Bolted Joints-examples

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13. BOLTED JOINTS

The calculation methods used for bolted joints The calculation methods used for bolted joints between, or to, hollow sections are basically not between, or to, hollow sections are basically not different from those used for any other type of joint in different from those used for any other type of joint in conventional steel construction.

conventional steel construction.

Most details given in this chapter are presented Most details given in this chapter are presented without (detailed) design formulae.

without (detailed) design formulae.

13.1 13.1 FLANGE PLATE JOINTS

FLANGE PLATE JOINTS

13.1.1 13.1.1 Flange plate joints to CH

Flange plate joints to CHS under

S under

axial tension load

For the flange plate joints shown in Fig. 13.1, various For the flange plate joints shown in Fig. 13.1, various investigations were carried out (Kato & Hirose, 1984; investigations were carried out (Kato & Hirose, 1984; Igarashi et al., 1985; Cao & Packer, 1997). Igarashi et al., 1985; Cao & Packer, 1997). Economical joints under tension load can be obtained Economical joints under tension load can be obtained if prying force is permitted at the ultimate limit state, if prying force is permitted at the ultimate limit state, with the connection proportioned on the basis of a with the connection proportioned on the basis of a yielding failure mechanism of the flange plates. In yielding failure mechanism of the flange plates. In CIDECT Design Guide No. 1 (Wardenier et al., 2008a) CIDECT Design Guide No. 1 (Wardenier et al., 2008a) formulae and tables are given, based on the work of formulae and tables are given, based on the work of Igarashi et al. (1985). In the context of this book, only Igarashi et al. (1985). In the context of this book, only the failure modes are presented (Fig. 13.2). It is the failure modes are presented (Fig. 13.2). It is preferable to design primary structural joints on the preferable to design primary structural joints on the basis of the yield resistance of the circular hollow basis of the yield resistance of the circular hollow section.

section.

13.1.2 13.1.2 Flange plate joints to RH

Flange plate joints to RHS under

S under

axial tension load

Research by Birkemoe & Packer (1986) and Packer et Research by Birkemoe & Packer (1986) and Packer et al. (1989) on bolted RHS flange plate joints with bolts al. (1989) on bolted RHS flange plate joints with bolts on two sides of the RHS only, see Fig. 13.3, showed on two sides of the RHS only, see Fig. 13.3, showed that in principle the strength of these joints can be that in principle the strength of these joints can be analysed on the basis of the traditional prying model analysed on the basis of the traditional prying model developed for T-stubs by Struik & De Back (1969). developed for T-stubs by Struik & De Back (1969). The location of the plastic hinge lines may be

The location of the plastic hinge lines may be adjustedadjusted for greater accuracy, i.e. the distance b in Fig. 13.4 is for greater accuracy, i.e. the distance b in Fig. 13.4 is adjusted to b' according to:

adjusted to b' according to:

ii tt 2 2 d d b b '' b b







(13.1)(13.1)

Detailed formulae are given by Packer & Henderson Detailed formulae are given by Packer & Henderson (1997) and Packer et al. (2009a).

(1997) and Packer et al. (2009a). Many tests have been carried out on

Many tests have been carried out on RHS flange plateRHS flange plate joints

joints with with bolts bolts on on 4 4 sides sides of of the the RHS, RHS, as as shown shown inin Fig. 13.3. A thorough study of this type of bolted joint Fig. 13.3. A thorough study of this type of bolted joint has been undertaken by Willibald et al. (2002, 2003a). has been undertaken by Willibald et al. (2002, 2003a).

