Patent Application
20210180634
This invention relates to masonry hardware in particular clay brick or soft stone block fasteners and wall ties.
Loadbearing cavity (aka hollow) wall construction is a form of masonry wall construction where two leaves of unreinforced clay brick masonry or soft stone block masonry (URM) are separated by a continuous air cavity. In recent times the two leaves are interconnected using some form of tie system. In earlier times a tie system was not used. Observations of building damaged in earthquakes and strong winds indicated that failure of URM construction, typically cavity walls, was critical in terms of structural stability and safety issues, and collapse of the outer masonry cavity wall layer due to wall bending failure was commonly encountered. Also observed was the poor quality of masonry construction, mortar strength and cavity wall ties that often corroded, resulting in a poor connection between the two masonry wall layers. Therefore, the capacity of wall ties to transfer lateral load was significantly diminished due to cross-sectional reduction. In a similar manner inadequate or missing shear and tension connections between the unreinforced masonry (URM) bearing wall and the floor or roof can cause issues. The most significant deficiency in URM bearing wall buildings is the lack of an adequate positive (i.e. mechanical) tie between the masonry walls and the floor and roof diaphragms. Ties are usually separated into two categories: tension ties and shear ties. Tension ties transfer out-of-plane inertial loads perpendicular to the face of the masonry back into the structural elements. Shear ties transfer loads from the structural elements into the wall where they are resisted by in-plane action of the wall. Tension ties help keep the walls from falling away from the diaphragms; shear ties help keep the diaphragm from sliding along parallel to the wall.
According to one example embodiment there is provided a masonry fastener, comprising:
Preferably the masonry is clay brick or soft stone masonry.
Preferably the clay bricks or stone blocks have up-to 35 MPa compression strength.
Preferably the bending angle is about 21.0°.
Preferably the tapered helical screw portions have a thread spacing of between about 6 mm and about 10 mm.
Preferably the thread spacing is about 8 mm.
Preferably the shank has a diameter between about 6 mm and about 10 mm.
Preferably the shank diameter is about 8 mm.
Preferably the shank has a length between about 160 mm and about 340 mm.
According to a further example embodiment there is provided a masonry wall tie, comprising:
Preferably the masonry is clay brick or soft stone masonry.
Preferably the clay bricks or stone blocks have up-to 35 MPa compression strength.
Preferably the bending angle is about 25.7°.
Preferably the tapered helical screw portions have a thread spacing of between about 5.5 mm and about 10 mm.
Preferably the thread spacing is about 6 mm.
Preferably the shank has a diameter between about 5.5 mm and about 10 mm.
Preferably the shank diameter is about 6 mm.
Preferably the second unthreaded portion is between about 25% and about 30% of the wall tie length.
Preferably the second unthreaded portion is about 28% of the wall tie length.
Preferably the second unthreaded portion length is between about 60 mm and about 90 mm. It is acknowledged that the terms “comprise”, “comprises” and “comprising” may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, these terms are intended to have an inclusive meaning—i.e., they will be taken to mean an inclusion of the listed components which the use directly references, and possibly also of other non-specified components or elements.
Reference to any document in this specification does not constitute an admission that it is prior art, validly combinable with other documents or that it forms part of the common general knowledge.
The accompanying drawings which are incorporated in and constitute part of the specification, illustrate embodiments of the invention and, together with the general description of the invention given above, and the detailed description of embodiments given below, serve to explain the principles of the invention, in which:
It may be desirable to create minimally intrusive and reversible strengthening (earthquake and/or wind loading retrofit) options for unreinforced masonry buildings with cavity type walls. The wall may be made of clay bricks or soft stone blocks. The clay brick may be fired clay bricks. Further it may be desirable to create a composite interconnection action between separate wall layers in unreinforced masonry buildings with cavity type walls.
The material strength of clay bricks or soft stone blocks/units can be vastly variable. The soft stone block material includes but are not limited to sandstone, limestone, tuff, or similar. The wall ties and fasteners discussed herein are applicable for use with stone blocks having up-to 35 MPa compression strength. Similar compression strength applies to fired clay brick.
