WO2013090455A1

WO2013090455A1 - Concrete building panel

Info

Publication number: WO2013090455A1
Application number: PCT/US2012/069291
Authority: WO
Inventors: An Chen
Original assignee: University Of Idaho
Priority date: 2011-12-13
Filing date: 2012-12-12
Publication date: 2013-06-20

Abstract

The present invention relates to a concrete building panel and a method of making a concrete building panel. In one embodiment, a concrete building panel comprises a first concrete panel and a second concrete panel associated with an insulative core, a fiber-reinforced polymer connector embedded in the first and second concrete panels and extending through the insulative core, and at least one fiber-reinforced polymer layer comprising one or more exterior surfaces of the concrete building panel. In another embodiment, a method of making a building panel comprises associating a fiber-reinforced polymer layer with a formwork, applying a bonding agent to the fiber-reinforced polymer layer, casting a first concrete panel, installing one or more connectors, installing an insulative core, installing one or more pre-stressing strands or reinforcement bars, and casting a second concrete panel on top of the insulative core.

Description

CONCRETE BUILDING PANEL

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of the earlier filing date of U.S.

provisional application No. 61/570,167, filed on December 13, 2011, which incorporated herein by reference in its entirety.

FIELD

The present invention relates to concrete building panels, structures comprising concrete building panels, and methods of manufacturing concrete building panels.

BACKGROUND

Conventional concrete building panels include two outer layers of precast, pre-stressed concrete separated by an inner layer of expanded polystyrene (EPS) or extruded polystyrene (XPS). The two outer layers of concrete can be connected by solid concrete zones, steel ties, wire trusses, or by fiber-reinforced polymer trusses to provide composite strength.

Concrete building panels are typically used as wall elements due to their favorable thermal insulation properties, compressive load strength, and out-of-plane flexural strength for wind and seismic loading. However, conventional concrete building panels are not well- suited for use as floor or roof members. More specifically, conventional concrete building panels require thick reinforced or pre- stressed concrete panels in order to withstand the large out-of-plane bending loads typical of floor and roof applications. Moreover, the thickness of the concrete panels needed to achieve the required strength often renders conventional concrete building panels too heavy for floor and roof applications and too thick to meet strict floor and roof zoning requirements and building codes. Conventional concrete building panels also suffer from inadequate water resistance, making them unsuitable for the stringent water resistance requirements of green roof applications. SUMMARY

Disclosed embodiments of the present invention provide building panels, particularly roof and floor panels, that address the deficiencies of known panels. Certain embodiments of the present invention concern a concrete building panel comprising a first concrete panel and a second concrete panel associated with an insulative core. The concrete building panel can further comprise a fiber-reinforced polymer connector embedded in the first and second concrete panels and extending through the insulative core. The concrete building panel can also comprise at least one fiber-reinforced polymer layer comprising one or more exterior surfaces of the concrete building panel.

Another embodiment concerns a method of making a building panel, comprising associating a fiber-reinforced polymer layer with a formwork, applying a bonding agent to the fiber-reinforced polymer layer, and casting a first concrete panel on top of the fiber-reinforced polymer layer. The method further comprises installing one or more connectors, installing an insulative core, and installing one or more pre-stressing strands or reinforcement bars above the insulative core. The method further comprises casting a second concrete panel on top of the insulative core such that the pre-stressing strands or reinforcement bars are embedded within the second concrete panel.

Another embodiment of the present invention comprises a structure having a plurality of walls and a transverse element. The transverse element comprises an insulative core, a first concrete panel, a second concrete panel, a fiber-reinforced polymer connector, and one or more fiber-reinforced polymer layers. The one or more fiber-reinforced polymer layers comprise one or more surfaces of the transverse element.

Another embodiment of the present invention concerns a method of making a structure, comprising associating a concrete building panel with a plurality of wall structures. The plurality of wall structures are oriented vertically, and the concrete building panel is oriented in a transverse manner adjacent the plurality of wall structures. The concrete building panel comprises an insulative core, a first concrete panel, a second concrete panel, one or more fiber-reinforced polymer connectors, and a fiber-reinforced polymer layer.

The foregoing and other objects, features, and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a concrete building panel.

FIG. 2 is a cross-sectional view of a concrete building panel having two fiber-reinforced polymer layers .

FIG. 3 is a perspective view of a fiber-reinforced polymer shell.

FIG. 4 is a cross-sectional view of a concrete building panel having fiber- reinforced polymer connectors arranged to form a grid.

FIG. 5A is a cross-sectional view of a concrete building panel having an elongated, curved fiber-reinforced polymer connector.

FIG. 5B is a cross-sectional view of the concrete building panel of FIG. 5A, wherein the fiber-reinforced polymer connectors are oriented perpendicular to the top surface of the concrete building panel.

FIG. 6 is a cross-sectional view of a concrete building panel without a connector.

FIG. 7 is a perspective view of a formwork.

FIG. 8 is a side elevation view of a structure including a concrete building panel.

FIG. 9 is a cross-sectional view of a concrete building panel having solid concrete ends.

FIG. 10 is a perspective view of the fiber-reinforced polymer shell of FIG. 3 further comprising holes.

FIG. 11 is a perspective view of another embodiment of a fiber-reinforced polymer shell.

