This application is related to U.S. patent application Ser. No. 14/016,998 filed on Sep. 3, 2013, U.S. patent application Ser. No. 13/187,311 filed on Jul. 20, 2011 (now U.S. Pat. No. 8,549,813), and U.S. patent application Ser. No. 12/959,912 filed on Dec. 3, 2010 (now U.S. Pat. No. 8,220,219). These patents and patent applications are also hereby incorporated by reference in their entirety.
This disclosure relates generally to reinforcing structures. More specifically, this disclosure relates to reinforcing assemblies having downwardly-extending working members on structurally reinforcing bars for concrete slabs or other structures.
Commercial concrete is a mixture of cement, sand, and stone aggregate that, after the addition of water, slowly hardens together into a rigid structure. Stresses within concrete structures are typically of three primary types: compressive (where particles are crushed together), tensile (where particles are pulled apart), and shear (where one section of a structure is pressured to slide upon an adjacent section).
Unreinforced concrete structures often have good resistance to compressive stresses. However, any significant tensile stresses tend to cause undesirable cracking and separation since concrete is relatively weak in tension. To address this problem, concrete structures are typically reinforced by embedding smaller solid members made of material(s) with high strength in tension. Typically, the smaller members include round steel bars with roughened surfaces, often called “reinforcing steel,” “reinforcing bar,” or “rebar.” Reinforced concrete structures are available commercially in many shapes and sizes, such as slabs, beams, footings, and flat foundations.
Unfortunately, in some concrete structures shear forces can be concentrated, and a condition called “diagonal tension” is created. When a flat concrete slab (such as a concrete floor slab) is suspended and supported by columns (usually of concrete), the weight of the slab and the load that the slab supports are transferred to the columns through relatively small zones of concrete surrounding the columns. Each of these zones is subject to (i) vertical shear forces resulting from the weight and load of the slab and (ii) internal horizontal shear stress resulting from high bending moments in that area. The combination of high vertical shear stress and high horizontal shear stress creates diagonal tension stress in areas around the columns. Diagonal tension stress is problematic because concrete is particularly weak in tension and the diagonal orientation of potential crack zones makes it difficult for typical rebar installation patterns to work effectively. Also, the relatively thin vertical dimension of the concrete slab can limit the length of rebar that can be used, further reducing its effectiveness.
For this reason, supported concrete structures are typically reinforced in the areas around columns or other supporting structures using short smooth vertical steel studs to provide reinforcement. This is done to prevent tensile failure, crack propagation, and consequent structural collapse. However, conventional approaches often provide reinforcement that helps restrain or minimize cracking or breaking only after the cracking or breaking has been initiated. These conventional approaches are typically unable to prevent cracking or breaking from occurring in the first instance. As a result, the concrete and steel studs generally operate sequentially rather than together. That is, the concrete carries much of the load until cracks occur, at which point significantly all of the load is transferred to the steel studs in the cracked area(s) of the concrete.
This disclosure provides reinforcing assemblies having downwardly-extending working members on structurally reinforcing bars for concrete slabs or other structures.
In a first aspect, a reinforcing assembly includes multiple longitudinally-extending support bars that are connected together. The reinforcing assembly also includes multiple working members each independently connected to one or more of the support bars. The working members are oriented diagonally with respect to a longitudinal axis extending along the support bars. Each working member includes a downwardly-extending side and a hooked or bent portion at an end of the downwardly-extending side.
Particular embodiments of the first aspect could have the following features, individually or in any suitable combination. The hooked or bent portions of at least some adjacent working members could be hooked or bent in opposite directions. The downwardly-extending sides of all working members could be substantially parallel with each other when the reinforcing assembly is viewed from a side. Each support bar could include a section that is bent and that is configured to be anchored within a supporting structure. Each support bar could be coupled to a structure that is configured to be anchored within a supporting structure. At least some of the working members could be spaced a variable distance apart. The hooked or bent portion of each working member could include a portion of the downwardly-extending side that is bent by at least 45°. The support bars could be connected to each other only at locations where the working members are connected to the support bars. The working members could be spaced apart such that the working members overlap in a side view of the reinforcing assembly, where the side view denotes a view in which the support bars extend left to right and the working members extend downward from the support bars. Each of the support bars and the working members could include one of: rebar and a threaded rod or bar. The support bars could be configured to engage bending moment tensile stresses in a supported structure, and the working members could be configured to extend down into a central portion of the supported structure to engage diagonal tension stresses.