It was revealed that RHS flange plate joints bolted on It was revealed that RHS flange plate joints bolted on all four sides could still be proportioned on the basis of all four sides could still be proportioned on the basis of the two-dimensional T-stub prying model of Struik & the two-dimensional T-stub prying model of Struik & De Back (1969), with some minor modifications. De Back (1969), with some minor modifications. Following the procedure for bolted RHS flange plate Following the procedure for bolted RHS flange plate joints

joints with with bolts bolts on on two two sides, sides, the the inner inner yield yield lines lines inin the flange plate can now be expected adjacent to the the flange plate can now be expected adjacent to the RHS outer face and hence the term t

RHS outer face and hence the term tii should be should be

deleted from eq. (13.1). The bolt pitch to be used is deleted from eq. (13.1). The bolt pitch to be used is the minimum of p from both sides. The dimension p, the minimum of p from both sides. The dimension p, the plate width or depth divided by the

the plate width or depth divided by the number of boltsnumber of bolts in that direction, is illustrated in Fig. 13.3. This in that direction, is illustrated in Fig. 13.3. This "minimum p" value is then used in the joint analysis "minimum p" value is then used in the joint analysis based of a two-dimensional prying model. In order for based of a two-dimensional prying model. In order for this design model to be valid, the centres of the bolt this design model to be valid, the centres of the bolt holes should not be positioned beyond the corners of holes should not be positioned beyond the corners of the RHS (as illustrated in Fig. 13.3).

the RHS (as illustrated in Fig. 13.3).

Detailed information can be found in CIDECT Design Detailed information can be found in CIDECT Design Guide No. 3 (Packer et al., 2009a).

Guide No. 3 (Packer et al., 2009a).

13.1.3 13.1.3 Flange plate joints to

Flange plate joints to CHS or RHS

CHS or RHS

under axial tension load and

moment loading

Design methods for bolted flange plate joints to date Design methods for bolted flange plate joints to date have generally been developed for axial tension have generally been developed for axial tension loading. Frequently, however, hollow sections are loading. Frequently, however, hollow sections are subjected to both axial tension load (N

subjected to both axial tension load (Nii) and bending) and bending

moment (M

moment (Mii). In such cases, a hypothetical "effective"). In such cases, a hypothetical "effective"

axial load can be computed (Kurobane et al., 2004) axial load can be computed (Kurobane et al., 2004) for use with the flange plate joint design procedures for use with the flange plate joint design procedures given in Sections 13.1.1 and 13.1.2:

given in Sections 13.1.1 and 13.1.2:

ii ii ii ii ii _A_A W W M M A A N N axial axial Effective Effective

_















(13.2)(13.2) where: where: A

Aii cross cross sectional sectional area area of of the the CHS CHS or or RHSRHS

W

Wii elastic elastic (or (or plastic) plastic) section section modulus modulus of of the the CHS CHS oror

RHS RHS

This procedure will be conservative, especially for This procedure will be conservative, especially for CHS, as it computes the maximum tensile normal CHS, as it computes the maximum tensile normal stress in the CHS or RHS and then applies this to the stress in the CHS or RHS and then applies this to the whole member cross section.

whole member cross section.

13.2 END JOINTS

Some bolted end joints are shown in Fig. 13.5. The Some bolted end joints are shown in Fig. 13.5. The flange of the tee in Fig. 13.5d, as well as the other flange of the tee in Fig. 13.5d, as well as the other flange plates perpendicular to the CHS or RHS flange plates perpendicular to the CHS or RHS

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section, must be sufficiently thick to effectively section, must be sufficiently thick to effectively distribute the load to the cross section (Wardenier et distribute the load to the cross section (Wardenier et al., 2008a; Packer et al., 2009a), see also Section al., 2008a; Packer et al., 2009a), see also Section 9.7.3.

9.7.3.

13.3 GUSSET PLATE JOINTS

For bolted gusset plate joints, the design can be For bolted gusset plate joints, the design can be based on the various possible failure modes, e.g. for based on the various possible failure modes, e.g. for aa tension member:

tension member: -

- Yielding of Yielding of the cross the cross sectionsection -

- Rupture of Rupture of the net the net areaarea -

- Rupture of the effective neRupture of the effective net area reduced for sheart area reduced for shear lag

lag

Similar to other bolted joints, the total net area is the Similar to other bolted joints, the total net area is the sum of individual net areas along a potential critical sum of individual net areas along a potential critical section of a member or gusset plate, see Fig. 13.6. If section of a member or gusset plate, see Fig. 13.6. If such a critical section comprises net areas loaded in such a critical section comprises net areas loaded in tension and segments loaded in shear, the shear tension and segments loaded in shear, the shear segments should be multiplied by the shear strength segments should be multiplied by the shear strength and the tension areas by the ultimate strength. and the tension areas by the ultimate strength. Eurocode 3 (EN 1993-1-1, 2005) specifies a

Eurocode 3 (EN 1993-1-1, 2005) specifies a γγMM factor factor

of 1,0 for yielding and 1,25 for ultimate strength of 1,0 for yielding and 1,25 for ultimate strength (rupture).

