Bmt Connections Man Low

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<p>Bull Moose Tube HSS Connections ManualA company1819 Clarkson RoadChesterfield, MO 63017(800) 325-4467FAX: (636) 537-2645www.bullmoosetube.come-mail: info@bullmoosetube.comFor additional information,contact your salesperson today at(800) 325-4467 or (636) 537-2600in the USA, or from Canadacall (800) 882-4666All information contained herein is accurate as known at the time of publication. Bull Moose Tube reserves the right to change product specifications without notice and without incurring obligation.8/991Foreword................................................................................................................... ..2Introduction............................................................................................................... ..3Framed Connections - Bolted Type Framing ..............................................4Simple Shear Connections - HSS Column to Wide Flange Connection .................. ..5Welds in the Center of the HSS.................................................................6Shear Tab................................................................................................7Design Procedure - Shear Tab to HSS ....................................................10The Single Angle....................................................................................13Slotted through plate ..............................................................................14Welds Located near Sidewall of the HSS.................................................14Double Angle Connections......................................................................15The Simple Tee......................................................................................16Beam Seats ...........................................................................................17ATLSS Connector ..................................................................................17Simple Shear Connections - HSS Beams to HSS Columns..................................... 18The Double Tee Connection....................................................................18The Double Angle Connection.................................................................18Separated Double Angle Connection .......................................................19Moment Connections - HSS to wide-flange.............................................................. 20Continuous Beams20Through Plates..21Strap Angles ..........................................................................................21Flange Diaphragms..22Column Face Reinforcement..23Moment Connection by Reinforcing the Beam Flanges .............................25Moment Connections - HSS to HSS......................................................................... 26Stepped Connections with b/D &lt; 0.85 ......................................................28Connections with b/D &gt; 0.8 .....................................................................28Reinforced Tube Connections .................................................................................. 30Plate Stiffener30Reinforcement with Haunches30Blind Fasteners ......................................................................................31Conclusions .............................................................................................................. 32References ............................................................................................332ForewordA comprehensive discussion of Hollow Structural Section (HSS) connections is beyond the scope of thisbooklet. However, a considerable body of design criteria does exist but much of it is scattered in pieces ofliterature and was not readily available to engineers at the time of its publication. After the initial publication ofthis booklet, Bull Moose Tube Company, in cooperation with the American Institute of Steel Construction. Inc.(AISC), the Steel Tube Institute of North America (STI), and the American Iron and Steel Institute (AISI)collaborated on a design book titled Hollow Structural Sections - Connections Manual, which is published bythe AISC. Copies are readily available through AISC.This booklet is limited to rectangular and square HSS and does not include extensive research and criteria thatis available for circular HSS. Even with rectangular HSS, most of the information concerns various types oftruss connections, where axially loaded branch members are directly welded to tubular chords or mainmembers. This guide is further limited to the case where the connection is intended to transmit moment andshear rather than an axial force.The information presented in this publication has been prepared in accordance with recognized engineeringprinciples and is for general information only. While it is believed to be accurate, this information should not beused or relied upon for any specific application without competent professional examination and verification ofits accuracy, suitability, and applicability by a licensed professional engineer, designer, or architect. Thepublication of the material contained herein is not intended as a representation or warranty on the part of BullMoose Tube Company, that this information is suitable for any general or particular use or of freedom frominfringement of any patent or patents. Anyone making use of this information assumes all liability arising fromsuch use.Caution must be exercised when relying upon other specifications and codes developed by other bodies andincorporated by reference herein since such material may be modified or amended from time to timesubsequent to the publishing of this edition. Bull Moose Tube Company bears no responsibility for suchmaterial other than to refer to it and incorporate it by reference at the time of the initial publication of this edition.3IntroductionWith superior compression capacities and natural aesthetic appeal, Hollow Structural Sections (HSS) are anexcellent choice for columns, trusses and building frame systems. Because of these attributes, the use of HSScontinues to increase in the U.S. and the rest of the world. However, designers and fabricators who have notworked with HSS still express uncertainties regarding connections to HSS. With this in mind, Bull Moose Tuberecognizes that connections to HSS require particular design consideration to achieve construction efficiencyand cost minimization.The connection of beams to HSS columns can be grouped into two general categories. One is the directconnection where the beam is welded to one of the column faces. This is often an HSS-to-HSS connection,although wide flange beams or other shapes could be welded to a column face. The other category is whereconnecting elements are used allowing for easy bolting of framing elements at once at the job site. This is byfar the most economical method of connecting HSS as well as open shapes. In fact, the standard boltedconnections that work so well for open profiles are often suitable for HSS. For simple connections, thoserequiring only shear resistance, HSS offer the same types of connecting elements as wide flange members. Infact, the load tables in the LRFD Simple Shear Connections should be used in the same manner for HSScolumns as it is for wide flange beams. This is why the cost of simple connections for HSS is generally thesame as wide flange members.4Framed Connections - Bolted Type