A reinforced structure includes a supported structure and a reinforcing assembly embedded within the supported structure. The reinforcing assembly includes the apparatus in accordance with the first aspect. The supported structure could be a concrete or other slab that is supported by a concrete or other column.
A method includes forming a supported structure having a reinforcing assembly positioned within the supported structure. The reinforcing assembly includes the apparatus in accordance with the first aspect. The supported structure could be a concrete or other slab that is supported by a concrete or other column.
In a second aspect, a reinforcing assembly includes one or more longitudinally-extending bars, where each bar is configured to provide structural reinforcement within a structure. The reinforcing assembly also includes multiple working members each independently connected to at least one of the one or more bars. The working members are oriented diagonally with respect to a longitudinal axis extending along the one or more bars. Each working member includes a downwardly-extending side and a hooked or bent portion at an end of the downwardly-extending side.
Particular embodiments of the second aspect could have the following features, individually or in any suitable combination. The one or more longitudinally-extending bars could include multiple longitudinally-extending bars connected together. The multiple bars could be connected to each other only at locations where the working members are connected to the bars. The working members could include first and second sets of working members located on different portions of the one or more bars, and the working members in the first set could be angled in a different direction from the working members in the second set. The hooked or bent portions of at least some adjacent working members could be hooked or bent in opposite directions. At least some of the working members could be spaced a variable distance apart. The hooked or bent portion of each working member could include a portion of the downwardly-extending side that is bent by at least 45°. The working members could overlap one another in a side view of the reinforcing assembly, where the side view denotes a view in which the one or more bars extend left to right and the working members extend downward from the one or more bars. The one or more bars could include one or more negative moment reinforcing bars. Each of the one or more bars and the working members could include one of: rebar and a threaded rod or bar. The one or more bars could be configured to engage bending moment tensile stresses in a supported structure, and the working members could be configured to extend down into a central portion of the supported structure to engage diagonal tension stresses.
A reinforced structure includes a supported structure and a reinforcing assembly embedded within the supported structure. The reinforcing assembly includes the apparatus in accordance with the second aspect. The supported structure could be a concrete or other slab that is supported by a concrete or other column.
A method includes forming a supported structure having a reinforcing assembly positioned within the supported structure. The reinforcing assembly includes the apparatus in accordance with the second aspect. The supported structure could be a concrete or other slab that is supported by a concrete or other column.
Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.
For a more complete understanding of this disclosure and its features, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:
For simplicity and clarity, some features and components are not explicitly shown in every figure, including those illustrated in connection with other figures. It will be understood that all features illustrated in the figures may be employed in any of the embodiments described in this patent document. Omission of a feature or component from a particular figure is for purposes of simplicity and clarity and not meant to imply that the feature or component cannot be employed in the embodiment(s) described in connection with that figure.
The slab structure 101 typically includes internal structural components that provide reinforcement. These internal components can represent any suitable structure(s) formed from any suitable material(s), such as reinforcing bar (“rebar”) 103 formed of carbon steel or other material(s). The rebar 103 can be placed down the length of the slab structure 101 and/or across the width of the slab structure 101 and is generally placed in the vicinity of the support column 102. In some embodiments, the rebar 103 extends across the top of the slab structure 101 (into and out of the view as shown), as well as across the bottom of the slab structure 101. However, both may not be needed, such as when rebar 103 is used across only the top of the slab structure 101.
In this example, a load or “reaction” area 104 of the slab structure 101 represents an area where large upward forces can exist, creating punching shear stresses in the slab structure 101. Here, the punching shear stresses are creating undesirable diagonal tension cracks 105 in the slab structure 101. The cracks 105 can form particularly in areas of high stress of the slab structure 101. Many times, the cracks 105 can form generally in the middle area of the slab structure 101 and can propagate upward and downward, often in a diagonal direction, if not impeded. As described in more detail below, various reinforcing assemblies are disclosed here that can help to reduce or even eliminate the formation of cracks caused by shear forces in a slab structure 101 or other similarly supported structure.
