Abstract:
A Flare Strut System including a plurality of strut pairs, each forming an assembly for transferring force between wall and a roof continuity element. Each assembly is comprised of two elongated strut elements, or load transfer members, each including a longitudinal rotation and adjustment member at one end thereof, a first end connector assembly for facilitating connection of one end of the strut element to a wall, and a second end connector assembly for facilitating attachment of the other end of the strut element to a continuity element connection assembly, the latter assembly being adapted to combine with a corresponding connection assembly and sandwich the continuity element therebetween. Each strut element is adapted to angularly intersect both the engaged wall and the continuity element at acute angles which are determined by the particular buildings design.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to devices used to interconnect and transfer forces between structural members such as the walls of a building and its roof framing system, and more particularly, to a strut system for providing direct, simplified and cost effective seismic connections that can articulate in three planes while transferring both tension and compression forces from the walls of new and existing concrete, concrete “tilt-up” and concrete block buildings to their diaphragm continuity elements. 
     2. Description of the Prior Art 
     Tilt-up buildings generally consist of those types of structures that are constructed with precast concrete wall panels that are precast horizontally on the ground, cured, and then tilted up into place. Concrete block walls are similar in character, but are built up block by block. Other concrete walls are typically cast in place. 
     The timber roof framing systems of older concrete, concrete tilt-up and concrete block buildings (hereinafter referred to generally as “concrete buildings”) that were built between the early to mid 1960&#39;s were generally constructed with longspan timber roof trusses and timber roof joists. The timber trusses in these buildings were typically oriented to span the short direction of the building. Spacing between these trusses generally varies between 16 and 24 feet. The roof joists generally consist of 2×8&#39;s, 2×10&#39;s, or 2×12&#39;s spaced at 24″ o.c., and span between the timber trusses. At the perimeter of the building the roof joists span between the timber trusses and the walls, where they are typically framed onto a timber ledger that is bolted to the wall. Roof sheathing for these buildings typically consists of ⅜″ or ½″ plywood. 
     After the mid 1960&#39;s, the roof timber framing systems of most concrete as well as other types of buildings were generally constructed with glulam beams, instead of longspan timber trusses, and used a “panelized” roof framing system instead of roof joists. These modifications to the roof framing systems were typically made for economic reasons. 
     A “panelized” roof framing system consists of timber purlins, timber sub-purlins (also known as stiffeners), and roof sheathing. The roof sheathing typically consists of 4′×8′ sheets of ⅜″ or ½″ plywood, and spans between the sub-purlins. These sub-purlins are generally 2×4&#39;s or 2×6&#39;s, and span between the purlins. The purlins typically consist of 4×12&#39;s or 4×14&#39;s and span between the glulam beams (or in some cases longspan timber trusses). The plywood sheathing is typically oriented with it&#39;s long dimension parallel to the sub-purlins, or perpendicular to the purlins. The sub-purlins are generally spaced 24″ apart. The purlins are typically spaced 8 feet apart to accommodate the length of the plywood sheathing. The glulam beams are typically spaced 20 to 24 feet apart. Sections of the panelized roof are typically fabricated on the ground and raised into place with a crane or forklift. 
     In buildings with timber framed roof diaphragms, the major roof framing elements, such as beams, girders, and trusses, are used as diaphragm continuity elements to form a plurality of spaced continuity lines that extend across the length and width of a building, i.e., a diaphragm continuity system. The purpose of a diaphragm continuity system is to provide a discrete structural system that provides for the transfer of seismic, wind, or other forces from the walls of a building into the roof diaphragm, and eventually to the structural elements intended to resist such forces. Forces from the walls are typically transferred to the diaphragm continuity elements through a sub-diaphragm. A sub-diaphragm is generally taken to be a localized area of the roof diaphragm that spans between diaphragm continuity elements and extends into the diaphragm a certain distance. This distance is dependent on the shear capacity of the sub-diaphragm and the forces that are to be transferred through the sub-diaphragm. 
     In areas subject to high seismicity, the connection between the walls of most older concrete buildings and their timber roof framing system is inadequate per the currently established seismic design standards for such buildings. Generally, this connection consists of only the nailing between the roof sheathing and the timber ledger that is bolted to the wall. This type of connection relies on a mechanism that subjects the ledgers to “cross grain bending”, a mechanism that is highly vulnerable to failure. The deficiencies associated with this type of connection were responsible for numerous failures and collapses of concrete buildings during the 1971 San Fernando Earthquake. As a result, this type of connection has been specifically disallowed since the 1973 Edition of the Uniform Building Code. It is generally recommended that concrete buildings with such deficiencies be retrofitted with new connections per the currently established seismic design standards and/or recommendations for such buildings. 