FIG. 12 is a plot of load data (y-axis) and displacement data (x-axis) for two concrete building panel specimens. DETAILED DESCRIPTION

FIG. 1 illustrates a first embodiment of a concrete building panel 10. In some embodiments, the panel 10 is configured for use as a structural floor or roof member in a structure. The concrete building panel can have an insulative core 12 disposed between first and second concrete panels 14, 16. The concrete building panel can also have a polymer layer, such as a fiber-reinforced polymer (FRP) layer 18, associated with the first concrete panel 14, and a connector 20, such as a FRP connector. The concrete building panel can be configured such that the first and second concrete panels, the FRP layer, the insulative core, and the FRP connector all act in a composite manner when subjected to out-of-plane bending and internal shear forces. In this application, "acting in a composite manner" or "composite action" refers to the individual components of the concrete building panel acting together and causing the concrete building panel to behave as if it were a member made of a single homogeneous material when subjected to loading. This allows the concrete building panel to be configured to withstand the loading conditions typical of roof and floor applications without a corresponding increase in weight and thickness.

The insulative core 12 can comprise a lightweight material, such as polymer foam, and can act to thermally and/or acoustically insulate the concrete building panel. The insulative core 12 can have a thickness of from about two inches to about six inches, depending upon the material and the particular application.

Desirably, the insulative core can be about four inches thick to achieve a suitable degree of thermal and acoustic insulation while maintaining a desirable overall thickness dimension of the concrete building panel. The insulative core 12, in combination with the FRP connector 20, provides an efficient thermal barrier due to the lack of thermally conductive materials, such as metals, often used in

conventional concrete building panels. This allows the concrete building panel 10 to be used in roof and floor applications without the additional layers of insulation that are typically required in combination with non-insulated structural members.

Suitable lightweight, insulative materials that can be used to form the insulative core 12 include, without limitation, polystyrene (e.g., extruded polystyrene, expanded polystyrene), an aliphatic polymer (e.g., extruded polypropylene), polyisocyanurate, or polyurethane. Desirably, the insulative core 12 can be pre-fabricated and installed during construction of the concrete building panel.

The insulative core 12 can be variably sized. In some embodiments, the insulative core 12 is sized such that it is shorter than the overall length of the concrete building panel 10 and thus terminates before first and second ends 70, 72 of the concrete building panel, as shown in FIG. 9. In this manner, the thickness of the first and second concrete panels 14, 16 can be increased such that the volume otherwise occupied by the insulative core 12 is instead occupied by concrete of the first and second concrete panels 14, 16. In the embodiment shown in FIG. 9, the FRP connector 20 extends through the ends 70, 72 of the concrete building panel. However, the FRP connector 20 need not extend beyond the insulative core 12, but may instead terminate at substantially the same location as the insulative core within the concrete building panel 10.

The first concrete panel 14 can comprise conventional or high-strength concrete (i.e., the compressive strength of the concrete can be greater than or equal to 5,000 psi), and can be located adjacent a top surface 22 of the insulative core 12. The first concrete panel 14 can achieve composite action with the FRP layer 18, and therefore the first concrete panel need not be reinforced (i.e., no reinforcing bar need be embedded in the first concrete panel) or pre-stressed (i.e., tensioned pre-stressing strand or cable need not be embedded in the first concrete panel). Thus, the first concrete panel can have a thickness of from about one-half inch to about five inches, depending on the application, because pre-stressing strand and reinforcing bar need not be accommodated. Desirably, the first concrete panel can have a thickness of about one inch to adequately balance the need for load-bearing strength with the need for weight reduction.

The composite action between the FRP layer and the first concrete panel thereby allows the concrete building panel to achieve the same or greater load- bearing capacity as compared to conventional building panels without the corresponding increase in weight. Additionally, the reduced thickness of the first concrete panel can lower the cost of the concrete building panel as compared to conventional building panels by reducing the quantity of concrete required. The reduced thickness of the first concrete panel can also contribute to an overall reduction in thickness of the concrete building panel, which can be critical for conforming to strict zoning requirements or other building standards for roof and floor applications. However, although the first concrete panel can achieve composite action with the FRP layer, a person of ordinary skill in the art will appreciate that the first concrete panel can comprise additional materials than those described, such as pre- stressed concrete or reinforced concrete, for additional strength.

The second concrete panel 16 can comprise conventional or high- strength concrete, as discussed above, and can be located adjacent a bottom surface 24 of the insulative core 12. The second concrete panel can comprise pre-stressed or reinforced concrete such that it can withstand the out-of-plane bending and internal shear forces associated with floor and roof applications. The second concrete panel can have a thickness of from about two inches to about five inches, depending on the application. Desirably, the second concrete panel can have a thickness of about three inches to adequately balance the need for load-bearing strength with the need for weight reduction.

The FRP layer 18 can comprise one or more woven fiber mats or sheets embedded in a polymer resin, and can be located adjacent a top surface 42 of the first concrete panel 14. Woven fiber sheets can be layered one on top of another until the desired strength properties and thickness are achieved. Suitable fibers include, for example, carbon fibers, glass fibers, or aramid fibers. In some embodiments, one or more of the woven fiber sheets can be layered such that the fibers are arranged in a particular orientation (i.e., at an angle Θ) with respect to the edge of the concrete building panel, where Θ is from zero degrees to ninety degrees. In this manner, the FRP layer 18 can be optimized for loading conditions in which a force or forces act in a particular direction on or within the concrete building panel.

Due to the desirable water resistance qualities of FRP materials, the FRP layer 18 can also act as a water or moisture barrier. When configured as the exterior-facing surface of the concrete building panel, such as, for example, when the FRP layer 18 is configured to comprise the exterior surface of a building into which the concrete building panel is incorporated, the FRP layer 18 can protect the other components of the concrete building panel from moisture-related degradation. Thus, the FRP layer 18 eliminates the need for a separate moisture barrier membrane. Elimination of the moisture barrier membrane can dramatically reduce the cost of the concrete building panel 10 over conventional building panels.