Although
As shown in
Multiple working members 204 are independently connected to the support bars 202. Each working member 204 here denotes a structure that is connected to the support bars 202, such as via structural welding, and that extends downward and away from the support bars 202. Each of the working members 204 could have any suitable cross-sectional shape, and each of the working members 204 could be formed from any suitable material(s), such as rebar. In some embodiments, each of the working members 204 is formed using #3 rebar. The working members 204 could have ribbed, knurled, or other roughened surfaces along their entire lengths.
In some embodiments, the support bars 202 are welded together (side-to-side) only at the points where the working members 204 are connected to the support bars 202, although other approaches could also be used. Moreover, in some instances, the entire reinforcing assembly 200 can be fabricated using only rebar (possibly only two sizes of rebar) with welded connections.
As shown in
The hooked end portion 208 denotes a portion of the downwardly-extending side 206 that is bent back. In this example, the hooked end portion 208 is bent by at least 180°, although any suitable amount of bend could be used to form the hooked end portion 208 (such as at least 90°, at least 225°, or at least 270°). Also, the hooked end portion 208 may or may not be curved along its entire length. In
The hooked end portions 208 of adjacent working members 204 can hook in alternate or opposite directions. In
The downwardly-extending side 206 of each working member 204 could have any suitable length, and the hooked end portion 208 of each working member 204 could have any suitable size and radius of curvature. In some embodiments, the hooked end portion 208 of each working member 204 has a radius of curvature of about one inch. Note that in this example, the downwardly-extending side 206 and the hooked end portion 208 of each working member 204 form a substantially planar working member 204, although this need not be the case.
As shown in
In some embodiments, the working members 204 are positioned so that at least some of the working members 204 overlap one another when the reinforcing assembly 200 is viewed from its side. In other words, these working members 204 are arranged so that, when the reinforcing assembly 200 is viewed from its side, part of one working member 204 is located over part of a neighboring working member 204 in a direction perpendicular to the longitudinal axis 210 of the support bars 202. The “side” view of the reinforcing assembly 200 is defined here as the view in which the support bars 202 extend left to right and the working members 204 extend downward from the support bars 202.
A spacing 214 between the working members 204 could be consistent along the length of the reinforcing assembly 200, or the spacing 214 between the working members 204 could vary. In some embodiments, the spacings 214 between adjacent pairs of working members 204 along the length of the reinforcing assembly 200 vary in different sections or vary continuously along the length of the reinforcing assembly 200. For instance, adjacent pairs of working members 204 closer to the support column 102 could have smaller spacings 214, while adjacent pairs of working members 204 farther from the support column 102 could have larger spacings 214. In particular embodiments, the smallest horizontal spacing 214 between two adjacent working members 204 could be about three to about four inches, and the largest spacing 214 between two adjacent working members 204 could be about ten inches.
The spacing(s) 214 and the length(s) of the working members 204 for any particular installation could be based on various factors. Example factors include the thickness of the slab structure 101, the load to be placed on the slab structure 101, the strength of the concrete or other material(s) forming the slab structure 101, and the size of the column 102. In general, any technique for increasing or decreasing the spacings 214 between at least some of the adjacent pairs of working members 204 along the length of the reinforcing assembly 200 could be used. Note that the use of smaller spacings 214 closer to the column 102 allows the reinforcing assembly 200 to provide greater reinforcement closer to the support column 102. However, variable spacing is not required in the reinforcing assembly 200.
As shown in
The reinforcing assembly 200 is shown here as being used in conjunction with additional reinforcement 220. The additional reinforcement 220 could denote the rebar 103 or other materials providing normal reinforcement within the slab structure 101. As can be seen here, the spacing(s) 214 of the working members 204 can be selected so that the working members 204 are located in areas where the additional reinforcement 220 is not.
As shown in
As shown in
Although the use of small (roughened) rebar could mean that more working members are required per installation, this provides an advantage in that it allows a more dispersed distribution of the individual working members in concrete than is provided by conventional approaches. As a result, the reinforcing can “blend” into the concrete material and act more as an integral part of the concrete itself.
