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  • Bulletin of the Transilvania University of BraovCIBv 2015 Vol. 8 (57) Special Issue No. 1 - 2015




    Abstract: This paper presents an overview of current state of knowledgeregarding bolted beam-to-column connections employed for moment-resisting framed steel structures. The connections of steel structures are oneof the determining factors of economy in structural steel work. Moreover themanual evaluation of bolted connection is a difficult task. The selection ofconnections is often based upon simplicity, duplication and ease of erection,which can be done with relatively unskilled workers and with basic tools.From this point of view the designer have to avoid complicated jointconfigurations with costly fabrication and laborious design. The state-of-theart report presented in this paper highlights the new tendencies in the field ofsteel beam-to-column bolted connections, and the importance of knowledgeof their behaviour.

    Key words: steel frames, beam-to-column steel joint, semi-rigid, boltedconnections.

    1Civil Engineering Faculty, Technical University of Cluj Napoca (Romania).

    1. Introduction

    Beam-to-column connections play acrucial role in the performance of momentresisting framed structures [1].

    The behaviour of beam-to-columnconnections is under extensive studieseven nowadays: the researchers conductexperimental, numerical and analyticalassessments.

    Since the 1994 Northridge and 1995Kobe earthquakes, bolted momentconnections have garnered considerableinterest for their application in seismic

    lateral resisting systems [2].However, the considerable amount of

    research conducted over the last twodecades has not produced many designprocedures that would allow theapplications of bolted connections either asfully-restrained or partially-restrained.

    There are several advantages providedby bolted joints like reduced cost andreduced complexity of execution.Compared to welded joints, boltedconnections are more ductile, haverelatively high capacity to dissipate energyand can be fitted relatively easy.

  • Bulletin of the Transilvania University of Braov Vol. 8 (57) Special Issue No. 1 - 201592

    Framed steel structures with momentresisting joints are recognized as highlydissipative structures in seismic design.

    According to Eurocode 8 rules thedissipative zones could be located either inelements or in beam-to-columnconnections. From this point of view deconfiguration of joint is an important task,in order that the resulted joint providesufficient resistance, rotation andflexibility [3]. After evaluation of jointperformances, these can be classified interms of strength, stiffness and ductility.

    In the structural analysis practice ofmulti-storey steel framed structure, thebeam-to-column connections areconsidered to be simplified, either rigid orpinned: rigid implies complete rotationalcontinuity and pinned implies no momenttransfer. Besides these classicalconnections there is another categorycalled semi-rigid.

    Analysis of frame structure with semi-rigid joints requires knowing the behaviorof joint moment-rotation behavior. Takinginto account the behavior of semi-rigidconnections results closer to the reality areobtained.

    The main advantage of a frame designusing semi-rigid joint behaviour is thatbeam moments are reduced leading tolighter beam. Assuming appropriate semi-rigid connections, the moments value canbecame more balanced.

    Figure 1 shows the cost effectiveness ofsemi-rigid joints. Although the literatureprovides a high volume of studies on semi-rigid behavior of joints, they are not usedas such in the usual designing practice.

    Fig. 1. Cost effectiveness of semi-rigidconnections [4]

    Most of the structural calculationprograms allow defining a flexibleconnection at the end of the bars in termsof rotational springs, but these moment-rotation curves are available for arelatively small number of joints types andtheir parameters.

    2. New Beam-to-Column ConnectionsBehind Classical Ones

    Several typical connections are providedin SR EN 1993 1-8: Design of steelstructures: Part. 1-8 Design of joints, orAISI standards, which, after all are similar.To give an example, one of the mostpopular beam-to-column connection indesign practice is the bolted end-plateconnection. Bolted end-plate connectionsare made by welding the beam to an end-plate and bolting the end-plate to a columnflange. The end-plate connectionconfiguration is shown in figure 2.

  • GHINDEA,M.,et al.: State-Of-The-Art Review On Bolted Steel Beam-To-Column Connections 93

    Fig. 2. Extended end-plate configuration[5]

    The behavior of this type of connectioncan be controlled by a number of differentlimit states including flexural yielding ofthe beam section, flexural yielding of theend-plates, yielding of the column panelzone, tension rupture of the end-plate bolts,shear rupture of the end-plate bolts, orrupture of various welded joints. The designcriteria provide sufficient strength in theelements of the connections to ensure thatthe inelastic deformation of the connectionis achieved by beam yielding [5].