Additionally, elimination of the separate moisture barrier can reduce the overall thickness of the concrete building panel 10, which can allow it to meet strict zoning requirements and other building regulations for roof and floor applications.

The bottom surface 26 of the FRP layer 18 can include a thin layer of polymer concrete (i.e., concrete utilizing a thermosetting resin to bind the aggregate). During construction of the concrete building panel, a bonding agent can be applied to the polymer concrete before the first concrete panel 14 is cast. When the first concrete panel is cast on top of the polymer concrete, the bonding agent facilitates the forming of a bond between the first concrete panel and the polymer concrete of the FRP layer 18. In this manner, the FRP layer 18 can achieve full composite action with the first concrete panel 14 when subjected to loading. The bond between the FRP layer and the first concrete panel can also reduce the incidence of crack formation in the first concrete panel, extending the life span of the concrete building panel over conventional building panels. The FRP layer 18 can have a thickness of from about 0.05 inch to about 0.2 inch, depending upon the design load and the type of fibers used. Desirably, using glass fibers embedded in a polymer resin, the FRP layer 18 can have a thickness of about 0.1 inch.

Alternatively, the FRP layer 18 and the first concrete panel 14 may be bonded together with a bonding agent without the use of polymer concrete.

As best shown in FIGS. 1 and 3, the FRP connector 20 can comprise an elongate member 28 having a plurality of projections 30. The FRP connector 20 can comprise one or more woven fiber mats or sheets embedded in a polymer resin and arranged in a layered fashion to achieve the desired shape. Projections 30 can be separated by gaps 32 having a lateral dimension a. In the embodiment shown, the dimension a is approximately equal to a lateral dimension β of the projections 30. However, alternatively, the relationship between a and β can comprise any desired ratio. The projections 30 become continuous when a is equal to zero.

In the embodiment shown, the projections 30 can extend into the second concrete panel 16 up to or beyond a midpoint 46 of the cross-section of the second concrete panel 16. In this manner, the FRP connector 20 transfers shear forces between the FRP layer 18, the first concrete panel 14, and the second concrete panel 16. This, in turn, allows the concrete building panel to act in a composite manner when subjected to loading. Desirably, the elongate member 28 and projections 30 can be integrally fabricated from single a piece of FRP material. Alternatively, the projections 30 and elongate member 28 can be separately fabricated and joined together to create the FRP connector 20.

As shown in FIG. 3, the FRP layer 18 can be associated with a plurality of FRP connectors 20 to form a FRP shell generally indicated at 34. The plurality of FRP connectors 20 can be arrayed in a spaced-apart relationship with the elongate members 28 affixed to the bottom surface 26 of the FRP layer 18. In this manner, the FRP shell 34 can act as a form for casting the first concrete panel during construction of the concrete building panel 10. The FRP connectors 20 can be arrayed as desired. In the embodiment shown, the FRP connectors 20 are arrayed in a generally parallel fashion along the length of the FRP layer 18. A lip portion 36 of the FRP layer 18 can overhang the outermost FRP connector 20 on each side of the FRP layer such that the projections 30 are not exposed at the sides of the concrete building panel. Alternatively, the FRP connectors can be arrayed in a perpendicular or criss-crossed fashion such that the projections 28 of respective FRP connectors are oriented at an angle relative to one another, such as at an angle ninety degrees from one another.

In some embodiments, the FRP connectors 20 can comprise one or more reinforcement holes 56 and/or one or more flow-promoting holes 58, as shown in FIG. 10. The reinforcement holes 56 can be located as desired, such as near tops 74 of the projections 30. Reinforcement bar or pre-stressing strand can be placed through the reinforcement holes 56 to tie multiple FRP connectors 20 together to strengthen the second concrete panel. The flow-promoting holes 58 can be located near or in the elongate member 28 such that concrete poured around the FRP connector 20 can flow through the flow-promoting holes 58 when fabricating the first concrete panel 14 and help prevent formation of voids.

Alternatively, the concrete building panel 10 can comprise the FRP shell 60 of FIG. 11. The FRP shell 60 comprises an FRP layer 18 and a plurality of FRP connectors 62 associated with the FRP layer 18 having elongate members 64 and projections 66. As shown in FIG. 11, the projections 66 are attached to the FRP layer 18 and the elongate members 64 are located above the FRP layer 18 a distance δ. The tops 68 of the projections 66 are a distance γ above the elongate members 64. Together, δ and γ define a height dimension of the elongate members 64. In the embodiment shown, the ratio γ / δ is about 0.7, although any suitable ratio may be used. In a manner similar to the FRP shell of FIG. 10, the FRP connectors 62 can comprise reinforcement holes 56 and flow-promoting holes 58. The reinforcement holes 56 can be located near the tops 68 of the projections 64, and reinforcement bar or pre-stressing strand can be placed through the reinforcement holes 56 to tie multiple FRP connectors 62 together to strengthen the second concrete panel. The flow-promoting holes 58 can be located near the FRP layer 18 such that concrete poured around the FRP connectors 62 can flow through the flow-promoting holes 58 when fabricating the first concrete panel 14 and help prevent formation of voids. The projections 66 can extend into the second concrete panel 16 in the manner of FRP shell 34. In this manner, the FRP connectors 62 transfer shear forces between the FRP layer 18, the first concrete panel 14, and the second concrete panel 16.

