Design and Analysis of Connections in Steel Structures E-Book

Alfredo Boracchini

• Herausgeber: Wiley-VCH
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 414

Veröffentlichungsjahr: 2018

Beschreibung

The book introduces all the aspects needed for the safe and economic design and analysis of connections using bolted joints in steel structures. This is not treated according to any specific standard but making comparison among the different norms and methodologies used in the engineering practice, e.g. Eurocode, AISC, DIN, BS.
Several examples are solved and illustrated in detail, giving the reader all the tools necessary to tackle also complex connection design problems.

The book is introductory but also very helpful to advanced and specialist audiences because it covers a large variety of practice demands for connection design. Parts that are not taken to an advanced level are seismic design, welds, interaction with other materials (concrete, wood), and cold formed connections./p

Leseprobe

Table of Contents

Cover

Copyright

Dedication

Preface

About the Author

Acknowledgments

List of Abbreviations

Software Download and its Limitations

Chapter 1: Fundamental Concepts of Joints in Design of Steel Structures

1.1 Pin Connections and Moment Resisting Connections

1.2 Plastic Hinge

References

Chapter 2: Fundamental Concepts of the Behavior of Steel Connections

2.1 Joint Classifications

2.2 Forces in the Calculation Model and for the Connection

2.3 Actions Proportional to Stiffness

2.4 Ductility

2.5 Load Path

2.6 Ignorance of the Load Path

2.7 Additional Restraints

2.8 Methods to Define Ultimate Limit States in Joints

2.9 Bolt Resistance

2.10 Yield Line

2.11 Eccentric Joints

2.12 Economy, Repetitiveness, and Simplicity

2.13 Man‐hours and Material Weight

2.14 Diffusion Angles

2.15 Bolt Pretensioning and Effects on Resistance

2.16 Transfer Forces

2.17 Behavior of a Bolted Shear Connection

2.18 Behavior of Bolted Joints Under Tension

References

Chapter 3: Limit States for Connection Components

3.1 Deformation Capacity (Rotation) and Stiffness

3.2 Inelastic Deformation due to Bolt Hole Clearance

3.3 Bolt Shear Failure

3.4 Bolt Tension Failure

3.5 Bolt Failure in Combined Shear and Tension

3.6 Slip‐Resistant Bolted Connections

3.7 Bolt Bearing and Bolt Tearing

3.8 Block Shear (or Block Tearing)

3.9 Failure of Welds

3.10 T‐stub, Prying Action

3.11 Punching

3.12 Equivalent Systems

3.13 Web Panel Shear

3.14 Web in Transverse Compression

3.15 Web in Transverse Tension

3.16 Flange and Web in Compression

3.17 Beam Web in Tension

3.18 Plate Resistance

3.19 Reduced Section of Connected Profiles

3.20 Local Capacity

3.21 Buckling of Connecting Plates

3.22 Structural Integrity (and Tie Force)

3.23 Ductility

3.24 Plate Lamellar Tearing

3.25 Other Limit States in Connections with Sheets and Cold‐formed Steel Sections

3.26 Fatigue

3.27 Limit States of Other Materials in the Connection

References

Chapter 4: Connection Types: Analysis and Calculation Examples

4.1 Common Symbols

4.2 Eccentrically Loaded Bolt Group: Eccentricity in the Plane of the Faying Surface

4.3 Eccentrically Loaded Bolt Group: Eccentricity Normal to the Plane of the Faying Surface

4.4 Base Plate with Cast Anchor Bolts

4.5 Chemical or Mechanical Anchor Bolts

4.6 Fin Plate/Shear Tab

4.7 Double‐Bolted Simple Plate

4.8 Shear (“Flexible”) End Plate

4.9 Double‐Angle Connection

4.10 Connections in Trusses

4.11 Horizontal End Plate Leaning on a Column

4.12 Rigid End Plate

4.13 Splice

4.14 Brace Connections

4.15 Seated Connection