Multiple working members 404 are independently connected to the support bars 402. Each of the working members 404 includes a downwardly-extending side 406 and a hooked end portion 408, and the hooked end portions 408 of adjacent working members 404 can hook in alternate or opposite directions. The downwardly-extending side 406 could be connected to one or both support bars 402 (equally or unequally). The hooked end portion 408 may or may not be curved along its entire length, and in this example part of the hooked end portion 408 is more straight than curved.
Each working member 404 is oriented diagonally with respect to a longitudinal axis 410 that extends along the support bars 402. An angle 412 between each working member 404 and the support bars 402 could have any suitable value, such as about 20° to about 70°. In particular embodiments, the angle 412 is about 35° or about 45°. The same angle 412 may or may not be used for each working member 404.
A spacing 414 between the working members 404 could be consistent or vary. If a variable spacing 414 is used, the spacings 414 could vary in sections or continuously along the length of the reinforcing assembly 400. Each longitudinally-extending support bar 402 can optionally terminate at the column 102 in a structure 416. This structure 416 is designed to extend into the support column 102 and may or may not extend into a column reinforcement 418 (such as support rebar). The reinforcing assembly 400 can be used in conjunction with additional reinforcement 420. The components 402-414, 418-420 shown in
Rather than representing bent portions of the support bars 402, the structure 416 includes one or more additional components that are connected to the support bars 402. For example, the structure 416 here can be formed by connecting one or more downwardly-extending bars to the support bars 402. The downwardly-extending bars could be formed of #3, #4, or #5 rebar or other structures that are welded or otherwise secured to the support bars 402. Note that while the structure 416 is shown as extending straight down in
In some embodiments, the working members 404 are positioned so that at least some of the working members 404 overlap one another when the reinforcing assembly 400 is viewed from its side. In other words, these working members 404 are arranged so that, when the reinforcing assembly 400 is viewed from its side, part of one working member 404 is located over part of a neighboring working member 404 in a direction perpendicular to the longitudinal axis 410 of the support bars 402. The “side” view of the reinforcing assembly 400 is defined here as the view in which the support bars 402 extend left to right and the working members 404 extend downward from the support bars 402.
As shown in
As shown in
In this example, a single support bar 602 could be used in the reinforcing assembly 600, although multiple support bars 602 could be used as described above. Also, the hooked end portion 608 of each working member 604 here can be bent at a smaller angle, such as an angle of at least 45°, although other angles including the ones described above could be used. In addition, each working member 604 can be bent so that the hooked end portion 608 extends along a longitudinal axis 610 of the support bar(s) 602 (away from a column 102), rather than extending traverse to the longitudinal axis 610 of the support bar(s) 602. Any individual one of these features or any combination of these features could be used in the reinforcing assemblies 200, 400, 500 described above. Although not shown, in some embodiments, the working members 604 are positioned so that at least some of the working members 604 overlap one another when the reinforcing assembly 600 is viewed from its side.
As shown in
Multiple working members 704 are independently connected to the support bars 702. Each working member 704 here denotes a structure that is connected to the support bars 702, such as via structural welding, and that extends downward and away from the support bars 702. Each of the working members 704 could have any suitable cross-sectional shape, and each of the working members 704 could be formed from any suitable material(s), such as rebar. In some embodiments, each of the working members 704 is formed using #3 rebar. The working members 704 could have ribbed, knurled, or other roughened surfaces along their entire lengths.
In some embodiments, the support bars 702 could denote structures that are already going to be used within the slab structure 101 or other supported structure, such as when the support bars 702 represent negative moment reinforcing bars. In those types of embodiments, the working members 704 could be added to the support bars 702 (typically but not necessarily in a shop) and may represent the only addition required to implement the reinforcing assembly 700 in the slab structure 101.
Also, in some embodiments, multiple support bars 702 are welded together (side-to-side) only at the points where the working members 704 are connected to the support bars 702, although other approaches could also be used. Moreover, in some instances, the entire reinforcing assembly 700 can be fabricated using only rebar (possibly only two sizes of rebar) with welded connections.
As shown in
The top end of the downwardly-extending side 706 could be connected to equal portions of the support bars 702, unequal portions of the support bars 702, or even to a single one of the support bars 702. The upper tip of the downwardly-extending side 706 could be connected to the support bars 702, or an upper portion of the downwardly-extending side 706 could be bent to run parallel to the support bars 702 and be connected to the support bars 702 along that upper portion.