The clay brick or soft stone block wall tie 200 connects unreinforced clay bricks or soft stone blocks 220, 225.
The clay brick or soft stone block wall tie 200 includes a shank having a first threaded portion 240 extending from the tip 242 of the clay brick or soft stone block wall tie 200 partially along the shank.
A third portion 230 is also threaded.
A second unthreaded portion 235 extends between the first threaded portion 240 and the third threaded portion 230. The diameter of the unthreaded portion 235 is in one embodiment of a greater diameter that the center core diameter of the first and third threaded portions 230, 240. The threads of the first portion 230 and third portion 240 are preferably sharp crested helical threads formed along the clay brick or soft stone block wall tie 200 shank.
Notches 245 may be formed on the crest of the helical thread along the length of the screw, more frequent end notches (saw teeth) may be formed in about the first three revolutions at the tip 242 in order to facilitate embedment of the crest into the masonry substrate
The notches 245 may facilitate embedment of the crest of the helical threads into the masonry substrate of the clay bricks or soft stone blocks.
The clay brick or soft stone block wall tie 200 forms an anchor device which is designed to be secured within a bore formed in a multi-leaf (wythe) masonry wall structure.
The clay brick or soft stone block wall tie 200 fasten itself into multi-leaf (wythe) masonry when it is screwed and will not be loosen from vibrations or use (such as earthquake or wind induced).
The thread 244 of the clay brick or soft stone block wall tie 200 is designed to cut a spiral groove into the masonry substrate when inserted into a predrilled hole and turned. The spiral groove cuts without damaging the surround clay brick or soft stone blocks.
The clay brick or soft stone block wall tie 200 is turned by a head 250 on the clay brick or soft stone block wall tie 200. The head 250 has in one embodiment a torx head 260, however other suitable head types including hex, square recess, pozi, p Phillips, slotted and hex head cap screw may be used.
The clay brick or soft stone block wall tie 200 may be suitable as a replacement of original wall ties and may provide high tensile capacity for earthquake and wind resistance of cavity and veneer type masonry construction.
Further the clay brick or soft stone block wall tie 200 may provide a high level of interleaf shear transfer for enhanced earthquake and wind resistance and may be used to secure multiple layers of masonry for a resilient interconnected masonry wall cross-section.
The clay brick or soft stone block wall tie 200 may be used without no resin or grout and there is no mechanical expansion. The clay brick or soft stone block wall tie 200 provides a quick, easy, non-disruptive installation.
In one embodiment the clay brick or soft stone block wall tie 200 may be recessed below face of masonry as seen in
The clay brick or soft stone block wall tie 200 threaded portions 230, 240 will typically have a thread spacing of between about 5.5 mm and about 10 mm. Preferably the thread spacing is about 6 mm.
The clay brick or soft stone block wall tie 200 shank diameter is between about 5.5 mm and about 10 mm. Preferably the shank diameter is about 6 mm.
The clay brick or soft stone block wall tie 200 shank length is between about 200 mm and about 340 mm depending on the size of the clay brick or soft stone block and the space between the clay bricks or soft stone block. In one embodiment the length is 240 mm.
While illustrated and described in reference to double brick or block cavities, the clay brick or soft stone block wall tie 200 could be used in a triple brick or block situation. In this situation the first or third threaded portions would be lengthened to suit depending on whether or not the double brick or block layer of a triple brick or block cavity was being passed through or screwed into.
The clay brick or soft stone block wall tie 200 is preferably manufactured using tempered steel to provide ductile response. Other materials (manganese, carbon, silicon, aluminum, phosphorus) may be used that provide a good ductile response.
EN 14592 provides a ductility measure with the level of performance measured from S1 to S3. S3 being the highest level. The test requires a fitting being bent three times to a bending angle. The degrees of bendability using this measure is expressed as:
α is expressed in degrees and d is the nominal diameter of the shank, in mm.
Ductility class S3 requires three repeated cycles at the bending angle before breaking of S3=2×α
In a typical embodiment
and
S3=2×α=12.84×2=25.7
Thus, the clay brick or soft stone block wall tie 200 would typically have a bending angle of about 25.7°. In a preferred embodiment the bending angle under complete three repeated cycles without rupture would be between about 12.5° and 26°.