In an alternative embodiment of the concrete building panel 10, a second FRP layer 38 can be associated with the second concrete panel 16 as shown in FIG. 2. The second FRP layer 38 can comprise one or more woven fiber mats or sheets embedded in a polymer resin. In a manner similar to the first concrete panel 14 and the first FRP layer 18, the second FRP layer 38 can be bonded to a bottom surface 40 of the second concrete panel using a bonding agent. In this manner, the second FRP layer 38 can contribute additional strength to the concrete building panel and can promote the composite action of its components. FIG. 4 illustrates another embodiment of a concrete building panel 100 comprising an insulative core 12, first and second concrete panels 14, 16, a FRP layer 18, and a FRP connector 102. The insulative core 12 can act to thermally and/or acoustically insulate the concrete building panel, and can have, but need not necessarily have, the same properties and construction as the insulative core described with respect to the concrete building panel of FIG. 1. The first concrete panel 14 can be located adjacent a top surface 22 of the insulative core 12, and the second concrete panel 16 can be located adjacent a bottom surface 24 of the insulative core 12. The first and second concrete panels 14, 16 can, but need not necessarily, have the same properties and construction as the first and second concrete panels described with respect to the concrete building panel of FIG. 1. The FRP layer 18 can comprise one or more woven fiber mats or sheets embedded in a polymer resin. The FRP connector 102 can comprise a plurality of elongated FRP members 104 arranged to form a grid structure, as exemplified by FIG. 4. The FRP members 104 can be embedded in both the first and second concrete panels and can extend through the insulative core such that end points 106 extend up to or past midpoints 44, 46 of the cross-sections of the first and second concrete panels, as shown in FIG. 4. Desirably, the FRP connector 102 can comprise a plurality of grid structures arranged within the concrete building panel in a spaced-apart relationship.

Desirably, the FRP members 104 can be embedded in the first concrete panel

14 such that they extend beyond the midpoint 44 of the thickness of the first concrete panel 14 without reaching the top surface 42 of the first concrete panel 14. Similarly, the FRP members 104 can be embedded in the second concrete panel 16 such that they extend beyond the midpoint 46 of the thickness of the second concrete panel 16 but do not reach the bottom surface 40. In this manner, the plurality of FRP members transfer shear stress between the FRP layer 18, first concrete panel 14, and second concrete panel 16, thereby contributing to the composite action of the concrete building panel 100. Alternatively, the concrete building panel 100 can comprise an additional FRP layer (not shown) associated with the second concrete panel 106 in the manner of the concrete building panel of FIG. 2. FIGS. 5 A and 5B illustrate another embodiment of a concrete building panel 200 comprising an insulative core 12, first and second concrete panels 14, 16, a FRP layer 18, and a FRP connector 202. The insulative core 12, the first and second concrete panels 14, 16, and the FRP layer 18 can comprise substantially the same properties and construction as described with respect to the concrete building panel of FIG. 1. The FRP connector 202 can comprise one or more elongated FRP members 204 configured to have curves 206 generally in the shape of a sinusoid or saw tooth. As shown in FIG. 5A, the one or more elongated FRP members 204 can be oriented such that the curves 206 propagate through the concrete building panel in a direction substantially parallel to a top surface 50 of the concrete building panel 200. The one or more elongated FRP members 204 can be embedded in the concrete building panel such that the one or more elongated FRP members 204 are embedded in the first and second concrete panels 14, 16 and extend through the insulative core 12. Desirably, the one or more elongated FRP members 204 can be configured such that apexes 208 of the curves 206 extend up to or beyond midpoints 44, 46 of the first and second concrete panels 14, 16, respectively. In this manner, the FRP connector 202 transfers shear stresses between the FRP layer 18, first concrete panel 14, and second concrete panel 16, thereby contributing to the composite action of the concrete building panel. Desirably, the one or more elongated FRP members 204 can be arranged in a spaced-apart relationship.

Alternatively, the one or more elongated FRP members 204 can be arranged such that the curves 206 propagate in a direction substantially perpendicular to the top surface 50 of the concrete building panel, as shown in FIG. 5B. In the illustrated perpendicular orientation, the elongated FRP members 204 can be configured such that endpoints 210 of the elongated FRP members 204 extend up to or beyond the midpoints 44, 46 of the first and second concrete panels 14, 16, respectively. In this manner, the elongated FRP members 204 can transfer shear stresses between the FRP layer 18, the first concrete panel 14, and the second concrete panel 16 in the manner described above. In yet another alternative embodiment of the concrete building panel, the FRP connector can be omitted entirely, as shown in FIG. 6. Turning now to methods of making a concrete building panel, the concrete building panel described herein lends itself to fast, efficient, low-cost construction. The first and second concrete panels can be cast in a controlled environment to help ensure structural quality, and the completed concrete building panel or panels can be transported to a job site with less labor than is required to make an in-situ roof or floor. A FRP layer 18 can be associated with a formwork 52 having a bed 54, shown in FIG. 7, such that the bottom surface 26 (FIG. 1) of the FRP layer 18 is exposed. Desirably, the FRP layer 18 can be pre-fabricated such that it is fully formed and cured at the time of concrete building panel fabrication. Once the FRP layer 18 is associated with the bed 54 of the formwork 52, the bottom surface 26 of the FRP layer 18 can be prepped by applying a bonding agent to the bottom surface 26. Once the bottom surface 26 is prepped, the first concrete panel 14 can be cast by pouring a concrete mixture or slurry on top of the FRP layer 18 to an appropriate thickness. The bonding agent causes the FRP layer 18 to form a bond with the concrete mixture of the first concrete layer 14, in turn causing the FRP layer 18 and the first concrete panel 14 to act in a composite manner when subjected to loading, as discussed above. In alternative embodiments, the bottom surface 26 of the FRP layer 18 can be treated with a layer of polymer concrete to which the bonding agent is applied before casting of the first concrete panel 14. Additionally, because the FRP layer 18 and the first concrete panel 14 can be bonded to one another during fabrication, the FRP layer 18 can act as the form for the top surface 42 of the first concrete panel, eliminating the need for concrete stripping once the concrete building panel is complete.

