JP2016524060A - Formwork whose thickness is reduced by the load of on-site cast slab - Google Patents

Abstract

Formwork device (1, 5) for forming concrete slab (17) and method of using the device. The device comprises a support element (6, 7) having an active layer (10), preferably bonded on both sides to a base sheet (8, 9). This layer (10) is selected to compress slowly over time when placed under load, and the compression rate is such that the slab is self-supporting (ie the concrete is hardened / hardened, preferably 2 days). The active layer is selected to continue to support the slab until such time as (over a period of 10 days). The base sheet (8) preferably has a surface with a relatively low coefficient of friction. When the two support elements (6, 7) are placed on top of each other in contact with the surface (8), the upper support element (6) is, for example, during an earthquake event, the lower support element (7 ).

Description

Status of Corresponding Applications This application is based on a provisional specification filed in connection with New Zealand Patent Application No. 611841, the entire contents of which are hereby incorporated by reference.

  The present invention relates to a part that forms the upper surface of a formwork and to its use in the construction of concrete slabs. In particular, this should not be understood as limiting, but may relate to situations where concrete slabs are used in combination with seismic isolation devices.

  When building a structure like a large building, some parts, such as concrete floor slabs, are supported on the building load bearing members, eg columns, beams, foundations, seismic isolation devices, or It is typically formed as a single structure, such as any mechanism used to transmit loads. This usually requires a temporary formwork that is made to contain and support the concrete slurry until it cures. After the concrete has acquired sufficient structural integrity to support at least its own weight, the temporary formwork may be removed. At this time, the total load of the slab moves to the load support member.

  This is a common method when, for example, a slab floor is formed on-site in a multi-storey building. The formed slab is supported by a formwork (usually a wooden or metal panel) supported from below by a temporary scaffold. The slab is fixed to a load support member, a base or the like of the building as necessary. When the concrete slab is cured, the temporary scaffold and formwork are removed leaving the slab fully supported by the load bearing member.

  However, in order for this system to work, sufficient space is required to assemble and remove the mold (if necessary). In conventional buildings, this is hardly a problem because the slab is usually formed above a base with a base and wall support that provides space for assembling the formwork. In some cases, the foundation can be the basement of a building and, with an attached wall, a slab floor formed on the ground.

  Different situations can occur in many modern buildings, including at least ground floor seismic isolation devices, either as part of a new construction or modification to an existing structure. Installing a seismic isolation device on a new first-floor slab that is injected above the basement can place the seismic isolation device on the top of the base wall or column, and before the slab is formed, Is generally not a problem because it can be placed in a default location.

  However, it may be a problem when the base is an existing concrete slab formed on the ground and a new slab is formed so that the two slabs are separated only by the seismic isolation device. The height of many conventional seismic isolation devices is such that the upper slab formwork can be assembled around the seismic isolation device, but the formwork is removed after the upper slab is poured It is very difficult.

  A further problem with this configuration is that there are often regulatory or at least good implementation requirements to inspect many types of seismic isolation devices during use. This requirement places a limit on the space between the slabs. That is, to perform the inspection, it must be high enough to allow human access between the slabs (or seismic isolation devices can be used around the outside of the building so that the inspection can be performed externally. Is located).

  One solution is to form a structure with low pillars that exceed the ground slab foundation. Seismic isolation devices can be placed at various locations on these columns. The pillar can be high enough to allow human access to inspect the seismic isolation device between the base slab and the upper slab, even if it is hungry.

  The disadvantages of this solution are the need for providing access between slabs and the additional height of the structure, as well as additional design constraints, as well as additional costs in the time, effort and material to form the web structure. That's what it means.

  For example, some seismic isolation systems that do not degrade over time or as a result of seismic events may not require inspection, and therefore do not need to provide human access between slabs. An example of such a seismic isolation system is a device known as a slider. That is, essentially a slider may be any device with two planes that have good load bearing capacity but low horizontal resistance to movement. Another form of slider, commonly referred to as a “friction pendulum”, typically uses a curved surface to provide a restoring force.