4.16 Connections for Girts and Purlins

4.17 Welded Hollow‐Section Joints

4.18 Connections in Composite (Steel–Concrete) Structures

4.19 Joints with Bolts and Welds Working in Parallel

4.20 Expansion Joints

4.21 Perfect Hinges

4.22 Rollers

4.23 Rivets

4.24 Seismic Connections

References

Chapter 5: Choosing the Type of Connection

5.1 Priority to Fabricator and Erector

5.2 Considerations of Pros and Cons of Some Types of Connections

5.3 Shop Organization

5.4 Culture

Reference

Chapter 6: Practical Notes on Fabrication

6.1 Design Standardizations

6.2 Dimension of Bolt Holes

6.3 Erection

6.4 Clearance Needed to Operate Tightening Wrenches

6.5 Bolt Spacing and Edge Distances

6.6 Root Radius Encroachment

6.7 Notches

6.8 Bolt Tightening and Pretensioning

6.9 Washers

6.10 Dimensions of Screws, Nuts, and Washers

6.11 Reuse of Bolts

6.12 Bolt Classes

6.13 Shims

6.14 Galvanization

6.15 Other Finishes After Fabrication

6.16 Camber

6.17 Grout in Base Plates

6.18 Graphical Representation of Bolts and Connections

6.19 Field Welds

6.20 Skewed Joints

References

Chapter 7: Connection Examples

Index

End User License Agreement

List of Tables

Chapter 02

Table 2.1 Eurocode joint sorting.

Chapter 03

Table 3.1 Stiffness modification coefficient H according to Eurocode.

Table 3.2 Values for class of bolts – Eurocode 3, it is a so‐called

nationally determined parameter

(

NDP

) and it may vary by country.

Table 3.3 Values for class of bolts – DIN 18800.

Table 3.4 Values for class of bolts – AISC (revisited for X‐type bolts).

Table 3.5 Area for standard metric bolt.

Table 3.6 Area for standard imperial bolts.

Table 3.7 Maximum design shear (

γ

M2

 = 1.25) for metric bolts.

Table 3.8 Design maximum tensile strength for metric bolts.

Table 3.9 Slip‐resistant connections [1], values of

k

s

.

Table 3.10 Slip‐resistant design from [1, 8], values of

μ

in the absence of specific tests.

Table 3.11 Values for the calculation of

ℓ

eff

for an unstiffened flange column.

Table 3.12 Values for calculating

ℓ

eff

for a stiffened column flange.

Table 3.13 Values for calculating

ℓ

eff

for an end plate.

Table 3.14 Formulas for evaluating

ℓ

eff

in a pair of bolts separated by a web in a column flange or end plate.

Table 3.15 Formulas for evaluating

ℓ

eff

for a bolt row in a plate extension.

Table 3.16

ℓ

eff

to be taken into consideration for a bolt row acting alone.

Table 3.17

ℓ

eff

to be taken into consideration for a bolt row acting in a group.

Table 3.18 Typical examples from [18].

Table 3.19

ω

as a function of

β

.

Table 3.20 For obtaining approximate values of

β

in the most common cases.

Table 3.21 Material properties in MPa (N mm

−2

); “thk” stands for thickness and “lim.” for limit.

Table 3.22

β

value for shear lag formula.

Table 3.23 Synthesis of instructions for evaluating buckling in gusset plates.

Table 3.24 Values of

f

pLT

used to check plate buckling.

Chapter 04

Table 4.1 Equations for calculating design moment resistance and rotation stiffness of base plates according to EC.

Table 4.2 Possible standard dimensions of plates inside concrete according to [10].

Table 4.3 Stiffener usefulness in helping limit states.

Table 4.4 Stiffness coefficients to evaluate when designing beam‐to‐column end plates according to [5].

Table 4.5 Stiffness coefficients to evaluate when designing beam‐to‐beam end plates.

Chapter 05

Table 5.1 Pros and cons of most common “simple” joint types.

Chapter 06

Table 6.1 Maximum bolt hole clearance (in mm) according to EN 1090.

