GB2103259A

GB2103259A - Earthquake resistant foundation

Info

Publication number: GB2103259A
Application number: GB08124194A
Authority: GB
Inventors: Ian Holman Platten-Higgins
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-08-07
Filing date: 1981-08-07
Publication date: 1983-02-16
Also published as: GB2103259B

Abstract

A timber frame building has vertical supporting columns (not shown) each including four wooden posts secured in spaced relation by panel members. Each supporting column is anchored by a foundation base assembly 1 partially disposed below ground level, the base portions of the wooden posts being received in and secured to spaced vertical metal tubes 2 of the base assemblies 1. The foundations further comprise a plurality of metal link straps 13, 15 which interconnect the base assemblies 1 and serve firstly to accurately locate the base assemblies 1 during construction of the building, and secondly to distribute stresses evenly throughout the foundations in the event of an earthquake. <IMAGE>

Description

SPECIFICATION Timber frame buildings This invention relates to timberframe buildings having partially prefabricated wooden superstructures and is particularly concerned with buildings designed to withstand the stresses created during an earthquake.

Timber frame buildings generally comprise of framed wall construction, where the vertical timber members of these walls known as "studs" transfer the loads down to the foundations. These vertical studs being strengthened by horizontal and diagonal bracing members. The technique used to construct such buildings offers important advantages over conventional building techniques and timber frame construction now represents a significant proportion of domestic and public building work taking place in the Western World.

Timber frame construction allows the building process to be split between off-site prefabrication of the various components and on-site erection and fitting out of the building. This leads to a reduction in the overall construction period and, correspondingly, a substantial reduction in overall cost. The prefabricated system can provide a secure and lockable shell which is weatherproof within a few days of starting work on-site and, therefore, the risk of working time being lost because of bad weather is far less than in the case of conventional buildings which remain open to the elements for far longer during the early stages of construction.

The prefabricated components may be made within carefully controlled factory conditions and thus to fine engineering tolerances. Therefore, quality control is improved and wastage reduced as compared with known building techniques which rely primarily on on-site construction.

Through the choice of suitable wall and ceiling panels together with the use of various insulating layers, timber frame buildings compare favourably with conventional buildings with regard to insulation and weather-resisting properties.

Timber frame buildings are inherently suitable for areas where the risk of earthquakes is high.

The rigid frame serves to evenly distribute the stresses created in the building during an earthquake and transmit the stresses down to the concrete foundations thereby reducing the probability of severe collapse.

In known timber frame building techniques, however, there are several important disadvantages particularly where the building is required to withstand severe earthquakes. The anchorage of the timber superstructure to the concrete foundations of the buildings has previously been achieved essentially at ground level and experience has shown that the anchorage of the supporting framework to the foundations is generally insufficiently strong to withstand a severe earthquake. Thus, although the timber frame itself may be able to withstand the stresses created during an earthquake, collapse of the building often occurs due to failure at ground level.

In addition, constructional difficulties are often encountered in anchoring the vertical columns to the foundations in that it is necessary to precisely position the columns with respect to each other before securing them to the foundations by, for example, concreting. It is often not possible to position the columns sufficiently accurately to enable the other components of the superstructure to be assembled within the required fine tolerances.

It is therefore an object of this invention to provide a timber frame building which is easier to construct and which has an increased resistance to earthquakes as compared with known buildings of this type.

Viewed from one aspect the invention provides a method of constructing the foundations for a timber frame building having vertical composite supporting columns, said method comprising levelling the site, digging therein a plurality of spaced holes, placing in each said hole a layer of concrete or the like, introducing a metal base assembly on said layer in each hole, each said base assembly including spaced vertical tubes adapted to receive the bases of posts of said columns, levelling said base assemblies, interconnecting and fine positioning said base assemblies by a plurality of metal link straps, filling in said holes with concrete to embed the assembly leaving the upper edges of said tubes exposed thereabove.

Viewed from a further aspect the invention provides a timber frame building having vertical composite supporting columns, said columns including spaced vertical posts each said column being anchored by a foundation base assembly partially disposed below ground level, wherein the bases of said posts extend below ground level and are received in, and secured to, spaced vertical metal tubes of said base assemblies, said base assemblies being positionally interconnected by a plurality of metal link straps.