(rupture). A failure mode

A failure mode of the of the gusset plate which also gusset plate which also must bemust be checked is yielding across an effective dispersion checked is yielding across an effective dispersion width of the plate, which can be calculated using the width of the plate, which can be calculated using the Whitmore (1952) effective width concept illustrated in Whitmore (1952) effective width concept illustrated in Fig. 13.7. For this failure mode (for one gusset plate), Fig. 13.7. For this failure mode (for one gusset plate), the strength is given by:

the strength is given by:

 



M M o o p p yp yp 1 1 p p )) 30 30 (tan (tan 2 2 g g tt f f N N Rd Rd ,, ii









(13.3)(13.3)

where the term



p represents the sum of the boltp represents the sum of the bolt pitches in a bolted connection or the length of the pitches in a bolted connection or the length of the weld in a welded connection, and

weld in a welded connection, and



MM =1,1. =1,1.

If the member is in compression, buckling of the If the member is in compression, buckling of the gusset plate must also be prevented.

gusset plate must also be prevented.

Fig. 13.8 shows some examples of bolted gusset plate Fig. 13.8 shows some examples of bolted gusset plate joints.

joints. It It must must be be borne borne in in mind mind that that fitting fitting of of thesethese connections is very sensitive with regard to connections is very sensitive with regard to dimensional tolerances and to deformations of the dimensional tolerances and to deformations of the welded gusset due to weld-induced distortions. Thus, welded gusset due to weld-induced distortions. Thus, care has to be taken to ensure fitting at site.

care has to be taken to ensure fitting at site.

When a member is connected by some, but not all When a member is connected by some, but not all parts of its cross section elements and if the net parts of its cross section elements and if the net section includes elements which are not connected, section includes elements which are not connected, the net area perpendicular to the load has to be the net area perpendicular to the load has to be

multiplied by a shear lag factor which depends on the multiplied by a shear lag factor which depends on the shape of the section, the number of connected faces shape of the section, the number of connected faces and the number of transverse rows of fasteners.

and the number of transverse rows of fasteners.

Such a case is illustrated in Fig. 13.8b where bolting Such a case is illustrated in Fig. 13.8b where bolting plates are welded to the sides of the RHS brace plates are welded to the sides of the RHS brace member. For welds parallel to the direction of load (as member. For welds parallel to the direction of load (as the four flare groove welds would be in Fig. 13.8b, the four flare groove welds would be in Fig. 13.8b, along the four corners of the RHS), the shear lag along the four corners of the RHS), the shear lag factor is a function of the weld lengths and the factor is a function of the weld lengths and the distance between them. For the RHS, the shear lag distance between them. For the RHS, the shear lag reduction factors can be applied to each of the four reduction factors can be applied to each of the four sides (two of width w = b

sides (two of width w = bii - t - tii, and two of width w = h, and two of width w = hii -

-ttii), to produce a total effective net area of the RHS), to produce a total effective net area of the RHS

reduced by shear lag. Suggested shear lag reduction reduced by shear lag. Suggested shear lag reduction factors for these four element areas, in terms of the factors for these four element areas, in terms of the weld length L

weld length Lww, are (CSA, 2009):, are (CSA, 2009):

- 1,00 when the weld Iengths (L

- 1,00 when the weld Iengths (Lww) along the RHS) along the RHS

corners are



2b 2bii (or 2h (or 2hiias applicable)as applicable)

- (0,5 + 0,25L

- (0,5 + 0,25Lww/b/bii) when the weld lengths along the) when the weld lengths along the

