EP1079044B1

EP1079044B1 - Structural support

Info

Publication number: EP1079044B1
Application number: EP00307351A
Authority: EP
Inventors: John Oswald Hare
Original assignee: Hare John Oswald
Current assignee: HARE, JOHN OSWALD
Priority date: 1999-08-25
Filing date: 2000-08-25
Publication date: 2010-08-11
Anticipated expiration: 2020-08-25
Also published as: GB2355483A; GB9920091D0; ATE477381T1; EP1079044A2; DE60044798D1; GB0021100D0; GB2355483B; EP1079044A3

Abstract

Method of pre-stressing two spaced components (2,10), such as a structural steel member (2) and a flat roof panel (10), wherein an expandable element (20'), preferably in the form of an inflatable tube of given length, is inserted in the space between the two components (2,10) and is expanded to generate a force acting between the two components (2,10), to pre-stress at least one of the components (2,10). Once the two components (2,10) have been pre-stressed, rigid spacing means (6) may be placed in at least part of the remainder of the space not occupied by the non-expanded element (20') and in engagement with both components (2,10). An inflatable tube (20) may be used as the expandable element (20') and may have its opposed ends (21) sealed in a fluid-tight manner by folding and clamping (22). <IMAGE>

Description

This invention relates to structural support especially, but not exclusively, to supporting existing roof panel structures of concrete and similar materials.
FR-A-2722819 discloses a method according to the pre-characterising part of claim 1 and a structure according to the pre-characterising part of claim 12. Its apparatus for the relative wedging or pressurising of two constructional components includes a pocket which comprises at least two opposite openings and which, once interposed between the two constructional components, contains a filler material of the mortar or synthetic resin type which has been injected in a liquid form through one of the two openings and is capable of solidifying at ambient temperature. The method consists of positioning the apparatus between the two constructional components with the two openings of the pocket free, injecting into the pocket the filler material through a first opening, until complete evacuation through the second opening of the air initially contained in the pocket, closing the second opening, and then, if appropriate, continuing the injection until the desired pressurization of the two constructional elements is achieved.
US-A-4,191,496 discloses a gas-bag supported structural foundation comprising at least one flexible, substantially air-tight bag adapted to be placed on the ground; a floor structure superimposed on the bag; a source of gas under pressure; conduits connecting the source of gas under pressure to the bag, and the bags to atmosphere; and, in the conduits, valve means responsive to changes in floor level and operative to direct the flow of gas to and from the bag as required to maintain the floor in a substantially level condition.
According to the disclosure in US-A-5397103 , large storage tanks are lifted, for inspection, repair and reconstruction by means of pressurised bags and support members. Lifting the tank allows for visual inspection under the tank for corrosion to prevent leakage of environmentally hazardous chemicals stored in the tank. The lifting bags are placed under the tank, inflated, and support timbers placed under the raised tank. The bags are then deflated, allowing the tank to rest on the support timbers. The deflated bags are raised by placing support timbers under the bags. The bags are again pressurised, further raising the tank. The steps are repeated until the tank is lifted to the desired height. Bags may also be placed under the floor after the wall or rim of the tank is lifted. This does not require cutting holes or welding of supports on the wall or floor. Ground suction is broken by raising one side of the tank with the lifting bags, placing supports as far as possible under the tank rim and depressurising the bags to rock the other side of the tank off the ground. A fulcrum method is also applied to use the partial weight of the tank as a leverage force to raise opposite sides of the tank alternately.
Over the past ten years, concerns have been expressed by local authorities, structural engineers and other interested parties about the in-service performance of reinforced autoclaved aerated concrete ("RAAC") panels, particularly RAAC roof panels.
Some flat roof applications have been of particular concern where long term deflections have become appreciable, with span deflection ratios of the order of 1:100 and above having been reported. In these situations, the deflected RAAC roof panels permit an increase to the imposed loading, due to additional standing rainwater causing further deflections that could in time cause the panels to fail.
In any event, RAAC panels have been used over the past twenty years or so as not only roof panels but also floor and wall components and have also been sold as not only structural members but also as insulating materials.
Inspection of existing sites incorporating RAAC roof panels has revealed excessive deflections thereof, some with span deflection ratios of more than 1:100, as discussed above. Noticeable surface cracking and, in some cases spalling, has been detected, thus causing major concern that sooner or later the panels will fail completely.
Accordingly, it is an object of the invention to provide support for a constructural component, such as an existing RAAC roof panel, which overcomes, or at least substantially reduces, the disadvantages associated with, say, existing flat roof structures and other structures, as discussed above.