The invention provides significant advantages over timber frame building systems and method previously known. The metal base assemblies which serve to anchor the composite supporting columns of the building are interconnected and fine positioned by the link straps prior to their being cemented into the ground. Thus, the positions of the base members may be accurately triangulated by the use of precisely sized lateral and diagonal straps and, after the holes have been filled in and the layer of cement added, the exposed tubes for the column posts are in exact predetermined positions. Therefore the vertical supporting columns and other parts of the superstructure may be assembled to within the required fine tolerances without difficulty.

The construction of the foundations allows the posts of the vertical composite columns to extend below ground level in the metal tubes of the base assemblies. This provides the building with increased stability and, correspondingly, improved resistance to earthquakes. Since the wooden posts are disposed in the metal tubes, they are protected against damp decay.

The link straps which interconnect the base assemblies form a symmetrical grid pattern which is concreted into the ground and this further increases the resistance to earthquakes in that stresses created in the structure are evenly and continuously distributed throughout the foundations. The provision of composite vertical supporting columns further increases the strength of the building so that it might withstand a severe earthquake without danger of severe collapse.

Viewed from a further aspect the invention provides a column base assembly for a timber frame building having vertical composite supporting columns, said base assembly comprising levelling means, a horizontal base plate having upwardly projecting spaced tubes rigidly attached thereto, said tubes being adapted to receive the bases of spaced posts of said columns, and means for selectively securing said tubes to one or more external link straps.

Viewed from a further aspect the invention provides a timber frame building having vertical composite supporting columns and horizontal load bearing beams, said vertical columns comprising vertical wooden posts secured in a spaced relationship to column panel members, wall panels being secured to said columns and beams.

In a preferred form of the invention, each composite supporting column comprises four vertical wooden posts which are rigidly secured in a spaced relationship by the column panel members. The posts extend below the panel members at the base of each column.

Correspondingly, the base assemblies each comprise four spaced vertical tubes adapted to receive and support the bases of the column posts. In a preferred embodiment of column base assembly, the levelling means comprise bolts which are disposed at the corners of the base plate and the means for securing the tubes to the link straps comprises a second horizontal plate which is rigidly secured to the tubes towards the upper edges thereof and includes one or more screw holes. The upper edges of one or more of the tubes may advantageously have one or more beam hangers secured thereto for supporting ground floor horizontal load bearing beams of the building. In this way the load bearing beams may be directly attached to the metal column base assemblies and the strength of the building is further increased. Preferably the horizontal load bearing beams comprise composite boxed beams.

The composite columns and horizontal beams may preferably have disposed therein layers of a suitable insulating material thereby increasing the heat insulation of the building.

In a preferred arrangement, the column posts extend beyond the column panels at the upper ends of the composite columns and in this way each column may be conveniently joined by a metal column connecting assembly to, for example, roof members, first floor vertical supporting columns or first floor horizontal load bearing beams. The column connecting assemblies may conveniently comprise spaced vertical metal tubes rigidly attached to a horizontal plate and adapted to receive the upper ends of the vertical column posts. The tubes are advantageously provided with beam hangers for the first floor horizontal load bearing beams.

Thus, in its preferred form, the invention provides a rigid structure of composite vertical columns and horizontal beams which may be one or more storeys high and which has an improved stability and is relatively easy and cheap to construct. The composite columns are preferably partially prefabricated and the column panels and horizontal beams are advantageously formed from plywood, timber and "Duripanel" a strong fire and termite resistant board consisting primarily of wood particles and cement. The rigid superstructure forms a secure skeleton frame to which the other components of the building such as wall panels, doors and windows may be conveniently secured.

Preferably, the wall panels each comprise spaced panels rigidly secured to a wooden frame.

The panels may conveniently have disposed therebetween layers of an insulating material and a layer of metal foil to provide the building with increased heat insulating and weather resistant properties. The wall units may also include a ventilated outer wall cavity to further increase insulation. The wall panels are preferably also partially formed from "Duripanel".