RHS corners are b

RHS corners are bii



L Lww < 2b < 2bii, or, or

- (0,5 + 0,25L

- (0,5 + 0,25Lww/h/hii) when the weld lengths along the) when the weld lengths along the

RHS corners are h

RHS corners are hii



L Lww < 2h < 2hii

- 0,75L

- 0,75Lww/b/bii when the weld lengths along the RHS when the weld lengths along the RHS

corners are L

corners are L_w_w < b < b_ii (or h (or h_iias applicable)as applicable)

13.4 SPLICE JOINTS

Fig. 13.9 shows a splice joint for circular hollow Fig. 13.9 shows a splice joint for circular hollow sections. This type of connection can, for example, be sections. This type of connection can, for example, be executed with four, six or eight strips welded executed with four, six or eight strips welded longitudinally on the periphery of the hollow sections longitudinally on the periphery of the hollow sections and connected by double lap plates, one on each and connected by double lap plates, one on each side.

side.

Lightly loaded splice joints in tension can be made as Lightly loaded splice joints in tension can be made as shown in Fig. 13.10 and for architectural appearance shown in Fig. 13.10 and for architectural appearance the bolts can be hidden. Using one plate on each side, the bolts can be hidden. Using one plate on each side, instead of the solution in Fig. 13.10, provides a more instead of the solution in Fig. 13.10, provides a more fabrication-friendly solution. Such an eccentric joint, fabrication-friendly solution. Such an eccentric joint, however, may have little stiffness and resistance to however, may have little stiffness and resistance to out-of-plane flexure under compression loading, thus out-of-plane flexure under compression loading, thus the designer should be confident that such a condition the designer should be confident that such a condition has been considered. Experimental and numerical has been considered. Experimental and numerical research on this RHS joint type, under tension loading, research on this RHS joint type, under tension loading, has been conducted by Willibald et al. (2003b).

has been conducted by Willibald et al. (2003b).

13.5 BEAM-TO-COLUMN JOINTS

Bolted beam-to-column joints can be designed in Bolted beam-to-column joints can be designed in various ways, mainly depending on the type of load various ways, mainly depending on the type of load that has to be transmitted. In general, shear joints are that has to be transmitted. In general, shear joints are simpler to fabricate than moment joints. Typical joints simpler to fabricate than moment joints. Typical joints

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are given in Figs. 13.11 to 13.15 without detailed are given in Figs. 13.11 to 13.15 without detailed description.

description.

13.6 BRACKET JOINTS

Some typical joints for lightly loaded beams are shown Some typical joints for lightly loaded beams are shown in Fig. 13.16.

in Fig. 13.16.

13.7 BOLTED SUBASSEMBLIES

Lattice structures are often connected to columns by Lattice structures are often connected to columns by bolted flanges, plates or Tee profiles. Some examples bolted flanges, plates or Tee profiles. Some examples are shown in Fig. 13.17.

are shown in Fig. 13.17.

13.8 PURLIN JOINTS

Fig. 13.18 shows some examples of purlin joints for Fig. 13.18 shows some examples of purlin joints for trusses with CHS or RHS chords.

trusses with CHS or RHS chords.

13.9 BLIND BOLTING SYSTEMS

Due to the closed nature of hollow sections, in many Due to the closed nature of hollow sections, in many cases additional welded plates are used for bolted cases additional welded plates are used for bolted joints.

joints. HoweverHowever, , solutionsolutions s are are then then not not aesthetiaestheticallycally appealing. Nowadays, bolting systems are available appealing. Nowadays, bolting systems are available which can be used when only one side of the which can be used when only one side of the connection is accessible. Blind bolting systems make connection is accessible. Blind bolting systems make use of either special types of bolts or inserts or special use of either special types of bolts or inserts or special drilling systems.

drilling systems.