The clay brick or soft stone block wall tie 200 may be installed using the following installation procedure:
In a further embodiment a clay brick or soft stone block fastener 400 illustrated in
Referring to
The first portion 485 has a tapered helical screw 444 along the longitudinal length of the first portion 485. The tapered helical screw commencing at a tip of the first end thereof and ending at the second portion. The tapered helical screw type of the first portion is optimised for clay bricks or soft stone blocks.
The second portion 480 has a tapered helical screw along a longitudinal length thereof. The tapered helical screw of the second portion 480 commences at the end of the first portion 485 and end at the head 450. The tapered helical screw type of the first portion is optimised for timber.
Notches 445 may be formed on the crest of the helical thread along the length of the screw, more frequent end notches (saw teeth) may be formed in about the first three revolutions at the tip 442 in order to facilitate embedment of the crest into the masonry substrate
The notches 445 may facilitate embedment of the crest of the helical threads into the masonry substrate of the clay bricks or soft stone blocks.
In other embodiments such as attaching metal to clay bricks or soft stone blocks the first and second portions may have a continuous thread type optimised for clay bricks or soft stone blocks.
The shank of the clay brick or soft stone block fastener 400 has ductility measured as the bending angle under complete three repeated cycles discussed above.
EN 14592 provides a ductility measure with the level of performance measured from S1 to S3. S3 being the highest level. The test requires a fitting being bent three times to a bending angle. The degrees of bendability using this measure is expressed as:
α is expressed in degrees and d is the nominal diameter of the shank, in mm.
Ductility class S3 requires three repeated cycles at the bending angle before breaking of S3=2×α
In a typical embodiment
and
S3=2×α=10.5×2=21.0
Thus, the clay brick or soft stone block fastener 400 would typically have a bending angle of about 21.0°. In a preferred embodiment the bending angle under complete three repeated cycles without rupture would be between about 10° and 22°.
The shank diameter of the clay brick or soft stone block fastener 400 is between about 6 mm and about 10 mm. Preferably the shank diameter is about 8 mm.
The tapered helical screw 444 portions 480, 485 of the clay brick or soft stone block fasteners 400 have a thread spacing of between about 5.5 mm and about 10 mm. Preferably the thread spacing is about 8 mm.
The thread 444 of first portion 485 of the clay brick or soft stone block fasteners 400 is designed to cut a spiral groove into the masonry substrate when inserted into a predrilled hole and turned. The spiral groove cuts without damaging the surround clay brick or soft stone block.
The thread 444 of second portion 480 of the clay brick or soft stone block fasteners 400 is designed to cut a spiral groove into timber or the like when inserted into a predrilled hole and turned.
The clay brick or soft stone block fasteners 400 is turned by a head 450 on the clay brick or soft stone block fasteners 400. The head 450 has in one embodiment a torx head 460, however other suitable head types including hex, square recess, pozi, p Phillips, slotted and hex head cap screw may be used.
The clay brick or soft stone block fasteners 400 shank length is between about 200 mm and about 400 mm but the length may be adjusted to suit the use of the clay brick or soft stone block fasteners 400. Likewise the proportion of the shaft optimized for screwing into brick/block or wood may be altered depending on the use.
The clay brick fasteners 400 is preferably manufactured using tempered steel to provide ductile response. Other materials (manganese, carbon, silicon, aluminum, phosphorus) may be used that provide a good ductile response.
The clay brick fasteners 400 may be installed using the following installation procedure:
Uses of the clay brick or soft stone block fasteners 400 may include masonry parapet securing; masonry wall to additional member connections (such as steel or timber strong-backs); and use as tension and shear dowels.
Additional uses of the clay brick or soft stone block fasteners 400 may include connecting plywood or wooden panels to clay bricks or soft stone blocks and use as masonry wall interleaf ties in cases such as poor interleaf (wythe) interconnection and where danger of delamination of the wall cross-section exists.
While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of the Applicant's general inventive concept.