Table 6.2 Maximum bolt hole clearance (in mm) according to AISC.

Table 6.3 Limit dimensions for base plate holes and washers according to AISC.

Table 6.4 Characteristic dimensions needed for standard wrenches.

Table 6.5 Characteristic dimensions needed for polygonal wrenches.

Table 6.6 Characteristic dimensions needed for hand‐driven socket wrenches.

Table 6.7 Characteristic dimensions needed for motor‐driven socket wrenches.

Table 6.8 Characteristic dimensions needed for pipe wrenches.

Table 6.9 Minimum and maximum wrench dimensions depending on bolt size.

Table 6.10 Distance

x

as in Figure 6.7 suggested by [4] for imperial bolts.

Table 6.11 Useful dimensions for IPE profiles.

Table 6.12 Useful dimensions for HEA profiles.

Table 6.13 Useful dimensions for HEB profiles.

Table 6.14 AISC tightening values.

Table 6.15 Tightening values according to EC [5].

Table 6.16 Tightening according to [2].

Table 6.17 Tightening according to [5] in hypothesis of perpendicular surfaces.

Table 6.18 “Average” dimensions for depth of common bolt heads and nuts.

Table 6.19 External diameter values for common washers.

List of Illustrations

Chapter 01

Figure 1.1 Lateral load resisting systems.

Figure 1.2 Braces emphasized esthetically in the John Hancock Tower of Chicago.

Figure 1.3 Valorization of internal braces (InterPuls, Reggio Emilia, Italy).

Figure 1.4 Buckling length coefficients (effective length factors) for braced systems.

Figure 1.5 Buckling length coefficients (effective length factors) for unbraced systems.

Figure 1.6 Column bases at the Milan Central Railway Station.

Figure 1.7 Base plate configurations that can be considered (last one excluded) as either a pin or a fully restrained connection.

Chapter 02

Figure 2.1 Moment‐rotation diagram defines the joint behavior.

Figure 2.2 Possible locations for the axis of the connection.

Figure 2.3 Possible locations of the joint axis.

Figure 2.4 Actions on springs are uniformly proportional to their own stiffness.

Figure 2.5 Connection with both welds and bolts sharing the load.

Figure 2.6 Path of the load.

Figure 2.7 Wrong connection because the load path concept was missed.

Figure 2.8 Effective width of a cantilevered plate loaded by a concentrated force.

Figure 2.9 Force diffusion from a beam flange (right‐hand side) into a column (left‐hand side).

Figure 2.10 Joint load versus joint configuration.

Figure 2.11 Behavior of a shear connection.

Figure 2.12 Preload effects.

Figure 2.13 Bolted connections in tension.

Figure 2.14 Different preload diagrams in a tension connection with prying action.

Chapter 03

Figure 3.1 Maximum possible “permanent” deformation: each plate adds 1 mm, which means 1 + 1 mm in the left horizontal member and an additional 1 + 1 mm on the right.

Figure 3.2 Shear planes and effects on bolts.

Figure 3.3 Packing plates in a splice connection.

Figure 3.4 Long joints.

Figure 3.5 Countersunk bolts.

Figure 3.6 Bolt tearing.

Figure 3.7 Bolt bearing.

Figure 3.8 DIN symbols.

Figure 3.9 Symbols according to EC.

Figure 3.10 AISC representation.

Figure 3.11 Representation of actual collapse.

Figure 3.12 Block shear possible modes.

Figure 3.13 Laboratory test dramatically shows the block shear phenomenon.

Figure 3.14 Weld deformation depending on the load angle.

Figure 3.15 Increase of number of weld passes to have larger throats (mm).

Figure 3.16 Net throat thickness of fillet welds.

Figure 3.17 Net throat thickness of a partial‐penetration weld.

Figure 3.18 Welding positions.

Figure 3.19 Most common weld symbols.

Figure 3.20 Stresses on the throat section of a fillet weld.

Figure 3.21 Instructions for intermittent fillet welds.