  The use of sliders is often combined with other types of seismic isolation devices. These seismic isolation devices, collectively referred to as dampers, dump seismic energy, limit the displacement of parts within acceptable limits, and in some cases restore the structure to its original configuration after an earthquake event . The friction pendulum slider referred to above is designed to function as a damper by providing a restoring force with a damping effect as a result of the curved geometry.

  An example of a damper is a steel plate formed in a “U” shape (UFP).

  When sliders and dampers are used, the upper slab must be fitted to the ground foundation or existing floor slab because only the gap between the ground foundation or existing floor slab needs to accommodate the relatively small height of the slider. May be placed relatively close together. In practice, the gap between the two slabs is too small for humans to access easily and may make it difficult to remove the upper slab formwork.

  The solution in this situation is to lower the formwork from above (if there are seismic isolation devices, glide bearings, sliders or anything else in place), then in place The concrete may be poured over the formwork with the intention of leaving the formwork. This means that if a structural formwork (eg an assembly structure that can be placed on a seismic isolation device and can withstand the weight of ready-mixed concrete) is not used, the formwork will transfer the load of the slab to the desired load bearing component. Rather, it is not always a good solution from an engineering point of view because it continues to support at least part of the load. Furthermore, structural molds are relatively expensive, increasing construction costs.

  This solution is another serious problem in that when a seismic event occurs, there can be significant frictional forces between the formwork that remains in place and the slab floor moving over it. Have These frictional forces, which depend on the downward load on the formwork, can hinder the movement of the structure, limit the ability of the seismic isolation devices, sliders or other supports and limit their ability to design. is there. The formwork may also become stationary with respect to the seismic isolation device, adding problems.

  It is an object of the present invention to address the above mentioned problems or at least provide the public with useful options.

  All references, including any patents or patent applications cited herein are hereby incorporated by reference. No reference is admitted to constitute prior art. The discussion of the reference states what the author claims, and the applicant reserves the right to challenge the accuracy and relevance of the cited document. Although many prior art publications are mentioned herein, this reference forms part of the common general knowledge in the field, either in New Zealand or in other countries. It will be clearly understood that it does not admit to do.

  Throughout this specification, the word “comprise”, variations thereof “comprises” or “comprising”, etc. means inclusion of the stated elements, integers or steps, or groups of elements, integers, steps, It will be understood that this does not mean excluding other elements, integers or steps, or groups of elements, integers, steps.

  Further aspects and advantages of the present invention will become apparent from the following description, given by way of example only.

  [Disclosure of the Invention]

  The present invention mainly discloses an apparatus for use in a formwork system for forming a concrete slab in the field and a method of using the apparatus in a situation where the formwork is left in place after the slab is poured. . Once the concrete has solidified, the load on the slab is supported by a load bearing member that remains in the formwork under the slab, with the load greatly reduced or essentially unloaded. The present invention provides a situation where removal of the formwork is not required (eg, it may remain hidden), or it is not possible, practical, or convenient to remove the formwork after the slab has been formed Intended for use in situations.

  One aspect of the present invention is that the formwork remains in place after forming the slab so that the friction between the slab and the support surface of the formwork is significantly reduced from prior art devices and methods. It is to provide an apparatus and method for forming a concrete slab for use in some forms of the apparatus.

  A feature of the present invention is to form a formwork for a concrete slab using a layer of active material that slowly compresses over time when placed under load.

  The general concept is that a formwork containing a layer of active material can initially support the weight of a newly poured concrete slab. The weight of the poured slab exerts a compressive force on the active material layer and reduces the thickness. Many materials compress under compressive loads, but the rate at which this occurs varies. In the present invention, the compression rate is such that the height of the contact surface of the formwork (ie, the upper surface of the formwork into which the concrete is poured) is maintained at a thickness comparable to the height of the load bearing structure, It is such that the layer of active material continues to support the slab until such time that the load bearing member is self-supporting (ie, the concrete has been cured / set). For clarity, it should be understood that comparable heights are ± 5 mm.