     In some buildings constructed prior to the 1973 Edition of the uniform Building Code, and in most constructed afterwards, the walls of concrete, concrete tilt-up, and concrete block buildings are attached to the roof diaphragm, or sub-diaphragms, with discrete walls ties. Such wall ties generally consists of timber blocks or struts that are interconnected with metal straps, rods, holddown type connection devices, such as those disclosed in U.S. Pat. No. 5,249,404, or a combination thereof, and are only designed to resist tension forces, or may consist of the recently developed wall tie system disclosed in U.S. Pat. No. 5,809,719. These “conventional” wall tie systems generally consist of many individual components that can take a significant amount of time to install, especially when the roof diaphragm is sloped (as is generally required for drainage, sometimes significantly) and the walls are not orthogonal to the diaphragm continuity elements. In many buildings, particularly older buildings with unblocked joisted non-panelized roof diaphragms, the sub-diaphragm shear capacity may be very limited, and require that those wall tie systems that rely on sub-diaphragms be extended from the wall into the roof diaphragm a significant distance in order to increase the depth of the sub-diaphragm, and hence reduce the sub-diaphragm shear stresses to within acceptable limits. Such conventional wall tie systems can be very costly. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a simplified and cost effective seismic connection mechanism for transferring both tension and compression forces from the walls of buildings to their diaphragm continuity elements. 
     Another object of the present invention is to provide a seismic connection of the type described for connecting the walls of concrete buildings to diaphragm continuity elements consisting of the major roof framing elements such as beams, girders and trusses. 
     Yet another object of the present invention is to provide a seismic connection of the type described which is capable of transferring both tension and compression forces from building walls into the overall roof diaphragm through the beams, girders and/or trusses thereof. 
     Still another object of the present invention is to provide a seismic connection of the type described that eliminates dependence on the sub-diaphragm as a means of preserving wall to diaphragm integrity. 
     Briefly, a preferred embodiment of the present invention includes either a single or a plurality of strut pairs, each forming an assembly for transferring force between a wall and a roof diaphragm continuity element. Each assembly is comprised of two elongated strut elements, or load transfer members, each including a member at one end that allows longitudinal adjustment and rotation thereof, a first end connector assembly for facilitating connection of one end of the strut element to a wall, and a second end connector assembly for facilitating attachment of the other end of the strut element to a diaphragm continuity element connection assembly, the latter assembly being adapted to combine with a corresponding connection assembly and sandwich the continuity element therebetween. Each strut element is adapted to angularly intersect both the engaged wall and the diaphragm continuity element at angles which are determined by the particular buildings design. 
     An important advantage of the present invention is that it provides a reliable load transfer mechanism for use in structurally attaching the walls of new or existing tilt-up, concrete or concrete block wall buildings to their major roof framing elements. 
     Another advantage of the present invention is that it provides a simplified connection mechanism that can be used to connect walls and roof framing elements intersecting each other at any angle, either horizontally, vertically or both. 
     A further advantage is that it includes relatively lightweight components that can be manually installed without the use of heavy lifts, jacks, etc. 
    
    
     These and other objects and advantages of the present invention will no doubt become apparent to those skilled in the art after having reviewed the following detailed description of the preferred embodiments illustrated in the several figures of the drawing. 
     IN THE DRAWING 
     FIG. 1 is a bottom plan view illustrating a flare strut assembly in accordance with the present invention. 
     FIG. 2 is an elevational view showing one strut of the assembly illustrated in FIG.  1 . 
     FIGS. 3 and 4 illustrate alternative embodiments of a strut member. 
     FIG. 5 is a plan view showing a wall connection end connector assembly. 
     FIG. 6 is an elevational cross-section taken along the lines 6—6 of FIG.  5 . 
     FIG. 7 is a plan view of a continuity member connection end connector assembly. 
     FIG. 8 is an elevational view partially sectioned along the lines 8—8 of FIG.  7 . 
     FIG. 9 is an elevational view illustrating a strut member engaging a block wall at an oblique angle. 