Figure 3.22 EC symbols for two T‐stub cases – how to calculate

m

.

Figure 3.23 Mechanisms of T‐stub failure.

Figure 3.24 Negligible prying action – symbols for minimum‐thickness formula.

Figure 3.25 Backing plates.

Figure 3.26 Examples of “position of a bolt row,” as in [1]: (1) external row near a stiffener; (2) external row; (3) internal row; and (4) internal row near a stiffener.

Figure 3.27 For estimating

α

in Tables 3.12 and 3.13.

Figure 3.28 Symbol representations from EC 1993‐1‐8. (a) End plate narrower than column flange, (b) end plate wider than column flange, and (c) angle flange cleats.

Figure 3.29 For calculating

for an end plate.

Figure 3.30 Angle flange cleat design parameters.

Figure 3.31 Equivalent system example.

Figure 3.32 Definitions of symbols.

Figure 3.33 Calculation according to BS.

Figure 3.34 Haunch.

Figure 3.35 Staggered bolts.

Figure 3.36 Bolted joint.

Figure 3.37 Welded joint.

Figure 3.38 The section can expand into a connected element.

Figure 3.39 Angles connected on one leg only.

Figure 3.40 Lug angle connection.

Figure 3.41 Instructions to evaluate

x

and

l

in bolted joints.

Figure 3.42 Evaluation of

l

in welds.

Figure 3.43 Literal symbols.

Figure 3.44 Detail to be considered when evaluating the net section in hollow sections.

Figure 3.45 Symbols used in formulas.

Figure 3.46 Possible configurations for brace connections. (a) Compact, (b) noncompact, (c) extended, (d) on one sinde, (e) chevron type.

Figure 3.47 Calculation of

l

avg

and

c

.

Figure 3.48 Stiffeners to apply according to [27].

Figure 3.49 Symbols for fin plate buckling.

Figure 3.50 Situations where structural integrity comes into play.

Figure 3.51 Lamellar tears.

Figure 3.52 How to calculate

a

eff

in Figure 3.53.

Figure 3.53 Criteria affecting the target value of Z

Ed

.

Figure 3.54 Limit states.

Chapter 04

Figure 4.1 Symbols.

Figure 4.2 Elastic method, symbols.

Figure 4.3 Geometry and loads.

Figure 4.4 Results.

Figure 4.5 Results of the simplified computation.

Figure 4.6 Examples of eccentric bolt groups where the centers of rotation and the balancing forces are drawn.

Figure 4.7 Graphical representation of the forces and the center of rotation.

Figure 4.8 Triangular distribution (center of compression on the bottom).

Figure 4.9 Possible situation where eccentricity is normal to the bolt plane.

Figure 4.10 Example geometry.

Figure 4.11 Left: initial try location; right: final location after computations.

Figure 4.12 Graphical representation for reckoning

m

and

n

.

Figure 4.13

m

and

n

for rectangular and circular hollow steel columns.

Figure 4.14 Small eccentricity.

Figure 4.15 Large eccentricity.

Figure 4.16 Critical dimension (width) in some example situations.

Figure 4.17 Regions of the base plate working in compression (axial load only).

Figure 4.18 Symbols in the EC for various base plate design situations.

Figure 4.19 Column base detail with a double plate to be considered for heavily loaded cases.

Figure 4.20 How to calculate the effective contact area according to [5]. (a) Short projection, (b) large projection.

Figure 4.21 Geometric representation of symbols.

Figure 4.22 Possible solutions for realizing anchor bolts according to AISC.

Figure 4.23 Cone of concrete radiating outward from the anchor.

Figure 4.24 Overlapping cones.

Figure 4.25 Eurocode anchor with washer.

Figure 4.26 Possible welding between columns to base plates.

Figure 4.27 Contact pressure generated by the shear key.

Figure 4.28 Procedure for positioning anchors and base plate.

Figure 4.29 Other possible solutions for the base detail.

Figure 4.30 Possible anchor bolt template made of angles.

Figure 4.31 Geometry.