With respect to the embodiment of FIG. 1, in which the FRP layer 18 comprises a plurality of FRP connectors to form an FRP shell, such as the FRP shells 34 or 60 of FIGS. 6, 10 or 11, respectively, an independent FRP connector installation step is not required. However, with respect to the embodiments of FIGS. 4, 5A and 5B, the FRP connectors 102 and 202, respectively, can be installed in the following manner. Once the concrete mixture for the first concrete panel 14 has been cast but before the concrete mixture has been allowed to cure, the respective FRP connectors 102, 202 can be installed. More specifically, with respect to the embodiment of FIG. 4, the FRP connectors 102 can be inserted into the concrete slurry a distance such that the endpoints 106 of the elongated FRP members 104 can extend up to or beyond the midpoint 44 of the cross-section of the first concrete panel 14. Similarly, with respect to the one or more elongated FRP members 204 of FIGS. 5 A and 5B, the elongated FRP members 204 can be inserted into the concrete slurry a distance such that the apexes 208 or endpoints 210, respectively, extend up to or beyond the midpoint 44 of the first concrete panel 14.

Once the FRP connectors are installed, the insulative core 12 can be installed adjacent a bottom surface 48 of the first concrete panel 14. The insulative core can be pre-fabricated, and can be installed such that the FRP connector extends through the entirety of the cross-section of the insulative core 12. With the insulative core in place, pre-stressing strand or cable can be installed in the formwork 52 and tensioned. A concrete mixture or slurry may then be poured on top of the insulative core to cast the second concrete panel 16 such that the pre-stressing strand is embedded within the second concrete panel. After the second concrete panel has reached the required release strength (i.e., the concrete has attained sufficient compressive strength such that the tension of the pre-stressing strand may be released), the pre-stressing strand may be cut or released, placing the second concrete panel into a pre-stressed state. Alternatively, reinforcing bar can be placed in the formwork 52 and the concrete mixture can be poured such that the reinforcing bar is embedded within the second concrete panel. Once the second concrete panel has cured or hardened, the completed concrete building panel can be removed from the formwork 52.

Turning now to methods of constructing a building incorporating a concrete building panel, one or more completed concrete building panels 10 can be associated with a plurality of wall structures 56 to form a roof structure or a floor structure in a building 58, as shown in FIG. 8. In multi-story buildings, the concrete building panels described herein can be incorporated into the floor of each story. The concrete building panels described herein can also be useful for special roof applications, such as roofs supporting vegetation, or "green roofs." The concrete building panels described herein can be particularly well-suited for the high loads and moisture associated with green roofs because of the bending strength imparted by the composite action of the concrete building panel and the water resistance characteristics of the FRP layer 18.

The following examples are provided to illustrate certain features of working embodiments. A person of ordinary skill in the art will appreciate that the scope of the present invention is not limited to the scope of the features exemplified by these examples.

Example 1

In a first working example, a first concrete building panel having an overall length of approximately nine feet and an overall width of approximately two feet was constructed and loaded to failure in a three-point bending test. The overall thickness of the first concrete building panel was about ten inches, wherein the FRP layer had a thickness of about 0.085 inch, the first concrete panel had a thickness of about three inches, the insulative core had a thickness of about four inches, and the second concrete panel had a thickness of about three inches. The second concrete panel was reinforced with two #5 (5/8 inch) longitudinal reinforcement bars and #4 (1/2 inch) transverse reinforcement bars placed at intervals of 18 inches as measured from the centers of the reinforcement bars (i.e, "18 inches on center"). The insulative core was made from expanded polystyrene. The first concrete building panel was fabricated to include a solid concrete zone twelve inches in length at each end of the first concrete building panel (i.e., the insulative core terminated twelve inches from each end of the first concrete building panel and the volume otherwise occupied by the insulative core was occupied by concrete). The concrete from which the first and second concrete panels were fabricated reached a compressive strength of 4,000 psi after curing for 28 days. The first concrete building panel was fabricated with the FRP connector of FIG. 11.

The first concrete building panel was placed on a strong floor and supported with pin and roller supports (i.e., one end of the first concrete building panel was supported by a cylindrical roller and the other end was supported by a steel pad). Sensor elements, including strain gages and linear transducers, were placed on and within the first concrete building panel, and a load was applied to the center of the first concrete building panel by a hydraulic press. The loading sequence proceeded in load increments of one thousand pounds. A load reduction of about 150 pounds was experienced prior to each load increase as the hydraulic press relaxed. At each incremental load, crack formation and propagation in the first concrete building panel was measured. Deflection of the first concrete building panel was measured by the strain gages at a sample rate of 10 Hz. The incremental loading sequence continued until the first concrete building panel failed.

