GB2573385A - Fire stopping thermal break balcony bracket - Google Patents

Abstract

A connection system has a fixing plate on a building structure to which balcony frame structure is bolted, and includes reinforcing bars which are cast into the structure of a building and which extend into the building structure and terminate at the edge of the building structure in a fixing plate. The fixing plate includes threaded bolt fixings which are used to attach the balcony frame structure to the building structure. Fire resistant insulation material is provided in front of the fixing plate, the fixing plate supporting the weight of the metal balcony in a cantilevered manner. A fire barrier abuts the fixing plate and the insulation material, extending between rear edge of a facade and the edge of the building structure.

Description

The present specification relates to fire stopping thermal break balcony bracket, that is, a bracket for bolting a balcony frame structure to a building which provides a thermal break and resists the spread of fire.

There are two commonly used modem balcony systems used for buildings where the building comprises floors made of concrete slabs. Firstly, the balcony may also predominantly comprise a concrete slab; in this design, reinforcing bars may run between the concrete slab of the main building floor and the concrete slab of the balcony. Since the edge of the concrete slab of the balcony and the edge of the concrete building floor face each other for the length of the balcony, it is common to include a fire-resistant layer between the two concrete slabs, such as shown in WO 2017/158123 (PLAKABETON). However, it is not always possible or desirable to use a concrete slab for a balcony, and the balcony system is a balcony structure formed often formed from a welded steel or aluminium frame, in this case it is not possible for reenforcing bars to run into the balcony structure and so the balcony is attached by means of bolting to a bracket that is itself attached to the concrete slab floor of the main building. This bracket usually includes a thermal break.

Thermal break brackets are brackets used to fix cantilevered balconies to buildings which include a thermal break to reduce undesirable heat loss/gains caused by the balcony structure existing outside the building. Without a thermal break, the balcony structure can act as a conductor to transmit i

unwanted heat or cold from the environment into the concrete structure and hence into the habitable spaces in the building resulting in loss of heating/cooling efficiency (and consequently excessive energy use) and often also condensation. This is a commonly used design solution. However, developments in technology put additional strain on this solution:

Developments in concrete and re-enforcement design mean that it is possible to meet demands of cost and design restrictions of the concrete slab or steel frame making up the building structure by utilising thinner concrete and steel thicknesses

However, increasing fire performance requirements demand improved fire barrier features be installed to resist the spread of fire from one floor to the next within the facade cavity and up the building and also demands that the use of flammable materials within the facade cavity should be avoided.

When designing a balcony thermal break bracket, the above challenges oppose each other, as the thickness of the concrete slab or steel frame is taken up almost entirely by the thermal break bracket, leaving little or no space to create an ideal fire barrier. The outcome is that the fire barrier is either made discontinuous (i.e it stops either side of the bracket), or is forced off the slab edge and abuts to the wall below. Neither of these solutions is optimal from a fire stopping point of view. The first of these solutions is what is usually recommended by balcony thermal break manufacturers, including guidance to clad the thermal break insulation in fire rated board, which is highly susceptible to workmanship inaccuracies. Also, due to the number of materials involved in this solution, changes to any of these materials can cause doubts about the actual fire integrity performance of the given installation.

There are a number of designs for cantilevered balcony brackets in existence. KR20160142470 (CHEONGWON CHEMICAL) CO LTD and KR20160116616 (MOKPO NAT UNIV INDUSTRY-ACADEMIA COOP GROUP) describe a balcony bracket having thermal breaks, but without any fire integrity features.

JP2017169180A (YOSHIZAKI RYO) shows a fire rated column to support a balcony. This column exists to support the balcony by providing vertical support, however this invention does not address the cantilevered balcony type. Also, this is fire rated (meaning that it is intended to maintain its structural performance in a fire for a given period of time), but it does not provide or contribute to a fire barrier which would help prevent the spread of fire up the facade of the building.

It is important to appreciate the distinction between something being “fire rated” versus something being a “fire barrier”. For the purposes of this document, the term Fire Rated generally applies to something which has a given level of fire resistance (i.e. it can maintain its structural performance for a given period or time under the relevant standard test conditions). Whereas a Fire Barrier is a device or material which provides a resistance to help prevent the spread of fire, usually within a cavity in the building envelope, to prevent the spread of fire for a given period of time under the relevant test conditions.