Figure 4.32 T‐stub parameters.

Figure 4.33 Possible solution (not used in the example) to comply with EC assumptions when anchors are outside the column width.

Figure 4.34 Shear lug pit detail.

Figure 4.35 Angle brace or strut connected by using an additional angle (called “lug angle” in the EC) in order to transmit higher axial forces.

Figure 4.36 Classical solution with the shear tab welded to the primary member flange (a) or web (b).

Figure 4.37 Shear tab welded also to the primary member flanges (or stiffeners).

Figure 4.38 Shear tab welded to the primary member top flange (or stiffener).

Figure 4.39 Notched configurations.

Figure 4.40 Notched flanges can help erection.

Figure 4.41 Both sides of the flanges are notched to allow positioning during erection.

Figure 4.42 (a) Reinforcing plate and (b) false flange.

Figure 4.43 Symbols in the formulas to check the rotation capacity.

Figure 4.44 Plasticization of the column due to horizontal forces; see Ref. [15].

Figure 4.45 Possible configuration, to be checked.

Figure 4.46 Simplified model that considers only the two external bolt pairs.

Figure 4.47 Beam web block shear pattern governing the design.

Figure 4.48 Possible different configuration.

Figure 4.49 Double‐bolted simple plate connection.

Figure 4.50 Double plate to connect an I‐ or H‐shaped brace (HE, IPE, W, UB, UC sections).

Figure 4.51 Connection geometry.

Figure 4.52 Possible connection to a column web.

Figure 4.53 Header plate, possible configurations.

Figure 4.54 End plate connected to a plate welded externally to the primary beam.

Figure 4.55 Header plate connection possible configuration.

Figure 4.56 Final design.

Figure 4.57 Examples (the first with a column‐to‐beam connection) of clip angles.

Figure 4.58 Final geometry.

Figure 4.59 Examples of connections in angles (a) and channels (b).

Figure 4.60 Equal‐leg angles, axes for slenderness calculations.

Figure 4.61 Welded intermediate connectors.

Figure 4.62 Beam leaning on column.

Figure 4.63 Different joints with rigid end plates.

Figure 4.64 Some possible configurations.

Figure 4.65 Triangular (elastic) distribution of forces.

Figure 4.66 Column web shear, different cases.

Figure 4.67 Reworking of a similar figure in [10] to show some types of stiffeners.

Figure 4.68 Possible alternative for web doubler plates on both sides.

Figure 4.69 Welding details from [21].

Figure 4.70 Symbols for formulas in [10].

Figure 4.71 Haunch and its compression force.

Figure 4.72 Cases with formulas in [22].

Figure 4.73 Figure proposed by [10] to illustrate the various limit states of an end plate.

Figure 4.74 Tolerance for end plates.

Figure 4.75 Initial geometry.

Figure 4.76 Horizontal stiffener added.

Figure 4.77 Final configuration.

Figure 4.78 Column splices: classical configuration (with the part leaning on the bottom) and another with flush end plate and cover plates only externally on flanges.

Figure 4.79 Classical beam splice (top) and with uniform top of steel (bottom).

Figure 4.80 Alternative systems for splicing columns of different sizes.

Figure 4.81 Designed splice.

Figure 4.82 Possible alternative design.

Figure 4.83 “Kidney” slot.

Figure 4.84 Brace example with a fin plate (shear tab) that connects both the beam and the brace gusset to the column.

Figure 4.85 Brace example with an end plate that connects both the beam and the brace gusset to the column.

Figure 4.86 KISS method force distribution.

Figure 4.87 Uniform force method.

Figure 4.88 UFM, variant 1.

Figure 4.89 UFM, variant 3.

Figure 4.90 Brace connection; the geometry of the gusset is designed to minimize eccentricities.

Figure 4.91 Dimensional details.

Figure 4.92 Seated supports: unstiffened (a), bearing pad (b), and stiffened (c).

Figure 4.93 Seat, parameters to calculate the supporting leg resistance.

Figure 4.94 Stiffened seat detail.

