EP4077826A1

EP4077826A1 - Modular composite action panel and structural systems using same

Info

Publication number: EP4077826A1
Application number: EP21854725.5A
Authority: EP
Inventors: Charles Besjak; Yunlu Shen; Matthew Streeter
Original assignee: Skidmore Owings and Merrill LLP
Current assignee: Skidmore Owings and Merrill LLP
Priority date: 2021-01-07
Filing date: 2021-12-30
Publication date: 2022-10-26
Also published as: AU2021416527A1; WO2022150224A1; CA3165038A1; CN115244260A; US20220213684A1; WO2022150224A9; JP2023514035A

Abstract

A prefabricated modular composite structural panel comprising a composite structural floor system. The structural panel comprises timber panels rigidly connected to steel stiffening elements aligned in the direction of span between supporting elements. By assembling multiple prefabricated panels in a modular array and adding concrete, a composite concrete floor system can be created which is adaptable to any building geometry. The timber panel acts in composite with the steel stiffening elements to function as formwork in the temporary condition with minimal or no shoring. In the permanent condition, the steel stiffening element is used to reinforce the concrete slab, and the timber panel can act in composite with the concrete slab to meet strength and serviceability requirements where permitted by code. Methods for connecting steel to timber components as well as methods for connecting panels to supporting beams are also disclosed. The structural panels can also be oriented vertically and tied together as required to create formwork for other building elements such as walls, columns, braces, and beams.

