A Connection for Timber Members

There is an increasing desire to reduce the carbon footprint of buildings and, because of this, buildings fabricated from timber are becoming increasingly attractive to developers.

The mechanical properties of timber are different to those of steel and concrete and, for this reason, steel and concrete are often favoured over timber when fabricating large buildings. Given the high carbon footprint of these materials, it is therefore necessary to increase the feasibility of large timber buildings. To do so, it is desirable to increase the maximum floor span that can be supported by timber frameworks. Known techniques have sought to increase the resistance of connections to moments applied between connected timber members. Increasing the moment-resisting properties of connections between timber members also increases the stability of timber frames, and hence buildings. Traditionally, efforts to improve the resistance of timber connections to moments have involved increasing the dimensions of the timber beam or column; however, this increases the weight, cost and build complexity of buildings, which is undesirable. Other solutions include installing diagonal truss supports or shear walls, however these solutions place great restrictions on the design of the buildings as such.

Some known timber connections designed to resist moments include a plurality of bolts that pass through a tight-fitting hole which extends through the entire thickness of the timber column or beam. The bolts are then fastened on both sides of the column or beam. As temperatures and moisture levels vary, these fittings often become over-tight or loose due to the different expansion and contraction of the wood and connectors. This results in poor connection performance.

Existing moment-resisting connections have typically low stiffness. They also suffer from not being able to dissipate a significant amount of energy. The low stiffness prevents the connections from supporting larger spans and the inability to dissipate energy results in connections that are at risk of catastrophic failure when exposed to high cyclical loads, such as those experienced during an earthquake. These connections are therefore unsuitable for use in areas prone to seismic events.

Another disadvantage of known connections is the time and complexity of their assembly. Often, known connections require extensive assembly on site to connect the timber members—for example requiring the drilling of holes, use of adhesive or screwing of multiple connectors directly into timber members while on site. This is not only prone to error (given the environment in which such connections are being assembled), but also very time consuming and therefore expensive in terms of labour cost.

Another key consideration for large-scale buildings is their modularity—that is, the ability for the spaces defined within the building to be changed and reconfigured. For example, it may be desirable to change the locations of internal floors or walls to meet the changing requirements of tenants over time. Known timber connections cannot readily be disassembled and reassembled. In order to disassemble known timber connections the connectors, timber members or both are damaged or destroyed, preventing their reuse. It would be desirable to provide a connection which is suitable to be assembled, disassembled and reassembled, to enable modular buildings. This would increase the useful life of buildings and avoid the need for expensive, time consuming and carbon-emitting development work to modify buildings over time.

The present disclosure overcomes the deficiencies of the prior art.

The present disclosure relates to a connection for connecting timber members. The connection may be for connecting one, two, three, four or more than four timber members. The use of timber in buildings in place of steel or concrete can allow buildings to be constructed with a significantly reduced carbon footprint and, as such, is seen as being critical to the sustainability of the construction industry moving forward.

The present disclosure also relates to a connection for use with structural members, including concrete members. It has been found that the benefits associated with the connection for timber members are also present when used with members made of other materials.

The connection is configured to be easily assembled and disassembled, allowing timber members to be readily connected and disconnected. This provides flexibility in terms of the use of partitions within buildings, allowing the internal space within a building to be reconfigured to accommodate a range of different uses. The connection therefore opens the door to modular buildings and architectural spaces. In doing so, the longevity and usefulness of buildings is increased and the carbon footprint of such buildings over their lifespans is reduced. This improvement is realised in part through the use of connector assemblies interconnected via bolts located in oversized holes.

Additionally, the ease with which the connections of the present disclosure can be assembled and disassembled allows a user to partially assemble the connection before arriving at the site and finishing assembly on site in a very short amount of time. This greatly reduces the time—and hence cost—associated with the fabrication of such connections and buildings as a whole.

Further to increased speed and convenience of assembly and disassembly, connections according to the present disclosure provide improved mechanical performance compared to existing timber connections. In particular, the present disclosure provides connections with the required moment resistance, but with far greater stiffness compared to existing solutions. This increased mechanical performance allows greater spans to be supported—increasing the range of buildings that can be fabricated using timber connections—as well as increasing the rigidity of buildings. The use of elongated anchor members which extend into and are fixed relative to the wooden member(s) contributes to this increased performance. Such connection components are less liable to performance degradation caused by moisture and temperature fluctuations and the resulting differential expansion and contraction, which can result in the loosening of connections in existing systems.

Connections according to the present disclosure employ oversized holes configured to accommodate friction grip bolts in a clearance-fit arrangement. This arrangement provides additional mechanical performance improvements in the form of increased energy dissipation. Many existing solutions rely on rigid connections employing interference or contact-fit bolts. The resulting joints are often rigid, but relatively brittle and, as such, are prone to failure during cyclic loading such as that experienced during an earthquake. The connections of the present disclosure improve upon existing designs through—among other things—the use of clearance fitting friction grip bolts, which improve energy dissipation characteristics and hence mechanical performance under cyclical earthquake loading, for example.