Figure 4.95 Typical profiles for purlins: Ω, C, RHS, Z.

Figure 4.96 Connection with bolted angle, suitable for C, Z, or RHS profiles.

Figure 4.97 Possible connection of Ω purlins with an upside‐down U‐shaped bent plate.

Figure 4.98 Possible connections bolted to the girt and welded to the column.

Figure 4.99 Possible completely bolted connections for girt‐to‐column joints.

Figure 4.100 Maximum suggested reference distance for expansion joints.

Figure 4.101 Given thickness.

Figure 4.102 Given geometry.

Figure 4.103 Possible joint scheme that allows translation and rotation; stainless steel and rubber parts might be required to be part of the system.

Figure 4.104 Alternative solution that allows the beam to slide.

Figure 4.105 “Old” beams made by riveted plates.

Figure 4.106 Dog bone.

Figure 4.107 Brace connection that can buckle out of plane, thus allowing a plastic hinge to develop.

Figure 4.108 Modified distance considering an ellipse.

Figure 4.109 Links in eccentric braces.

Chapter 06

Figure 6.1 Notches can ease erection.

Figure 6.2 Example of a beam partially notched on flanges to help its insertion during erection.

Figure 6.3 Situations where some parts cannot be reached during erection.

Figure 6.4 Standard wrenches.

Figure 6.5 Polygonal wrench.

Figure 6.6 Pipe and socket wrenches.

Figure 6.7 Distance

x

for Table 6.10.

Figure 6.8 Eurocode limits.

Figure 6.9 DIN 18800 indications.

Figure 6.10 Australian standard AS 4100 indications.

Figure 6.11 Allowable encroachment.

Figure 6.12 Possible instructions (in mm) for notches.

Figure 6.13 Top flange notch example.

Figure 6.14 Direct tension indicator.

Figure 6.15 Twist‐off round head bolt.

Figure 6.16 Single lap joint.

Figure 6.17 Tapered (beveled) washers.

Figure 6.18 Shims prebolted in the shop for shipping.

Figure 6.19 Finger shims.

Figure 6.20 Graphical representation of hot dip galvanization of a steel profile.

Figure 6.21 Minimum hole (not optimal) for zinc drainage.

Figure 6.22 Optimal details (various situations are represented) to avoid galvanizing problems).

Figure 6.23 Reinforced base plate: note the half‐moon‐shaped cut to drain zinc.

Figure 6.24 Composite column – connection designed outside the encased part.

Figure 6.25 Possible troubles due to camber – the geometry at erection (on the right‐hand side) does not fit with design geometry (on the left).

Figure 6.26 Possible symbols for holes and corresponding bolt sizes.

Figure 6.27 Bent plate welded over the main member web and bolted to the notched secondary member similarly to a fin plate.

Figure 6.28 Double angle welded to the primary web (stiffener on the back side possible) and bolted to the secondary member (notched).

Figure 6.29 Plate butt welded to the secondary web and bolted to the primary web.

Figure 6.30 Plate welded to the secondary member (notched on flanges on one side) and field welded to the column web.

Figure 6.31 Fin plate (shear tab) inclined as necessary on column web and bolted to the beam.

Figure 6.32 Fin plate (shear tab) inclined as necessary on column flange and bolted to the beam.

Figure 6.33 Fin plate inclined as in Figure 6.32 but laterally; stiffeners on the column are likely necessary.

Figure 6.34 End plate welded to secondary and bolted to only half flange of the column; solution to be calculated carefully because of the position of the bolts.

Figure 6.35 Representation of Figure 6.34 but the bolt position, whenever possible, will allow a better performance.

Figure 6.36 Bent plate bolted to the web secondary and to the primary flange (half of it).

Figure 6.37 Bent plate welded (or bolted) to the column flange and bolted to the secondary beam (or brace) on the left; two double angles bolted to the column flange (bolts through the other plate) and welded (or bolted) to the web of the beam.

Figure 6.38 Shear‐tab‐like plate skewed and welded over the main beam and bolted to the notched secondary.