Description

MODULAR COMPOSITE ACTION PANEL AND STRUCTURAL SYSTEMS USING SAME RELATED APPLICATION [0001] This application claims the benefit of priority to U.S. Patent Application No. 17/143,543 filed January 7,.2021, the entirety of which is incorporated herein by reference to the extent permitted by law. BACKGROUND [0002] The present disclosure generally relates to the construction of structural systems. More specifically, the disclosure relates to construction of floor, ceiling, and wall systems. [0003] Structural floors are one of the main components of building structural systems. They carry loads (such as occupants, furniture, and equipment) to structural beams and columns, which in turn transfer the loads to the foundation. Conventional modern structural floors are typically constructed from concrete due to its versatility in creating different shapes of floor plates, its ability to span long distances when acting in composite with steel reinforcement, and its resistance to vibrations and sound transfer. Timber floors are also used, typically with a concrete topping slab. However, in most jurisdictions timber floors are currently not permitted in high-rise buildings with 6 or more stories above ground level without extensive limitations due to concerns that fire would significantly reduce their load carrying capacity. [0004] During construction of concrete floors, wet concrete needs to be supported by a form until the concrete is set. Commonly used forms for structural floors include: leave- in-place corrugated metal deck forms, typically used in steel buildings; temporary plywood formwork supported on closely spaced shoring, typically used in concrete buildings; and precast concrete panels that act in composite with the cast-in-place topping slab during building service, typically used in precast concrete buildings. The metal deck forms are commonly used to span approximately 10’ without shoring, but at longer spans the depth of corrugation required to stiffen the form results in excessive floor thickness and higher cost. Trussed deck is commonly used in Asian markets in lieu of corrugated metal deck in steel buildings: a rebar lattice truss is used to stiffen the flat metal. Trussed deck is typically limited to the same span range as corrugated metal deck. The temporary plywood formwork also has drawbacks: shoring for the plywood formwork interferes with construction activities on the floors below, the time required for shoring and formwork to remain in place impedes construction schedule, and the plywood forms are typically discarded after removal, creating negative environmental impact. The precast concrete panels typically require temporary shoring for longer spans. [0005] The Filigree Wideslab System (Mid-State Filigree Systems, Inc.1992) consists of reinforced precast floor panels that serve as permanent formwork, with a steel lattice truss projecting from the top of the precast unit to stiffen the panel (refer to product document). However, similar to other precast concrete panel forms, they are heavy to transport and lift into place. [0006] In addition, most occupied spaces use an additional ceiling finish such as dry wall or timber below the structural slab, particularly metal decks. This incurs additional material and labor cost, as well as increased environmental impact. SUMMARY [0007] Disclosed herein are one or more inventions relating to a prefabricated modular composite action panel, structural systems employing the composite action panel, methods of fabricating the composite action panel, and methods of erecting structural systems employing the composite action panel. [0008] The disclosed composite action panel can provide a lightweight formwork that can achieve long spans without shoring, and at the same time remain in place as an attractive permanent ceiling finish. Even more efficiency can be achieved if the formwork can act in composite with concrete as part of a structural system. To that end, lightweight timber panels with stiffening elements fabricated from conventional concrete reinforcements can serve this purpose. [0009] As used herein: “Timber” includes natural and manmade wood unless stated otherwise. “Timber” and “lumber” are used interchangeably herein. “Timber panel” means a layer of timber whether comprised of one sheet or multiple sheets of timber and whether a given sheet of timber is single or multi-ply. “Composite action panel” means a panel embodying principles disclosed herein. It may also be referred to as a timber-rebar truss panel, a lumber-rebar truss panel, or a prefabricated modular panel. “Galloping” means a serpentine profile in reference to the bent shape of a steel rod or bar, including a sinusoidal characteristic. “Prefabricated” means built in advance and transportable to an installation site for installation at the installation site. [00010] In an embodiment, a composite action panel comprises: steel stiffening elements aligned parallel to each other and each extending along a span direction; and a timber panel secured to the steel stiffening members via structural connectors, wherein, the steel stiffening members function as a first chord and a web element of the composition action panel and the timber panel functions as a second chord of the composite action panel, and the steel stiffening members and the timber panel achieve composite action and truss behavior. In an embodiment, the structural connectors are positioned at discrete locations along the steel stiffening members. In an embodiment, the structural connectors secure the steel stiffening elements and the timber panel continuously along the span direction. In an embodiment, the steel stiffening members and the timber panel are connected together by means of connector structures comprising metal plates to which the steel stiffening elements are welded or bolted, and fastener elements selected from the group consisting of mechanical fasteners, nails, spiked plates, and adhesive. In an embodiment, the timber panel is selected from the group consisting of cross-laminated timber(CLT), nail-laminated timber(NLT), dowel-laminated timber(DLT), and glue-laminated timber(GLT). In an embodiment, the steel stiffening element are either three-dimensional or planar rebar trusses. In an embodiment, each steel stiffening member comprises a three- dimensional rebar truss comprising (a) a deformed rebar as the top chord, two continuous bars bent to form two web diagonals and secured to the deformed rebar, and two bottom bars, each attached to a respective base of the web diagonals, the web diagonal bars being bent in a galloping fashion. In an embodiment, each steel stiffening member comprises a planar truss comprising (a) a top bar, (b) one continuous web diagonal bent in a galloping fashion, and (c) one bottom bar attached to the base of the web diagonal. In an embodiment, the steel stiffening elements comprise perforated metal plates or prefabricated steel shapes. In an embodiment disclosed herein, the composite action panel is prefabricated. In an embodiment, the steel stiffening elements extend in both the span direction and another direction traversing the span direction. In an embodiment, a structural element, comprises: a composite action panel according to any of the prior embodiments; and concrete or cementitious material in which the steel stiffening elements are embedded. In an embodiment, the structural element is part of a roof system, a floor system, a wall, a column, a brace, or a beam. In an embodiment, the structural element is part of a roof system or a floor system. In an embodiment a composite monolithic system, comprises: a plurality of composite action panels according to any of the embodiment above; splice reinforcements between adjoining composite action panels; and concrete or cementitious material embedding the steel stiffening elements. In an embodiment, the composite monolithic system is a floor system or a roof system. In an embodiment, the composite monolithic system further comprises a support framework supporting the floor system or the roof system, the support framework being selected from the group consisting of steel beams, precast concrete beams, a cast-in place concrete beams, or timber beams. In an embodiment of a composite monolithic system the composite panels are either simple spans between the supporting framework or continue across a top of the supporting framework with openings for the concrete slab to achieve composite action with the support framework. In an embodiment of a monolithic structural system, the timber panel can be designed to contribute to the strength and/or serviceability of the structural floor in the permanent condition, with the timber panel and concrete thicknesses selected based on desired participation from the timber panel, and additional shear connectors added for desired level of composite action. In an embodiment, a method comprises: prefabricating a composite action panel according to any of the prior embodiments; transporting the composite action panel to an installation site; supporting the composite action panel in a desired orientation; and embedding the steel reinforcement elements in a concrete slab. As can be appreciated, the timber panels act in composite with the steel stiffening elements to support wet weight of concrete in the temporary condition, and can be designed to span with minimal or no shoring up to typical spans of one-way or two-way reinforced concrete slabs. In the permanent condition, the steel stiffening element can be used to reinforce the concrete slab, and the timber panel can act in composite with the concrete slab to meet strength and serviceability requirements. The underside of the timber panel preferably is protected with a protective layer during construction, and can serve as a visually pleasing ceiling finish in the permanent condition. The prefabricated formwork preferably is prepared in advance, reducing site labor and increasing construction speed. The significant reduction of shoring allows construction activity to take place on the levels below, further reducing construction schedule. By assembling multiple prefabricated composite action panels in a modular array, a floor system can be created which is adaptable to any building geometry. The prefabricated composite action panels are lightweight and stackable, facilitating transportation and erection. The leave-in timber ceiling finish eliminates the need for additional ceiling material, reducing overall environmental impact. The system is versatile and can be used with steel framing, concrete cast-in place beams and columns, precast concrete systems, and timber framing. Other systems, methods, features, and advantages of the one or more disclosed inventions will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the invention(s), and be protected by the accompanying claims. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an implementation of the system disclosed herein, together with the description, explain the advantages and principles of the disclosed system. In the drawings: FIG 1 is a perspective view of an illustrative example of a single composite action panel that can be used as a composite timber floor system panel after the placement (pouring) of concrete or cementitious material which is consistent with principles disclosed herein. FIG 2 is a perspective view of an illustrative example of a single composite action panel prior to the placement of concrete which is consistent with principles disclosed herein. FIG. 3 is an exploded view of an exemplary composite action panel or timber-rebar truss panel depicting individual components of the timber-rebar truss panel shown in FIG.2 prior to assembly of the timber-rebar truss panel shown in FIG.2. FIG. 4a is a perspective view of an exemplary rebar truss assembly depicting the components of a single rebar truss assembly that may be employed as a steel stiffening element of the single timber-rebar truss panel shown in FIG.3. FIG 4b is an exploded view of the exemplary rebar truss assembly shown in FIG.4a. FIG.5a is a plan view of the prefabricated rebar truss illustrated in FIG.4a. FIG. 5b is an elevation view of the prefabricated rebar truss illustrated in FIG.4a. Refer to FIG.5a for location of section 5b. FIG.6a is a section view cut at a typical cross section of the prefabricated rebar truss illustrated in FIG.4a. Refer to FIG.5b for location of section. FIG. 6b is a section view cut at the end of the prefabricated rebar truss illustrated in FIG.4a. Refer to FIG.5b for location of section. FIG. 6c is a section view cut at the end looking perpendicular to the span direction of the prefabricated rebar truss illustrated in FIG.4a. Refer to FIG.5a for location of section. FIG.7 is a plan view of the illustrative single composite action panel shown in FIG. 2 which illustrates the layout of the prefabricated rebar truss and the transverse reinforcement shown in FIG.3. FIG. 8a & FIG. 8b are longitudinal and transverse elevation views of the composite action panel assembly shown in FIG. 7 taken along lines 8a-8a’ and 8b-8b’, respectively. FIG. 9 is a plan view showing the connectors laid out on the timber panel 10 as shown in the illustrative single composite timber floor system panel shown in FIG. 2. FIG.10a is a plan detail of a corner of the timber panel and connector plate assembly as shown in section 10a in FIG.9 FIG. 10b is a plan detail of a side edge of the timber panel and connector plate assembly as shown in section 10b in FIG.9 FIG.11a is a section detail cut at the end of the illustrative composite action panel shown in FIG.2 which is consistent with the current disclosure, as shown by section 11a in FIG.9 FIGS. 11b & 11c are additional section details cut through the composite action panel shown in FIG.2, as shown by sections 11b and 11c, respectively, in FIG.9. FIGS.12a-f depict sections of alternative connection types that can be used to make a positive connection between the timber panel and rebar truss cage components depicted in FIG. 3. Any of these connection types may be used in combination with any of the other connection types to form a positive connection between the timber panel and rebar truss cage. FIG. 13a is a perspective view of an illustrative structural system using structural steel for the beam (end 42 a side 43) and column 41 framing, and a series of the prefabricated modular composite action panels 50 (refer to FIG. 2) to construct a floor system. FIG. 13b is a plan view of the illustrative structural system shown in FIG ₁₃ showing the modular nature of the disclosed composite action panels when employed on structural steel framing. FIG. 14 is a section depicting the side connection detail between two adjacent composite action panels of the modular system as shown by section 14 in Fig. 13b. This section depicts the mechanism that is installed between composite action panels to prevent bleeding of concrete during the construction process. FIG.15a is a section detail showing an end support detail of a prefabricated modular composite action panel supported by a steel wide flange beam at an interior support condition, as shown by section 15a in FIG.13b. FIG. 15b & 15c are section details of alternate details of a prefabricated modular composite action panel supported by a steel wide flange beam at an interior support condition. FIG. 15b shows a configuration in which the timber portion of the prefabricated composite action panel is installed below the top of steel elevation thereby reducing overall structural depth. FIG.15c is a detail showing the composite action panel running continuously over the interior steel support beam. Refer to FIG.13b for location of interior support conditions in a multi-composite action panel modular layout. FIG.16a is a section detail showing an end support detail of a prefabricated modular composite action panel supported by a steel wide flange beam at an edge support condition as shown in section 16a in FIG.13b. FIG.16b is an alternative section detail showing an end support detail of a prefabricated modular composite action panel supported by a steel wide flange beam at an edge support condition. Refer to FIG. 13b section 16a for location of section. Similar to the alternative shown in FIG. 15b, this alternative configuration is such that the timber portion of the prefabricated composite action panel is installed below the top of steel elevation thereby reducing overall structural depth. FIG.17a is a section detail showing an end support detail of a prefabricated modular composite action panel supported by a cast-in-place concrete beam at an interior support condition. Refer to section cut 15a in FIG.13b for section cut locations. FIG.17b is a section detail showing an end support detail of a prefabricated modular composite action panel supported by a cast-in-place concrete beam at an edge support condition. Refer to section cut 16a in FIG.13b for section cut locations. FIG 18 is a perspective view of a potential hoisting configuration of a single prefabricated modular composite action panel. FIG. 19a is a general flow chart outlining the primary steps and materials involved in the fabrication and erection of a modular composite timber floor system consistent with principles disclosed herein. FIG. 19b is a flow chart outlining the fabrication process of a single prefabricated modular composite action panel consistent with principles disclosed herein. FIG.19c is a flow chart outlining the erection process of a structural floor system using one or more prefabricated composite action panels consistent with principles disclosed herein. FIG. 20 is a perspective view showing a single bay of an exemplary structural system and identifies the primary element types used in a typical structural system. FIG. 21a is a perspective view illustrating the primary components of a prefabricated modular timber beam element. FIG. 21b is a perspective view illustrating the primary components of a prefabricated modular timber column element. FIG. 21c is a perspective view illustrating the primary components of a prefabricated modular timber wall element. DETAILED DESCRIPTION Reference will now be made in detail to one or more implementations in accordance with a prefabricated modular composite action panel consistent with the principles disclosed herein as illustrated in the accompanying drawings. The prefabricated modular composite action panel, may be incorporated into a floor or roof system of a building or other structure and used to resist area loads as well as to provide a continuous diaphragm at each level of application. The modular nature of the composite action panel allows flexibility such that a system utilizing the composite action panel may be tailored to fit any building geometry with a series of repetitive composite action panel elements preferably connected as illustrated in the accompanying drawings and description. The