  According to one aspect of the invention, there is provided a support element for use as a part of a formwork for manufacturing a concrete slab, the support element comprising a layer of active material attached to a base sheet, The active material has a thickness that decreases slowly over 2-10 days under the load of the poured concrete slab.

  In a particularly preferred embodiment, the thickness of the active material layer decreases over the time required for the poured concrete to harden and harden. In most cases, this can be about 2-10 days after the time that the slab can support its own weight (on the associated support member) without flexing or requiring support from the formwork. .

  In a preferred embodiment, the base sheet has a coefficient of friction of less than 0.4.

  In some embodiments, the base sheet includes a thermal insulator.

  In a preferred embodiment, the active material layer is sandwiched between two underlying sheets.

  Preferably at least one of the two underlying sheets has a relatively low coefficient of friction, preferably less than 0.4.

  The use of a base sheet having a relatively low coefficient of friction can provide advantages during seismic events. For example, a low friction base sheet can allow the slab to slide relatively easily over the support element. If two low-friction base sheets are used, the support element can also move relatively easily over the formwork that supports it.

  Including a heat insulating material in the base sheet can reduce heat loss from the slab and can reduce the heating cost in the building.

  The thickness of the active material layer can vary depending on the number of variables. Examples include, but are not limited to, the type of slab to be supported, the mass of the slab to be supported, the compressibility of the active material, the rate at which the thickness of the active material is reduced, and / or supported. One or more of the desired solidification times of the structure can be included.

  In a preferred embodiment, the thickness of the active material is in the range of 10 mm to 50 mm.

  In a preferred embodiment, the active material includes an encapsulated void.

  In a preferred embodiment, the encapsulated void contains a fluid.

  In a preferred embodiment, the surface of the encapsulated void is flexible.

  In a preferred embodiment, the surface of the encapsulated void is permeable to fluid within the encapsulated void when under load.

  In a preferred embodiment, the encapsulated void includes a surface that is permeable to the fluid contained within the encapsulated void so that the fluid is removed from within the encapsulated void over the time that the load is applied. Released. In the present invention, the permeability of the surface of the encapsulated void is selected such that at least a portion of the fluid leaks over a duration of 2 to 10 days under the load of the injected slab concrete.

  Further, in a preferred embodiment, the encapsulated void includes a flexible surface so that fluid loss of the encapsulated void results in a decrease in the volume of the encapsulated void, which can be The formed voids are crushed, thus reducing the thickness of the active material layer.

  In a particularly preferred embodiment, the active material includes a layer formed from a plurality of encapsulated voids. Preferably, the void is filled with fluid. Preferably, the fluid is air.

  In a preferred embodiment, the layer of active material is formed from an array of air filled encapsulated voids.

  In a preferred embodiment, the air-filled encapsulated void array is formed from a plastic material.

  In a preferred embodiment, the plastic material is a polyethylene film.

  The layer of active material as described above may be similar to the layer of material known as Bubble Wrap®. Similar to Bubble Wrap®, the layer of active material according to the invention may consist of a single layer of encapsulated voids filled with air, or a multilayer of any required thickness. It may be composed of any number of single layers stacked on top of each other to create a structure.

  Furthermore, the permeability of the plastic film used to form the voids may be varied to control the rate at which air passes through the film under load. In the present invention, the permeability of the plastic film is such that the void volume decreases slowly over 2 to 10 days.

  Reference is made by the remainder of this document to a layer of active material, such as a single layer (or layers) of bubble wrap. However, for those skilled in the art, the basic concept of the present invention is a slow decrease in the thickness of the active material under load, so that only a reference to an active material such as bubble wrap is not given as a limitation, It will be appreciated that other materials will have this property. Indeed, it is anticipated that slowly compressing foams (eg, but not limited to, foamed polyurethane foam materials) may also be used in the present invention.

  According to another aspect of the invention, a formwork for a concrete slab is provided. Here, the formwork includes a layer of active material having a thickness, and the formwork is configured to support a load of poured concrete, and the active material is loaded over the time it takes for the concrete to set. It is configured to reduce the thickness below.