FramingWelding tube - to - tube connections is difficult and expensive in the field. Therefore, it is important to haveframed connections similar to those used with wide flange columns to facilitate field erection. The calculationmethods used for bolted connections between hollow sections are basically no different than those used for anyother types of connections in conventional steel construction. The closed profile does, however, in some caseslead to a special approach to the calculation process.For simply supported behavior to be achieved, connections must provide a certain degree of flexibility in orderto accommodate beam end rotations as a beam deflects under load. A full moment connection, which preventsbeam end rotation relative to the column, implies an increased moment transfer to the column with increasingconnection stiffness.However, most of the connections that will be examined in this section are considered hinged or very nearlyhinged. There are almost invariably two alternatives for hinged type connections obtained as follows.The hinge is located on the axis "a" and a suitable arrangement of bolts gives a slight fixity of the jointupon the beam with the resulting moment, M2, acting on the latter.The hinge is located on the "b" axis (a single bolt for instance) and it is the column that reacts themoment, M2.Figure 1 shows the basic arrangement of the conventional type of connection indicating the possible loadingconditions and appropriate notationQ: Vertical reaction at support pointH: Horizontal reactionM1: Bending moment transmitted by the beamM2: Bending moment due to the eccentricity of the attachment: M2 = Q.eFigure 1 - Load Conditions for Simple Connections5Simple Shear Connections - HSS Column to Wide Flange ConnectioniA major consideration in the design of this type of framing system is the field connection between the beamsand columns. Normally a simple connection is shop welded to the beam or column and field bolted once at thejob site. The most economical method is to use a simple framing connection that transmits the beam shear witha minimal moment. A satisfactory simple framing connection of an open profile beam to a hollow sectioncolumn should consider the following:1) Adequate shear strength to carry the beam reaction2) Enough flexibility so that the bending moment transmitted to the column will be minimal3) The ability to carry any small moment without failure of the connection or connectors.4) A connection configuration that does not cause excessive deformation of the column wall5) A reasonably clean cost effective detail for fabricatorsCommon practice for simple field connections is to shop weld connecting elements to the beam or column andcomplete the connection in the field with bolting. A variety of standard simple framing connections have beendeveloped over the years for wide flange columns but most of them have been adopted for HSS columns aswell. These include:Double anglesTeesSingle anglesAngle beam seatsShear tabs or wing platesEnd platesATLSS connector (self guiding)6Except for the beam seat, the connecting element is attached to the web of the beam. However, theseconnections can be used with tubular beams if a structural tee end cap is welded to the beam so that the stemfunctions in a similar manner as the web of a wide-flange. These connections must be designed to reduce anysecondary loads to the minimum in particular by bringing the center lines of the chord and lattice members tomeet at the same point. It is advisable, in the case of main structural components, to arrange the web memberssymmetrically in relation to the median plane of these components and to attach them in a symmetrical manner.Welds in the Center of the HSSThe two types of connections that have welds near the center of the face of the HSS the shear tab and thesingle angle, which will be discussed in detail in the next several pages. The corresponding weld pattern isshown in Fig. 2Figure 2 - Shear Tab and Single Angle Welds7Shear TabOne of the most efficient and economical methods of connecting a beam to a tubular column is the shear tab.Recent research by Dr. Donald Sherman at the University of Milwaukee, Wisconsin quite clearly indicates thatthe shear tab is a safe, economical means for connecting a beam to a tubular column. In fact, this researchindicates that through-plating is often an unnecessary connection that can be avoided if certain criteria areconsidered. The primary purpose of Sherman's research was to develop design guidelines for shear tabs onHSS columns and to establish the limit states of such connections. The conclusion of this study is that theshear tab did not reduce the column capacity in comparison to the through plate and that bolt tightening hadmore of an impact than the connection type. This conclusion is shown in Graph 1.Graph 1 Shear Tab Column Test8The study of any connection begins with the identification of the critical failure modes encountered underextreme loading. These have been identified1 as 1) shear failure of bolts 2) yielding of gross plate area 3)fracture of the net plate area and 4) bearing failure of the beam web set. To avoid shear failure of the bolts, arelationship for bolt diameter and tab thickness has been established and is shown below:t tab dBolt/2 + 1/16Also, the tab thickness is limited to 9/16" or less. Taking this into consideration, there are certain combinationsof HSS thickness, tab thickness and common bolt diameters that should be used. These are summarized inTable 1, below.tHSSttabtbolts3/16 5/16 3/4, 7/8, 11/4 7/16 3/4, 7/8, 15/16, 1/2, 5/8 7/16 3/4, 7/8, 1 1/2 7/8, 1 9/16 1Table 1 - Combinations of Shear Tab Connection ParametersThe other consideration when analyzing failure of the HSS column connection is the additional limit stateintroduced by the flexible tube wall. The tube wall in this instance may experience a bending failure caused byyield line development or punching shear failure. Figure 3 illustrates the yield line mechanism. However,because the depth of the shear tab is much larger than its thickness, high strains are likely to develop at theedge of the plate producing a localized failure, such as the plate pulling out or punching into the tube wall. Thiswill occur before a sufficient number of yield lines develop and cause failure.9Figure 3 - Yield Line Failure Figure 4 - Punching Shear FailureFigure 4 illustrates the punching shear failure. Failure in this instance is defined as the point at which appliedload exceeds the shear resistance of the tube wall around the perimeter of the tab. To prevent this failure,thickness of the tube wall must exceed some fraction of the thickness of the tab so that the shear tab yieldsbefore the tube wall fractures in shear. The equation for the tube wall thickness is defined below and is used inconjunction with the equation for bolt shear failure to produce Table 1.Fy(tab) t (tab) 1.2 Fu (HSS) t (HSS)For those connections, which failed during Sherman's study, all experienced a shear yielding of the gross areaof the tab. However, all of the connections exhibited the possibility of multiple failure modes. To remove thepossibility of weld failure it is recommended that welding to HSS be done in accordance to AWS section D1.1that gives procedures to assure good welding practice.Local moments are an important consideration in the design of connecting elements. The moment developed inthe connection depends on the reaction eccentricity, which...</p>