The wall units may be conveniently attached to the framework of the building so that the outer surfaces of the wall panels align with the outer surfaces of the composite beams and columns, thus forming flush wall surfaces.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings in which; Figure 1 is a foreshortened perspective view of a column base assembly in accordance with the invention.

Figure 2 is a side elevational view of the base assembly shown in Figure 1 incorporated in part of the foundations of a timber frame building.

Figure 3 is a plan view on a reduced scale of part of the foundations of a timber frame building, incorporating the base assembly of Figure 1, in accordance with the invention.

Figure 4 is a side elevational view of a unit for constructing a composite supporting column for a timber frame building.

Figure 5 is a plan view of a composite supporting column formed from two of the units of Figure 4.

Figure 6 is a perspective view of a column connecting member in accordance with the invention.

Figure 7 is a side elevational view of a horizontal load bearing beam in accordance with the invention.

Figure 8 is a cross sectional view of the beam shown in Figure 7.

Referring firstly to Figure 1, a steel column base assembly 1 for the foundations of a timber frame building comprises four spaced vertical tubes 2 of square cross-section which are welded to, and extend upwardly from, a horizontal base plate 3. A second horizontal plate 4, having downwardly projecting strengthening flanges 5 along two of its sides, is welded to the inner surfaces of the tubes 2 towards the upper edges thereof. The components of the base assembly are preferably fabricated from mild steel having a thickness of approximately 5 mm and the tubes 2 are generally of the order of 1 metre in length.

Three of the vertical tubes 2 are shown with triangular beam hangers 6 welded to the upper edges of their outer surfaces; the beam hangers 6 each include a horizontal supporting plate 7 for supporting horizontal load bearing beams of the building. As will become apparent, the total number of beam hangers 6 provided on a particular column base depends on the eventual location of the column base in the foundations of the building.

The base plate 3 of the column base is provided with levelling bolts 8 at its corners and the second, higher, horizontal plate 4 has a number of holes 9 drilled therein. The column base assembly 1 may be completely prefabricated off site to within the required fine tolerances in factory conditions.

The preferred method of constructing the foundations for a timber frame building including spaced composite supporting columns will now be described with reference to Figures 2 and 3.

The entire site is firstly levelled and, as in conventional building techniques, a layer of hard core or suitable building aggregate is added. A plurality of generally square spaced holes 10 are then dug at locations corresponding to the eventual locations of the vertical composite supporting columns of the building. The base of each hole is coated with a smooth layer 11 of reinforced concrete and a column base assembly 1 is then placed in each hole so the levelling bolts 8 rest on the layer 11 of concrete. As seen in Figure 2, the depth of the holes 10 relative to the length of the vertical tubes 2 of the base assemblies 1 is such that, when the base assemblies are disposed in the holes 10, the upper edges of the tubes 2 together with the beam hangers 6 and the upper horizontal plates 4 are above ground level 12.Each base assembly 1 is then accurately levelled by adjusting the levelling bolts 8 so that the tubes 2 are precisely vertical.

As shown in Figure 3 the base assemblies are then interconnected by a plurality of metal link straps 13 which are secured to the upper horizontal plates 4 by means of bolts 14. Diagonal link straps 1 5 are then bolted to the interconnecting link straps and the column bases 1 are thus accurately triangulated and precisely positioned over the entire area of the foundations.

The link straps 13, 1 5 are also prefabricated to within fine tolerances in factory conditions. After the link straps 13, 1 5 have been firmly secured, the holes 10 are filled in with concrete and the surface of the foundations is coated with a smooth layer of cement 1 6 which covers the link straps 13, 1 5 and the upper horizontal plates 4 of the base assemblies 1 but leaves the upper edges of the tubes 2 and the beam hangers 6 exposed.