  In a preferred embodiment, the layer of active material is oriented substantially parallel to the plane of the support surface of the formwork, wherein the support surface supports the concrete to be poured during use and is located closest to the concrete. It is the surface of a formwork. In some examples, the support surface may be in direct contact with the concrete being poured, while in other examples, the support surface is like a sheet used to form a moisture barrier (DPM). There may be a sheet of covering material.

  In a preferred embodiment, the formwork includes structural elements substantially as described above.

  In a preferred embodiment, the surface of the structural element forms the support surface of the formwork. Preferably, the surface of the structural element forming the support surface is a base sheet.

  The advantage of using a base sheet as a support surface is that it protects the active material from scratches or other damage that may occur when forming the formwork or pouring concrete onto or around the formwork. It can be done. Other advantages may include reducing the frictional force between the slab and the support element and between the support element and the remaining formwork. Along with adding the integrity of the structural elements under load, the additional insulation from a properly selected substrate sheet reduces heat loss through the slab and the heat released by the concrete during curing and solidification. Can help protect the active material from.

  In a preferred embodiment, the formwork comprises a plurality of structural elements.

  In a preferred embodiment, the plurality of support elements are arranged on top of each other such that the underlying sheets of each structural element having a coefficient of friction of less than 0.4 are in contact with each other.

  In a particularly preferred embodiment, each outer surface of the support element is formed by a base sheet, wherein the smooth surface of the base sheet has a coefficient of friction of less than 0.4 and the other rough surface of the base sheet is zero. Have a coefficient of friction greater than .4.

  In a preferred embodiment, the first surface of the support element is formed by the smooth surface of the base sheet.

  In a preferred embodiment, the second surface of the support element is formed by the rough surface of the base sheet.

  In a preferred embodiment, the two support elements are stacked in contact with each other's first, smooth surface and on the outside of the two support elements with a second, rough surface.

  In this embodiment, the rough surface on the outside of the base sheet firmly grasps the slab (upper) and the base (lower), while the two support elements are in contact with each other because the two smooth faces of the base sheet are in contact. Can provide an advantage in the event of an earthquake event. This can further reduce the frictional force between the slab and the support element.

In another aspect of the invention, a method is provided for forming a concrete slab to be supported on an upper surface of one or more load bearing members, wherein the method is used to support concrete when injected. The formwork includes a support element having a layer of active material that compresses slowly under load, the surface of the support element forming a support surface for the formwork into which concrete is poured to form a concrete slab, The method is
Prepare the formwork to cover the space around the load bearing structure, which will be included under the concrete slab when poured
Sealing the space between the top surface and the support surface of the load support structure to form a continuous surface on which concrete can be poured; and
Pour concrete on a continuous surface,
Including the steps of
Here, the step of preparing the formwork includes forming the formwork such that the initial level of the support surface is at substantially the same level as the top level of the load support structure, and
Here, the thickness of the active material of the support element decreases slowly over 2-10 days under the load of the poured concrete slab.

  Preferably, the method includes the step of placing the reinforcing element in the volume filled by the slab prior to the step of injecting the concrete.

  In a preferred embodiment, the upper portion of the one or more load bearing members includes a seismic isolation device.

  In a preferred embodiment, the seismic isolation device is a slider.

  In a preferred embodiment, the slider is a friction pendulum slider.

The present invention can have more advantages over the prior art formwork and methods, including: That is,
Produces low to zero frictional interaction between the concrete slab and the formwork by reducing the normal force supported by the formwork, and the slab moves relatively easily over the formwork during an earthquake event to enable;
Providing a method of manufacturing two concrete slabs in close proximity with one on the other, where these slabs are separated by either a device such as a seismic isolation device or the formwork of the present invention And the slabs can move relative to each other with a relatively low frictional force between them.

