Patent Publication Number: US-9903119-B2

Title: Flange-to-flange connection of precast concrete members

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 62/154,288, filed Apr. 29, 2015. Said U.S. Provisional Application Ser. No. 62/154,288 is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to the field of construction and more particularly to connection of precast concrete members. 
     BACKGROUND 
     A double tee beam is a load-bearing structure that resembles two T-beams connected to each other side by side. The strong bond of the flange (horizontal component) and the two vertical components (also known as stems) creates a structure that is capable of withstanding high loads while having a long span. Floor systems of modern parking structures, for example, use precast double tee beams, which are joined flange-to-flange using connectors anchored in the flange of the double tee beams, to form an integral multi-beam floor. 
     A type of conventional flange-to-flange connector uses a thin twisted plate pre-embedded in the flange. Two twisted plates aligned with each other across the gap between double tees are welded together at the jobsite using a loose steel plate to connect the flanges. This type of flange-to-flange connector creates a flexible connection, which has been criticized for lack of fatigue capacity and failure of welds if the welding is not done properly by certified welders. In addition, this type of flange-to-flange connector requires caulking (sealant) to seal the gap between the flange edges, with a life expectancy of five to ten years, thus requiring significant maintenance expenses. 
     SUMMARY 
     An embodiment of the present disclosure is directed to an apparatus. The apparatus may include a first anchored plate secured to a first set of anchoring bars and a second anchored plate secured to a second set of anchoring bars. The apparatus may also include a first alignment plate configured to mate with the first anchored plate and a second alignment plate configured to mate with the second anchored plate. The apparatus may further include at least one shim configured to be positioned between the first anchored plate and the second anchored plate. A bolt may be configured to secure the first and second alignment plates with the first and second anchored plates, respectively, and when the bolt is tightened, the bolt pulls the first and second alignment plates and the first and second anchored plates together to form a rigid connection. 
     A further embodiment of the present disclosure is directed to a structure. The structure may include a first concrete member and a second concrete member connected to the first concrete member utilizing a plurality of connectors. Each connector may include a first anchored plate secured to the first concrete member and a second anchored plate secured to the second concrete member. Each connector may also include a first alignment plate configured to mate with the first anchored plate and a second alignment plate configured to mate with the second anchored plate. At least one shim may be configured to be positioned between the first anchored plate and the second anchored plate, and a bolt may be configured to secure the first and second alignment plates with the first and second anchored plates, respectively, wherein when the bolt is tightened, the bolt pulls the first and second alignment plates and the first and second anchored plates together to form a rigid connection between the first concrete member and the second concrete member. 
     An additional embodiment of the present disclosure is directed to a method. The method may include: providing a plurality of connectors for connecting a first concrete member to a second concrete member, each of the plurality of connectors comprising a first anchored plate secured to the first concrete member and a second anchored plate secured to the second concrete member; bolting each of the plurality of connectors using a bolt, further comprising: providing a first alignment plate configured to mate with the first anchored plate; providing a second alignment plate configured to mate with the second anchored plate; positioning at least one shim between the first anchored plate and the second anchored plate; and tightening the bolt to pull the first and second alignment plates and the first and second anchored plates together to form a rigid connection between the first concrete member and the second concrete member; and sealing one or more gaps between the first concrete member and the second concrete member. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the present disclosure. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate subject matter of the disclosure. Together, the descriptions and the drawings serve to explain the principles of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The numerous advantages of the disclosure may be better understood by those skilled in the art by reference to the accompanying figures in which: 
         FIG. 1  is an isometric view of a flange-to-flange connector in accordance with the present disclosure; 
         FIG. 2  is an exploded view of a flange-to-flange connector; 
         FIG. 3  is an isometric view of the flange-to-flange connector shown in  FIG. 2  in a fully assembled configuration; 
         FIG. 4  is a cross-sectional top view of a properly aligned flange-to-flange connector; 
         FIG. 5  is a cross-sectional top view of a misaligned flange-to-flange connector due to normal construction tolerances; 
         FIG. 6  is an exploded view of a flange-to-flange connector similar to  FIG. 2  but for a larger flange and load transfer; 
         FIG. 7  is an illustration depicting a construction method configured to securely join two precast concrete members using flange-to-flange connectors in accordance with the present disclosure; and 
         FIG. 8  is an illustration depicting shear keys that may be defined in the gaps between two precast concrete members in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the subject matter disclosed, which is illustrated in the accompanying drawings. 