     FIG. 10 is a partially broken plan view schematically showing use of the flare strut stem of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1 of the drawing wherein a bottom plan view of a segment of a concrete wall  10  and building roof  12  are depicted, it will be appreciated that the panelized roof structure consists of main supporting beams or trusses  14  that form diaphragm continuity members that span between the walls and rest upon support columns or posts  16  either formed integral with or attached to the adjacent wall. In this case, the illustrated continuity member  14  is a large glulam beam (See FIG.  2 ). Spanning between adjacent beams are purlins  16 , and spanning between the purlins  16  or a purlin and a ledger beam  18 , are sub-purlins  20 . And finally, attached to and spanning between subpurlins are rectangular sheets  22  of roof sheathing. 
     Mounted to the wall and roof structure, typically at each junction of continuity beam and wall, are flare strut assemblies  23 , including first and second struts  24  and  26 , and their associated end fastening subassemblies  28  and  30 . 
     The Flare Strut System of the present invention provides an alternate to conventional wall tie systems that might consist of strap and block systems, rod and block systems, strap and strut systems, rod and strut systems, or the recently developed DS Dragline System (developed for “tilt-up” buildings with panelized roof framing systems, (See U.S. Pat. No. 5,809,719). These conventional wall tie systems generally consist of many individual components that can take a significant amount of time to install, especially when the roof diaphragm is sloped (as is required for drainage, sometimes significantly) and the walls are not orthogonal to the diaphragm continuity elements, and rely on a subdiaphragm (a localized area of the roof diaphragm that spans between diaphragm continuity elements) to transfer forces from the walls to the diaphragm continuity elements. In many tilt-up” type buildings, particularly older buildings with unblocked joisted (non-panelized) roof diaphragms, the subdiaphragm shear capacity may be very limited, and require that those wall tie systems that rely on subdiaphragms be extended from the wall into the roof diaphragm a significant distance in order to increase the depth of the subdiaphragm, and hence reduce the subdiaphragm shear stresses to within acceptable limits. Such wall tie systems can be very costly. Since the present invention provides for a direct connection between the walls of a “tilt-up” or other concrete walled building and its diaphragm continuity elements, the subdiaphragm is bypassed, and any capacity related problems associated with that subdiaphragm are eliminated. Furthermore, since the strut assemblies of the present invention install simply and quickly, the installation costs associated therewith can be significantly less than those associated with conventional systems. 
     As indicated above, the preferred embodiment of the FS Flare Strut System is comprised of a combination of struts  24 ,  26  designated “Flare Strut (FS)”, a first end connector assembly  28  designated “End Connection Type  1  (EC- 1 )” which provides for the attachment of the Flare Strut to the wall, and a second end connector assembly  30  designated “End Connection Type  2  (EC- 2 )”, which provides for the attachment of the flare strut to a roof framing element (beam, girder, or truss). A Shear Transfer Plate (STP) for both EC- 1  and/or EC- 2 , may be included as required. 
     As depicted in FIG. 3, the flare strut consists of a Strut Element (SE), an Interface Plate (IP), a Pipe Element (PE), and a Coupler Element (CE). The SE generally may consist of either a structural steel pipe (round) or tubular (square or rectangular) section. Generally, square rectangular tubing will most often used for the SE, as it is readily available, and typically lighter than an equivalent pipe section. The SE is attached to the IP by welding or brazing. The IP consists of either a square (typically), round, or multi sided steel plate, and is then welded or brazed to the PE, serving to attach the SE to the PE. The PE consists of a steel pipe section (that may also be solid round stock or threaded rod) with external (or internal) right hand (or left hand) threads, and is threaded into (or onto) the CE. The CE consists of a steel pipe section (that may also be solid round stock or threaded rod if provided with external threads) with internal (or external) right hand (or left hand) threads. The threaded connection between the PE and the CE allows the FS to freely rotate about the longitudinal axis of the FS, thus providing the FS System with one degree of articulation, as well as allowing the overall length of the FS to be adjusted for field fit-up. 
     Both the SE and CE of the flare strut may be attached to either EC- 1  or EC- 2  type connectors since both EC- 1  and EC- 2  are attached to the strut ends with a single pin bolt passed through the bores. This provides the FS System with a second degree of articulation. As shown in FIGS. 1 and 2, both the EC- 1  (wall) connector  28  and the EC- 2  connector  30  (diaphragm continuity element) are attached to their designated building element with a single connection bolt. This provides the FS System with a third degree of articulation. 