1 shows a support element according to an embodiment of the invention. 1 shows a formwork according to an embodiment of the present invention. FIG. 3 shows an exploded perspective view of a method of forming a slab according to an embodiment of the present invention. Sectional drawing immediately after slab pouring is shown. Sectional drawing after hardening of a slab is shown. The cross-sectional schematic diagram of the foundation and formwork by one Embodiment of this invention is shown. The cross-sectional schematic diagram of the apparatus which forms the seismic isolation slab by embodiment of this invention using the formwork shown in FIG. 4 is shown. FIG. 2 shows a perspective view of an experimental arrangement for testing the method of the present invention. Figure 2 shows a cross-sectional view of an experimental arrangement for testing the method of the present invention. FIG. 8 shows the results of an experiment using the arrangement of FIG.

Further aspects of the invention will become apparent from the following description given by way of example only and with reference to the accompanying drawings.
[Best Mode for Carrying Out the Invention]

  Referring to FIG. 1, a support element according to one embodiment of the present invention is shown, generally indicated by arrow 1 and including a layer of active material in the form of a Bubble Wrap® layer 2. In other embodiments, the active substance may be any layer of compressible material, preferably a compressible material, where the rate of change of the thickness of the layer of material under load (ie, creep) is Relatively slow (ie takes up to 10 days or more than 10 days).

  The embodiment shown in FIG. 1 shows an active material layer formed from five layers of bubble wrap 2 arranged on top of each other. In other embodiments, the active material layer has any number of layers of bubble wrap with one on top of the other depending on the desired load carrying capacity and the desired compressibility, among other factors. May be. For example, a relatively large number of layers may be required to support a building structure having a large mass and to compensate for compression of the support elements due to the additional weight. In other situations, support elements used in relatively light building structures may require only one or two layers of active material.

  The size, shape, and permeability of the bubble wrap layer can be selected to suit a particular application.

  The layer of the bubble wrap 2 in FIG. 1 a is sandwiched between the first base sheet 3 and the second base sheet 4. The base sheet 3 has an outer surface formed from an aluminum foil and includes an inner layer of a heat insulating material such as an XPE foam. The thermally active layer may provide thermal insulation or may be configured to reflect the heat generated when the concrete sets and return it to the concrete. In some embodiments, the base sheet 4 may also include a thermally active layer. Further insulation between the base sheet 3 and the base sheet 4 is provided by the bubbles in the bubble wrap layer 2.

  The base sheet 4 has an outer surface with a relatively low coefficient of friction, such as PE-coated or laminated kraft paper foil.

  In other embodiments, the structural element may include only a single base sheet rather than two. In still other embodiments, there may be any number of base sheets and an intermediate base sheet between the active material layer / bubble wrap. A structural element having one or more inner backing sheets may provide greater cohesion between adjacent layers, especially for structural elements having a relatively large number of bubble wraps.

  It will be appreciated that in some embodiments, the surface of the bubble wrap may be sufficient for use as a single base sheet or multiple base sheets.

  It will be appreciated that the characteristics of the support element 1 and the base sheet 3, 4 may vary depending on the substrate on which the support element is disposed. For example, if the substrate is a substantially hard and flat structure, the support element 1 may be flexible and only the base sheets 3, 4 serve to prevent the flow of concrete to the active material. In other situations, the support element 1 may be supported on an irregular or partially open surface such as a scaffold or a temporary support structure. In such a case, the first base sheet 3 may be formed from a rigid material of the required thickness, or an additional rigid layer may be used to provide support to the concrete.

  The layer of the active material 2 is the distance between the inner surfaces of the base sheets 3, 4, that is, the thickness of five layers of bubble wrap under no load (other than atmospheric pressure), the initial thickness.

  A feature of the present invention is that the thickness of the active layer, that is, the combined thickness of the five layers of the bubble wrap 2 shown in FIG. 1, decreases when a load is applied to the surface (3 or 4) of the structural element 1. That is. Since the layer of bubble wrap coordinates the load support, the load initially flattens the bubbles leading to a reduction in the initial relatively fast structural element thickness.