     Embodiments in accordance with the present disclosure are directed to flange-to-flange connectors for precast concrete members (e.g., double tee beams) and construction methods using such flange-to-flange connectors. The flange-to-flange connectors disclosed herein are easy to install, easy to maintain, and are intended to provide structural performance comparable to monolithically and continuously placed concrete between the stems of precast concrete flanged members. The flange-to-flange connectors disclosed herein also allow for generous construction tolerances and misalignments, which may be appreciated for various reasons. 
     Referring generally to  FIGS. 1 through 6 , a flange-to-flange connector  100  configured in accordance with an embodiment of the present disclosure is shown. The flange-to-flange connectors  100  can be utilized to securely join two precast concrete members  102  and  104  together using only bolted connections, effectively eliminating the requirement for certified welders and issues associated with low fatigue capacity of welded connectors and excessive deflections and rotations of the flange edges. 
     As shown in  FIGS. 1 and 2 , the flange-to-flange connector  100  configured in accordance with the present disclosure includes a pair of anchored plates  106  secured to their respective anchoring bars  114 , which are anchored in the precast concrete members  102  and  104 . The anchoring bars  114  may be shop-welded (which is a common practice in the precast concrete industry) to the anchored plates  106  in some embodiments. However, if fatigue capacity is a concern, the anchoring bars  114  may be implemented as headed bars, for example, which can be secured to the anchored plates  106  without welding at all. It is contemplated that the anchoring bars  114  may range from approximately ⅜ inches to 1 and ¼ inches in diameter and approximately 12 inches or greater in length. In some embodiments, the anchoring bars  114  may extend the full width of the precast concrete members  102  or  104 , and doubly used as the base reinforcement in the flanges. Alternatively, shorter anchoring bars  114  may be utilized to serve similar purposes, as long as the anchoring bars  114  are positioned to create continuity with the flange base reinforcement to allow the tensile forces to be transmitted across the double tee flanges. 
     The anchored plates  106  may be formed using ductile steel casting, but other techniques and/or materials may be utilized to form the anchored plates  106  without departing from the spirit and scope of the present disclosure. The anchored plates  106  may be configured to satisfy certain structural requirements, so the height, width, and/or the thickness of the anchored plates  106  may vary without departing from the spirit and scope of the present disclosure. In a particular implementation where the flange-to-flange connector  100  is used to connect 4-inch thick flanges for a parking structure, for example, the height of the anchored plates  106  may be configured to be approximately 2 inches to allow for concrete cover of approximately 1 inch on the top and the bottom of the anchored plates  106 . 
     In some embodiments (e.g., as shown in  FIG. 2 ), the anchored plates  106  may define one or more longitudinal indentations (grooves)  108  extending longitudinally (horizontally with respect to the orientation presented in  FIG. 2 ) along at least a portion (e.g., approximately 5 inches along the width) of the anchored plates  106 . The anchored plates  106  may also define one or more transverse indentations (teeth)  110  extending transversely (vertically with respect to the orientation presented in  FIG. 2 ) along at least a portion of the anchored plates  106 . 
     The grooves  108  and the teeth  110  may be defined in this manner to help properly and securely receive a pair of alignment plates  118 . In some embodiments, the alignment plates  118  may define lugs  120  and teeth  122  that are configured to mate with the grooves  108  and the teeth  110  defined on the anchored plates  106 . A bolt  116  and a nut  120  may be utilized to secure the alignment plates  118  against their corresponding anchored plates  106 . The bolt  116  may range from approximately ¾ inches in diameter (e.g., ASTM A325 grade 120 ksi) to approximately 1 and ⅜ inches in diameter (e.g., ASTM A490 grade 150 ksi) or greater. The nut  120  may be configured according to the capacity of the bolt  116 . 