prefabricated nature of the composite action panel allows composite action panels to be shop fabricated, improving construction tolerances, and increasing speed of construction while eliminating the need for separate tradesmen to field install slab reinforcement. Exemplary embodiments of the composite action panel of this disclosure and systems employing same are illustrated in the accompanying drawings and description. However, the composite action panel may be implemented such that any combination of the primary materials (timber, steel and concrete) presented herein may be utilized at any point during the lifespan of a structural system to achieve a structural floor or roof system, other systems as disclosed herein. A modular composite timber floor system consistent with principles disclosed herein enables the reduction or elimination of temporary formwork and shoring while utilizing traditional building materials to increase speed of construction and reduce overall building costs. Additional benefits of the proposed disclosure include but are not limited to: lightweight and stackable making for easy transportation and erection, introduces sequestered carbon into the project thus improving sustainable performance, and provides an attractive visual finish potentially eliminating the need for a hung ceiling. FIG 1 is a perspective view of an illustrative example of a single composite timber floor system employing one or more composite action panels consistent with principles disclosed herein. As seen in FIG.1 the modular composite timber floor system panel includes a timber panel 10 connected to steel reinforcement 20 via connectors 30 which form a composite action panel. Concrete 40 (shown in phantom for easier understanding) is cast on top of the composite action panel(s), encasing and embedding all of the steel reinforcement. In this exemplary description, the timber panel 10, rebar trusses 20 and connectors 30 are prefabricated and combined into one or more composite action panels and shipped to site. Once installed the one or more composite action panels are installed on site, and then the concrete 40 is cast in place creating a monolithic floor system. FIG.2 illustrates this prefabricated composite action panel prior to placement of concrete 40. The timber panel 10 illustrated in FIG.1 shows an exemplary size and shape of timber panel, however it is possible to implement panels of any shape and size in accordance with principles of the present disclosure. Although the timber panel 10, illustrated in FIG. 1, shows a cross laminated timber profile with 3 ply thickness, any number of ply’s may be used. The timber panel must be sufficiently strong to act as part of a composite concrete form. Alternate means of lamination are also possible including, but are not limited to, dowel laminated timber, nail laminated timber & glue laminated timber panels. In addition, as noted above, the timber can be made of natural or man-made wood. In this illustrative example, the steel reinforcement 20 is composed of deformed steel bars and round steel rods. However, alternative types of steel reinforcement can be used to achieve composite action between the other materials (timber 10 & concrete 40). These alternative types include but are not limited to steel plates, perforated steel plates and rolled steel sections. Further this illustrative example shows an exemplary size and configuration of steel reinforcement, however steel reinforcement 40 can be configured in a variety of ways to achieve the required strength and serviceability performance. FIG.3 is an exploded perspective view of the illustrative example shown in FIG. 2. FIG. 3 shows the timber panel 10 at the base of the illustrative assembly or composite action panel. Connectors 30 allow for a structural connection between the timber panel 10 and the prefabricated rebar trusses 21. In this illustrative example, the connector plate 30 is connected to the timber panel 10 via self-tapping lag screws 32, as shown in FIG 11a-11c. This is just one potential method of connection between the timber panel 10 and the connectors 30. Alternate connection techniques will be described in more detail in the following discussion (refer to FIGS.12a-12f). The rebar trusses 21 are welded to the connectors 30 at all points of contract. In this illustrative example, the composite action panel is designed and detailed as a 1-way system, meaning the composite action panel spans in the span direction or length of the rebar trusses (long direction in the figure) and is supported at both of its ends in the cross-span or transverse direction (the short ends in the figure). The rebar trusses 21 are configured to run parallel to this span direction. By connecting a series of rebar trusses 21 in parallel via the connectors 30 to the timber panel ₁₀, a prefabricated composite action panel is created. Transverse reinforcement ₂₂ is provided in the direction perpendicular to the span. In this illustrative example, transverse reinforcement 22 is provided as additional reinforcement bars which are wire tired in place using standard construction techniques, however it is possible that the transverse reinforcement bars 22 are integrated into the rebar trusses 21 to contribute to the composite action panel’s composite strength and allow for 2-way system applications. FIG.4a is a perspective view of a single rebar truss 21 illustrated in FIG.3 and described above. The rebar truss 21 is a 3-dimensional truss that is made up of one straight continuous top deformed bar 21A, two inclined continuous diagonal bars 21B which are bent in a galloping fashion, two straight continuous bottom deformed bars 21C, two horizontal end support bars 21D (one at each end) and two vertical end support bars 21E (one at each end). All bars are welded together at points of contact to create a single three-dimensional rebar truss 21. FIG. 4b is a perspective view of an explosion diagram of the components described above in FIG.4a. The inclined continuous diagonal bars 21B are welded to the top bar 21A and bottom bat 21C. Bottom bars 21C are welded to the horizontal end support bars 21D which are welded to the vertical end support bars 21E. The vertical end support bars 21E are also welded to the top bar 21A. As previously noted, this represents but one preferred rebar truss configuration. Other configurations may be implemented consistent with the principles of the present disclosure. FIG.5a is a plan view of the prefabricated rebar truss 21 illustrated in FIG. 4a. Sections 5b & 6c are used as reference for the sections shown in FIG.5b & 6c. FIG. 5b is an elevation view of the prefabricated rebar truss 21 illustrated in FIG.4a. Refer to FIG.5a for location of the section 5a. This elevation shows an example of galloping configuration of the inclined diagonal bar 21B. As shown, the galloping diagonal bar 21B has horizontal segments which occur at regular spacing at both the top and bottom of the truss allowing sufficient contact between the diagonal bar 21B and the top and bottom bars 21A and 21C respectively. The horizontal segments of the diagonal bar 21B are shown in this preferred embodiment, but are not required as long as sufficient contact between the diagonal bars 21B and top and bottom bars (21A & 21C) is achieved. This truss profile is created from a continuous piece of round steel rod, however truss behavior may be achieved using an alternate configuration as previously noted. Any truss configuration which allows for composite action between the rebar cage 21 and the timber panel 10 would be consistent with the principles disclosed herein. Sections 6a & 6b are used as reference for the sections shown in FIG.6a & 6b. FIG.6a is a section view cut at a typical cross section of the prefabricated rebar truss 21 illustrated in FIG.4a. Refer to FIG.5b for location of section. As shown in this section, the top bar 21A is pinched between the two inclined diagonal bars 21B, and a weld is made between these two along this contact. Also shown in this section is the location of the bottom bar 21C relative to the inclined diagonal bar 21B. FIG.6b is a section view cut at the end of the prefabricated rebar truss 21 illustrated in FIG. 4a. Refer to FIG. 5b for location of section. As shown in this section, the top bar 21A sits above the vertical end support bar 21E and the bottom bars 21C sit above the horizontal end support bar 21D. The horizontal end support bar 21D runs interior to the vertical end support bar 21E. Each of these bars are connected via welds at the locations of contact. FIG. 6c is a section view cut at the end looking perpendicular to the span direction of the prefabricated rebar truss 21 illustrated in FIG. 4a. Refer to FIG. 5a for location of section. This section shows the relationship between the bottom and top bars 21C & 21A respectively and the support bars (horizontal & vertical, 21D & 21E respectively). Further, this section shows the horizontal segments of the inclined diagonal bars 21B as well as the termination of the diagonal bars 21B at the end of the rebar truss 21. FIG. 7 is a plan view of the illustrative composite action panel shown in FIG. 2. This FIG. 7 shows how the prefabricated rebar truss 21 and the transverse reinforcement 22 are laid out on the timber panel 10 below. A series of rebar trusses running in the direction of the span are placed in a parallel configuration and equally spaced across the width of the timber panel. Similarly, transverse