13.9.1 Systems using bolts and inserts

Special types of bolts and systems allow one to bolt Special types of bolts and systems allow one to bolt from one side of a hollow section. A number of from one side of a hollow section. A number of patented blind bolting systems is available, e.g. Huck patented blind bolting systems is available, e.g. Huck "Ultra Twist Blind Bolt" and Lindapter "HolloFast" and "Ultra Twist Blind Bolt" and Lindapter "HolloFast" and "HolloBolt". The latter, which uses a special insert and "HolloBolt". The latter, which uses a special insert and a standard bolt, has been investigated by CIDECT a standard bolt, has been investigated by CIDECT (Sidercad & British Steel, 1996; Yeomans, 1998) with (Sidercad & British Steel, 1996; Yeomans, 1998) with regard to its axial, shear and bending capacity (see regard to its axial, shear and bending capacity (see Fig. 13.19).

Fig. 13.19).

The systems are based on the principle that after The systems are based on the principle that after bringing them in from one side, the bolts are torqued bringing them in from one side, the bolts are torqued and a "bolt head" forms on the inside of the connected and a "bolt head" forms on the inside of the connected plies.

plies.

The design rules for blind bolting systems are based The design rules for blind bolting systems are based on typical failure modes, i.e.

on typical failure modes, i.e. -

- Punching shear of the fastener through Punching shear of the fastener through the columnthe column face

face

-

- Yielding of Yielding of the column fthe column face (yield ace (yield line patternline pattern around the bolts)

around the bolts)

- Bolt failure in shear, tension or a combination of - Bolt failure in shear, tension or a combination of

both both

13.9.2 Drilling system

The Flowdrill system, see Fig. 13.20, is a special The Flowdrill system, see Fig. 13.20, is a special patented method for extruded holes. CIDECT has patented method for extruded holes. CIDECT has carried out research (Yeomans, 1994; British Steel, carried out research (Yeomans, 1994; British Steel, 1996) to assess the load bearing capacity of this type 1996) to assess the load bearing capacity of this type of joint in structural hollow sections.

of joint in structural hollow sections.

Flowdrilling is a thermal drilling process (Fig. 13.21) to Flowdrilling is a thermal drilling process (Fig. 13.21) to make a hole through the wall of a hollow section by make a hole through the wall of a hollow section by bringing a tungsten carbide bit into contact with the bringing a tungsten carbide bit into contact with the hollow section wall and generating sufficient heat by hollow section wall and generating sufficient heat by friction to soften the steel. As the bit moves through friction to soften the steel. As the bit moves through the wall, the metal flows to form an internal bush. In the wall, the metal flows to form an internal bush. In the next step, the bush is threaded using a roll tap. the next step, the bush is threaded using a roll tap. Conventional bolts are then used in this tapped hole. Conventional bolts are then used in this tapped hole. Bolting to hollow sections with wall thicknesses up to Bolting to hollow sections with wall thicknesses up to 12,5 mm can be recommended by using the Flowdrill 12,5 mm can be recommended by using the Flowdrill method, see Yeomans (1994).

method, see Yeomans (1994).

13.10 NAILED JOINTS

As

As an an alternaalternative tive to to bolting bolting or or welding, welding, steel steel circularcircular hollow sections can be nailed together to form reliable hollow sections can be nailed together to form reliable structural joints. Up to now, this method of connection structural joints. Up to now, this method of connection has only been verified for splice joints between two has only been verified for splice joints between two co-axial tubes (see Fig. 13.22). In such a joint, one co-axial tubes (see Fig. 13.22). In such a joint, one tube can fit snugly inside the other, in such a way that tube can fit snugly inside the other, in such a way that the outside diameter of the smaller equals the inside the outside diameter of the smaller equals the inside diameter of the larger. Nails are then shot fired and diameter of the larger. Nails are then shot fired and driven through the two wall thicknesses and arranged driven through the two wall thicknesses and arranged symmetrically around the tube perimeter.

