GB2470230A

GB2470230A - A load-bearing member having a rigid portion and a flexible portion

Info

Publication number: GB2470230A
Application number: GB0908423A
Authority: GB
Inventors: David Reid
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-05-15
Filing date: 2009-05-15
Publication date: 2010-11-17
Also published as: GB0908423D0; EP2430259A2; WO2010131053A3; WO2010131053A2; JP2012526936A; US20120042587A1

Abstract

A load-bearing member 10 comprises: a rigid portion 12 adapted to bear a load until the load reaches a predetermined load and thereafter to have a reduced or nil load bearing capacity; and a flexible portion 20 adapted to bear the load after the predetermined load is reached. The rigid portion and the flexible portion cooperate to bear the load such that the member can transform from rigidly bearing, to flexibly bearing the load when the predetermined load is reached. The member could be a beam, a column, or a bolt 10, and may find particular application in earthquake protection. One embodiment of a bolt according to the invention is in the form of a hollow rigid member 12 containing a flexible wire-like member 20. Such a bolt fastener could be used to fix fagade panels (110) to walls (112),

Description

Flexible Member The present invention relates to normally rigid members including: structural components such as beams, columns and the like; and connecting components such as mechanical fasteners. In particular, but not exclusively, the invention relates to apparatus having an improved performance during dynamic loading, such as destructive vibrations and movements created during earthquakes; and a method of limiting damage to both the integrity of a structure and its non-structural elements due to relative displacement or acceleration forces or dynamic loading.

During construction of any structure within the built environment, for facilities such as buildings, bridges, platforms and the like, it is common to rigidly connect structural components using compression fixings or welding. However, seismic wave propagation (expressed as Rayleigh, Love, Primary or Secondary waves) and the associated movements of an earthquake or explosion can cause severe shock waves and intense vibrations which affect base structural components at the foundation of the structure and, in turn, can adversely affect any other structural components which are directly or indirectly rigidly connected to the base components. These types of disturbance can cause damage to, or even *:::: the collapse of, the structure. * *

Also, non-structural components of buildings, such as electrical plant, HVAC :.:. equipment, windows, ceilings, and external cladding are typically rigidly S...

.*?5 connected to the building. These non-structural components typically represent * * around seventy percent of a building value, and the contents of the building can be many times the value of the building. Damage to these non-structural * components in an earthquake can result in enormous financial loss, significant business interruption and loss of essential post earthquake services as well as, directly or indirectly, risk to life and injury. Damage surveys of earthquakes have shown that, in many cases, buildings which have only suffered minor structural damage have been rendered uninhabitable and hazardous to life owing to the failure of mechanical and electrical systems and damage to the architectural elements. For all these reasons, the preservation of non-structural components may be equal in importance to maintaining the integrity of the building structure.

Non Structural elements such as cladding may be damaged during an earthquake due to two distinct mechanisms, namely, relative displacement or acceleration. In particular, it is common for facade elements of the structure to be distorted and shaken free from the exterior surface of the structure. This can be, directly or indirectly, a hazard or risk to life.

It is therefore desirable to structurally isolate non-structural components of buildings to prevent or reduce damage, such as caused by earthquakes. One method of doing this is to provide a flexible, rather than rigid, means of connecting non-structural components to structural components of a structure such as a building.

It may also be desirable to provide flexible means of connecting structural components to dampen or decrease the transmission of vibrations during a severe event such as an earthquake. However, such flexible connecting means can be impractical during construction or normal conditions of service for a ** number of reasons. For instance, construction requires predictable, fixed tolerances which may not be achievable using flexible connectors. Also, a :.:. structure with excessive flexibility may at least be perceived to be unsafe. S...

**?5 Furthermore, the flexible connector may be a compression fixing but the flexibility * ** of the connector may hinder fastening of the connector. For instance, in a connector with a torsional flexibility, the flexibility will act as biasing means during * fastening which will bias the connector in an unfastening direction. It is desirable to provide a means of connecting structural components which provides compressive rigidity during normal in service conditions and dynamic flexibility during excessive dynamic loading conditions.