CA2971211 (DOW CORNING) describes a thermal break for an anchor (though not specifically for balconies) but considers fire rating performance only to the extent that it describes how it will fail in the event of fire.

The object of the present invention is to provide connection system for attachments to buildings that both provides a fire barrier, providing fire integrity of at least 120mins, i.e preventing the spread of fire up the building cavity (as illustrated by the BS8414 test) and has good thermal insulation qualities for metal bolted-on balconies. The present invention is unsuitable for concrete balconies, as a concrete to concrete connection requires an alternative design constituting re-enforcing bars which are cast into the concerete slab and also cast into the concrete of the balcony.

According to the present invention, there is provided a connection system A connection system for providing a fixing plate 4.3 on a building structure 1 to which balcony frame structure is bolted, comprising:

re-enforcing bars 4.4 which are cast into the structure of a building and which extend into the building structure 1 and terminate at the edge of the building structure 1 in a fixing plate 4.3 the fixing plate 4.3 including threaded bolt fixings 4.2 which are used to attach the balcony frame structure fire resistant insulation material 4.1 in front of the fixing plate 4.3 the fixing plate 4.3 supporting the weight of the metal balcony in a cantilevered manner a fire barrier 2 abutting the fixing plate 4.3 and the insulation material 4.1, extending between rear edge of a facade and the edge of the building structure

1.

Thus a bracket, comprising generally the fixing plate and the fire insulation material, is provided to conveniently attach a balcony such as a metal balcony to a concrete slab of a building structure, while also providing a fire resistant barrier.

References to the terms forward and front, are used herein to designate the frame of reference of an observer facing the balcony from outside the building, and references to the terms rear and rearwards are to be similarly interpreted.

Figure la: shows a front elevation of the bracket.

Figure lb: shows an longitudinal section of the bracket.

Figure 2a: shows a front elevation of the bracket with hidden detail shown.

Figure 2b: shows a longitudinal section of the bracket with hidden detail shown.

Figure 3: shows an isometric view of the bracket.

Figure 4: shows an isometric view of the bracket once installed in a concrete slab.

Figure 5: shows an isometric view of the bracket once installed in a concrete slab with the fire barriers installed.

Figure 6: shows an isometric view of the bracket once installed in a concrete slab with the fire barriers and tape installed.

Figure 7: shows an isometric view of the bracket once installed in a concrete slab with the balcony stub installed.

Figure 8: shows an isometric view of the balcony stub in detail.

Figure 9: shows a section of the bracket once installed in a concrete slab with the fire barrier, balcony stub and in this application shows the brickwork installed.

Referring to figures la and lb, the bracket 4 comprises an insulation block 4.1, and a back plate 4.3.

The insulation 4.1 provides both a thermal break and continuity of the fire barrier, due to being made from a material that can withstand very high temperatures. This is made predominantly from ceramic or stone fibres, perhaps including an acrylic adhesive layer and graphite filler and is commercially available.

The insulation 4.1 and the back plate 4.3 are both similarly shaped when considered from the front elevation, each side having two outwardly projecting ledges 10, 11 at the same height, so that the width (i.e. the horizontal distance between the side edges 12, 13) of the upper section of the insulation 4.1 and the back plate 4.3 is smaller than the width (i.e. the horizontal distance between the side edges 14, 15) of the lower section. Ideally, the ledges 10, 11 are horizontal, while the side edges 12, 13, 14, 15 are vertical. Typically, the distance each edge 10, 11 projects horizontally is the same on both sides.

The bracket 4 also includes through bores 18 through which upper and lower longitudinal re-enforcement bars 4.4 pass. These longitudinal re-enforcement bars 4.4 extend backwards from the bracket 4 to into the concrete slab forming a floor of the building and a common feature of concrete formed structures; a small length of the longitudinal re-enforcement bars 4.4 extends forward from the bracket 4 to provide fixing points 4.2. These are threaded fixing points are made from stainless steel, to which the balcony stubs 5 are bolted. Four longitudinal re-enforcement bars 4.4 are shown here, but the number may of course be varied.