  However, it is a feature of bubble wraps (and other active materials according to the invention) that the thickness continues to decrease under continuous application of load. In the case of bubble wrap, after initial planarization, the bubbles slowly lose air under load due to the permeability of the polyethylene film that forms the bubbles in the bubble wrap. The air loss rate, and thus the flattening speed of the film for a given load, can be controlled by selecting the appropriate permeability for the bubble wrap material. This means choosing different materials to form bubble wrap bubbles, or increasing (or decreasing) the bubble wall thickness to reduce (or increase) the compression rate of the bubble wrap layer. May be included.

  A feature of the present invention is the use of the load bearing properties of the bubble wrap layer to support the load while the concrete is solid, but the load is progressively transferred from the bubble wrap to another load support structure or device. You can do it in a way. When forming a concrete slab, the compression rate is selected to provide the necessary reduction in thickness over the time that the concrete forming the slab sets (typically 2 to 10 days).

  A formwork according to a preferred embodiment of the present invention is indicated generally by the arrow 5 in FIG. In this embodiment, the layer of active material is composed of two support elements generally indicated by brackets 6, 7. Each support element is bonded to a base sheet having a smooth outer surface 8 and a rough outer surface 9. A smooth surface is indicated by a thick line in FIG. 2, while a rough surface is indicated by a short vertical line extending from the thick line. Several layers of bubble wrap 10 (three layers in FIG. 2) are sandwiched between two underlying sheets.

  The support elements 6 and 7 of the mold 5 are in turn supported on a rigid platform indicated at 18 in FIG. This may be a base concrete slab or a traditional skeleton hard platform. The latter form may also include a scaffold or the like as in the prior art form.

  To form the slab 17, concrete is poured into the rough surface 9 of the upper support element 6 (see FIG. 3a).

  FIG. 3 a shows an enlarged view of the formwork 16 as used for the construction of the seismic isolation slab 17 formed on the base 18. The base-isolated concrete slabs 17 are supported by a seismic device in the form of a slider each having a slide base 19 and a slide plate 20, where the slide plate 20 and the upper surface 21 of the slide base 19 intersect each other during an earthquake event. And is designed and configured to slide easily.

  In other embodiments, the seismic device may be any other suitable device well known in the art, such as a lead rubber based anti-vibration material.

  The formwork 16 as essentially shown in FIG. 2 includes a support element 22 disposed on a base 18 around a slide base 19 of the slider. This is achieved by forming an opening 23 that penetrates the mold 16 to coincide with the position of the slide base 19. The lateral dimensions of the openings 23 are such that they are larger than the lateral dimensions of the slide base 19 and smaller than the lateral dimensions of the slide plate 20. This arrangement provides a void around each slide base (see 29 in FIG. 4), which provides a buffer zone when the support element moves relative to the slide base during an earthquake event. Can do. Further, when the upper end of the opening 23 is covered by the slide plate 20, the slide plate is supported on all sides of the mold 16 and provides an essentially continuous surface (once held with tape, etc.).

  In a preferred embodiment, the support element 22 is in the form of a sheet, for example as illustrated in layer 6 of FIG. In alternative embodiments, the support element 22 may be in the form of a panel or tile. In embodiments where the support element is in the form of a panel or tile, the opening may not be required because the panel or tile can be arranged to fill mainly the space around the base of the slider on the base. Absent.

  Once in place, the contact surface 24 of the support element 22 is located at substantially the same height as the upper surface 21 of the slide base 19. The slide plate 20 is disposed on each opening 23. The slide plate 20 provides an interface between the isolated slab 14 and the upper surface 21 of the slide base 19. The slide plate 20 also functions with the support element 22 to create a formwork in which the seismic isolation slab 14 is formed. To provide a waterproof seal, adjacent panels, tiles or sheets of support elements 22 are taped together.

  A layer 25 of moisture barrier (DPM) is disposed on the layer formed by the support element 22 and the slide plate 20, and the top and support surfaces of the load support member to form a continuous surface into which concrete is poured. Seal the space between. The DPM may form a moisture barrier under the seismic isolation slab 17 and may provide protection to the outer surface of the mold 16 from abrasive concrete slurry (when poured).