The human body has a mechanism for resisting and reducing damage from unexpected forces and this relies upon the elastic properties of the tendon. For example there are certain configurations of bones and joints within the skeletal frame that provide axial rigidity in normal circumstances but also precipitate the tendons to stretch in response to non-axial loads.

Compression fasteners or tension elements for resisting lateral loads form part of many structural systems. However, to overcome existing design, engineering and building constraints and performance limitations, it is desirable to create a means of mechanical anchor, with tendon like responsiveness, that uses passive embedded, tension potential and elastic deformation in the dynamic way proposed.

According to a first aspect of the present invention there is provided a load bearing member comprising: a first rigid portion adapted to bear a load until the load reaches a predetermined load and thereafter have a reduced or substantially no load bearing capacity; and a second flexible portion adapted to bear the load after the predetermined load is reached, wherein the first rigid portion and the second flexible portion cooperate to bear the load such that the load bearing member is enabled to transform from .: rigidly to flexibly bearing the load when the predetermined load is reached.

* .. .2.5 *.S.

The term "flexible" is intended to cover any means that allows the second portion to deflect in one or more directions under loading. This includes but is not limited *:*** to: a property, such as an elasticity, viscoelasticity or plasticity, of a material forming the second portion; or a geometric configuration that promotes bending, buckling, stretching, compression or rotation of the second portion; or a mechanical arrangement.

The first rigid portion may be adapted to fail at the predetermined load. The first rigid portion may include a weakening feature adapted to fail at the predetermined load. Failure at the predetermined load may be due to a material forming the first rigid portion reaching a failure value. The failure may be due to fracture or plastic collapse or elastic buckling of the material. The weakening feature may be adapted to respond more to particular types of loading and less to other types of loading.

The weakening feature may be provided at a predetermined axial location. A weakening feature may be provided at a plurality of predetermined axial locations.

Alternatively, the load bearing member may include switching means and load sensing means and the load bearing member is adapted to switch from the first rigid portion to the second flexible portion for bearing the load when the predetermined load is reached. The load bearing member may be adapted to switch from the second flexible portion to the first rigid portion for bearing the load when the load falls below the predetermined load.

The first and second portions may be configured to bear a load in parallel. The *., first rigid portion may be arranged to bear the majority of the load prior to the predetermined load is reached. * S. *1 * S.. *

*�=5 The second flexible portion may be provided as an inner core of the structural member and the first rigid portion may substantially surround the inner core.

*..I.* * The first rigid portion may be provided as a hollow tubular member. The second flexible portion may be provided as an inner wire or the like provided within the tubular member. The second flexible portion may be provided with anchor points at each end of the inner wire.

Alternatively, the second flexible portion may be formed by removing material from a solid member to form a waist portion. The first rigid portion may be provided as a collar member provided around the waist portion.

The first rigid portion and second flexible portion may be provided as an insert for retrofitting to a conventional structural member.

The load bearing member may comprise a beam, column, bracket, hanger, strut, axle, cable, pipe, pipe joint, or the like.

Alternatively, the load bearing member may comprise a compression fastener such as a bolt, nut, rawlplug screw, washer, nail, clamp or the like.

The load bearing member may comprise a fastener and include a washer member. The washer member may comprise a resilient material, such as rubber.

The washer member may include a recess or cavity adapted to allow displacement of the second flexible portion. The cavity may contain a gas such as air. The washer may include an aperture having an entrance for the fastener and an exit spaced apart from the entrance and the entrance may be oversized relative to the fastener. * I a...

The load bearing member may include a sleeve member. The sleeve member may include a joint portion at a location corresponding to the predetermined axial location. The joint portion may be flexible. The joint portion may comprise a * concertina member. Alternatively, the joint portion may be rigid until the :. predetermined load is reached and thereafter flexible. The joint portion may be :: adapted to fail at the predetermined load.

