BOLTED SLOTTED BEAM WEB CONNECTION DESIGNS

Abstract

A structural steel beam-to-column field bolted connection includes a column having a column flange and a beam. The beam includes a first beam flange and a second beam flange. The beam also includes a beam web extending between the first beam flange and the second beam flange. The beam web defines at least one slot that extends from a distal end of the beam along a length of the beam and terminates at a stress relief hole. The connection includes an end plate. The beam is welded to the end plate and the end plate is bolted to the column flange.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/846,252, entitled “BOLTED SLOTTED BEAM WEB CONNECTION DESIGNS”, filed on May 10, 2019, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Existing beam to column connection technology oftentimes requires welding at least a portion of the connection (such as a portion of a beam to a portion of a column) in the field. In some instances, due to location and/or other environmental conditions, this can lead to problems with quality control of the weld. Additionally, some existing beam to column connections may require the use of a shear plate. Moreover, existing connections (such as end plate connections) may be susceptible to undesirable lateral torsional buckling and/or may exhibit large stress and/or strain gradients across and through the beam flanges at the column connection. Some known beam to column connections may also result in larger than desirable amounts of beam shear being placed upon flanges of the beam at the column connection. Embodiments of the invention provide solutions to these and other issues.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention relate to structural steel connections in steel moment frames that are typically made with rolled or built-up structural shapes. The designs presented herein combine the attributes of the design methodology and technology of both slotted web connections and end plate connections. The beam components of the connection that includes the welded end plate and beam web slots can be shop prepared, while the completed beam-to-column connection can be made by field bolting the end plate of the slotted beam to the column flange in the structural frame.

According to one aspect, a structural steel beam-to-column field bolted connection is described herein. The connection may include a column having a column flange and a beam. The beam may include a first beam flange and a second beam flange, as well as a beam web extending between the first beam flange and the second beam flange. The beam web may have at least one slot adjacent to the beam flange that extends from a distal end of the beam along a length of the beam and may terminate at a stress relief hole. The connection may also include an end plate. The beam may be welded to the end plate and the end plate may be bolted to the column flange.

According to another aspect, a method of forming a bolted slotted web beam-to-column connection is described herein. The method may include welding an end plate onto a distal end of a beam and bolting the end plate to a flange of a column.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of various embodiments may be realized by reference to the following figures.

FIG. 1A depicts a side view of a bolted slotted web connection using a four bolt arrangement according to embodiments.

FIG. 1B depicts a front view of the bolted slotted web connection of FIG. 1A.

FIG. 2A depicts a side view of a bolted slotted web connection using a six bolt arrangement according to embodiments.

FIG. 2B a front view of the bolted slotted web connection of FIG. 2A.

FIG. 3A illustrates the force distribution in a bolted slotted web connection in accordance with the present invention.

FIG. 3B is a section view of the beam of FIG. 3A.

FIG. 4 is a flowchart depicting a process for forming a bolted slotted web connection in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The ensuing description provides exemplary embodiments only, and is not intended to limit the scope, applicability or configuration of the disclosure. Rather, the ensuing description of the embodiments will provide those skilled in the art with an enabling description for implementing multiple embodiments. It will be understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of this disclosure.

The Bolted Slotted Web (BSW) connections described herein is a bolted steel beam-to-steel column connection that utilizing attributes of end plate (EP) and slotted web (SW) beam-to-column connections. In some embodiments of BSW moment connections, slots may be formed in a beam web such that the slots are parallel and adjacent to the flanges of the beam. These slots, which start at the end of the beam and are typically one third to one half the nominal beam depth in length and are typically one eighth to one quarter inch in width, are terminated at a round stress relief hole with a radius greater than the slot width. The beam flanges and web are welded to an end plate which is field bolted to the column flange to form a beam-to-column moment connection that has both seismic and wind applications.

The embodiments of the present invention relate to structural steel connections in steel moment frames made typically with rolled or built up structural shapes. The connection design presented herein utilizes attributes of slotted web and end plate connections as described herein. The beam components of the connection that include the welded end plate and beam web slots are shop prepared. The completed beam-to-column connection in the structural frame is made by field bolting the end plate to the column flange. By separating the beam flanges with slots in the web in the region of the connection to the column, essentially all the beam shear is resisted by the beam web and a portion of the beam moment at the connection. The slots eliminate lateral torsional buckling of the beam at the connection as well as the beam flange shear. These attributes result in near uniform stress and strain gradients across and through the beam flanges which increases the connection fatigue life.