reinforcement bars 22 running perpendicular to the span are placed in a parallel configuration and equally spaced across the length of the timber panel. FIG. 8a & FIG. 8b are longitudinal and transverse section views, respectively, of the composite action panel shown in FIG.7. Refer to FIG.7 for section cut locations. FIG.8a shows an exemplary distribution of transverse reinforcement 22 as well as the elevation of the prefabricated rebar truss 21 as it relates to the timber panel 10. FIG. 8b shows an exemplary distribution of prefabricated rebar trusses 21 across the width of the timber panel 10 as well as the elevation of the transverse reinforcement 22 relative to the top bar 21A and bottom bar 21C. Refer to FIGS. 5 & 6 for details of the rebar truss assembly. FIG. 9 is a plan view of the connectors 30 laid out on the timber panel 10 as shown in the illustrative composite action panel shown in FIG. 2. As shown in this figure, the exemplary composite action panel has three steel connector plate types. The typical interior connector plates 31A are continuous strips of steel plate which run transverse to the composite action panel span and are located to ensure contact between the inclined diagonal bars 21B (refer to FIGS.5a & 5b) and the interior connector plate 31A. This contact allows for welding between the interior connector plate 31A and the inclined diagonal bars 21C. The end connector plates 31B are located at both ends of the composite action panel. Similar to the interior connector plates 31A, the end connector plates 31B are continuous strips of steel plate which are positioned to ensure contact with the inclined diagonal bars 21B, allowing for weld between the end connector plates 31B and the inclined diagonal bars 21B. End connector plate 31B size may be adjusted to prevent seepage of wet concrete during the placement of concrete on site. The side connector plate 31C is a single continuous strip of steel plate located on one side of the timber panel 10. The edge-most inclined diagonal bar 21B is welded to the side connector plate 31C. In this illustrative example, lag screw fasteners 32 are used to connect the connector plates 30 with the timber panel 10. Alternative connection types include but are not limited to those shown in FIG.12a-12f. FIG. 10a is a plan detail of a corner of the timber panel 10 and connector plate 30 assembly. This detail shows the side connector plate 31C extending beyond the timber panel 10. This extension allows the connector plate to also function as a pour stop at the end and side connection. Refer to FIG.13-16 for more detail on composite action panel end and side connections. It is also possible to extend the end connector plate 31B beyond the timber panel as required to accommodate the end connection detail, refer to FIG.16a. FIG. 10b is a plan detail of a typical edge of the timber panel 10 and connector plate 30 assembly. The prefabricated rebar trusses 21 have been included in fine line form in this detail to illustrate the overlap between these trusses 21 and the connectors plates (interior 31A and edge 31C). FIG.11a is a section detail cut at the end of the illustrative composite action panel shown in FIG.2 which is consistent with the current disclosure. Refer to FIG.9 for section cut location. This detail shows the end connector plate 31B flush with the timber panel 10 at the end support condition. Refer to FIG. 13-16 for more detail on composite action panel end and side connections. Although this is used as an exemplary configuration of the end plate 31B, rebar truss 21 and timber panel 10, alternative configurations are possible which are consistent with principles disclosed herein. This detail also shows the lag screw fasteners 32 which connect the end connector plate 31B and the interior connector plate 31A to the timber panel. Alternative connection types include but are not limited to those shown in FIG.12a-12f. FIGS.11b & 11c are additional section details cut through the illustrative composite action panel shown in FIG. 2 which is consistent with the current disclosure. Refer to FIG.9 for section cut location. Similar to FIG.11a these section details illustrate the fasteners 32 used to connect the interior connector plates 31A to the timber panel. Further, FIG.11b shows the contact between the rebar truss 21 and the interior connector plate 31A. The rebar truss 21 and interior connector plate 31A are welded together over this contact length. FIGS.12a-12f are isolated section details looking in the transverse direction of the illustrative panel shown in FIG 2. These details show alternative means of connections which allow for composite action between the rebar truss assembly 21 and the timber panel 10. Note, means of connecting the rebar truss assembly 21 to the underlying timber panel 10 include, but are not limited to those presented in FIGS.12a-12f. FIGS 12a shows lag screw fasteners 33A connecting the connector plates 30 to the timber panel 10. In this configuration, the rebar truss 21 is welded to the connector plate 30. These lag screw fasteners 33A may also be installed in an inclined orientation as shown in FIG.12b. Alternate means of mechanical connections are shown in FIGS.12c & 12d which include nails 33B and a punched metal plate 33C. The punch metal plate 33C, sometimes referred to as a spike plate, is a component typically used in the construction of timber trusses, but can also serve as a sufficient load transfer mechanism in the current disclosure. Connection between steel and timber components may also be via epoxy methods. This includes but is not limited to connecting the connector plates 30 directly to the timber panel 10 via epoxy 33D, as well as connecting the rebar truss 21 directly to the timber panel 10 via epoxy. FIG. 13a is a perspective view of an illustrative structural system using structural steel for the beam (end 42 and side 43) and column 41 framing, and a series of the prefabricated modular composite action panels 50 (refer to FIG.2) to construct the floor system. Composite action panels are shown representatively in this FIG. and the detailed steel trusses have not been included for clarity. As shown in this exemplary system, the modular floor system panels 50 are installed adjacent to one another and span between end support members 42. In addition to providing structural stability of the system, side support members are provided parallel to the longitudinal face of the prefabricated modular composite action panels 50 to act as edge support for the end composite action panel. FIG. 13b is a plan view of the illustrative structural system shown in FIG 13a. This plan clearly illustrates the modular nature of the disclosed composite action panels. Prefabricated Modular composite action panels 50 can be shaped and sized based on the structural system geometry to allow repetition of the same module to develop an overall floor system. Shown in this figure is a system using structural steel for framing elements, however, additional systems include but are not limited to reinforcement concrete framing, per-cast reinforced concrete framing, pre-stressed reinforced concrete framing, timber framing and any combination of these framing types. FIGS.13a & 13b also illustrate the additional splice reinforcement required at the interface of adjacent composite action panels. Main splice reinforcement bars 25A and transverse splice reinforcement bars 25B are required at each interior end and side of the modular composite action panels 50 respectively. Hooked edge reinforcement 25C is also required around the edges of the floor systems. These additional reinforcement bars can be installed at any point during the transportation and erection process prior to the placement of concrete. FIG.14 is a section detail taken at the side connection between two adjacent modular composite action panels 50. Refer to FIG 13b for location of section cut. This detail shows an exemplary water stop mechanism which prevents the seepage of concrete through a potential seam 11 caused by erection tolerances. Although the detail shown in this example utilizes a thin strip of plywood 14 that may be field installed to connect the adjacent composite action panels and prevent the seepage of wet concrete, alternative water stopping mechanisms include but are not limited to, a thin gauge metal strip (refer to side connector plate 31C, FIG. 9), tape or a rubber gasket. One might also detail the timber panels 10 to have an offset top ply to allow for a natural overlap of the timber panels as is commonly done in construction using CLT panels as floor panels. FIG.15a is a section detail showing an end support detail of a prefabricated modular composite action panel 50 supported by a steel wide flange beam at an interior support condition 41A. Refer to FIG.13b for section cut locations. In this illustrative detail both adjacent timber panels 10 are bearing directly on the steel end support beam flange 41A. The prefabricated modular composite action panels 50 are sized and erected to ensure composite beam action can be achieved between the end support member 41A and the concrete 40 via the steel shear stud 44. Additional main splice reinforcement 25A are provided across the support line to achieve slab continuity. An erection strap 15 or equivalent is required in this configuration to ensure stability of the prefabricated modular composite action panel 50 during the temporary condition, prior to the placement