  Before pouring the concrete slurry, the slide base 19 and the slide plate 20 need to be fixed to each other and to the foundation slab 18. This is accomplished by securing the slide base and slide plate to the base 18 and seismic isolation slab 17 (when poured), as schematically shown in FIG. This section shows two rebar pins 26 that are used to secure the slide base 19 in place on the base 18. A fixed plate 27 is disposed on the slide plate 20, and two rebar pins 28 are located in a channel formed through the fixed plate 27, DPM 25, slide plate 20, and located in the upper portion of the slide base 19. Thus, these parts are fixed in place with each other.

  FIG. 4 also shows a cavity 29 between the support element 16 (and therefore the formwork) and the slide base 19. Moreover, it is clear from FIG. 4 that the slide plate 20 overlaps the upper surface of the mold.

  The seismic isolation slab 17 is formed on the formwork support elements 16 by pouring concrete slurry into the formwork, as shown in FIG. The support element 16 typically compresses under the weight of the concrete so that the lower surface of the seismic isolation slab 17 is below the upper surface of the slide plate (see arrow 30). However, when the concrete slurry hardens, the active layer of the mold has sufficient load bearing capacity to support the weight of the concrete slurry.

  Over time, the bubble wrap 10 forming the active layer (7, 8) continues to slowly release air from within the bubbles due to the permeability of the membrane containing the bubbles under pressure to support the weight of the concrete. This slowly reduces the thickness of the active layer as the concrete sets. When the concrete sets, there is a natural tendency for the load to be gradually transferred to any load bearing member under the slab, in this case to the slide base 19 at the top of the load bearing member. When set, it is expected that more than 90% of the total weight of the suspended slab will be transferred by the slide base 19 / support member and less than 10% will be transferred by the formwork. This reduction in load support can reduce the frictional force between the slab mold 17 and the mold as much as 90% or more. Further reductions can be expected as a result of the low coefficient of friction of the surfaces 12, 13 (FIG. 2) between the two structural elements forming the active layers 6, 7 of the mold 16.

  When the concrete is sufficiently hardened, the slide plate 20 is fixed to the slab 17, so that the pins 28 are removed from the fixed plate 27. The shafts holding the pins 28 can be closed and finished at the surface.

  A formwork behavior post including an active layer was tested using the apparatus shown schematically in FIG. 7 showing an experimental arrangement for testing the load bearing performance of a support element according to a preferred embodiment of the present invention. can do. This experimental arrangement includes a formwork 31 containing a wooden box 32 (500 × 500 × 250 mm) located on top of a support element 33 having a foil layer 34 and six layers of bubble wrap 35. The support element 33 is located on a base 36 including a flat timber panel 37 and a weigh scale 40. Thus, the weigh scale measures the weight of the timber 37, the support element 33, and most importantly, the weight supported by the support element 33.

The four reinforcing bars 41 are located at the corners of the mold 31. The rebar 41 passes directly through the timber panel 37 and the support element 33 and is placed directly on the concrete floor 38. The rebar 41 is monitored for creep to determine if the support element 33 will decrease in thickness too quickly. If the support element 33 decreases too quickly, the reinforcing bar 41 is pushed up via the timber panel 37 and the support element 33. The wooden box 32 standing on the upper side of the support element 33 is filled with ready-mixed concrete slurry 42 (total (0.06 m ³ ) + cement (20 kg) + water (8 liters)).

  The level of concrete is marked on the rebar 41 at the point 43 where they put the concrete.

  The weight measured by the weigh scale 40 is monitored over a period of 260 hours.

  The purpose of the experiment is to measure the change in weight supported by the support element 33 as the concrete hardens.

  The result is illustrated in FIG. 8, which shows the weight measured by the weigh scale 40 as a function of the time elapsed since the concrete was poured.

  Measurements were taken every hour. After 260 hours, the scale 28 measured 14.5 kg (that is, 10% of the original weight).