The load bearing member may include transformation indicating means adapted to indicate when the load bearing member has transformed from rigidly to flexibly bearing the load. The transformation indicating means may comprise colour coding or movement of a flag member from a first position to a second position.

A testing device may be provided for determining whether the load bearing member has transformed from rigidly to flexibly bearing the load. The testing device may cooperate with the transformation indicating means. Alternatively, the testing device may be adapted to investigate the state of the first rigid portion.

The load bearing member may be formed from any suitable material, such as steel, aluminium, plastic or composite. The first rigid portion may be formed from a first material and the second flexible portion from a second different material.

The first material may be selected for its failure characteristics. The second material may be selected for its flexibility and/or strength.

The compression fastener may be adapted for fastening a facade, such as a brick or stone slip system, or any other type of decorative or non decorative element to a structure such as a building.

The load bearing member may form part of the facade of a building. The facade may comprise a plurality of facade elements, such as brick or stone slips, which are attached to a support which is fastened to an exterior surface of the building using a plurality of fasteners. One or more of the fasteners may comprise the S...

first rigid portion and the second flexible portion. * .. * * . **. .

The support may be configured to cover a substantial portion of the exterior surface. * S.

S * ..

* * The facade may include a matrix material interposing the support and the exterior surface. The matrix material may comprise a first layer of compressible material, such as foam, and a second layer of rigid material. The second layer may include a plurality of cavities. The second layer may be a honeycomb material.

According to a second aspect of the present invention there is provided a method of supporting a load within a structure using a load bearing member, the method comprising: providing the load bearing member with a first rigid portion adapted to have a load bearing capacity until a predetermined load is reached and thereafter have a reduced or substantially no load bearing capacity; and providing the load bearing member with a second flexible portion adapted to bear the load after the predetermined load is reached.

The method may include adapting the first rigid portion to fail at the predetermined load. The method may include selecting a material forming the first rigid portion which will reach a failure value at the predetermined load. The method may include configuring the first rigid portion to fracture, plastically collapse or elastically buckle at the predetermined load.

The method may include providing the second flexible portion as an inner core of the structural member and the first rigid portion as substantially surrounding the inner core.

The method may include providing the first rigid portion as a hollow tubular member and the second flexible portion as an inner wire or the like provided within the tubular member. The method may include providing anchor points at i.:'' each end of the inner wire. *

Alternatively, the method may include forming the second flexible portion by :.: removing material from a solid member to form a waist portion and providing the : first rigid portion as a collar member around the waist portion.

The method may include retrofitting the first rigid portion and second flexible portion to a conventional structural member.

The method may comprise supporting a plurality of facade elements provided on the exterior surface of a building. The facade elements may be attached to a support which is fastened to an exterior surface of the building using a plurality of fasteners. One or more of the fasteners may comprise the first rigid portion and the second flexible portion.

The method may include interposing a matrix material between the support and the exterior surface. The matrix material may comprise a first layer of compressible material, such as foam, and a second layer of rigid material. The second layer may include a plurality of cavities. The second layer may be a honeycomb material.

According to a third aspect of the present invention there is provided a facade system which is installable on the exterior surface of a structure, the facade system comprising: a plurality of facade elements; a support for supporting the facade elements and which is attachable to the exterior surface using a plurality of fasteners; and a matrix material interposing the facade elements and the exterior surface, wherein the matrix material comprises a first layer of compressible material and a second layer of rigid material.

: The first layer may comprise a foam material. * S..

The second layer may include a plurality of cavities. The second layer may be a * honeycomb material.

S..... * .

The matrix material may interpose the support. Alternatively, the matrix material may be adapted to provide the support.

One or more of the fasteners may comprise a first rigid portion and a second flexible portion.