The data from the first working example are plotted in the load-displacement curve of FIG. 12 as "FRP Connector 1." The data establishes that the first concrete building panel was displaced approximately one inch under a load of approximately 15,000 pounds, and failed at a load of approximately 15,300 pounds.

Example 2

In a second working example, a second concrete building panel having an overall length of approximately nine feet and an overall width of approximately two feet was constructed and loaded to failure in a three-point bending test. The overall thickness of the second concrete building panel was about ten inches, wherein the FRP layer had a thickness of about 0.085 inch, the first concrete panel had a thickness of about three inches, the insulative core had a thickness of about four inches, and the second concrete panel had a thickness of about three inches. The second concrete panel was reinforced with two #5 (5/8 inch) longitudinal reinforcement bars and #4 (1/2 inch) transverse reinforcement bars placed at intervals of 18 inches as measured from the centers of the reinforcement bars (i.e, "18 inches on center."). The insulative core was made from expanded polystyrene. The second concrete building panel was fabricated to include a twelve-inch solid concrete zone at each end of the second concrete building panel (i.e., the insulative core terminated twelve inches from each end of the concrete building panel and the volume otherwise occupied by the insulative core was occupied by concrete). The concrete from which the first and second concrete panels were fabricated reached a compressive strength of 4,000 psi after curing for 28 days. The second concrete building panel was fabricated with the FRP connector of FIG. 10.

The second concrete building panel was placed on a strong floor and supported with pin and roller supports (i.e., one end of the concrete building panel was supported by a cylindrical roller and the other end was supported by a steel pad). Sensor elements, including strain gages and linear transducers, were placed on and within the second concrete building panel, and a load was applied to the center of the second concrete building panel by a hydraulic press. The loading sequence proceeded in load increments of one thousand pounds. A load reduction of about 150 pounds was experienced prior to each load increase the hydraulic press relaxed. At each incremental load, crack formation and propagation in the second concrete building panel was measured. Deflection of the second concrete building panel was measured by the strain gages at a sample rate of 10 Hz. The incremental loading sequence continued until the second concrete building panel failed.

The data of the second working example are plotted in the load-displacement curve of FIG. 12 as "FRP Connector 2." The data establish that the second concrete building panel was displaced approximately one inch under a load of approximately 12,600 pounds, and failed at a load of approximately 12,800 pounds.

In view of the many possible embodiments to which the principles of the disclosed invention may be applied, a person of ordinary skill in the art will recognize that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims.

Claims

We claim:

1. A concrete building panel, comprising:

a first concrete panel and a second concrete panel associated with an insulative core;

a fiber-reinforced polymer connector embedded in the first and second concrete panels and extending through the insulative core; and

at least one fiber-reinforced polymer layer comprising one or more exterior surfaces of the concrete building panel.

2. The concrete building panel of claim 1, wherein a bottom surface of the fiber-reinforced polymer layer and a top surface of the first concrete panel are bonded to one another.

3. The concrete building panel of claim 2, wherein the bottom surface of the fiber-reinforced polymer layer and the top surface of the first concrete panel are bonded to one another with polymer concrete.

4. The concrete building panel of claim 1, wherein the second concrete panel is pre-stressed concrete.

5. The concrete building panel of claim 1, wherein the second concrete panel is reinforced concrete.

6. The concrete building panel of claim 1, wherein the fiber-reinforced polymer layer comprises interwoven fibers.

7. The concrete building panel of claim 6, wherein the interwoven fibers of the fiber-reinforced polymer layer comprise at least one of carbon fibers, glass fibers, or aramid fibers.

8. The concrete building panel of claim 1, wherein the fiber-reinforced polymer layer comprises a plurality of sheets of interwoven fibers arranged one on top of another.

9. The concrete building panel of claim 8, wherein the fibers are oriented in a predetermined orientation.

10. The concrete building panel of claim 1, wherein the fiber-reinforced polymer connector comprises a plurality of fiber-reinforced polymer members arranged to form a grid.

11. The concrete building panel of claim 1, wherein the fiber-reinforced polymer connector comprises an elongate member having a plurality of projections extending from the elongate member.

12. The concrete building panel of claim 11, wherein the projections extend upwardly from the elongate member.

13. The concrete building panel of claim 11, wherein the projections extend upwardly and downwardly from the elongate member.

14. The concrete building panel of claim 11, wherein the projections of the elongate members are separated by gaps.

15. The concrete building panel of claim 14, wherein the gaps are approximately equal to a lateral dimension of the projections.

16. The concrete building panel of claim 11, wherein the projections comprise one or more holes for positioning of pre-stressing strands or reinforcement bars.

17. The concrete building panel of claim 11, wherein the projections comprise one or more holes to promote a flow of concrete around the projections when making the concrete building panel.

18. The concrete building panel of claim 1, wherein the fiber-reinforced polymer connector comprises one or more elongated members having curves.

19. The concrete building panel of claim 18, wherein the curves propagate in a direction substantially parallel to a top surface of the building panel.

20. The concrete building panel of claim 18, wherein the curves are generally in the shape of a sinusoid.

21. The concrete building panel of claim 18, wherein the curves are generally in the shape of a saw tooth.

22. The concrete building panel of claim 1, wherein the first concrete panel has a thickness of from about 0.5 inch to about five inches.

23. The concrete building panel of claim 22, wherein the first concrete panel has a thickness of about one inch.

24. The concrete building panel of claim 1, wherein the second concrete panel has a thickness of from about three inches to about five inches.

25. The concrete building panel of claim 24, wherein the second concrete panel has a thickness of about three inches.

26. The concrete building panel of claim 1, wherein the insulative core has a thickness of from about two inches to about six inches.