     In some embodiments, the anchored plates  106  may define openings  112  that are large enough to accommodate the diameter of the bolt  116 . It is contemplated, however, that the openings  112  may be designed to provide a longitudinal tolerance (e.g., an extra inch) in certain embodiments. As shown in  FIG. 5 , defining the openings  112  with a tolerance effectively allows the flange-to-flange connector  100  to accommodate anchored plate  106  misalignments up to the tolerance provided by the openings  112 , which may be appreciated in various applications. 
     It is also contemplated that the openings  112  may be designed as U-shaped openings, allowing the bolt  116  to be received directly from the top (with respect to the orientation presented in  FIG. 2 ) of the anchored plates  106 , which is a feature that may be appreciated in certain (e.g., space-constrained) applications. It is to be understood, however, that the openings  112  are not required to be designed as U-shaped openings. The openings  112  depicted in  FIG. 6 , for example, do not define U-shaped openings; instead, the openings  112  depicted in  FIG. 6  only allows the bolt  116  to be received from the side (with respect to the orientation presented in  FIG. 6 ) of the anchored plates  106 . 
     It is further contemplated that the flange-to-flange connector  100  may be designed to accommodate gaps that may exist between the anchored plates  106 . In some embodiments, one or more shims  124  may be utilized to fill such a gap  126 . The shims  124  may be made of materials such as hard plastic or the like. As the bolt  116  is tightened, the alignment plates  118 , the anchored plates  106 , and the shims  124  are all pulled together, effectively forming a rigid connection that provides structural performance comparable to monolithically and continuously placed concrete between the stems of precast concrete flanged members. It is noted that the rigid connections formed using flange-to-flange connectors  100  configured in accordance with the present disclosure eliminate the need to form and cure concrete at job sites, allowing the time, cost, and construction complexity to be reduced significantly compared to conventional construction methods. 
     Referring now to  FIG. 7 , a construction method  200  configured to securely join two precast concrete members  102  and  104  using flange-to-flange connectors  100  in accordance with the present disclosure is shown. More specifically, the flange-to-flange connectors  100  located along the two precast concrete members  102  and  104  may be bolt connected in a step  202 . It is noted that the step  202  may be carried out according to a particular bolting sequence because even though the two precast concrete members  102  and  104  may be substantially identical, there is still a possibility that the top surfaces of the precast concrete members  102  and  104  may not be exactly aligned at the same elevation at each connection location. It may therefore be appreciated to start the bolting sequence at the opposite ends of the two precast concrete members  102  and  104  and work toward the center. Weights may be applied to the member ( 102  or  104 ) located at the higher elevation to force vertical alignment of the two members. The grooves and the lugs previously described will provide the necessary fine tuning of the vertical alignment. Once all the bolts are installed and tightened, another round of tightening may be performed using a technique known as snug tightening. 
     After the bolts are adequately snug-tightened, flowable high strength low shrinkage grout may be poured into the gap between the precast concrete members  102  and  104  in a step  204 . The bottom of the gap may be filled with backer rod and sealed with a sealant to prevent grout from leaking. In some embodiments, the gap between the precast concrete members  102  and  104  may form (optional) shear keys as depicted in  FIG. 8  (and also in  FIG. 1 ). It is contemplated that these shear keys may provide resistance to vertical and longitudinal shear in the plane formed by the precast concrete members  102  and  104 . 
     It is to be understood that while the flange-to-flange connectors  100  configured in accordance with the present disclosure may be utilized for constructing parking structures, the references to parking structures are merely exemplary and are not meant to be limiting. It is contemplated that the flange-to-flange connectors  100  configured in accordance with the present disclosure may be produced in various dimensions, sizes, or shapes for various purposes without departing from the spirit and scope of the present disclosure. It is contemplated that dimensions, sizes, shapes, and hardware implementations of flange-to-flange connectors configured in accordance with the present disclosure may vary from the descriptions above without departing from the spirit and scope of the present disclosure. 
     The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled”, to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably couplable”, to each other to achieve the desired functionality. 
     It is believed that the present disclosure and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components without departing from the disclosed subject matter or without sacrificing all of its material advantages.