Building construction method

A building construction method uses wall frames having a moveable top track. The track is fixed in a raised position so as to be load-bearing during construction, allowing construction work to progress quickly. When supporting concrete columns have cured, the fixing can be released allowing the track to move into a lowered position and for the building load to transfer to the columns.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is the United States National Stage entry of PCT/AU2018/050977, filed Sep. 10, 2018, which claims priority to Australian application No. AU2017903701, filed Sep. 12, 2017, and Australian application No. AU2018901613, filed May 10, 2018 the entirety of each of which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to the construction of buildings. It has been devised as a method for construction of multi-storey buildings, with particular application to buildings with more than two storeys.

BACKGROUND TO THE INVENTION

Building regulations in some countries require that, in general, a building of more than three storeys must have its load bearing walls made of concrete or masonry. These regulations are due to fire resistance requirements. It is possible to construct a building with loads carried by steel or timber frames which is structurally sound, however such frames can be significantly weakened by fire.

Buildings constructed using masonry are generally built gradually from the ground up, in courses. Beyond a certain level, it is necessary for grout in the masonry to cure before further loads are applied. In practice, this means that each storey must be allowed to cure before construction of a higher storey begins.

Buildings constructed using precast concrete can be built more quickly. Nonetheless, they can still require the individual panels to be connected to each other, typically by grouting. In addition to the inherent expense and difficulty in using precast panels (notably transport and movement costs associated with heavy panels) the use of such panels still has considerable ‘wait’ time associated with it.

In recent years, it has become more common to construct buildings using a system of ‘permanent formwork’, whereby the building walls are laid out using lightweight, hollow wall panels, and concrete is then poured into the panels and allowed to cure to provide structural strength. While the costs of transporting and moving such panels is considerably less than using precast concrete, the system requires complete curing of the concrete within the panels of each level before a floor can be placed upon it.

All of the above systems have the further limitation that, in general, it is necessary to wait until the load bearing walls and columns have been secured and, where necessary, cured before fixing internal walls within the structure. Indeed, often it is necessary to complete the entire load-bearing structure of a building before non load-bearing walls can be located.

US patent application number 2010/0058687 describes a system of permanent formwork as described above, with the formwork partially supporting loads being placed above it. Following curing of the concrete columns, the load is shared by the concrete and the permanent formwork.

The present invention proposes an alternative construction system which seeks to alleviate some of these limitations, at least in part.

For the avoidance of doubt, the term ‘columns’ as used herein broadly encompasses vertical load bearing building elements; including traditional columns having a relatively even length:width ratio, blade columns, and blade walls where the length may be much greater than the width.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a method of constructing a building, the method including the steps of:

forming a building frame, the frame including a plurality of vertical channels, the frame being sufficiently strong to bear load from at least one higher storey, the frame defining a load path for the load of the at least one higher storey;

at least partially forming at least one higher story;

filling the channels with a curable substance;

allowing the curable substance in the channels to cure and to form columns within the building; and

creating a break in the load path of the frame and thus transferring the load from the at least one higher storey from the building frame to the cured columns.

It will be appreciated that the transfer of load from the building frame to the cured columns is complete, with none of the final load being carried by the frame.

It will also be appreciated that building frame will bear a significant proportion of the load of the higher storey, but may not bear the entire load. In some instances, the present invention envisages sharing the entire load of the higher storey between the building frame and some temporary props. It will be understood the required number and load capacity of the temporary props will be substantially reduced when used in conjunction with the present invention.

Advantageously, this allows for building to continue while the columns cure, with the load of higher stories being borne by the building frame. On completion of the building, the cured columns become the load bearing members preferentially to the frame, thus meeting the requirements of the building codes.

It is preferred that the building frame is formed from structural steel. In a preferred embodiment the building frame is formed of cold-rolled section steel with a nominal thickness in the order of between 0.75 mm and 1.6 mm.

It is preferred that the curable substance is concrete.

Preferably, the method includes the step of locating deck formwork atop the building frame, with the channels fluidly connected to the deck formwork. The step of filling the channels with the curable substance can then occur at the same time as the curable substance is poured into formwork to complete a floor surface above the building frame.

It is preferred that at least some main internal wall frames are located at the same time that external wall frames are located. For instance, when apartments are being constructed frames for separating walls can be included. It is possible for the walls of an entire level to be completed at the same time, although this is not always desirable as it may make inspection difficult. The use of internal wall frames permits access for internal fitout of lower floors while higher floors are being constructed.

The building frame preferably includes vertical studs and horizontal tracks. The building frame preferably includes a load transfer means created by securing one track, preferably a top-most track, to the studs using at least one removable fixing member. The step of creating a break in the load path may be achieved by removal of the fixing member(s).

Alternatively, the building frame may include a shear head arranged to shear at a load greater than that of a single higher storey but less than the entire structure at its completed load. In this embodiment the break in the load path may be effected by allowing the shear head to shear following curing of the columns, resulting in vertical loads being taken by the columns rather than by the frame.

According to a second aspect of the present invention there is provided a wall frame component including vertical studs and horizontal tracks, the wall frame having a top-most track moveable between a relatively raised position and a relatively lowered position, the wall frame including removable fixing members which maintain the top-most track in its raised position, whereby removal of the fixing members allows the top-most track to move into its lowered position.