The first rigid portion may be adapted to fail at the predetermined load. Failure at the predetermined load may be due to a material forming the first rigid portion reaching a failure value.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a side view of a fastener according to a first embodiment of the invention; Figure 2 is a cross sectional side view of the fastener of Figure 1; Figure 3 is a cross sectional end view of the fastener of Figure 1; Figure 4 is a cross sectional side view of a fastener according to a second embodiment of the invention; Figure 5 is a side view of the fastener of Figure 1 fastening a panel to a wall of a *:::: building; and I... * . S...

Figure 6 is a perspective view showing a number of variations of washers that can be used with a fastener according to the invention. I... * I I...

* Figures 1 to 3 show a load bearing member which in this embodiment is in the :. : form of a bolt 10. The bolt 10 has a first rigid portion comprising a shaft 12 :: having a hollow portion 14. The shaft 12 includes a weakening feature in the form of fracture Unes 16 at a distance 100 from the head 18 of the bolt 10.

The bolt will be subject of various types of loading such as tension, shear and torsion, and torque will be applied to fasten the bolt 10. The number, depth and direction of the fracture lines 16 are selected so that the shaft 12 will catastrophically fail at a predetermined load. Therefore, the shaft 12 is adapted to bear a load until the load reaches a predetermined load and thereafter will have no load bearing capacity. Also, the direction of the fracture lines 16 can be selected to promote failure from a particular type of loading. For instance, in Figure 1, the fracture lines 16 are normal to the longitudinal axis of the bolt 10.

Therefore, tensile and shear loads are more likely to cause fracture than, say, torsional loads. Such loads are more commonly produced during the dynamic loading associated with wave propagation and seismic movement from earthquakes. This feature also minimises the likelihood of undesirable catastrophic failure during fastening of the bolt 10.

A second flexible portion in the form of a connector wire 20 is provided within the hollow portion 14 between two anchor points. The wire is selected to sustain a load which exceeds the intended in service loading demands and therefore a greater load than the predetermined load. Therefore, like a performance enhancing tendon, the wire 20 will bear the load after the predetermined load is reached.

The hollow portion 14 of the bolt 10 is particularly suitable for resisting bending loads since the material is offset from the centreline of the shaft 12. The wire 20 will be flexible during bending as it is positioned at the centreline. A wire has an .:�=5 elasticity which allows a degree of elongation during tensile loading. To increase the possible displacement in this direction, the wire 20 may be provided with some slackness. * ** ** I * * *

:: It can be seen that the hollow portion 14 and the wire 20 are configured to bear the load in parallel. However, the hollow portion 14 will bear the majority of the load prior to the predetermined load being reached.

Figure 4 shows an alternative embodiment of the load bearing member, still in the form of a bolt 10 and like features are given like reference numerals.

A waist portion 22 is formed by removing material from a convention bolt shaft which effectively acts as the flexible wire of the first embodiment due to its reduced diameter. A collar 24 is provided around the waist portion 22 which is formed from a brittle material. The brittle material is selected to fail at the predetermined load and thereafter the waist portion 22 will bear all of the loading.

In an alternative embodiment, which can be based on the first or the second embodiments, the first rigid portion and second flexible portion can be provided as an insert for retrofitting to a conventional bolt.

There are many other ways of forming the load bearing member. The flexible portion could be cast in to the rigid portion. Or the flexible portion could be mounted at the exterior or around the rigid portion, such as a spring member coiled around the flexible portion and having an end attached to the rigid portion on both sides of the fracture lines 16.

Figure 5 shows the bolt 10 of the first embodiment fastening a facade panel 110 to a wall 112 of a building. The location of the fracture lines 16 is predetermined so that they are located at the interface of the panel 110 and wall 112. This is S...

important as, if the fracture lines 16 are located within the wall then the wall could L:)5 restrict flexibility, whereas if the fracture lines 16 are located within the panel then the panel could be damaged or vibrations could be propagated from the wall to the panel.

:: A range of bolts 10 of the invention can be provided with the fracture lines 16 ata variety of locations to correspond to different standard or non-standard thickness of panels or elements. For standard panels, the fracture lines 16 simply have to be located at a distance from the head 18 which corresponds to the thickness of the panel being used. For non-standard panels, packer elements, such as washers or straps, can be provided between the head 18 and the panel to ensure that the fracture lines 16 are located at the interface.