Thus, the base assemblies 1 and the network of link straps 13, 1 5 are firmly cemented into the ground with only the upper edges of the precisely positioned vertical tubes 2 and the beam hangers 6 left visible. The metal components of the foundations form a rigid integral unit with the tubes 2 extending below ground level to a depth of approximately 1 metre and, in the event of an earthquake, stresses which are created in the foundations tend to be evenly distributed by the link straps. It should be appreciated that, although a particular configuration of link straps 13, 15 is illustrated, conceivably additional straps may be provided, or alternatively a wire mesh included which extends between and is linked to the straps, in order to enhance further even distribution of stresses.Obviously, the required pattern of link straps will depend on the likelihood of severe earthquakes occurring in the geographical area where the building is to be constructed.

Referring to Figures 4 and 5 the construction of a composite supporting column for a timber frame building, will now be described. Each column 17 is formed from two prefabricated column units 21 each comprising two composite vertical spaced wooden posts 1 8 which are glued and nailed to a plywood panel 22. The column units are faced both sides with elongate panels 19 of a material preferably formed from "Duripanel" a strong termite and fire resistant material consisting primarily of wood particles bound together with cement. Two such column units 21 are jointed on site by transverse linking and bracing panels 20 consisting of plywood and Duripanel bonded together and secured to an inwardly projecting part 42 of the composite posts. Thus there is formed a single column 1 7 having a square cross section.The column 1 7 is then provided with facing panels 23 preferably of Duripanel which are nailed to the outer surfaces of the posts 18. A layer of insulating material 24 is included between the inner panel 19 and the plywood panel 22 of the prefabricated column units and between the site fixed panels 20, 23 of the column. This is to increase the insulating properties of the columns. The outer faces of panels 20 and 22 are faced with aluminium foil as a vapour barrier and panels 1 9 and 22 of the outer side of the column when the column is at the corner of the building. These cavities are then ventilated so as to dry out any moisture permeating through the outer facing material. The cavities 31, 32 of the column 17 which are to be adjacent the outside walls of the building are preferably ventilated so that any moisture permeating through the outer facing material is dried out.

The bases 25 of the four posts 18 of each column 17 extend below the panels 19, 20, 22, 23 and are precisely sized and spaced to fit snugly within the four vertical tubes of a column base member. Similarly, the top portions 26 of the posts 18 extend above the panels 19, 20, 22, 23.

The construction of the skeleton frame work of the building is both quick and straightforward once the foundations have been completed. The bases 25 of the four posts 18 of each column 17 are placed in the four vertical tubes 2 of a column base assembly 1, the upper edges of which are exposed, and are firmly screwed thereto. Thus, the bottom of each posts 18 extend down to approximately one metre below ground level and is protected against damp decay by the metal tube. The posts are preferably treated with a suitable preservative to ensure further against damp decay.

Each column 1 7 is therefore firmly anchored by its respective column base assembly 1 The vertical columns 12 are interconnected by horizontal load bearing beams which are disposed just above ground level and secured to the exposed beam hangers 6 of the base assemblies 1. As shown in Figure 3, each base assembly 1 is provided with the appropriate number of beam hangers 6 such that parallel pairs of load bearing beams may interconnect adjacent column base members 1.

A metal column connecting member 27 (Figure 6), of similar construction to the base assemblies, comprising four vertical tubes 28 welded to a plate 29 is secured to the top portions 26 of the posts 18 of each column, the top portions 26 of the posts 18 being received by and screwed to the tubes 27. The column connecting member is provided with beam hangers 30 similar to the base assembly beam hangers 6 and thus the tops of adjacent supporting columns may be interconnected by parallel pairs of horizontal load bearing beams in a similar manner to the bases of of the columns.

A preferred embodiment of a composite horizontal load bearing beam 3 is illustrated in figures 7 and 8. The beam 33 comprises an elongate plywood panel 34 having elongate timber flanges 35 and lateral timber spacing struts 36 nailed either side thereof. The end spacing struts 36 and the bottom and top surfaces of the ends of the flanges 35 may be conveniently shaped to an appropriate thickness so as to fit snugly within the beam hangers. Facia panels 39 of Duripanel are then attached and define cavities 40, 41. The outer cavity 41 is preferably ventilated while the inner cavity 40 may be packed with a suitable insulating material.

The outer face of the plywood panel 34 may be covered with a layer 38 of metal foil which acts as a vapour barrier.