The hooked end portion 708 denotes a portion of the downwardly-extending side 706 that is bent back. In this example, the hooked end portion 708 is bent by at least 180°, although any suitable amount of bend could be used to form the hooked end portion 708 (such as at least 45°, as at least 90°, at least 225°, or at least 270°). Also, the hooked end portion 708 may or may not be curved along its entire length. In
The hooked end portions 708 of adjacent working members 704 can hook in alternate or opposite directions. In
The downwardly-extending side 706 of each working member 704 could have any suitable length, and the hooked end portion 708 of each working member 704 could have any suitable size and radius of curvature. In some embodiments, the hooked end portion 708 of each working member 704 has a radius of curvature of about one inch. Note that in this example, the downwardly-extending side 706 and the hooked end portion 708 of each working member 704 form a substantially planar working member 704, although this need not be the case.
As shown in
In the example shown in
The reinforcing assembly 700 could be fabricated in any suitable manner. For example, the reinforcing assembly 700 could be constructed by welding or otherwise attaching the working members 704 to one or more continuous support bars 702. As another example, separate reinforcing assemblies (such as any of the reinforcing assemblies described above) could be welded or otherwise attached together at their support bars 702.
In some embodiments, the working members 704 are positioned so that at least some of the working members 704 overlap one another when the reinforcing assembly 700 is viewed from its side. In other words, these working members 704 are arranged so that, when the reinforcing assembly 700 is viewed from its side, part of one working member 704 is located over part of a neighboring working member 704 in a direction perpendicular to the longitudinal axis 710 of the support bars 702. The “side” view of the reinforcing assembly 700 is defined here as the view in which the support bars 702 extend left to right and the working members 704 extend downward from the support bars 702.
A spacing 714 between adjacent working members 704 could be consistent along the length of the reinforcing assembly 700 (except in a central area where the support bars 702 pass through the support column 102), or the spacings 714 between adjacent working members 704 could vary. In some embodiments, the spacings 714 between adjacent pairs of working members 704 along the length of the reinforcing assembly 700 vary in different sections or continuously moving out from a center of the reinforcing assembly 700. For instance, adjacent pairs of working members 704 closer to the support column 102 could have smaller spacings 714, while adjacent pairs of working members 704 farther from the support column 102 could have larger spacings 714. In particular embodiments, the smallest horizontal spacing 714 between two adjacent working members 704 could be about three to about four inches, and the largest spacing 714 between two adjacent working members 704 could be about ten inches.
The spacing(s) 714 and the length(s) of the working members 704 for any particular installation could be based on various factors. Example factors include the thickness of the slab structure 101, the load to be placed on the slab structure 101, the strength of the concrete or other material(s) forming the slab structure 101, and the size of the column 102. In general, any technique for increasing or decreasing the spacings 714 between at least some of the adjacent pairs of working members 704 along the length of the reinforcing assembly 700 could be used. The use of smaller spacings 714 closer to the column 102 allows the reinforcing assembly 700 to provide greater reinforcement closer to the support column 102. However, variable spacing is not required in the reinforcing assembly 700.
As noted above, the one or more support bars 702 here could denote one or more negative moment reinforcing bars, which are often found in concrete slabs or other structures. In these embodiments, the working members 704 could be secured to some or all of the negative moment reinforcing bars in the area of a support column 101.
The reinforcing assembly 700 is shown here as being used in conjunction with additional reinforcement 720. The additional reinforcement 720 could denote the rebar 103 or other materials providing normal reinforcement within the slab structure 101. As can be seen here, the spacing(s) of the working members 704 can be selected so that the working members 704 are located in areas where the additional reinforcement 720 is not.
As shown in
The working members 704 can be placed diagonally on the support bars 702 to engage any nascent crack 105 in the slab structure 101 at a 90° or near 90° angle with respect to the crack 105 itself. This provides improved or maximum efficiency in terms of aligning the working members 704 to directly oppose the diagonal tension (splitting) forces. With diagonal placement, each working member 704 engages a much larger percentage of the potential crack zone per unit length as compared to a vertical orientation. The diagonal placement also enables each working member 704 to engage up to twice as many crack zones per unit. Further, the compact size and alignment of the working members 704 allow the working members 704 to penetrate downward, even between densely-packed top rebar concentrations, and to engage the full depth of structural slab thickness.