27. The concrete building panel of claim 26, wherein the insulative core has a thickness of about four inches.

28. The concrete building panel of claim 1, wherein the fiber-reinforced polymer layer has a thickness of from about 0.05 inch to about 0.2 inch.

29. The concrete building panel of claim 28, wherein the fiber-reinforced polymer layer has a thickness of about 0.1 inch.

30. The concrete building panel of claim 1, wherein the insulative core comprises polystyrene.

31. The concrete building panel of claim 30, wherein the polystyrene comprises extruded polystyrene.

32. The concrete building panel of claim 30, wherein the polystyrene comprises expanded polystyrene.

33. The concrete building panel of claim 1, wherein the insulative core comprises an aliphatic polymer.

34. The concrete building panel of claim 33, wherein the aliphatic polymer comprises polypropylene.

35. The concrete building panel of claim 1, wherein a length of the insulative core is less than an overall length of the concrete building panel.

36. A method of making a concrete building panel, comprising:

associating a fiber-reinforced polymer layer with a formwork;

applying a bonding agent to the fiber-reinforced polymer layer;

casting a first concrete panel on top of the fiber-reinforced polymer layer; installing one or more connectors;

installing an insulative core;

installing one or more pre-stressing strands or reinforcement bars above the insulative core; and

casting a second concrete panel on top of the insulative core such that the pre-stressing strands or reinforcement bars are embedded within the second concrete panel.

37. The method of claim 36, wherein the bonding agent forms a bond between the fiber-reinforced polymer layer and the first concrete panel.

38. The method of claim 36, wherein the fiber-reinforced polymer layer comprises a layer of polymer concrete to which the bonding agent is applied.

39. The method of claim 38, wherein the polymer concrete and the bonding agent form a bond between the fiber-reinforced polymer layer and the first concrete panel.

40. The method of claim 36, wherein the fiber-reinforced polymer layer comprises at least one of carbon fibers, glass fibers, or aramid fibers embedded in a polymer resin.

41. The method of claim 36, wherein the first concrete panel is cast to a thickness of from about 0.5 inch to about five inches.

42. The method of claim 41, wherein the first concrete panel is cast to a thickness of about one inch.

43. The method of claim 36, wherein the second concrete panel is cast to a thickness of from about three inches to about five inches.

44. The method of claim 43, wherein the second concrete panel is cast to a thickness of about three inches.

45. The method of claim 36, wherein the insulative core has a thickness of from about two inches to about six inches.

46. The method of claim 45, wherein the insulative core has a thickness of about four inches.

47. The method of claim 36, wherein the insulative core comprises polystyrene.

48. The method of claim 47, wherein the polystyrene comprises expanded polystyrene.

49. The method of claim 47, wherein the polystyrene comprises extruded polystyrene.

50. The method of claim 36, wherein the insulative core comprises an aliphatic polymer.

51. The method of claim 50, wherein the aliphatic polymer comprises polypropylene.

52. The method of claim 36, wherein the one or more connectors comprise a plurality of fiber-reinforced polymer members arranged to form a grid.

53. The method of claim 36, wherein the one or more connectors comprise elongate members and a plurality of projections extending from the elongate members.

54. The method of claim 53, wherein the projections extend upwardly from the elongate member.

55. The method of claim 53, wherein the projections extend upwardly and downwardly from the elongate member.

56. The method of claim 53, wherein the projections comprise one or more holes for positioning of pre-stressing strands or reinforcement bars.

57. The method of claim 53, wherein the projections comprise one or more holes to promote a flow of concrete around the projections when making the concrete building panel.

58. The method of claim 53, wherein the projections of the elongate members are separated by gaps.

59. The method of claim 58, wherein the gaps are approximately equal to a lateral dimension of the projections.

60. The method of claim 36, wherein the one or more connectors comprise elongate members having curves.

61. The method of claim 60, wherein the curves propagate in a direction substantially parallel to a top surface of the building panel.

62. The method of claim 60, wherein the curves are generally in the shape of a sinusoid.

63. The method of claim 60, wherein the curves are generally in the shape of a saw tooth.

64. The method of claim 36, wherein the one or more connectors comprise fiber-reinforced polymer connectors.

65. The method of claim 36, wherein the one or more connectors are pre- installed on the fiber-reinforced polymer layer before the fiber-reinforced polymer layer is associated with the formwork.

66. The method of claim 36, wherein a length of the insulative core is less than an overall length of the concrete building panel.

67. A structure having a plurality of walls and a transverse element, the transverse element comprising:

an insulative core;

a first concrete panel;

a second concrete panel;

a fiber-reinforced polymer connector; and

one or more fiber-reinforced polymer layers comprising one or more surfaces of the transverse element.

68. The structure of claim 67, wherein the transverse element is a roof.

69. The structure of claim 67, wherein the transverse element is a floor.

70. The structure of claim 67, wherein the first concrete panel is adjacent a top surface of the insulative core and the second concrete panel is adjacent a bottom surface of the insulative core.

71. The structure of claim 70, wherein the one or more fiber-reinforced polymer layers are adjacent a top surface of the first concrete panel.

72. The structure of claim 72, wherein the one or more fiber-reinforced polymer layers are bonded to the top surface of the first concrete panel.

73. The structure of claim 67, wherein the second concrete panel is pre- stressed or reinforced concrete.

74. The structure of claim 67, wherein the fibers of the one or more fiber- reinforced polymer layers comprise at least one of carbon fibers, glass fibers, or aramid fibers.