Such BSW connections provide numerous advantages over existing EP and SW connection designs. For example, BSW connections in accordance with the present disclosure eliminate the lateral torsional mode of beam buckling at the connection that may be experienced in EP connections. This attribute is important for perimeter beams that support the exterior cladding of the building. BSW connections also eliminate the need to weld the beam flanges and the beam web to a column flange as needed with SW connections. In fact, the presently disclosed BSW connections may eliminate the need for most or all field welds, as most or all of the welding may be done in the shop where higher quality control are more easily maintained. Additionally, BSW connections in accordance with the present disclosure eliminate the need for a shear plate required for SW connections, and may eliminate large stress and strain gradients across and through beam flanges as well as a large component of beam shear in the beam flanges that are associated with EP connections. Rather, in the BSW connections described herein, the beam flanges essentially resist only moment loads or forces.

Turning now to FIGS. 1A and 1B, one example of a four bolt BSW connection is illustrated. BSW connection uses a combination of SW and EP connection methodology to form a bolted rigid beam-to-column connection. As illustrated, a beam 100 may be an I-beam or a W-beam having a top flange 102 and a bottom flange 104. A beam web 106 extends between and connects the top flange 102 and the bottom flange 104. The beam web 106 includes at least one slot 108 that extends along a length of the beam 102 at positions proximate the top flange 102 and/or bottom flange 104. The beam web 106 more commonly includes a pair of slots 108 that are positioned on opposing sides of the beam web 106 adjacent the top flange 102 and the bottom flange 104 as illustrated in FIG. 1A. The slots 108 may be formed (such as by thermal cutting) at a distal end of the beam 100 and extend between about one third to one half of a nominal beam depth in length, although other lengths of slots 108 may be utilized. As illustrated in FIG. 3A, in some embodiments a length of the slots 108 may be determined by l_s<l_p+l_b/10 based upon the web hinge length (A-B) and typically l_s<d_beam/2, where d_beam is the beam depth, l_s is the slot length, l_p is the plate length, and l_b is a clear span of the beam/2. Each slot 108 may terminate in a round stress relief hole 110 that has a larger diameter than a width of the slot 108. In FIG. 3A, h represents the story height.

A column 112 includes a first flange 114 and a second flange 116, as well as a column web 118 that extends between and connects the first flange 114 and the second flange 116. In the BSW connection, the beam 100 is shown with the beam web 106 being secured to the second flange 116 of the column 112 via an end plate 120 that is positioned between the distal end of the beam 100 and the second flange 116 of the column 112. The distal end of the beam 100 is secured to the end plate 120 via one or more welds, such as a fillet weld, a complete joint penetration weld, a partial joint penetration weld, and/or other weld formed at the distal end of the beam web 106, first flange 102 and/or second flange 104. Any weld may be formed within a shop before the beam is transported to the field for installation.

The end plate 120 and beam 100 is secured to the column 112 by bolting or otherwise fastening the end plate 120 to the second flange 116 of the column 112. As shown here, four bolts 122 are used to secure both the top and bottom of the end plate 120 to the second flange 116 of the column 112 so that a total of eight bolts are used to secure the beam 100 to the column 112 as shown in FIG. 1B. Specifically, a bolt 122 is positioned on each side of the beam web 106 on both an interior side and exterior side of the first flange 102 so that the four bolts 122 form a generally rectangular arrangement. Four bolts are similarly oriented with respect to the beam web 106 and second flange 104 in a generally rectangular arrangement. The strength and position of the pre-tensioned bolts 122 and/or the end plate 120 dimensions may be determined using existing strength and placement standards, such as those provided by the American Institute of Steel Construction (AISC) design guides.

In some embodiments, BSW connections may need to be able to handle larger beam web shear forces. In such embodiments, a six bolt BSW connection may be used, such as that illustrated in FIGS. 2A and 2B. The six bolt connection may be formed in a similar manner to the connection described in FIGS. 1A and 1B, but may include two additional bolts 222 that are positioned on the interior side of the top flange 202 and bottom flange 204. For example, as illustrated in FIGS. 2A and 2B, a single bolt 222 is positioned on an exterior side of the top flange 202 and on each side of the beam web 206 while a pair of bolts 222 is positioned on an interior side of the top flange 202 and on each side of the beam web 206. Thus, six bolts are used to secure the end plate 220 to the column near the top flange 202. Similarly, a single bolt 222 is positioned on an exterior side of the bottom flange 204 and on each side of the beam web 206 while a pair of bolts 222 is positioned on an interior side of the bottom flange 204 and on each side of the beam web 206. Thus, six bolts are also used to secure the end plate 220 to the column near the bottom flange 204. Twelve bolts are used in all to attached the beam 200 to the column.