Post-installation adjustment means can be provided. In particular, the bolt 10 can be adjusted so that the fracture lines are at the interface.

In certain situations, more than one panel may be being fastened to the wall 112.

The bolt 10 can be adapted to have fracture lines 16 at more than one location along its shaft 12, with each location corresponding to an interface of the panels or of a panel and the wall 112. Such a bolt 10 could also be useful for cavity walls.

IS During normal conditions, the bolt 10 acts as a conventional bolt supporting static loading from the weight of the panelling. The hollow portion 14 will support the majority of this static loading. During an earthquake, the wall 112, which is directly or indirectly rigidly connected to structural components at the ground, will vibrate which will exert dynamic loading on the bolt 10. When this dynamic loading reaches the predetermined load, the hollow portion 14 will fracture and the wire 20 will then take up the loading. The wire provides the dynamic flexibility and inherent strength required. Therefore, the panel 110 will still be fastened to the building but in a more flexible manner which accommodates relative displacement between the panel 110 and the wall 112. * *. * * *** S

* The bolt 10 can be configured such that, after the hollow portion 14 has fractured, * a portion of the hollow portion 14 is sacrificed or released. The remaining :. portions can provide a failsafe retaining capability.

S..... *

A washer may be provided which is formed from a resilient material such as rubber. This increases the flexibility of the bolt 10 both before and after the predetermined load has been reached. And by allowing a greater relative displacement, the washer can also increase the predetermined load which may be desirable. The washer can comprise two rigid plates which sandwich a rubber material, with an aperture through the washer for receiving the bolt 10. The rubber material allows relative lateral displacement of the two plates during dynamic loading. The aperture at the outer plate (adjacent to the head 18) can be made to be oversized relative to the bolt outer diameter to accommodate pivoting of the bolt 10 relative to the outer plate (the side walls of the aperture will not restrain the bolt 10 from pivoting). Alternatively, the aperture at the inner plate can be oversized.

The washer can also include a recess or cavity to allow greater displacement of the wire 20 after the predetermined load has been reached. The recess provides a volume of space allowing unrestrained movement of the bolt 10 other than at the outer plate. The recess also, by removing material from the washer, allows greater deformation of the washer caused by dynamic movement of the bolt 10.

In the case of the washer having a cavity, this cavity can be filled with a gas such as air. This arrangement does not interfere with dynamic movement of the bolt but assists in the washer returning to its non-deformed state.

Examples of such washers are given in Figure 6 which shows washers both with and without the recess. As shown in certain examples, the washer can be adapted for a single bolt or for many and can even be provided as a full panel. S...

Also, the washer can be adapted to fit to a corner of the building. * *. * .

It is common, when fastening a fastener to a substrate, to use a sleeve inserted *..

into the substrate for receiving the fastener. The sleeve protects the fastener from corrosion. The load bearing member according to the invention can include a sleeve which has a joint portion at a location corresponding to the predetermined axial location of the fracture lines 16. The joint portion can be flexible such as being formed as a concertina member which allows bending, compression and elongation, or the joint portion can be rigid until failure at the predetermined load and thereafter flexible. In an alternative embodiment, the sleeve can be adapted to provide the second flexible portion of the load bearing member.

The load bearing member can be provided with transformation indicating means to indicate when the load bearing member has transformed from rigidly to flexibly bearing the load. This may comprise colour coding in which the colour appears or changes when the load bearing member has transformed. Or a flag member could be provided which changes from a first position to a second position when the load bearing member has transformed. Or a sensor may be embedded which detects the transformation and sends a signal to a visual or auditory alarm device. The alarm device can be provided at the load bearing member or may be remote.