75. The structure of claim 67, wherein the fiber-reinforced polymer connector is embedded in the first and second concrete panels and extends through the insulative core.

76. The structure of claim 67, wherein the fiber-reinforced polymer connector comprises a plurality of fiber-reinforced polymer members arranged to form a grid.

77. The structure of claim 67, wherein the fiber-reinforced polymer connector comprises an elongate member having a plurality of projections extending from the elongate member.

78. The structure of claim 77, wherein the projections extend upwardly from the elongate member.

79. The structure of claim 77, wherein the projections extend upwardly and downwardly from the elongate member.

80. The structure of claim 77, wherein the projections comprise one or more holes for positioning of pre-stressing strands or reinforcement bars.

81. The structure of claim 77, wherein the projections comprise one or more holes to promote a flow of concrete around the projections when making the transverse element.

82. The structure of claim 77, wherein the projections of the elongate members are separated by gaps.

83. The structure of claim 82, wherein the gaps are approximately equal to a lateral dimension of the projections.

84. The structure of claim 67, wherein the fiber-reinforced polymer connector comprises one or more elongated members having curves.

85. The structure of claim 84, wherein the curves propagate in a direction substantially parallel to a top surface of the transverse element.

86. The structure of claim 84, wherein the curves are generally in the shape of a sinusoid.

87. The structure of claim 84, wherein the curves are generally in the shape of a saw tooth.

88. The structure of claim 67, wherein the insulative core comprises polystyrene.

89. The structure of claim 88, wherein the polystyrene comprises extruded polystyrene.

90. The structure of claim 88, wherein the polystyrene comprises expanded polystyrene.

91. The structure of claim 67, wherein the insulative core comprises an aliphatic polymer.

92. The structure of claim 91, wherein the aliphatic polymer comprises polypropylene.

93. The structure of claim 67, wherein the first concrete panel has a thickness of from about 0.5 inch to about five inches.

94. The structure of claim 93, wherein the first concrete panel has a thickness of about one inch.

95. The structure of claim 67, wherein the second concrete panel has a thickness of from about two inches to about five inches.

96. The structure of claim 95, wherein the second concrete panel has a thickness of about three inches.

97. The structure of claim 67, wherein the fiber-reinforced polymer layer has a thickness of from about 0.05 inch to about 0.2 inch.

98. The structure of claim 97, wherein the fiber-reinforced polymer layer has a thickness of about 0.1 inch.

99. The structure of claim 67, wherein a length of the insulative core is less than an overall length of the transverse element.

100. A method of making a structure, comprising:

associating a concrete building panel with a plurality of wall structures, the plurality of wall structures being oriented vertically, the concrete building panel being oriented in a transverse manner adjacent the plurality of wall structures; wherein the concrete building panel comprises an insulative core, a first concrete panel, a second concrete panel, a fiber-reinforced polymer connector, and a fiber-reinforced polymer layer.

101. A building panel, comprising:

an insulative core having a top surface and a bottom surface, the top surface and the bottom surface being substantially parallel;

a first concrete panel having a top surface and a bottom surface, the top surface and the bottom surface being substantially parallel, the bottom surface of the first concrete panel being adjacent the top surface of the insulative core;

a second concrete panel having a top surface and a bottom surface, the top surface and the bottom surface being substantially parallel, the top surface of the second concrete panel being adjacent the bottom surface of the insulative core; one or more connectors embedded in the first and second concrete panels and extending through the insulative core, the one or more connectors offset from one another at intervals, the one or more connectors oriented substantially perpendicular to the top and bottom surfaces of the first and second concrete panels; and

a fiber-reinforced polymer layer comprising at least one sheet of interwoven fibers embedded in a polymer resin, the fiber-reinforced polymer layer having a top surface and a bottom surface, the top surface and the bottom surface being substantially parallel, the bottom surface of the fiber-reinforced polymer layer being adjacent the top surface of the first concrete panel, the bottom surface of the fiber- reinforced polymer layer being bonded to the top surface of the first concrete panel such that the fiber-reinforced polymer layer and the first concrete panel act in a composite manner when subjected to shear loads and bending loads.

102. A method of making a building panel, comprising:

associating a fiber-reinforced polymer layer with a formwork having a bed, the fiber-reinforced polymer layer having a top surface and a bottom surface;

positioning the fiber-reinforced polymer layer on the bed of the formwork such that the bottom surface faces upward; applying a bonding agent to the bottom surface of the fiber-reinforced polymer layer;

casting a first concrete panel on top of the bottom surface of the fiber- reinforced polymer layer, the first concrete panel having a top surface and a bottom surface, the first concrete panel being cast such that the top surface of the first concrete panel bonds to the bottom surface of the fiber-reinforced polymer layer as the first concrete panel cures;

installing one or more fiber-reinforced polymer connectors such that the one or more fiber-reinforced polymer connectors are embedded in the first concrete panel and extend upward from the first concrete panel in an orientation

perpendicular to the bottom surface of the first concrete panel;

installing a low-density insulative core having a top surface and a bottom surface such that the top surface of the insulative core is adjacent the bottom surface of the first concrete panel, the one or more fiber-reinforced polymer connectors extending through the insulative core;

installing a plurality of pre-stressing strands or reinforcement bars above the insulative core; and

casting a second concrete panel on top of the bottom surface of the insulative core such that the plurality of pre-stressing strands or reinforcement bars are embedded within the second concrete panel, the one or more fiber-reinforced polymer connectors being embedded in the second concrete panel.