of concrete. Alternative means of providing temporary stability include but are not limited to, timber to steel bolted connections and timber to timber connections. Alternative interior panel end support methods include but are not limited to those shown in FIGS.15b & 15c. As shown in FIG.15b, the connection may be made by direct bearing of the end connector plate 31B and the end support beam 41A. The connection may also be made by running a continuous timber panel 10 across the top of the support beam 41A as shown in FIG. 15c. In the case of the detail illustrated in FIG. 15c, additional considerations are required to notch the timber panel 10 to ensure composite action between the support beam 41A and the concrete 40, if composite action is desired. FIG.16a is a section detail showing an end support detail of a prefabricated modular composite action panel 50 supported by a steel wide flange beam at an edge support condition 41A. Refer to FIG. 13b for section cut locations. Similar to FIG. 16a, the timber panel 10 is bearing directly on the steel end support beam flange 41A. Also, similar to FIG 16a, the prefabricated modular composite action panels 50 are sized to ensure composite beam action can be achieved between the end support member 41A and the concrete 40. The edge of slab top reinforcement 26A at this location is hooked as per typical reinforced concrete detailing standards, and edge of slab nosing bars 26B are provided as shown in this exemplary detail. Refer to FIG. 15b description above for information on alternative exterior end support configurations shown in FIGS.16b. FIG.17a is a section detail showing an end support detail of a prefabricated modular composite action panel 50 supported by a reinforced concrete beam at an interior support condition 41B. Refer to FIG.13b, section 15a for section cut locations. As shown in this detail, the timber panel 10 is supported by beam formwork 12 used to form the interior concrete end support member 41B. The potential performance of the beam formwork 12 includes, but is not limited to, temporary formwork which is removed after the curing of concrete, permanent formwork which is left in place for the duration of the structures lifespan or as a permanent integral part of the structural system which is composite with the concrete beam. The beam formwork may or may not require additional shoring 13 and still be consistent with the current disclosure. FIG. 16a is a section detail showing an end support detail of a prefabricated modular composite action panel 50 supported by a steel wide flange beam at an edge support condition 41A. Refer to FIG.13b for section cut locations. Regarding the sequence of installation, in this illustrative example, the beam formwork 11 would be installed first, then the prefabricated modular composite action panel 50. Lastly the beam stirrups 27B, longitudinal bars 27A and main splice reinforcement 25A are installed. It is also possible for some of these components to be integrated together to increase speed of construction. FIG.17b is a section detail showing an end support detail of a prefabricated modular composite action panel 50 supported by a reinforced concrete beam at an edge support condition 41B. Refer to FIG. 13b section 16a for section cut locations. Refer to FIG. 17a description for discussion on beam formwork 11 configuration and erection sequence. As shown in this section, the main splice bar 25A for an exterior concrete end support element 41B is hooked into the beam. FIG 18 is a perspective view of a potential hoisting configuration of a single prefabricated modular composite action panel 50. As shown in this figure, the composite action panel 50 can be lifted by 4 connection points 52B at which secondary cables 52A connect, and tie back to the primary cable 54. The present disclosure allows for hoisting directly from the rebar cage. Additional fasteners are provided as required at hoist connection points to ensure adequate withdrawal capacity is available. Additional hoisting hardware may be included on the prefabricated modular composite action panel to increase connection capacity as required. Although this figure only illustrates a single composite action panel being hoisted, it is possible to hoist multiple composite action panels at a single time. FIG. 19a is a general flow chart outlining the primary steps and materials involved in the fabrication and erection of a modular composite timber floor system consistent with principles disclosed herein. As shown in this figure and described in detail above, the timber panel 10, connectors 30 and steel reinforcement elements (rebar truss) 20 make up the prefabricated modular composite action panel 50. However, prior to fabrication of any composite action panel, detailed shop drawings of individual composite action panel pieces as well as the erection drawings must be generated to establish the geometry of each composite action panel to be fabricated. This detailing step may be done with traditional 2-dimensional shop drawings, or by using parametric 3-dimensional documentation tools. Once the composite action panel geometries are established through the documentation process, the composite action panels are fabricated. FIG.19b provides a flow chart detailing a suitable fabrication process, preferably performed in a shop or off- site from where the composite action panels are to be installed. After the composite action panels are shop fabricated, they can be shipped to the site where they are erected based on the erection plans. FIG. 19c provides a flow chart detailing an erection process. Once erected, concrete is placed (poured), resulting in a structural system, which in this illustrative embodiment is a monolithic floor or roof system. With continuing reference to Fig. 19A, in step S1, the detailed shop drawings of individual composite action panel pieces as well as the erection drawings are generated to establish the geometry(ies) of each composite action panel to be fabricated. In step S2, the timber panel 10 and the steel reinforcement elements 20 are secured to each other by way of connectors 30, such as those described above. In step S3, the prefabricated composite action panel results. In step S4, the prefabricated composite action panel is transported to an erection site. In step S5, the prefabricated composite action panel (and typically others) is placed into position at the erection site, for example, as a floor member, wall member, or ceiling member and temporarily joined with other structural components as described above such as other composite action panels, and concrete is poured into the form. Once the concrete (or cementitious material) has cured, the additional form members are removed in step S6 and the result is an installed modular composite timber and truss panel, which in Fig.19A is described as a floor panel as an example only. FIG.19b is a flow chart outlining the fabrication process of a single modular timber floor system panel consistent with principles disclosed herein. As shown in this fabrication flowchart, each component of the prefabricated modular composite action panel has unique fabrication requirements at the front end of the process (reference steps S3.1- S3.3). Once each component is fabricated, they are combined to form a composite action panel. Depending on the connection methodology, the fabrication steps during the connection sequence vary, Refer to FIG.12a-12f and the related description above for and understanding of these various connection types. With continuing reference to Fig. 19b, in step S1, the detailed shop drawings of individual composite action panel pieces as well as the erection drawings are generated to establish the geometry(ies) of each composite action panel to be fabricated. In steps S2.1, S2.2 & S2.3, raw materials are procured for fabrication of each individual component. In steps S3.1, S3.2, and S3.3, each composite action panel component is fabricated to the specified geometries per the individual piece drawings. The timber panel can be fabricated using standard industry techniques. The connectors can be fabricated by cutting plate pieces to length/size and then drilling holes in the plates. The reinforcement elements (steel truss) can be fabricate by cutting steel bars to length, bending the diagonal bars into the galloping shape and then welding all of the bars together as described above. In steps S4.1 and S4.2, additional prep work is performed on the timber panel as required per the specified connection type. In this example, it is determined if epoxy connections are to be used. If yes, then the timber panel is either routed to provide pockets to receive the connection plates or ripped to provide dado grooves for the connection plates. In step S5 the steel reinforcement elements (steel trusses) are connected to the connector plates based on the methods described above. In this embodiment, they are welded together. Alternatively, if the steel trusses are shipped individually and the connector plates are connected to the timber panel independent of the steel truss, this step can be performed later in the process, for example, in step S8. In step S6, the transverse reinforcement (transverse rebar) is installed. Note, if the steel trusses are shipped individually and the connector plate is connected to the timber panel independent of the steel truss, this step can be performed later in the process, for example in step S9. In steps