Referring to figures 2a, 2b and 3, the bracket 4 may also include bent reenforcement bars 4.5. These re-enforcement bars are approximately z shaped, with two parallel outer sections joined by a central section, the angle between the outer sections and the central section being approximately 45 degrees; these bent re-enforcement bars 4.5 are also a common feature of cast concrete building sections. Each bent re-enforcement bars 4.5 is situated in the insulation 4.1 so that a single outer section extends through the back plate 4.3, parallel to the longitudinal re-enforcement bars 4.4. The back plate 4.3 includes apertures to accommodate the bent re-enforcement bars 4.5. The bent re-enforcement bars 4.5 are welded to the upper and lower re-enforcement bars 4.4 respectively so as to resist shear force between the upper and lower reenforcement bars 4.4. Two bent re-enforcement bars 4.5 are shown here, though the number may of course be varied.

At the point where the upper and lower re-enforcement bars 4.4 pass through the backplate 4.3, these are affixed to the backplate by fillet welds.

Referring to figure 4, the bracket is cast into the concrete slab 1, being secured by casting-in the re-enforcement bars 4.4 and 4.5. The back plate 4.3 abuts the concrete slab 1 in order to locate the bracket correctly against the concrete slab 1 .Diagonal bracing links may also be included. The concrete slab 1 forms the floor slab between levels of the building. This also forms the abutment for the fire barrier.

Referring to figure 5, the bracket 4 is placed against the edge of the concrete slab 1 with the longitudinal re-enforcement bars 4.4 extending through the apertures of the back plate 4.3 and insulation 4.1, the back plate 4.3 locating the bracket 4 flat against the concrete slab 1. A fire barrier 2 is positioned against the edge of the concrete slab 1, either side of the bracket 4, the fire barrier 2 being in two pieces. The fire barrier 2 locates against and abuts the side edges 12, 13 of the upper section of the insulation 4.1 and fire barrier 2, and rests upon the ledges 10, 11 of the insulation 4.1 and back plate 4.3. The step provided by the ledges 10, 11 creates a stepped joint between the insulation and the fire barrier such that any discrepancies in installation do not create gaps in the fire barrier.

The fire barrier 2 may be formed of commercially available proprietary fire break material, and usually providing at least 60 minutes of fire resistance, and typically higher values such as 90 minutes or 120 minutes under the relevant test conditions, depending on the building design.

The fire barrier 2 and the insulation 4.1 can be secured together with the aid of commercially available stainless steelspikes, usually provided as part of the fire barrier system and are designed for this purpose. This assists the abutment of the fire-break to the balcony bracket, the support spike or spikes ideally penetrate both insulating materials to hold them tightly together.

Referring to figure 6, a smoke barrier 3 comprising a foil tape is placed over the upper side of the bracket 4, extended also some distance over the fire barrier 2 so that the interface between the bracket 4 and the fire barrier 2 is sealed against the passage of smoke. This is a commercially available product usually from the Fire Barrier supplier. The smoke barrier 3 may be joined to the bracket 4 and fire barrier 2 by adhesive, and may join the bracket 4 and fire barrier 2, either alone or in conjunction with the spikes between the bracket 4 and fire barrier 2.

Referring to figure 7, a balcony stub 5 is attached to the bracket 4 using the fixing points 4.2. A balcony stub 5 is a common component for bridging a cavity and providing alignment for the balcony, and is designed to allow adjustment in order to take up tolerance in the installation; it is typically fabricated to suit the project from welded steel sections.

The balcony stub 5 is modified to include steel web features 16 which abut tightly to the fire break 2 in order to prevent any openings which fire could break through. This also facilitates the fitment of further smoke barrier 3 or other sealing medium if needed.

Referring to figure 8, the balcony stub 5 comprises a first plate 22, separated by a second plate 20 by a shaft 23. As previously described, the shaft 23 also provides web features 16 which comprise fins that extends laterally from the shaft 23, so that the cavity formed when the balcony stub 5 extends through the building facade is divided by the shaft 23 and the web features 16 to provide a fire break. The first plate 22 includes apertures 24 (typically four apertures) for connection to the bracket 4 using the fixing points 4.2, here shown capped with nuts 25. The second plate 20 includes apertures 26 for attachments to the balcony.

Referring to figure 9, in use, the bracket is installed in the concrete slab 1 and the fire barrier 2 is installed, ensuring that the fire barrier 2 abuts tightly to the insulation of the bracket 4.1, and the concrete slab 1. The fire barrier 2 thus provides a barrier within the cavity between the building structure edge and the exterior facade. The exterior facade can be of the many typical forms used depending on the design of the building, and may include brick, aluminium panels, composite panels, concrete panels, glass panels, timber etc.