A testing device may be provided for determining whether the load bearing member has transformed. The testing device may cooperate with the transformation indicating means. Alternatively, the testing device may be adapted to investigate the state of the first rigid portion, such as by testing the flexibility of the load bearing member.

While the foregoing description relates to a bolt, it can be appreciated that the invention can apply to any fastener such as a nut, screw, rawlplug, washer, nail, clamp or the like. * 0* * * ** *

* However, it should also be appreciated that the invention may relate to a structural component (a structural part of the building) such as a beam, column or :: bracket, or it may relate to an insert for such a component.

*S,**, * * Considering again Figure 5, the flexible connector is particularly suitable for attaching a facade system to a building. To further inhibit damage to the facade, the facade can include a matrix material interposing the support for facade elements (not shown) and the exterior surface. The matrix material can comprise a first layer of compressible material, such as foam, and a second layer of rigid material.

The foam layer has a mesh layer either side bonded on to it using an adhesive.

The foam layer allows greater relative displacement but is relatively structurally weak. The second layer, being rigid, is stronger. The second layer can be a honeycomb material which includes a number of cavities. These act to absorb vibrations and so limit the propagation of vibrations to the facade elements.

The embodiment also increases the in-plane shear performance of the facade and its attached elements by enhancing the ability to resist seismic shear forces.

This ability to improve and maintain vertical resistance after sustaining significant in-plane shears is due to the embodiment capability to deliver a secure and an elastic response upon demand. Therefore a decrease or loss of in-plane shear strength and stiffness in the facade or (conceivable) out-of-plane structural failure can to some extent be abridged by this embodiment.

Whilst specific embodiments of the present invention have been described above, it will be appreciated that departures from the described embodiments may still fall within the scope of the present invention. S.. * S S... S *S * S S *5s * S... * S S... * S. S* S * S

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Claims

Claims 1. A load bearing member comprising: a first rigid portion adapted to bear a load until the load reaches a predetermined load and thereafter have a reduced or substantially no load bearing capacity; and a second flexible portion adapted to bear the load after the predetermined load is reached, wherein the first rigid portion and the second flexible portion cooperate to bear the load such that the load bearing member is enabled to transform from rigidly to flexibly bearing the load when the predetermined load is reached.
2. A load bearing member as claimed in claim 1, wherein the first rigid portion is adapted to fail at the predetermined load.
3. A load bearing member as claimed in claim 2, wherein the first rigid portion includes a weakening feature adapted to fail at the predetermined load.
4. A load bearing member as claimed in any preceding claim, wherein failure at the predetermined load is due to a material forming the first rigid portion reaching a failure value.
5. A load bearing member as claimed in claim 3, wherein the weakening *. feature is adapted to respond more to particular types of loading and less to other types of loading.

:
6. A load bearing member as claimed in any preceding claim, wherein the weakening feature is provided at a predetermined axial location.
7. A load bearing member as claimed in claim 6, wherein a weakening feature is provided at a plurality of predetermined axial locations.
8. A load bearing member as claimed in claim 1, including switching means and load sensing means, and wherein the load bearing member is adapted to switch from the first rigid portion to the second flexible portion for bearing the load when the predetermined load is reached.
9. A load bearing member as claimed in any preceding claim, wherein the first and second portions are configured to bear a load in parallel.
10. A load bearing member as claimed in any preceding claim, wherein the first rigid portion is arranged to bear the majority of the load prior to the predetermined load is reached.
11. A load bearing member as claimed in any preceding claim, wherein the second flexible portion is provided as an inner core of the load bearing member and the first rigid portion substantially surrounds the inner core.
12. A load bearing member as claimed in claim 11, wherein the first rigid portion is provided as a hollow tubular member and the second flexible portion is *::::0 provided as a wire member provided within the tubular member. I...
13. A load bearing member as claimed in any preceding claim, wherein the second flexible portion is formed by removing material from a solid member to *. form a waist portion.
14. A load bearing member as claimed in claim 13, wherein the first rigid :h portion is provided as a collar member provided around the waist portion.
15. A load bearing member as claimed in any preceding claim, wherein the first rigid portion and second flexible portion are provided as an insert for retrofitting to a conventional load bearing member.
16. A load bearing member as claimed in any preceding claim, comprising a beam, column, bracket, hanger, strut, axle, cable, pipe, or pipe joint.
17. A load bearing member as claimed in any of claims 1 to 15 comprising a compression fastener.
18. A load bearing member as claimed in claim 17, including a washer member comprising a resilient material.
19. A load bearing member as claimed in claim 18, wherein the washer member includes a recess or cavity adapted to allow displacement of the second flexible portion.