Although the use of small (roughened) rebar could mean that more working members are required per installation, this provides an advantage in that it allows a more dispersed distribution of the individual working members in concrete than is provided by conventional approaches. As a result, the reinforcing can “blend” into the concrete material and act more as an integral part of the concrete itself.
There are also multiple instances of post-tensioned cables 802 extending through the slab structure 101 and the support column 102 in different directions. The post-tensioned cables 802 are routinely used in concrete slabs or other structures to provide reinforcement against tensile stresses.
Note that in this example, there are reinforcing assemblies 700 extending through the slab structure 101 both through the area where the support column 102 joins the slab structure 101 and next to the area where the support column 102 joins the slab structure 101. Also note that this occurs in different directions through the slab structure 101. However, this need not be the case. For example, while there are four reinforcing assemblies 700 traveling up and down in
During use, the reinforcing assemblies 200, 400, 500, 600, 700 in
The ability to transmit horizontal and vertical forces within a slab structure 101 into the support bars is different from how various conventional approaches operate. For example, steel studs (such as in the STUD-RAIL system) are not designed to capture and transmit horizontal forces into support bars and are instead designed to provide vertical reinforcement within a slab. Moreover, horizontal flat bars in systems like the STUD-RAIL system are smooth and are not used to resist horizontal forces on the flat bars. In addition, vertical studs such as in the STUD-RAIL system are not designed to grip concrete along their entire lengths but are instead designed to include smooth shafts that connect upper and lower flanges together. When diagonal cracks begin to form, the load of the concrete is transferred to the flanges and then to the shafts of the vertical studs, and the shafts can actually elongate. As a result, when cracks due to diagonal tension stresses begin to form, the fractured surfaces can slip along the smooth shafts, and the cracks extend into longer and wider cracks. These wider cracks can be particularly detrimental to the integrity of the overall structure because they could lead to a condition known as “loss of aggregate interlock,” which allows differential slippage between the surfaces to occur and a failure sequence to begin.
In contrast, the reinforcing assemblies in
In
Note that the support bars in the reinforcing assemblies are located on top of the reinforcing assemblies rather than on bottom of the reinforcing assemblies within the slab structure 101. It has been discovered that when a concrete slab undergoes deformation due to punching shear stress, the top of the concrete slab near a column experiences excessive bi-axial tensile stress, while the bottom of the concrete slab near the column experiences excessive compressive stress. If the support bars are located at the bottom of a reinforcing assembly with the working members extending upward, the free ends of the working members may be unable to maintain anchorage with the concrete at the top of the slab due to the excessive bi-axial horizontal tensile stress, which reduces the compressive strength of the concrete in that area.
Arranging the support bars at the top of the reinforcing assemblies allows the support bars to provide tensile reinforcement for the top of the slab structure 101. Also, running multiple support bars together horizontally provides a wider bearing area to support the vertical tensile forces in the working members. Moreover, arranging the support bars at the top of the reinforcing assemblies allows the free ends of the working members to be located near the bottom of the slab structure 101. This is where compressive stress due to bending enhances the compressive strength of the concrete so that it can more efficiently grip the bottom ends of the working members, which can help to maintain a secure bond with the hooked end portions of the working members. This is the opposite of the condition that occurs at the top of the concrete slab.
In addition, the bars and working members of the reinforcing assemblies are often described above as being formed from rebar. However, other material(s) could be used to form the bars and/or working members of the reinforcing assemblies. For example, rather than rebar, each bar and/or working member of a reinforcing assembly could be formed using a “threaded” bar or rod. As a particular example, each bar and/or working member of a reinforcing assembly could be formed using a threaded steel bar or rod. Similar to a bolt or screw, a threaded bar or rod includes at least one thread that wraps around a bar or rod along at least part of the length of the structure. The thread or threads help to engage the concrete around the threaded structure. Such a structure could be fabricated in any suitable manner, such as by machining at least one thread along part or all of the length of a bar or rod. Other types of structures could also be used to form the bars and/or working members, such as other structures having surface characteristics that enable the bars and/or working members to grip or engage concrete.