The smoke barrier 3 is not here shown in figure 9; the use of the smoke barrier may not be necessary for all requirements. In use, a waterproof membrane will usually be installed down the facade lining and around the bracket also. After which the balcony stub 5 is installed and sealed to the fire barrier 2, followed by the facade finish 6. In a traditional cavity it is important that the fire barrier 2 abuts tightly to the inside of the facade in order to prevent any openings for fire to break through.

A balcony may now be attached to the balcony stubs 5 so installed in the conventional manner. The brackets can be used in pairs, but usually with more than two to secure a cantilevered balcony to the building structure 1.

The outer face of the insulating material can be coated with an intumescent material so that it expands to fill the cavity in the event of fire. The bracket 4 and balcony stub 5 may be used to attach other fittings to the building. In “rainscreen” applications, the fire barrier 2 does not fully fill the cavity but instead a ventilation gap is allowed. In “rainscreen” applications particularly, the fire barrier 2 includes an intumescent material designed to expand and fill this gap in the event of fire.

The bracket 4 can therefore be cast into the concrete floor structure of the building, bridging the cavity to the facade with a fire barrier within itself. This bracket 4 provides fixings 4.2 for the balcony stub 5, to which the cantilevered balcony can in turn be fixed. A cantilevered balcony will typically require two or more brackets depending on the size, shape and weight of the balcony design for the building.

The fire barrier 2 within the bracket consists of an insulant, in one embodiment made predominantly from mineral or ceramic fibre, adhered with acrylic adhesive and graphite filler may be used.

The primary advantage of the system is that it enables continuity of the horizontal fire barrier with one material in the cavity through the balcony bracket, where previously this was not possible. In practice this gives a number of desirable outcomes:

The horizontal fire barrier is straight without creating a detail which is an un- tested combination of materials.

- The horizontal fire barrier consists of a single material without complex on-site fabrication using a number of materials.

Abutments between dissimilar materials to form the fire barrier are eliminated.

The simpler construction process enables a reduction in labour required 10 and improve surety of quality.

Many variations are possible without departing from the scope of the present invention as defined in the appended claims.

Claims (9)

1. A connection system for providing a fixing plate (4.3) on a building structure (1) to which balcony frame structure is bolted, comprising:

re-enforcing bars (4.4) which are cast into the structure of a building and which extend into the building structure (1) and terminate at the edge of the building structure (1) in a fixing plate (4.3) fire resistant insulation material (4.1) in front of the fixing plate (4.3) a fire barrier (2) abutting the fixing plate (4.3) and the insulation material (4.1), extending between rear edge of a facade and the edge of the building structure (lithe fixing plate (4.3) including threaded bolt fixings (4.2) which are used to attach the balcony frame structure the fixing plate (4.3) supporting the weight of the metal balcony in a cantilevered manner

2. A connection system according to claim 1 wherein the insulation material (4.1) is shaped to include a step or profile that the fire barrier (2) rests on or interlocks with.

3. A connection system according to either previous claim wherein a balcony stub (5) is included, the balcony stub (5) comprising a first balcony stub plate (22) for attachment to the fixing plate (4.3) of the connection system, and a balcony stub plate (20) for attaching to the balcony, and a shaft (23) for spanning the building facade thickness.

4. A connection system according to any previous claim wherein re-enforcing bars (4.4) secure the fixing plate (4.3) to the building which extend through the fixing plate (4.3) for connection of the balcony stub (5).

5. A connection system according to claim 4 wherein re-enforcing bars (4.4) extend through the fixing plate (4.3) and insulation material (4.1) to provide the fixing points according to claim 3.

6. A connection system according to any previous claim wherein a smoke impermeable layer or layers is included to bridge the outer edge of the interface between the insulation material (4.1) and the fire barrier (2).

7. A connection system according to any of claims 3 to 4 wherein the shaft (23) includes laterally extending fins (16) to divide the volume between the first plate and the second plate in a manner to impede the spread of fire.

8. A connection system according to any previous claim wherein there is included an intumescent material to seal gaps in facade in the event of fire.

9. A connection system according to any previous claim wherein fire resisting insulation envelops the re-enforcing bars (4.4).