     As an alternate, the FS may be modified as shown in FIG. 4 with the addition of an Interface Sleeve (IS) to form a Flare Strut Head (FSH). This head configuration allows for either a bolted connection or an aligned and welded connection between the SE and the Flare Strut Head (FSH) and thus permits an installer to combine the FSH with a field cut and drilled SE to readily accommodate strut length variations or changes in the field. 
     The EC- 1  connector is illustrated in detail in FIGS. 5 and 6 and consists of a base plate  40  and two connection plates  42  welded thereto. The plates  42  have matching holes  43  for receiving a connection bolt or pin (not shown). The base plate may be square, rectangular, round, or multi sided, and is provided with at least one hole  44  for receiving a connection bolt or pin (not shown). The connection plates may be square, rectangular, or otherwise shaped to provide the installer and inspector with a visual reference as to the allowable limits the strut to be attached thereto may be skewed relative to the EC- 1  connector. Both the base plate and the connection plate may be modified as required to minimize the eccentricity between the line of action LAS along the strut and the line of action LAB along the connection bolt  46 , and/or minimize the bearing pressure that the base plate might exert upon the building element to which it is to be attached. 
     If the shear capacity of the connection bolt  46  attaching the EC- 1  connection to the building element is inadequate, then additional shear capacity can be derived with the installation of a Shear Plate (SP). The shear plate may consist of a square, rectangular, round, or multi-sided steel plate that is provided with holes  48  and  50  for concrete (or masonry) anchors  52  and  54 , and perhaps additional holes (not shown) for nails, screws or lag bolts. 
     The EC- 2  connector is illustrated in detail in FIGS. 7 and 8 and consists of a base plate  60  and two connection plates  62  welded thereto. The plates  62  have matching holes  63  for receiving a connection bolt or pin. The base plate may be square, rectangular, round, or multi-sided, and is provided with a least one hole  64  for receiving a connection bolt or pin (not shown). The connection plates may be square, rectangular, or otherwise shaped to provide the installer and inspector with a visual reference as to the allowable limits the strut to be attached thereto may be skewed relative to the EC- 2  connector. Both the base plate and the connection plate may be modified as required to minimize the eccentricity between the line of action LAS along the strut and the line of action LAB along the connection bolt and/or minimize the bearing pressure that the base plate might exert upon the building element to which it is to be attached. 
     If the shear capacity of the connection bolt attaching the connection EC- 2  connection to the building element is inadequate, then additional shear capacity can be derived with the installation of a Shear Plate (SP). The shear plate may consist of a square, rectangular, round or multi-sided steel plate that is provided with holes for nails, screws, lag bolts or bolts. 
     Momentarily returning to FIG. 1, it will be noted that the connector assemblies  30  on each side of beam  14  are connected together by a common bolt  31  that is extended through the holes  64  (FIGS. 7 and 8) as well as through a hole drilled through beam  14 . If shear plates SP are, used, they may be either independently by nailing, screwing, etc., or may be joined by bolts extending through bolt holes (not shown) formed in the beam and plates SP. Ideally, the assemblies  30  will be aligned. 
     But, in some cases, they can be staggered so long as provisions are made to resolve the unbalanced forces. The angle at which each strut intersects beam  14  is a matter of engineering design. 
     In FIG. 9 an installation of the present invention to a concrete block building having a steeply sloped roof is depicted in partial cross-section to illustrate that the subject strut assembly can accommodate an angular connection angled at acute angles in more than one plane. This is permitted by rotation of the strut in one place, about its connecting pin and rotation of the strut in a second plane by rotating the connector about its attachment bolt. 
     FIG. 10 is a plan view depicting an exemplary installation of the FS System in a building having two orthogonally disposed walls  70  and  72  and two walls  74  and  76  that are at least in part non-orthogonally oriented relative to the other walls. As shown, a strut assembly  80  is installed at each intersection of a beam or other roof diaphragm continuity element  82 . Note that the non-orthogonal wall segments  77  and  78  are accommodated by simply shortening the length of one of the struts in each strut assembly. 
     The walls  72  and  76 , and wall segments  77  and  78  are interconnected in this drawing using the apparatus and techniques disclosed in U.S. Pat. No. 5,813,181. 
     Although the present invention has been described in terms of specific embodiments it is anticipated that alterations and modifications thereof will no doubt become apparent to those skilled in the art. It is therefore intended that the following claims be interpreted as covering all such alterations and modifications as fall within the true spirit and scope of the invention.