnp-2003-complete specification granted.pdf
00305-delnp-2003-correspondence-others.pdf
00305-delnp-2003-correspondence-po.pdf
00305-delnp-2003-description (complete).pdf
00305-delnp-2003-petition-138.pdf
| Patent Number | 196740 | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Indian Patent Application Number | 00305/DELNP/2003 | |||||||||
| PG Journal Number | 36/2008 | |||||||||
| Publication Date | 05-Sep-2008 | |||||||||
| Grant Date | 16-Mar-2007 | |||||||||
| Date of Filing | 05-Mar-2003 | |||||||||
| Name of Patentee | MARA-INSTITUT D.O.O., HR | |||||||||
| Applicant Address | VARAZDINSKA 65, MARTIJANEC, 42232 DONJI MARTIJANEC, CROATIA, STATE OF NATIONALITY-HR | |||||||||
Inventors:
|
||||||||||
| PCT International Classification Number | E04C 3/294 | |||||||||
| PCT International Application Number | PCT/HR01/00045 | |||||||||
| PCT International Filing date | 2001-10-02 | |||||||||
PCT Conventions:
|
||||||||||