    Excessive extending of the end-platewith properly stiffener will lead to thehammer-headed connections. Hammer-heads have the effect of increasing thelever arm between the compression andtension forces within the joint and ofreinforcing the end-plate submitted tobending.

    A newer bolted moment-resistingconnection is the T-stub configuration. Atypical T-stub connection is shown infigure 3.

    Fig. 3. Typical T-Stub Connection (Leon,et al., 2000, Roeder, 2000) [5]

    The failure mechanism of an equivalentT-stub is described by yield line models.The model of the equivalent T-stub can beused to calculate the load-bearing capacityof the basic components of boltedconnections. Experimental data providedby Leon (2000) served as the basis forestimating the stiffness and the strength ofthe T-stub connection [5].

    In the following, some newly developedconnection configuration are presented. Oneof them is named Kaiser bolted bracketconnection.

    In a Kaiser bolted bracket (KBB) momentconnection, a cast high-strength steelbracket is fastened to each beam flange andbolted to the column flange as shown infigure 4. The Kaiser bolted bracket (KBB)moment connection is designed to eliminatefield welding and facilitate frame erection.

    The obtained connections is full-strengthone, while the bracket configuration isproportioned to develop the probablemaximum moment strength of theconnected beam.

  • Bulletin of the Transilvania University of Braov Vol. 8 (57) Special Issue No. 1 - 201594

    Fig. 4. Kaiser bolted bracket connection[5]

    Yielding and plastic hinge formation areintended to occur primarily in the beam atthe end of the bracket away from thecolumn face (Figure 5).

    Fig. 5. Kaiser Bolted Bracket connectionfailure [6]

    Another innovative connection is theConXtech ConXL moment connection,which is designed to provide robust costeffective moment framing, whileeliminating field welding and facilitatingfast frame erection. The ConXtech

    ConXL moment connection permits full-strength, fully restrained connection ofwide flange beams to concrete-filledsquare hollow section, built-up boxcolumns using a high-strength, field-boltedcollar assembly.

    Figure 6 shows the connection geometryand major connection components. Eachcollar assembly is made up of forged collarcorners and collar flanges.

    Fig. 6. Configuration of Conxtech Conxspatial connection


    Beams are shop-welded to forged flangeand web fittings (collar flange assembly)and are field-bolted together throughforged column fittings (collar cornerassembly) that are shop welded to thecolumns [5]. Beams may be provided withreduced beam section (RBS) cut-outs ifnecessary to meet strong-column/weak-beam criteria. ConXL connections may beused to provide moment connections tocolumns in orthogonal frames. All momentbeams connecting to a ConXL node(intersection of moment beams andcolumn) must be of the same nominaldepth.

  • GHINDEA,M.,et al.: State-Of-The-Art Review On Bolted Steel Beam-To-Column Connections 95

    Figure 7 shows an application of suchconnectors.

    Fig. 7. Conxtech Conx connection(

    Another typology of connections appearsdue to the extensive application ofrectangular hollow sections. As field weldis not a desired solution in this case,particular connections were developedusing blind bolts.

    Figure 8 presents a RHS beam-to-columnconnection using hollow-bolts and anglecleats.

    Fig. 8. Rhs beam-to-column connectionsusing angles and blind bolts


    Rectangular hollow sections (RHS) aremore suitable for structural applications likeH shaped, owing to their efficient structuralperformance and attractive appearance.

    Blind bolts have a lot of advantages, suchas one-side fastening, quick, construction,reliable behaviour and good seismicperformance, and are expected to be widelyused in engineering projects [11].

    Figure 9 shows a blind-bolt typologynamed hollo-bolt

    Fig. 9. Hollo-bolt(

    A newly proposed innovative boltedbeam-to-column connections are those,where the column is made of high strengthsteel while the beam are made of mildcarbon steel [8] (Figure 10). These jointsare full-strength non-dissipative and theplastic hinge will form at the beamextremity in the beam, while the jointremain elastic.

    Fig. 10. High-strength steel column andmild carbon steel beam full-strength

    connection [8]

  • Bulletin of the Transilvania University of Braov Vol. 8 (57) Special Issue No. 1 - 201596

    Beam-to-column connec


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