While the embodiments herein are described using four and six bolt arrangements, it will be appreciated that other numbers of bolts may be used based on the load requirements of a particular application. Additionally, while show in generally rectangular arrangements, other bolt arrangements may be possible.

Returning to FIG. 3A, the force distributions in a BSW connection are illustrated for a cantilever beam model subjected to an ultimate end load, P_u. The end load P_u may be computed from the following equation in which l_b and l_p are previously defined, Z_b is the beam plastic modulus, and Fy is the beam material yield strength:

P_u=Z_bF_y/[l_b−l_p]

FIG. 3B is a section view of the beam of FIG. 3A. As illustrated in FIG. 3B, the beam flange forces in the region of the connection, shown as tension T and compression C, are uniform from the outboard end of the slots to the end plate. The beam web moments M_A,web and M_B,web and the beam web shears V_A and V_B are also illustrated in FIG. 3B. The relation between the cantilever beam load P_u and these forces and moments is determined by the following equations:

V_A=V_B=P_u

T=C=F_yA_flg

M_A,web=M_B,web+P_ux[l_s−l_p]

M_A,flg=M_B,flg+Tx[d_beam−t_flg]

In the following equations, A_flg is the area of the respective flange, M_A,flg and M_B,flg are the flange moments, t_flg is the beam flange thickness. Beam slot lengths depend upon both beam properties and the moment frame geometry using slotted beam web technology as shown, for example, in FIGS. 1A, 1B, 2A, and 2B. The inelastic region in this connection as shown occurs from end of the beam slots to the end plate at the flange of the column. The centroid of the “beam plastic hinge”, includes the beam flanges and the beam web as shown, is one half the length of the slots from the face of the column.

FIG. 4 is a flowchart of a process 400 for forming a bolted slotted web beam-to-column connection. Process 400 may be used to form any of the BSW connections described herein. At block 402, an end plate is welded to a distal end of a beam. This welding may be done in a shop setting so as to maintain the high quality control standards. At block 404, the end plate (and beam) are bolted onto a column flange. In some embodiments, a four or six bolt arrangement may be utilized, such as those arrangements described in conjunction with FIGS. 1A-2B.

It should be noted that the systems and devices discussed above are intended merely to be examples. It must be stressed that various embodiments may omit, substitute, or add various procedures or components as appropriate. Also, features described with respect to certain embodiments may be combined in various other embodiments. Different aspects and elements of the embodiments may be combined in a similar manner. Also, it should be emphasized that technology evolves and, thus, many of the elements are examples and should not be interpreted to limit the scope of the invention.

Specific details are given in the description to provide a thorough understanding of the embodiments. However, it will be understood by one of ordinary skill in the art that the embodiments may be practiced without these specific details. For example, well-known structures and techniques have been shown without unnecessary detail in order to avoid obscuring the embodiments. This description provides example embodiments only, and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the preceding description of the embodiments will provide those skilled in the art with an enabling description for implementing embodiments of the invention. Various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the invention.

The methods, systems, devices, graphs, and tables discussed above are examples. Various configurations may omit, substitute, or add various procedures or components as appropriate. For instance, in alternative configurations, the methods may be performed in an order different from that described, and/or various stages may be added, omitted, and/or combined. Also, features described with respect to certain configurations may be combined in various other configurations. Different aspects and elements of the configurations may be combined in a similar manner. Also, technology evolves and, thus, many of the elements are examples and do not limit the scope of the disclosure or claims. Additionally, the techniques discussed herein may provide differing results with different types of context awareness classifiers.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly or conventionally understood. As used herein, the articles “a” and “an” refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element. “About” and/or “approximately” as used herein when referring to a measurable value such as an amount, a temporal duration, and the like, encompasses variations of ±20% or ±10%, ±5%, or +0.1% from the specified value, as such variations are appropriate to in the context of the systems, devices, circuits, methods, and other implementations described herein. “Substantially” as used herein when referring to a measurable value such as an amount, a temporal duration, a physical attribute (such as frequency), and the like, also encompasses variations of ±20% or ±10%, ±5%, or +0.1% from the specified value, as such variations are appropriate to in the context of the systems, devices, circuits, methods, and other implementations described herein. As used herein, including in the claims, “and” as used in a list of items prefaced by “at least one of” or “one or more of” indicates that any combination of the listed items may be used. For example, a list of “at least one of A, B, and C” includes any of the combinations A or B or C or AB or AC or BC and/or ABC (i.e., A and B and C). Furthermore, to the extent more than one occurrence or use of the items A, B, or C is possible, multiple uses of A, B, and/or C may form part of the contemplated combinations. For example, a list of “at least one of A, B, and C” may also include AA, AAB, AAA, BB, etc.