S7.1, S7.2, S7.3 the connector plates are attached to the timber panel based on the selected method. In step S7.1, connector plates are attached using self-tapping lag screw. Alternatively or additionally, in step S7.2 connector plates are attached using nails and minimal self-tapping screws. Alternatively or additionally, in step S7.3 the connector plates are attached to the timber panel using epoxy. As can be appreciated, typically, only one type of attachment method would be used, but, depending on the requirements and/or circumstances, two or more attachment method may be used. As mentioned above, if the steel trusses are shipped/transported individually, steps S8 and S9 can be performed. In step S8, the steel trusses would be welded to the connector plates. In step S9, the transvers rebar would be attached. FIG. 19c is a flow chart outlining the erection process of a single prefabricated modular timber floor system panel consistent with principles disclosed herein. As shown in this flowchart, the present disclosure may be implemented in a building or other structure that is constructed using a wide range of material types. Depending on the base building material type, various construction techniques may be implemented to create a structurally stable system allowing installation of panels one at a time, or in groups. Depending on the end connection detailing, panels may require temporary connections to be made, thus ensuring stability of the system prior to the placement of concrete. The following is a basic description of an exemplary construction process consistent with the flow chart provided in FIG.19c which may be used to construct a floor slab system using this disclosure: In a step 10, a determination is made as to the type of building structural material to be employed. In this description, three types are shown: steel, concrete, and heavy timber. The type of building structure material impacts the way in which the support framing is erected and support details for the composite action panels. In step S11.1, steel framing is erected for steel structures. In step S11.2, pre- cast elements such as columns, walls, braces and beams are erected for pre-cast concrete buildings. Alternatively, in step S11.3 forms into which concrete is to be poured are erected for the structural elements such as columns, walls and braces. In step 11.4, timber framing is erected for timber buildings timber as the structural material. If the building structural material is non-precast concrete, i.e., cast-in-place concrete, following step S11.3, in step S12, the support framing is formed by pouring concrete into the forms erected in step S11.3 to create, e.g., the vertical structural elements. Support framing may be constructed using any commonly accepted building materials and techniques. This specification discloses flexible connection details allowing the composite action panels to be installed using a variety of support types. In step S13, temporary or permanent formwork for floor beams is install. In steps S14.1, S14.2, and S15 the prefabricated composite action panels are hoisted into place. In S14.1 plural panels are hoisted to a staging location. And then in step S14.2, the composite action panels are distributed and placed in their final locations. Alternatively, in step S15, an individual composite action panel is hoisted into place. The exact location of a composite action panel depends on the modular layout of all panels, e.g., on a given floor, and is also dependent on the support type and allowable construction tolerances of the support. In step S16, it is determined whether the rebar cage will extend beyond end of CLT. If the answer is no, then in step S17.1 the composite action panels are secured in place, with the requirements for securing the composite action panels being based on end connection type. If the answer is yes, then in step 17.2, splice reinforcement and additional edge reinforcement for the composite action panels are installed as noted above. Typical mild reinforcing steel bar is used for splices between adjacent panels, however alternative splice details which are accepted by the authority having jurisdiction for a given project may also be employed. In step S18, concrete is poured and the composite action panel steel stiffening members are embedded in the concrete. Shoring can be provided as needed for the composite action panels and/or support beams prior to the pouring of concrete. In step S19, any temporary formwork and shoring is removed. In step S20, protective layers from the timber panel (i.e., that surface of the timber panel that is to be left exposed) are removed. If the composite action panels are used in a flooring system, the timber can be left exposed to provide a timber panel ceiling for a lower floor. FIG. 20 is a perspective view showing a single bay of an exemplary structural system 60 and identifies the primary element types used in a typical structural system. This FIG. 20, in combination with the FIGS. 21a-21c and the preceding figures will be used to describe how the modular composite action panel disclosed herein can also be applied to the other typical elements of a structural system. In this way, it is possible that the embodiment described in this disclosure be used to form the entire structural system of a building or individual elements apart from slab elements which have been described in detail through the previous figures. The typical elements shown in this exemplary single bay system are the slab 50A incorporating one or more composite action panels, beam elements 61, column elements 62, braces elements 63 and wall elements 64. Refer to the first paragraph of the detailed description portion of this specification for a description of slab elements 50A performance characteristics. Beam elements 61 are horizontal elements which support the slab 50A and are supported by column elements 62, wall elements 64 or other beam elements. Column element 62 and wall element 64 are vertical elements which support slab element 50A and beam element 61 and transfer building loads to the foundation system. Brace elements 63 are diagonally oriented, and typically connected adjacent vertical elements, but can also connect beam elements to vertical elements. FIG. 21a is a perspective view illustrating the primary components of a prefabricated modular timber beam element 61. Similar to the composite action panels described in detail above and illustrated in the earlier figures, the beam element consists of timber panels 10, connector elements 30, and steel reinforcement 61A. As with the composite action panels, the timber 10 and steel reinforcement elements 61A are prefabricated off site and joined together and then transported to an installation site as a modular package making for rapid and precise installation. The two elements, timber 10 and steel reinforcement 61A can be made to act compositely by coupling them with the connector elements 30. Unlike the slab element 50A, the beam element 61 can have three outer sides of timber, creating a trough in which concrete can be placed on-site. An additional tie element 61B can be provided as required to stabilize the vertical portions of the beam element 61 in the temporary condition. FIG. 21b is a perspective view illustrating the primary components of a prefabricated modular timber column element 62. This configuration is also applicable for the prefabricated modular timber column element 63. Similar to the previous elements described, the column 62 (and brace 63 of FIG.20) consist of prefabricated timber panels 10 joined with steel reinforcement 62A using connector elements 30. The column and brace elements are unique in that they have four outer sides of timber which form a hollow tube. Following erection, concrete is placed in the tube, creating a structural element with potential composite behavior consistent with the previous descriptions offered in this disclosure. Similar to the beam elements and consistent with standard construction practices, ties are provided which connect opposing timber faces to ensure stability under the hydrostatic pressure of wet concrete. FIG. 21c is a perspective view illustrating the primary components of a prefabricated modular timber wall element 64. Wall elements 64 consist of timber panels 10 prefabricated with steel reinforcement 64A via a connector element 30 on the interior face of each composite action panel. Two composite action panels can be installed opposite each other with stabilizing cross ties 64B, leaving space between the composite action panels for concrete to be placed on-site. Each composite action panel can be installed separately, or a pair of composite action panels can be prefabricated together and installed as a double-sided wall form. The outer sides of the wall element will then be made of timber. The forgoing description of an implementation of the disclosure has been present for the purpose of illustration and description. It is not exhaustive and does not limit the disclosure to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practicing the disclosure. Accordingly, while various embodiments of the present disclosure may have been described, it will be apparent to those of skill in the art that many more embodiments and implementations are possible that are within the scope of this disclosure. Accordingly, the present disclosure is not to be restricted except in light of the attached claims and their equivalents