Accordingly, a first aspect of the invention resides in a method comprising inserting in a space between a constructional component and a structural component a hollow element, and introducing a fluid into said hollow element, such that it acts between the two components to generate a force therebetween deflecting said constructional component away from said structural component and thus pre-stressing said constructional component , characterised in that said hollow element is inflated from a deflated or partially inflated condition to act between the two components as aforesaid and in that, once said constructional component has been deflected away by a required degree, spacing means comprising a self-setting material is placed in at least part of the remainder of said space not occupied by said hollow element and in engagement with said two components and in that said self-setting material subsequently sets rigidly.
A second aspect of the invention resides in a structure comprising: a constructional component; an associated structural component supporting said constructional component; and a hollow element inserted in a space between the constructional component and the structural component and deflecting said constructional component away from said structural component,
characterised in that said hollow element is in an inflated condition and in that the structure includes rigid spacing means comprised of self-set material in at least part of a remainder of said space not occupied by said hollow element and in engagement with both of the components.
The inflatable element may be in the form of an inflatable tube cut to a required length and having its ends sealed in a fluid-tight manner. The element may also be provided with a valve for inflation purposes.
In a preferred embodiment, the inflatable element is formed from a generally flat hose, preferably of composite rubber with plastics, such as, polyester and/or nylon, reinforcing webbing and a heavy duty, protective outer plastics sheath, which is cut to a required length, as will be explained in more detail hereinbelow, and has its opposed ends folded at least once and then clamped to provide a fluid-tight seal at each end. A valve is provided in the wall of the tube in a conventional manner, for inflation purposes.
In this manner, the ends of the tube or hose do not have to be glued or vulcanised to provide the required fluid-tight seal, as it has been found that gluing or vulcanising does not yield a sufficiently effective bond between the tube or hose material to effect a fluid-tight seal which can withstand pressures of up to 250 p.s.i. (1,725 kPa/17.25 bar).
In an example of the invention, a flat roof panel spaced from a structural steel member is deflected with respect to the member to increase the spacing therebetween, an inflatable element, preferably elongate, in a non- or partially- inflated condition, is inserted in the space between the two components and the element is inflated to a predetermined pressure in dependence upon a known pressure/deflection relationship, to cause the panel to be deflected away from the member by a required amount.
Thus, once the two components have been pre-stressed, rigid spacing means, such as a structural cement, concrete, mortar or grout, can be placed in at least part of the remainder of the space not occupied by the inflated element and in engagement with both components.
During inflation of the element, at least the constructional component of the spaced components may be caused, by the resulting forces, to move with respect to and away from the other component and this effect is particularly useful when the invention is applied to existing roof panels, such as, RAAC roof panels, which have experienced long-term in-service deflections.
In a preferred embodiment to be described in more detail hereinbelow and as indicated above, inflatable tubes are employed and the amount of movement of the roof panels away from an associated structural member (METSEC lattice beam), such as a structural steel cradle, can be determined in advance in dependence upon a known pressure/deflection relationship which can be represented in the form of a graph.
Thus, for a required movement or deflection of, say, a previously-deflected roof panel away from an associated structural component, one or more inflatable elements can be inflated to a predetermined pressure in dependence upon a given inflation pressure/deflection relationship.
With such roof structures, and as indicated above, the other structural component may be in the form of a cradle, preferably a structural steel cradle, such as one constructed from components manufactured and sold by METSEC plc, in which case the inventive method may be used to refurbish an existing flat roof structure of RAAC roof panels, with the structural cradle, as the other structural component, being connected to existing main beams supporting the roof panels.
Such a structural steel cradle, as designed by METSEC plc, may comprise secondary beams or joists supported on primary beams or joists which, in turn, are preferably bolted or bracketed to the existing, roof panel-supporting main beams. The top flanges of the secondary beams or joists may be suitably packed-up to follow the general contours of the underside/soffit of the roof panel(s).
Thus, by inserting one or more inflatable elements between the cradle, subsequent inflation of the or each element causes it to act between the cradle and the roof panel(s), to deflect the latter upwardly from the cradle, thereby pre-stressing the panel(s) (and the cradle).
Since an inflatable element is employed, the roof panel(s) or other constructional component can be deflected away from the cradle or other structural component by a predetermined amount in dependence upon a known inflation pressure/deflection relationship.
In order that the invention may be more fully understood, embodiments in accordance therewith will now be described by way of example and with reference to the accompanying drawings in which:

Figure 1 is a plan view of a typical layout of both primary and secondary joists of a structural steel cradle in association with existing joists of a flat roof structure;
Figure 2 is a section along the line II-II of Figure 1;
Figure 3 is a section along the line III-III in both Figures 1 and 2;
Figure 4 is an enlarged view of the portion marked IV in Figure 2;
Figure 5 is a partial elevation of the roof structure shown in Figure 1 at the final installation stage;
Figure 6 is an elevation, in partial section, of another flat roof structure embodying the invention at the final installation stage;
Figure 7 is a diagrammatic plan view of the embodiment shown in Figure 6 during installation thereof;
Figure 8 is a graph showing the relationship between the pressure within an inflatable element and the corresponding deflection of a roof panel; and
Figure 9 is a side elevation of a preferred form of inflatable element.

Referring firstly to Figures 1 to 4 of the accompanying drawings, a typical grid plan of a flat roof structure with RAAC roof panels is shown in Figure 1 and comprises a structural steel cradle consisting of primary beams or joists 1 positioned at, say, 1.8m centres and supported on a continuous or sectional angle 3 bolted to existing roof beams or joists 4 which, in-service, have supported the RAAC roof panels which have undergone, again in-service, deflection in a downward direction between adjacent existing beams or joists 4.
The structural steel cradle further comprises secondary beams or joists 2 intersecting and connected to the primary beams or joists 1 and positioned at one third of the span between the existing beams or joists 4.
The top flange 5 of each secondary beam or joist 2 is suitably packed-up to follow the general contours of the underside of the corresponding RAAC roof panels (10 in Figure 5).
The remainder of the space between the beams or joists 1, 2 of the structural steel cradle and the underside of the RAAC roof panels has inserted therein a deflated, inflatable tube 20, such as that shown in Figure 9.
The length of the tube 20 is determined by the corresponding dimensions of the beams or joists 1, 2 of the structural steel cradle and the RAAC roof panels.
Depending upon the required degree of deflection of the roof panel(s) 10 away from the adjacent beams or joists 1,2 of the structural steel cradle, the or each tube 20 is inflated to a corresponding pressure in accordance with a given relationship, as shown graphically in Figure 8.
Thus, for example, a required upward deflection of a roof panel 10 of, say, 5 mm, necessitates the corresponding inflatable tube(s) 20 to be inflated to a pressure of 20.00 psi (138 kPa/1.38 bar), as can be seen from the graph of Figure 8.
Once the or each tube 20 has been inflated to the required pressure and, as a consequence, the RAAC roof panel(s) 10 has been deflected by the required amount upwardly away from the corresponding beams or joists 1,2, structural, self-setting mortar 6 is forced between a lipped, upper flange 7 of the beam or joists 1,2 upon which the now-inflated tube 20' rests, and the underside of the now upwardly-deflected roof panel 10.
In this manner, inflation of the tube 20 to the required pressure, as shown at 20' in Figure 5, generates a force which acts between the associated beam or joist 1,2 and the roof panel 10, to cause the latter to deflect upwardly away from the former by the required distance, whilst also pre-stressing or pre-loading the roof panel 10 (and the beam or joist 1,2).
Referring now to Figures 6 and 7, in this embodiment two inflatable tubes are employed and are shown in their inflated condition at 20'. As can be seen, the inflated tubes 20' carry out the same function as the single tube 20' of Figure 5 but extend along respective opposed edges of the lipped flange or plate 7 of the secondary beam or joist 2, with the structural self-settable mortar 6 located therebetween.
In this manner, the inflated tubes 20' can be deflated and removed for subsequent re-use.
Figure 7 shows a more detailed view of the arrangement of the tubes 20', with one tube extending along the length of the beam or joist 1,2 and a pair of shorter tubes 20' located along the opposed edge of the lipped flange or plate 7, with a central gap 31 between adjacent ends of the pair of tubes 20' and respective gaps 32 between their other opposed ends and the adjacent intersecting beams or joists 2,1.
During installation, and after the tubes have been inflated to the required pressure, structural self-setting mortar is pumped through the gap 31 in the direction of the arrow A and flows between the opposed, inflated tubes 20', exiting at opposed end gaps 32, to ensure that the whole of the space defined between the opposed inflated tubes 20', the lipped upper flange or plate 7 of the beam or joist 1,2 and the underside of the associated RAAC roof panel 10, is filled with mortar.
Again, the pressure within the inflated tubes 20' is determined by the graph shown in Figure 8, to provide the required upward deflection of the roof panel 10 away from the beam or joist 1,2.
Turning now to the inflatable tube 20 shown in Figure 9, this comprises a flexible synthetic plastics or rubberized flat tube or hose cut to the required length and having its ends sealed in a fluid-tight manner by folding, as shown at 21. Preferably, the tube 20 comprises plastics reinforcing webbing embedded in its walls, with a heavy duty, protective outer plastics sheath.
A pair of clamping plates 22 is applied to each folded end 21 of the tube 20, to ensure the integrity of the fluid-tight seal and to strengthen the ends of the tube against failure during and after inflation.
A valve 24 is provided for the inflation and/or deflation of the tube 20, to which a pressure gauge may be attached to monitor the pressure within the tube 20 during inflation.
The advantages of the invention can be summarized as follows:

reduced number of activities when compared with conventional structural roof refurbishment;
reduced disruption to the user;
reduced costs;
environmentally friendly;
work can be carried out piecemeal;
reduced building down time;
existing roof panels can be made to out-perform their original life expectancy resulting in a better option than replacing them totally.

Claims

A method comprising inserting in a space between a constructional component (10) and a structural component (2) a hollow element (20), and introducing a fluid into said hollow element (20), such that it acts between the two components (2,10) to generate a force therebetween deflecting said constructional component (10) away from said structural component (2) and thus pre-stressing said constructional component (10), characterised in that said hollow element (20) is inflated from a deflated or partially inflated condition to act between the two components (2,10) as aforesaid and in that, once said constructional component (10) has been deflected away by a required degree, spacing means (6)comprising a self-setting material is placed in at least part of the remainder of said space not occupied by said hollow element (20) and in engagement with said two components (2,10) and in that said self-setting material subsequently sets rigidly.
A method according to claim 1, wherein the self-setting material is pumped into at least part of said remainder.
A method according to claim 1 or 2, wherein said spacing means comprises a structural cement, concrete, mortar or grout.
A method according to any one of claims 1 to 3, wherein more than one inflatable element (20) is inserted into said space.
A method according to any preceding claim, wherein the or each inflatable element (20) is elongate.
A method according to claim 5, wherein the or each inflatable element (20) is cut to a required length.
A method according claim 5 or 6, wherein the or each inflatable element (20) has its opposed ends (21) sealed in a fluid-tight manner prior to inflation thereof.
A method according to claim 7, wherein said opposed ends (21) are sealed in said fluid-tight manner by each being folded at least once and then clamped (22).
A method according to any preceding claim, wherein said constructional element (10) comprises reinforced, autoclaved, aerated concrete.
A method according to any preceding claim, wherein the or each element (20) is inflated to a predetermined pressure in dependence upon a known inflation pressure/deflection relationship depending upon said required degree of deflection.
A method according to any preceding claim, wherein said deflecting counteracts a long-term in-service deflection.
A structure comprising: a constructional component (10); an associated structural component (2) supporting said constructional component (10); and a hollow element (20) inserted in a space between the constructional component (10) and the structural component (2) and deflecting said constructional component (10) away from said structural component (2),
characterised in that said hollow element (20) is in an inflated condition and in that the structure includes rigid spacing means (6) comprised of self-set material in at least part of a remainder of said space not occupied by said hollow element (20) and in engagement with both of the components (2,10).
A structure according claim 12, wherein the rigid spacing means (6) is a structural cement, concrete, mortar or grout.
A structure according claim 12 or 13, wherein more than one hollow element (20) in an inflated condition is in the space between said constructional component (10) and said structural component (2).
A structure according to any one of claims 12 to 14, wherein the or each element (20) is elongate.
A structure according to claim 15, wherein the or each element (20) has its opposed ends (21) sealed in a fluid-tight manner.
A structure according to claim 15 or 16, wherein said opposed ends (21) are sealed in said fluid-tight manner by each having been folded at least once and then clamped (22).
A structure according to any one of claims 12 to 17, wherein said constructional element (10) comprises reinforced, autoclaved, aerated concrete.