The friction properties of the mating surfaces in the friction coupling may be adjusted by surface treatment. Examples of suitable surface treatments include sandblasting, polishing, or adding surface layers. A surface layer may be added by applying a paint, galvanizing with zinc, aluminium, or other metal alloys, or adding a layer in between the friction surfaces (sheet or shims) of some metal alloy or the like.

Connections according to the present disclosure may have a first operational range in which mechanical load is taken up by friction forces within the joint—this is enabled via the combination of bolts and an oversized hole. In the first operational range, there may not be contact between the outer circumference of the bolt and the inner circumference of the hole. The first operational range may be the dominant range used throughout the majority, if not all, of the operational life of the connection. It may provide the mechanical performance required for standard day-to-day use and, thanks to the energy dissipation properties of a friction connection, may provide improved performance over known connectors, as discussed above. The connections of the present disclosure may, however, also enable a second operational range in which mechanical load is taken up by direct contact between the bolt and the inner circumference of the oversized hole in which it is located. The second operational range may only be used in exceptional circumstances, e.g. during one-off peak loading scenarios.

An additional benefit to using oversized holes is the improved ease, reliability and speed with which the connections can be fabricated on sight. By increasing the hole size—and doing so in a manner that still enables suitable mechanical performance—fabricators can more easily assemble connections. Given the large number of connections that may be present in a building, this greatly reduces the time it takes to erect a building as a whole.

According to the disclosure is a connection, for example for connecting a timber member to a second member. The connection may comprise a first timber member; a first connector assembly, a plate and at least one bolt. The first connector assembly may be associated with the first timber member; the first connector assembly comprising : a plurality of elongate anchor members, each anchor member comprising a first end extending into and fixed with respect to the first timber member; and a second end protruding from the first timber member. Each of the anchor members may define a hole perpendicular to a longitudinal axis of the anchor member for receiving a bolt. The plate may be connected or connectable to a second member and may define at least one hole for receiving a bolt. The or each bolt may be configured to extend through at least one of the anchor members and plate. Wherein for the or each bolt, at least one of the corresponding anchor member hole or plate hole may be oversized so as to receive the corresponding bolt with a clearance fit. The or each bolt may be configured to clamp the plate and anchor member such that relative movement of the plate and first connector assembly is resisted, for example by friction caused by the clamping force provided by the plurality of bolts.

The at least one bolt may be a first plurality of bolts.

The connection may connect a timber member to a second member, where relative movement is primarily resisted by friction forces. The friction forces may derive from the clamping force between the anchor member(s) and plate. The bolts may provide this clamping force. The bolts may be, or used as, friction grip bolts. As discussed elsewhere herein, using frictional forces to provide mechanical performance within connections has many benefits.

The connection may be between two or more adjacent members, e.g. timber members. The connection may be generally applied to any connection between adjacent members and, as such may be suitable for connecting two, three, four, five or more than five proximal members.

The members may be arranged perpendicular to each other, such that one forms a column and the other a beam. Alternatively, the members may be arranged parallel or aligned with each other. The present connection is suitable for connecting members regardless of their relative orientation.

The connection may further comprise: a second timber member; and a second connector assembly associated with the second timber member. The second connector assembly may comprise a plurality of second elongate anchor members, each anchor member comprising a first end extending into and fixed with respect to the second timber member, and a second end protruding from the second timber member. Each of the anchor members may define a hole perpendicular to a longitudinal axis of the anchor member for receiving a bolt. The connection may further comprise a second plurality of bolts, each of the second plurality of bolts configured to extend through at least one of the second anchor members and plate.

In the above example, the connection is between two timber members and the plate is connected to the second timber member via a second connector assembly. In other examples, the plate may be otherwise connectable to the second timber member—for example the plate may be integral with the member, at least partially embedded within the member or adhered to the member.

A connection between two timber members may comprise two connector assemblies—one associated with each of the members and having anchor members extending therein. Where more than two members are being connected, the connection may comprise further connector assemblies—for example one for each member.

For each second bolt: at least one of the corresponding anchor member hole or plate hole may be oversized so as to receive the corresponding bolt with a clearance fit; and each bolt may be configured to clamp the plate and anchor member such that relative movement of the plate and first connector assembly is resisted, for example by friction caused by the clamping force provided by the plurality of bolts.

The connector assemblies of the respective members may be connected to one another via the plate. The connection between at least one—and optionally multiple—of the connector assemblies and the plate is achieved by means of clamping the respective anchor member and plate together such that friction forces resist relative movement. Such a method for supporting the forces experienced in such a connection provides an arrangement which not only meets the necessary mechanical performance requirements, but provides significant benefits in terms of increasing the spans that can be supported and improving earthquake performance, among other things.

The use of oversized holes allows the mechanical load to be supported by frictional forces, rather than via direct abutment of the bolt with the hole. This can be achieved when only one of the plate and anchor member has an oversized hole, or when both of the plate and anchor member have an oversized hole. In some examples only one of these has an oversized hole, in some cases both do.

The use of the term “oversized” may refer to a hole that has a larger diameter than the outer diameter of the bolt that it is receiving—for example such that there is a clearance fit with the bolt, and the bolt outer circumference does not interfere with the inner surface of the hole during normal use.