Claims

CLAIMS What is claimed is: 1. A composite action panel comprising: steel stiffening elements aligned parallel to each other and each extending along a span direction; and a timber panel secured to the steel stiffening members via structural connectors, wherein, the steel stiffening members function as a first chord and a web element of the and the timber panel functions as a second chord of the composite action panel, and the steel stiffening members and the timber panel achieve composite action and truss behavior.

2. The composite action panel of claim 1, wherein the structural connectors are positioned at discrete locations along the steel stiffening members.

3. The composite action panel of claim 1, wherein the structural connectors secure the steel stiffening elements and the timber panel continuously along the span direction.

4. The composite action panel of claim 1, wherein the steel stiffening members and the timber panel are connected together by means of connector structures comprising metal plates to which the steel stiffening elements are welded or bolted, and fastener elements selected from the group consisting of mechanical fasteners, nails, spiked plates, and adhesive.

5. The composite panel of claim 1 , wherein the timber panel is selected from the group consisting of cross-laminated timber(CLT), nail-laminated timber(NLT), dowel-laminated timber(DLT), and glue-laminated timber(GLT).

6. The composite panel of claim 1, wherein the steel stiffening element are either three-dimensional or planar rebar trusses.

7. The composite action panel of claim 1, wherein each steel stiffening member comprises a three-dimensional rebar truss comprising (a) a deformed rebar as the top chord, two continuous bars bent to form two web diagonals and secured to the deformed rebar, and two bottom bars, each attached to a respective base of the web diagonals, the web diagonal bars being bent in a galloping fashion.

8. The composite action panel of claim 1, wherein each steel stiffening member comprises a planar truss comprising (a) a top bar, (b) one continuous web diagonal bent in a galloping fashion, and (c) one bottom bar attached to the base of the web diagonal.

9. The composite action panel of claim 1, wherein the steel stiffening elements comprise perforated metal plates or prefabricated steel shapes.

10. The composite action panel of claim 1, wherein the composite action panel is prefabricated.

11. The composite action panel of claim 1, wherein the steel stiffening elements extend in both the span direction and another direction traversing the span direction.

12. A structural element, comprising: a composite action panel according to claim 1; and concrete in which the steel stiffening elements are embedded.

13. The structural element of claim 12, wherein the structural element is part of a roof system, a floor system, a wall, a column, a brace, or a beam.

14. The structural element of claim 13, wherein the structural element is part of a roof system or a floor system.

15. A composite monolithic system, comprising: a plurality of composite action panels according to claim 1; splice reinforcements between adjoining composite action panels; and concrete embedding the steel stiffening elements.

16. The composite monolithic system of claim 15, wherein the composite monolithic system is a floor system or a roof system.

17. The composite monolithic system of claim 16, further comprising a support framework for the floor system or the roof system, the support framework being selected from the group consisting of steel beams, precast concrete beams, a cast-in place concrete beams, or timber beams.

18. The composite monolithic system of claim 17, wherein the composite panels are either simple spans between the supporting framework or continue across a top of the supporting framework with openings for the concrete slab to achieve composite action with the support framework.

19. The composite monolithic system of claim 17, wherein the timber panel can be designed to contribute to the strength and/or serviceability of the structural floor in the permanent condition, with the panel and concrete thickness selected based on desired participation from the timber panel, and additional shear connectors added for desired level of composite action.

20. The composite monolithic system of claim 17, wherein void forms may be attached to the top of the timber panels to reduce the amount of concrete within the slab.

21. A method comprising: prefabricating a composite action panel according to claim 1; transporting the composite action panel to an installation site; supporting the panel in a desired orientation; and embedding the steel reinforcement elements in a concrete slab.

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