symmetrically around the tube perimeter. As

As an an alternaalternative, tive, two two tubes tubes of of the the same same outsideoutside diameter can be joined by means of a tubular collar diameter can be joined by means of a tubular collar over both tube ends; in this case nails are again over both tube ends; in this case nails are again inserted by driving them through the two tube walls. inserted by driving them through the two tube walls. Research to date has covered a range of tube sizes Research to date has covered a range of tube sizes with various diameter-to-thickness ratios, tube wall with various diameter-to-thickness ratios, tube wall thickness and lack of fit (Packer, 1996). The observed thickness and lack of fit (Packer, 1996). The observed failure modes were nail shear failure, tube bearing failure modes were nail shear failure, tube bearing failure, and net section fracture of the tube. These failure, and net section fracture of the tube. These failure modes have been identified for both static and failure modes have been identified for both static and fatigue loading. Simple design formulae, derived from fatigue loading. Simple design formulae, derived from bolted and riveted joints, have been verified for both bolted and riveted joints, have been verified for both these load cases.

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Fig. 13.1 Bolted CHS flange plate joint Fig. 13.1 Bolted CHS flange plate joint

Fig. 13.2 Failure modes for bolted CHS flange plate joints Fig. 13.2 Failure modes for bolted CHS flange plate joints

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p p pp pp p p p p p p pp pp p p p p

Fig. 13.3 Bolted RHS flange plate joints Fig. 13.3 Bolted RHS flange plate joints

Fig. 13.4 RHS flange plate joint with bolts at two sides of the RHS Fig. 13.4 RHS flange plate joint with bolts at two sides of the RHS

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Fig. 13.5 Bolted end joints Fig. 13.5 Bolted end joints

Bolt hole

Bolt hole diamdiameter eter d’d’ Shear segments Shear segments Inclined segments

Inclined segments Tension segment

Tension segment _{Bolt hole}_{Bolt hole diam}_diameter_{eter d’}_d’

Shear segments Shear segments Inclined segments Inclined segments Tension segment Tension segment

Total net area for critical section A-A

Total net area for critical section A-A is the sum of the individual segments:is the sum of the individual segments:

For

For tension tension segment segment : : AAnn = (g = (g11 - d’/2) - d’/2) tt

For

For shear shear segment segment : : AAgvgv = L t = L t

For each inclined segment : A

For each inclined segment : Ann = (g = (g22 - d’) t + (s - d’)t + (s22/4g/4g22)) tt

Fig. 13.6 Calculation of total net area for a gusset plate Fig. 13.6 Calculation of total net area for a gusset plate

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, , , ,

Fig. 13.7 Whitmore criterion for

Fig. 13.7 Whitmore criterion for gusset plate yieldinggusset plate yielding

Fig. 13.8 Some examples of bolted gusset plate joints Fig. 13.8 Some examples of bolted gusset plate joints

Fig. 13.9 Bolted splice joint for CHS Fig. 13.9 Bolted splice joint for CHS

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Fig. 13.10 Hidden bolted splice joint Fig. 13.10 Hidden bolted splice joint

IP

IPE orE or HE cHE cutut ofoff f IP

IPE orE or HE cHE cutut ofoff f

Fig. 13.11 I section beam-to-CHS

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a a bb c c dd e e ff

Fig. 13.12 I section beam-to-RHS

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a

a bb

c

c dd

Fig. 13.13 Moment joints between open section beams and CHS or RHS columns Fig. 13.13 Moment joints between open section beams and CHS or RHS columns

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Fig. 13.14 RHS sections connected to I section columns Fig. 13.14 RHS sections connected to I section columns

Fig. 13.15 Knee joint assemblies for portal frames Fig. 13.15 Knee joint assemblies for portal frames

Fig. 13.16 Bracket joints Fig. 13.16 Bracket joints

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Fig. 13.17 Bolted joints for lattice girder supports Fig. 13.17 Bolted joints for lattice girder supports

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Fig. 13.18 Purlin joints Fig. 13.18 Purlin joints

Fig. 13.19 Lindapter "HolloFast" connection Fig. 13.19 Lindapter "HolloFast" connection

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Fig. 13.20 Flowdrill connection for joining end plates or angles to RHS Fig. 13.20 Flowdrill connection for joining end plates or angles to RHS

Fig. 13.21 Flowdrill process Fig. 13.21 Flowdrill process

Fig. 13.22 Nailed CHS joint Fig. 13.22 Nailed CHS joint