The wall panels may be constructed in a similar manner to the load bearing beams 33. Each may include an inner cavity having insulating material disposed therein and an outer ventilated cavity; a metal foil vapour barrier may also be included to increase the weathering properties. As with the load bearing beams, parallel pairs of wall panels may extend between adjacent vertical supporting columns.

Thus, there is formed a rigid skeleton structure consisting of composite vertical supporting columns, firmly anchored below ground level, which are interconnected by parallel pairs of horizontal lead bearing beams both at their upper and lower ends. In the case of a single storey building, the metal column connecting members are adapted to joint the vertical columns to the rafters of the roof, which may also take the form of composite columns. If a taller building is required then the connecting members 27 are adapted to joint the ground floor vertical columns to higher vertical composite columns; in this case the higher horizontal beams which interconnect the columns serve to support the first floor joists.

The superstructure forms very secure skeleton frame which is easy and quick to construct and to which the other components of the building such as roofs, joists, wall panels, doors and windows may be conveniently secured. The completed building is considerably more resistant to the stresses created during an earthquake than known buildings of timber frame construction.

Claims (Filed on 6 Aug 1982) 1. A timber frame building having vertical composite supporting columns, said columns including spaced vertical posts, each said column being anchored by a foundation base assembly partially disposed below ground level, wherein the bases of said posts extend below ground level and are received in, and secured to, spaced vertical metal tubes of said base assemblies, said base assemblies being positionally interconnected by a plurality of metal link straps.

2. A building as claimed in claim 1 wherein each said base assembly comprises a horizontal base plate having upwardly projecting spaced tubes rigidly attached thereto, and a second horizontal plate rigidly secured to the tubes towards the upper edges thereof to which the link traps are connected.

3. A building as claimed in claim 1 or 2 wherein the upper edges of one or more of said tubes have one or more beam hangers secured thereto supporting ground floor horizontal load bearing beams of the building.

4. A building as claimed in any of claims 1 to 3 further comprising column connecting assemblies disposed at whe top of the composite supporting columns, each connecting assembly comprising spaced vertical metal tubes rigidly attached to a horizontal plate and adapted to receive the upper ends of respective column posts.

5. A building as claimed in claim 4 wherein the connecting assembly tubes are provided with beam hangers for first floor horizontal load bearing beams.

6. A building as claimed in any preceding claim wherein each composite supporting column comprises four vertical wooden posts rigidly