Having described several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. For example, the above elements may merely be a component of a larger system, wherein other rules may take precedence over or otherwise modify the application of the invention. Also, a number of steps may be undertaken before, during, or after the above elements are considered. Accordingly, the above description should not be taken as limiting the scope of the invention.

Also, the words “comprise”, “comprising”, “contains”, “containing”, “include”, “including”, and “includes”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, acts, or groups.

Claims

1. A structural steel beam-to-column field bolted connection, comprising:

a column having a column flange;

a beam comprising: a first beam flange and a second beam flange; and a beam web extending between the first beam flange and the second beam flange, wherein the beam web defines at least one slot that extends from a distal end of the beam along a length of the beam and terminates at a stress relief hole; and

an end plate, wherein: the beam is welded to the end plate; and the end plate is bolted to the column flange.

2. The structural steel beam-to-column field bolted connection of claim 1, wherein the connection eliminates lateral torsion buckling of the beam in a region of the connection.

3. The structural steel beam-to-column field bolted connection of claim 1, wherein the connection provides a near uniform state of stress and strain in the first beam flange and the second beam flange in a region of the connection.

4. The structural steel beam-to-column field bolted connection of claim 1, wherein the connection eliminates beam flange shear forces in the connection.

5. The structural steel beam-to-column field bolted connection of claim 1, wherein the connection obtains a near uniform stress distribution across and through the first beam flange and the second beam flange in the connection.

6. The structural steel beam-to-column field bolted connection of claim 1, wherein the connection eliminates field welding of the connection.

7. The structural steel beam-to-column field bolted connection of claim 1, wherein the end plate is bolted to the column flange using a four bolt arrangement on a top and a bottom of the end plate.

8. The structural steel beam-to-column field bolted connection of claim 1, wherein the end plate is bolted to the column flange using a six bolt arrangement on a top and a bottom of the end plate.

9. The structural steel beam-to-column field bolted connection of claim 1, wherein a length of the at least one slot is determined by the equation ls<lp+lb/10.

10. The structural steel beam-to-column field bolted connection of claim 1, wherein the beam web define two slots that each extend from the distal end of the beam along the length of the beam and that each terminate at a stress relief hole.

11. The structural steel beam-to-column field bolted connection of claim 10, wherein each slot of the two slots is approximately equal in length.

12. The structural steel beam-to-column field bolted connection of claim 1, wherein the first beam flange, the second beam flange, and the beam web are each welded to the end plate.

13. The structural steel beam-to-column field bolted connection of claim 1, wherein the stress relief hole is round and has a larger dimension than a width of the at least one slot.

14. A method of forming a bolted slotted web beam-to-column connection, comprising:

welding an end plate onto a distal end of a beam; and

bolting the end plate to a flange of a column.

15. The method of forming a bolted slotted web beam-to-column connection of claim 14, wherein bolting the end plate comprises using a four bolt arrangement on a top and a bottom of the end plate.

16. The method of forming a bolted slotted web beam-to-column connection of claim 14, wherein bolting the end plate comprises using a six bolt arrangement on a top and a bottom of the end plate.

17. The method of forming a bolted slotted web beam-to-column connection of claim 14, further comprising forming at least one slot in a beam web of the beam, wherein the at least one slot extends from a distal end of the beam along a length of the beam and terminates at a stress relief hole.

18. The method of forming a bolted slotted web beam-to-column connection of claim 17, further comprising forming a second slot in the beam web, wherein the second slot extends from the distal end of the beam along the length of the beam and terminates at a second stress relief hole.

19. The method of forming a bolted slotted web beam-to-column connection of claim 18, wherein the slot and the second slot are approximately equal in length.

20. The method of forming a bolted slotted web beam-to-column connection of claim 14, wherein welding the end plate onto the distal end of the beam comprises welding a first beam flange, a second beam flange, and a beam web onto the end plate.