  After 260 hours, the creep at bar 29 was checked and a change of about 1 mm was measured. This is related to the known degree of shrinkage in the concrete during the solidification process, and the concrete supported by the bubble wrap 35 for the concrete so that it has sufficient structural integrity to maintain its weight. Indicates that it was fully cured in the time spent.

  It should be understood that aspects of the present invention have been described by way of example only and modifications and additions may be made without departing from its scope as defined in the appended claims. is there.

Claims (28)

A support element for use as a part of a formwork for producing a concrete slab,
Including a layer of active material attached to the base sheet, the active material having a thickness that slowly decreases over a period of 2-10 days under the load of the poured concrete slab,
Support element.   The support element according to claim 1, wherein the base sheet has a coefficient of friction of less than 0.4.   The support element according to claim 1, wherein the base sheet includes a heat insulating material.   The support element according to claim 1, wherein the layer of active material is sandwiched between two base sheets.   The support element according to claim 1, wherein the thickness of the active material is in the range from 10 mm to 50 mm.   The support element according to claim 1, wherein the active material comprises an encapsulated void.   The support element of claim 6, wherein the encapsulated void comprises a fluid.   The support element according to claim 7, wherein the fluid is air.   9. A support element according to any one of claims 6 to 8, wherein the surface of the encapsulated void is flexible.   The support element according to claim 9, wherein the surface of the encapsulated void is formed from a plastic material.   The support element according to claim 10, wherein the plastic material is a polyethylene film.   12. A support element according to any one of claims 9 to 11 wherein the surface of the encapsulated void is permeable to fluid contained within the encapsulated void under load.   13. The permeability of the encapsulated void surface is such that at least a portion of the fluid leaks over a period lasting 2-10 days under the load of the poured concrete slab. Support element.   14. A support element according to any preceding claim, wherein the active material layer comprises a plurality of encapsulated voids.   The support element of claim 14, comprising a plurality of layers of encapsulated voids.   16. A support element according to claim 14 or 15, wherein the layer of active material is formed from an array of enclosed voids filled with air.   17. A support element according to any one of the preceding claims, wherein the surface of the structural element forms a support surface for a formwork into which concrete is poured to form a concrete slab.   The support element according to claim 17, wherein the support surface is a base sheet of the support element. A method of forming a concrete slab supported on an upper surface of one or more load bearing members, wherein the formwork used to support the concrete slab when injected is slowly compressed under load The method includes: a support element having a layer of active material that forms a support surface of a formwork into which concrete is poured to form a concrete slab;
Prepare the formwork to cover the space around the load bearing structure, which will be contained under the concrete slab when injected,
Sealing the space between the upper surface and the support surface of the load support structure to form a continuous surface into which concrete can be poured; and
Injecting concrete into a continuous surface,
Including the steps of
Here, the step of preparing the formwork includes forming the formwork such that the initial level of the support surface is at substantially the same level as the top level of the load support structure, and
Here, the thickness of the active material of the support element decreases slowly over 2-10 days under the load of the injected concrete slab,
Method.   20. The method of claim 19, comprising placing reinforcing elements in the volume filled by the concrete slab prior to injecting the concrete.   21. A method according to claim 19 or 20, wherein the surface of the structural element forming the support surface is a base sheet.   22. A method according to any one of claims 19 to 21, wherein the formwork includes a plurality of components.   23. A method according to any one of claims 19 to 22, wherein the formwork includes two or more support elements disposed on top of each other.   24. The method of claim 23, wherein the support elements are placed on top of each other such that the underlying sheets of each support element having a coefficient of friction less than 0.4 are in contact with each other.   25. A method according to any one of claims 19 to 24, wherein the upper portion of the one or more load bearing members comprises a seismic isolation device.   26. The method of claim 25, wherein the seismic isolation device is a slider.   26. The method of claim 25, wherein the slider is a friction pendulum slider.   26. The method of claim 25, wherein the seismic isolation device is a lead rubber seismic isolation device.

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