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The bases 25 of the four posts 18 of each column 17 extend below the panels 19, 20, 22, 23 and are precisely sized and spaced to fit snugly within the four vertical tubes of a column base member. Similarly, the top portions 26 of the posts 18 extend above the panels 19, 20, 22, 23. The construction of the skeleton frame work of the building is both quick and straightforward once the foundations have been completed. The bases 25 of the four posts 18 of each column 17 are placed in the four vertical tubes 2 of a column base assembly 1, the upper edges of which are exposed, and are firmly screwed thereto. Thus, the bottom of each posts 18 extend down to approximately one metre below ground level and is protected against damp decay by the metal tube. The posts are preferably treated with a suitable preservative to ensure further against damp decay. Each column 1 7 is therefore firmly anchored by its respective column base assembly 1 The vertical columns 12 are interconnected by horizontal load bearing beams which are disposed just above ground level and secured to the exposed beam hangers 6 of the base assemblies 1. As shown in Figure 3, each base assembly 1 is provided with the appropriate number of beam hangers 6 such that parallel pairs of load bearing beams may interconnect adjacent column base members 1. A metal column connecting member 27 (Figure 6), of similar construction to the base assemblies, comprising four vertical tubes 28 welded to a plate 29 is secured to the top portions 26 of the posts 18 of each column, the top portions 26 of the posts 18 being received by and screwed to the tubes 27. The column connecting member is provided with beam hangers 30 similar to the base assembly beam hangers 6 and thus the tops of adjacent supporting columns may be interconnected by parallel pairs of horizontal load bearing beams in a similar manner to the bases of of the columns. A preferred embodiment of a composite horizontal load bearing beam 3 is illustrated in figures 7 and 8. The beam 33 comprises an elongate plywood panel 34 having elongate timber flanges 35 and lateral timber spacing struts 36 nailed either side thereof. The end spacing struts 36 and the bottom and top surfaces of the ends of the flanges 35 may be conveniently shaped to an appropriate thickness so as to fit snugly within the beam hangers. Facia panels 39 of Duripanel are then attached and define cavities 40, 41. The outer cavity 41 is preferably ventilated while the inner cavity 40 may be packed with a suitable insulating material. The outer face of the plywood panel 34 may be covered with a layer 38 of metal foil which acts as a vapour barrier. The wall panels may be constructed in a similar manner to the load bearing beams 33. Each may include an inner cavity having insulating material disposed therein and an outer ventilated cavity; a metal foil vapour barrier may also be included to increase the weathering properties. As with the load bearing beams, parallel pairs of wall panels may extend between adjacent vertical supporting columns. Thus, there is formed a rigid skeleton structure consisting of composite vertical supporting columns, firmly anchored below ground level, which are interconnected by parallel pairs of horizontal lead bearing beams both at their upper and lower ends. In the case of a single storey building, the metal column connecting members are adapted to joint the vertical columns to the rafters of the roof, which may also take the form of composite columns. If a taller building is required then the connecting members 27 are adapted to joint the ground floor vertical columns to higher vertical composite columns; in this case the higher horizontal beams which interconnect the columns serve to support the first floor joists. The superstructure forms very secure skeleton frame which is easy and quick to construct and to which the other components of the building such as roofs, joists, wall panels, doors and windows may be conveniently secured. The completed building is considerably more resistant to the stresses created during an earthquake than known buildings of timber frame construction. Claims (Filed on 6 Aug 1982)

1. A timber frame building having vertical composite supporting columns, said columns including spaced vertical posts, each said column being anchored by a foundation base assembly partially disposed below ground level, wherein the bases of said posts extend below ground level and are received in, and secured to, spaced vertical metal tubes of said base assemblies, said base assemblies being positionally interconnected by a plurality of metal link straps.

secured in a spaced relationship by column panel members and said base assemblies each comprise four said spaced vertical tubes.

7. A method of constructing the foundations for a timber frame building having vertical composite supporting columns, said method comprising levelling the site, digging therein a plurality of spaced holes, placing in each said hole a layer of concrete or the like, introducing a metal base assembly on said layer in each hole, each said base assembly including spaced vertical tubes adapted to receive the bases of posts of said columns, levelling said base assemblies, interconnecting and fine positioning said base assemblies by a plurality of metal link straps, filling in said holes with concrete to embed each assembly leaving the upper edges of said tubes exposed thereabove.

8. A column base assembly for a timber frame building having vertical composite supporting columns, said base assembly comprising levelling means, a horizontal base plate having upwardly projecting spaced tubes rigidly attached thereto, said tubes being adapted to receive the bases of spaced posts of said columns, and means for selectively securing said tubes to one or more external link straps.

9. A column base assembly as claimed in claim 8 wherein the levelling means comprise bolts which are disposed at the corners of the base plate and the means for securing the tubes to the link straps comprises a second horizontal plate which is rigidly secured to the tubes towards the upper edges thereof and includes one or more screw holes.

10. A timber frame building having vertical composite supporting columns and horizontal load bearing beams, said vertical columns comprising vertical wooden posts secured in a spaced relationship by column panel members, wall panels being secured to said columns and beams.

11. A timber frame building as claimed in claim 10 wherein the composite columns and horizontal beams have disposed thereinlayers of insulating material.

12. A timber frame building as claimed in claim 10 or 11 wherein the wall panels each comprise spaced panels rigidly secured to a wooden frame.

13. A timber frame building as claimed in claim 1 2 wherein the panels have disposed therebetween a layer of insulating material and a layer of metal foil.

1 4. A timber frame building substantially as herein described with reference to the accompanying drawings.

1 5. A method of constructing the foundations for a timber frame building substantially as herein described with reference to the accompanying drawings.