IS
20. A load bearing member as claimed in claim 19, wherein the cavity contains a gas.
21. A load bearing member as claimed in any of claims 18 to 20, wherein the washer includes an aperture having an entrance for the fastener and an exit spaced apart from the entrance, and wherein the entrance is oversized relative to the fastener.
22. A load bearing member as claimed in any of claims 17 to 21, including a *. sleeve member.

.
23. A load bearing member as claimed in claim 22, wherein the sleeve member includes a joint portion at a location corresponding to the predetermined axial location.
24. A load bearing member as claimed in claim 23, wherein the joint portion is flexible.
25. A load bearing member as claimed in any preceding claim, including transformation indicating means adapted to indicate when the load bearing member has transformed from rigidly to flexibly bearing the load.
26. A load bearing member as claimed in any preceding claim, wherein the first rigid portion is formed from a first material and the second flexible portion is formed from a second different material.
27. A load bearing member as claimed in any preceding claim, wherein the load bearing member is adapted for fastening a facade to a building.
28. A method of supporting a load within a structure using a load bearing member, the method comprising: providing the load bearing member with a first rigid portion adapted to have a load bearing capacity until a predetermined load is reached and thereafter have a reduced or substantially no load bearing capacity; and providing the load bearing member with a second flexible portion adapted to bear the load after the predetermined load is reached. *:::
29. A method as claimed in claim 28, including adapting the first rigid portion to fail at the predetermined load. * *e * * * S.. S*.
30. A method as claimed in claim 29, including selecting a material forming S...the first rigid portion which will reach a failure value at the predetermined load.s:"
31. A method as claimed in any of claims 28 to 30, including providing the first rigid portion as a hollow tubular member and the second flexible portion as an inner wire provided within the tubular member.
32. A method as claimed in any of claims 28 to 30, including forming the second flexible portion by removing material from a solid member to form a waist portion, and providing the first rigid portion as a collar member around the waist portion.
33. A method as claimed in any of claims 28 to 32, wherein the load bearing member comprises a fastener.
34. A method as claimed in claim 33, including supporting, using a support, a plurality of facade elements provided on the exterior surface of a building, and fastening the support to the exterior surface using at least one load bearing member.
35. A facade system which is installable on the exterior surface of a structure, the facade system comprising: a plurality of facade elements; a support for supporting the facade elements and which is attachable to the exterior surface using a plurality of fasteners; and a matrix material interposing the facade elements and the exterior surface, wherein the matrix material comprises a first layer of compressible material and a second layer of rigid material. I...
36. A facade system as claimed in claim 35, wherein the first layer comprises . a foam material. *..*:.:
37. A facade system as claimed in claim 35 or 36, wherein the second layer include a plurality of cavities.
38. A facade system as claimed in Claim 37, wherein the second layer comprises a honeycomb material.
39. A facade system as claimed in any of Claims 35 to 38, wherein the matrix material interposes the support.
40. A facade system as claimed in any of Claims 35 to 38, wherein the matrix material is adapted to provide the support.
41. A facade system as claimed in any of Claims 35 to 40, wherein one or more of the fasteners comprises a first rigid portion and a second flexible portion.
42. A facade system as claimed in any of Claims 35 to 41, including a washer formed from a resilient material. * * * ** S S... * . *.. * *S * S S S.. S S... * S S*S * S. S. S * SSS5*555SS S