When the top-most track is in its relatively raised position, the wall frame component preferably includes a load path transferring load from the top-most track to the vertical studs via at least one removable fixing member. It will be appreciated that removal of the fixing members causes a break in the load path.

The top-most track may include apertures which are arranged to align with corresponding apertures in the vertical studs when the top-most track is in its relatively lowered position. In this way the top-most track may be fixed in its relatively lowered position by the use of fasteners if desired.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to the Figures,FIG. 1shows a schematic view of one level of a multi-storey building. The level includes a base slab10, upon which wall frames12are arranged. The wall frames12in this embodiment have been arranged to form the layout of internal and external walls above the slab10.

The wall frames12are formed from cold-rolled steel section. Typical wall thicknesses are in the order of 90 mm. The steel is typically between 0.75 mm and 1.6 mm nominal thickness. The wall frames12are constructed so as to be able to bear relatively high vertical loads.

The wall frames12are arranged such that vertical channels14can be located at desired intersections. The channels14are created by the use of column shutters16located at the desired locations, as shown inFIG. 2. The vertical channels14are generally rectangular in cross section, and are sized such that when filled with concrete to form columns the concrete columns have a greater vertical load capacity than the wall frames12.

Once the wall frames12and the column shutters16are in position, a framework deck20can be fixed atop the wall frames12, with appropriate reinforcing in place. The framework deck20is arranged such that voids in the deck20locate over the openings to the vertical channels14. Reinforcing rods22are positioned within the vertical channels14, extending above the deck20. This can be seen inFIG. 3. If required, additional temporary props can be installed beneath the deck20.

Concrete can then be poured to simultaneously form columns24within the vertical channels14and a suspended slab26. The wall frames12are sufficiently strong to take the weight of the suspended slab26, either on their own or in conjunction with temporary props. This is shown inFIGS. 4 and 5.

As soon as the suspended slab26is dry, wall frames12can be located atop the suspended slab26to form the next floor of the building. While this is occurring, work on building services such as plumbing and electricity can commence on the wall frames10of the lowest floor. The concrete of the slab26and the columns24will cure to their final strength over time, but during this time the load will be taken by the wall frames12. This can be seen inFIG. 6.

The above process can be repeated for further floors.

The wall frames12are formed from vertical studs30and three horizontal tracks: a base track32, and intermediate track34and a top track36. This can be seen inFIGS. 7 to 9.

The vertical studs30each have a lower end40and an upper end42. The vertical studs are slightly crimped at the lower end40so as to locate within the base track32, with the base track32and the vertical studs30being of about the same width. The lower end40of vertical studs30and the base track32each include screw receiving apertures44which are inwardly indented. In this way the base track32can be fixed to the vertical studs30by means of screws46, which are effectively countersunk so as to provide a reasonably planar surface of the wall frame12.

The intermediate track34has outer ends which are crimped so as to locate within the vertical studs30. The arrangement is such that the outside of the intermediate track34is generally co-planar with the outside of the vertical studs30.

A central region of each vertical stud30includes screw receiving apertures44which are inwardly indented, as do outer ends of the intermediate track34. In the same way as the base track, the intermediate track34can be fixed to the vertical studs30by means of screws46, which are effectively countersunk so as to provide a reasonably planar surface of the wall frame12.

The top track36and its connection to the upper end42of the vertical studs30is largely a mirror image to that of the base track32. The vertical studs are slightly crimped at the upper end42so as to locate within the top track36, with the top track36and the vertical studs30being of about the same width. The upper end42of the vertical studs30, and the top track36, each include screw receiving apertures44which are inwardly indented. In this way the top track36could be fixed to the vertical studs30by means of effectively countersunk screws.

The arrangement of the top track36differs from that of the base track32by the inclusion of holding screws50.

The arrangement where the screw receiving apertures44of the upper end42of the vertical studs30are aligned with those of the top track36represents a relatively lowered position of the top track36. In use, the top track36is held in a relatively raised position, with the top track36being fixed to the vertical studs in this relatively raised position by the holding screws50.

In practice, the wall frames12as described above are built having a top track36held in its raised position by the holding screws50. This means that the weight of the suspended slab26passes through from the top track36to the vertical studs30through the holding screws50. The suspended slab26is supported by the wall frames12in this fashion. The wall frames12thus define a load path through the top track36, the holding screws50and the vertical studs30to the slab10.

Once the columns24have cured, the holding screws50can be removed. Removal of the holding screws50allows movement of the top track36between its relatively raised and lowered positions, relative to the slab26. With the removal of the holding screws50the vertical load of the slab26(and higher storeys) is taken by the columns24, with the wall frames12no longer being load bearing. The removal of the holding screws50thus creates a break in the load path defined above.

This means that, in effect, the wall frames12are load bearing during construction of the building, allowing for an extremely fast-paced construction. Following construction, they cease to be load bearing, with the load bearing elements being concrete as required by the building codes.

It will be appreciated that this represents a complete transfer of load from the wall frames12to the columns24.

In an alternative embodiment, the holding screws50may be designed to shear under a particular loading, for instance the loading of two higher stories. The shearing of the holding screws50will serve the same purpose of transferring load from the wall frames12.

It will be appreciated that the column shutters16may be non-load bearing. Alternatively, the column shutters16may be formed in a similar fashion to the wall frames12and form part of the load bearing capacity of the wall frames12prior to load transfer.