The plate may be separably connectable to the second member, or connected to (e.g. integral with, welded to, embedded in) the second member.

The plate may define a plurality of holes aligned with those of the anchor members of the first connector assembly. For each bolt, both of the corresponding first connector anchor member hole and plate hole may be oversized so as to receive the corresponding bolt with a clearance fit.

Where a second connector assembly is present, the plate may define a plurality of holes aligned with those of the anchor members of the second connector assembly. For each bolt, both of the corresponding first connector anchor member hole and plate hole may be oversized so as to receive the corresponding bolt with a clearance fit

In some examples, the connection may comprise a plurality of plates—each plate being associated with a portion of the anchor members. Each plate may have one hole, or multiple holes, as described herein. Where multiple plates are present, each may otherwise be as described herein.

In an assembled form, each bolt extends through at least one (and optionally two, or more than two) anchor members and the plate, (or one of the plates if multiple plates are present).

The plate may be arranged perpendicularly to the end surfaces of the first and/or second member. The plate may be arranged in the same plane as that in which the first and second members extend.

The plate may comprise a set of holes for each connector assembly. A first set of holes may be arranged on a first end of the plate, a second set of holes may be arranged on a second end of the plate. The holes of each set may be evenly spaced across a side of the plate or, alternatively, may be grouped.

The plate may comprise more holes than the corresponding number of anchor members, the additional holes being for connecting to ancillary members or connectors for providing additional functionality.

The plate can have any geometrical shape e.g. triangular, rectangular, circular, elliptical, polygonal or polygonal with cut-outs.

The plate may comprise an assembly of plane plates. The plane plates may form a polyhedron (like tetrahedron or pyramid). Each (sub-)plate can have a different plane orientation (having different surface normal vectors). This may allow for fastening of timber members oriented in different planes in space.

The holes of the or each connector assembly may be defined in the second ends of the anchor members such that each bolt extends through the plate and the second end of an anchor member.

The anchor members may be rigidly fixed with respect to the first timber member by means of an elongated rod that extends into the timber member. Such an arrangement may provide a particularly robust coupling and be less susceptible to performance degradation caused by expansion/contraction of components due to moisture and/or temperature fluctuations.

The anchor members may be screwed into the first timber member, or adhered to the first timber member using a chemical adhesive.

Each anchor member may comprise a rod and a bracket. The rod may comprise a screw thread for screwing into the respective timber member. The bracket may be at the second end of the rod. The bracket may define the hole, perpendicular to the axis of the rod.

The bracket may be screwed onto a second end of the rod, distal from that extending into the timber member. The bracket screw thread may be different and discrete from the screw thread for attaching the anchor member to the timber member. The bracket may have screw threads on two opposing sides. This may allow a serial like coupling of the brackets.

The ratio of the length to the diameter of the elongate anchor members may be at least 10:1. The length of the elongate anchor members may be equal to, or longer than, 200 mm, 400 mm, 600 mm, 800 mm or 1000 mm. The length of the anchor members may be between 5 and 50 times the diameter of the elongate anchor members. Anchor members that are fixed with respect to the first timber member by means of a screw thread may benefit from being longer than those that are glued to the timber member.

The anchor members may comprise pairs of anchor members arranged flanking the plate, such that each bolt extends through a pair of anchor members. The anchor members may be arranged in pairs with two anchor members per bolt.

Each anchor member may extend into the respective timber member at any angle. The anchor member may extend into the respective timber member perpendicular to a surface or grain direction of the timber member. This arrangement may be of particular interest when the anchor member is being glued in the timber member. The anchor member may extend into the respective timber member at an oblique angle to a surface or grain direction of the timber member. This arrangement may be of particular interest when the anchor member is being screwed into the timber member. Each anchor member may extend into the respective timber member at any angle with respect to the grain direction or surface of the respective timber member. For example, each anchor member may extend into the respective timber member at substantially one of 50°, 55°, 60°, 65°, 70°, 75°, or 80° with respect to the grain direction or surface of the respective timber member.

The angle at which the anchor members are arranged within their respective timber members will affect the performance of the connection. Importantly, controlling the angle of the respective members avoids collision between adjacent members of the same connector assembly or another connector assembly.

The anchor members of at least one pair of anchor members may have the same orientation with respect to the longitudinal axis of the respective timber member. The anchor members of at least one pair of anchor members may be arranged such that the first ends diverge from one another (e.g. as they extend into the respective timber member).

One of the connector assemblies may comprise two pairs of anchor members. The anchor members of each pair may have the same orientation with respect to the longitudinal axis of the first timber member. The two pairs of anchor members may be symmetrical about the longitudinal axis of the first timber member. The other of the connector assemblies may comprise four pairs of anchor members. The anchor members of each pair may be arranged such that the first ends diverge from one another (e.g. as they extend into the respective timber member).

The first connector assembly may comprise at least four adjacent anchor members. A first and fourth anchor member may each be arranged at a first angle to the surface of the first timber member; and a second and third anchor member, located between the first and fourth anchor members, may each be arranged at a second angle to the surface of the first timber member.