Although
In addition, any of the features shown or described with respect to one or some of the figures could be used in the other figures, even if not shown or described with respect to the other figures. As a particular example, one or more negative moment reinforcing bars, while described as possibly being used as the support bar(s) 702, could also be used in any of the other reinforcing assemblies described above. As another particular example, while the working members 704 in
Note that multiple support bars in the reinforcing assemblies described above may or may not have the same length and/or ends that are aligned with or attached to one another. For example, in some embodiments, one of the support bars could be shorter than the other support bar, or support bars of equal or unequal lengths could be offset from each other. This may allow, for example, one support bar to extend farther away from a column or other supporting structure than the other support bar. As a particular example, one support bar could extend farther away from the column or other supporting structure than the other support bar by about one or two feet. If the support bars extend through the column as in
A particular use of the reinforcing assemblies described in this document could be as follows (of course, other uses are possible). Two types of flexural stresses are typically present in an elevated concrete slab on either side of a loaded support member, typically a concrete column, or a drop panel. One is horizontal flexural tension in the upper portion of the slab due to negative bending moments. The other is diagonal (to the horizontal direction) tension due to the interaction between vertical shear stresses resulting from the slab load and horizontal shear stress caused by flexural bending. Current practice for flexural tension reinforcement is to use straight rebar distributed or tied in bundles at the top of the slab.
Horizontal tensile stresses may be at a maximum immediately adjacent to the column and can diminish moving away from the column. The vertical shear due to gravity loads could interact with horizontal bending shear and deflect some of that stress into a diagonal alignment, which could lead to diagonal tension. In other words, high bending stresses do not simply disappear as they move away from the column but may actually curve downward. The tension created by this curvature is accommodated using tensile reinforcement, which can be provided by the welded or other connections to the support bars at the top ends of the working members in the reinforcing assemblies. The reinforcing assemblies can therefore uniquely provide continuous reinforcement to substantially match the pattern of stress in the slab.
Diagonal tension stresses tend to cause cracks in a direction diagonal to the horizontal axis of the slab. The working members can be positioned perpendicular or substantially perpendicular to the orientation of the cracks as described above to provide reinforcement. However, since the working members are diagonal to the slab thickness, the working members might be too short to develop the necessary or desired bond to the surrounding concrete at the top ends of the working members. The top ends of the working members can therefore be welded or otherwise attached to the support bar or bars (possibly made of larger rebar), which serves as an anchorage and helps to eliminate the need for long bond lengths at the top ends. At the bottom ends of the working members, anchorage is provided by the loops or hooks, which can be sufficient since the concrete at the bottom of the slab is under bi-axial compression and therefore does not need normal bond lengths to develop its strength. The support bars at the top of the slab continue to engage the bending moment tensile stresses in the top of the slab.
The welded connections between the support bars and the working members can provide a continuous and essentially curved pattern of tensile reinforcement throughout a stressed area. These welded connections allow the horizontal support bars to maintain their primary function as reinforcement for tensile stress, such as due to negative bending near the supporting column, while also serving as an anchorage to the top ends of the diagonal working members. Ordinarily, the design of rebar assumes that tensile stresses are in straight alignment. When the tensile stresses are deflected from a straight line, the rebar deflects accordingly in order to be effective, but curvature of rebar creates stress concentrations at the point of curvature and requires lateral anchorage at that point. The welded or other connections of the working members to the support bars provide a unique and efficient solution to this condition. Simply hooking the working members at their top ends has proven to be ineffective in various use scenarios.
It may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like.
The description in the present application should not be read as implying that any particular element, step, or function is an essential or critical element that must be included in the claim scope. The scope of patented subject matter is defined only by the allowed claims. Moreover, none of the claims is intended to invoke 35 U.S.C. § 112(f) with respect to any of the appended claims or claim elements unless the exact words “means for” or “step for” are explicitly used in the particular claim, followed by a participle phrase identifying a function.
While this disclosure has described certain embodiments and generally associated methods, alterations and permutations of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of example embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure, as defined by the following claims.
This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 62/363,168 filed on Jul. 15, 2016 and U.S. Provisional Patent Application No. 62/436,134 filed on Dec. 19, 2016. Both of these provisional applications are hereby incorporated by reference in their entirety.
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