Chapter 07

Figure 7.1 Tie plates for large channels.

Figure 7.2 Beam‐to‐beam fin plate (extended shear tab) welded to the primary top flange and half web.

Figure 7.3 Beam‐to‐column moment connection with horizontal pipe brace also framing into it.

Figure 7.4 Extended shear tab (fin plate) welded to horizontal stiffeners and column web.

Figure 7.5 Tube brace (or, generally speaking, a diagonal) going through a beam.

Figure 7.6 Full‐depth shear tab (fin plate) welded to primary beam and bolted to secondary beam.

Figure 7.7 Channel (likely a stair stringer) bolted to the column web (stiffener on the back).

Figure 7.8 Fin plate with a stiffener on the opposite side.

Figure 7.9 Diagonal angle(s) supporting a beam (likely a cantilever).

Figure 7.10 End plate in a corner.

Figure 7.11 Channels connected on flanges.

Figure 7.12 Central detail of a cranked K (or Y or inverted‐V) brace.

Figure 7.13 Connection to column of a girt realized with a channel.

Figure 7.14 Sloped beam end plate framing into a column.

Figure 7.15 Brace connection of a pipe into column and beam.

Figure 7.16 Joint of a channel (possibly a stair stringer) into a column.

Figure 7.17 Truss detail.

Figure 7.18 End plate with central stiffener between wide flange type I beams.

Figure 7.19 Fully bolted detail to connect C‐shaped purlins with a stabilizing profile.

Figure 7.20 Angles framing into a beam.

Figure 7.21 End plate on column web.

Figure 7.22 Welded apex between beams leaning on a central column.

Figure 7.23 Heavy angle (probably a brace) bolted to plate welded to column weak side.

Figure 7.24 Bolted connections in a truss having a rotated I beam as lower chord (stiffeners actually suggested opposite to the plate).

Figure 7.25 Pipe connected to column flange.

Figure 7.26 Vertical pipe braces bolted to column weak axis.

Figure 7.27 End plate between beams of the same size.

Figure 7.28 Angles connected to a beam (stiffener to be noted).

Figure 7.29 Omega‐shaped purlins connected to supporting beam.

Figure 7.30 Joint on column weak side: on the left angles and on the right‐hand side a beam bolted through double angles.

Figure 7.31 Vertical L brace on column; main beam leaning on column (horizontal plates for bolting) and secondary beam bolted to it with double angles.

Figure 7.32 End plate between beams of different heights (primary beam actually shallower); stiffeners on both sides of the main beam.

Figure 7.33 Double‐angle connection: false flanges added to secondary beam to make up for notches on the flanges.

Figure 7.34 Another all‐bolted double‐angle connection with top notch on secondary beam.

Figure 7.35 Sloped beam stiffened with central plate and bolted to column.

Figure 7.36 Detail of a plate welded to rafter and bolted to C purlins.

Figure 7.37 Detail of C girts connected to a column in a corner.

Figure 7.38 Beam‐to‐beam shear tab (fin plate) with top notch on secondary beam.

Figure 7.39 Two C girts connected to column.

Figure 7.40 Beam‐to‐column flexible end plate.

Figure 7.41 Detail at the intersection of X braces in double angles.

Figure 7.42 Beam connected by a flexible end plate to column weak side (stiffener added).

Figure 7.43 End‐plate splice between consecutive beams.

Figure 7.44 End‐plate connection between consecutive beams with different depth.

Figure 7.45 All‐bolted splice (double plates on web and double plates on flanges).

Figure 7.46 Roof detail, C purlins bolted to rafters positioned over central column.

Figure 7.47 All‐bolted double angle with reinforcing plate welded to secondary beam to make up for the top notch.

Figure 7.48 Main beam supported by column and notched secondary beam bolted to it with double angles.

Figure 7.49 Angle welded to column flange to support the

RHS

(

rectangular hollow section

) girts.

Figure 7.50 Moment connection with bottom haunch, web doubler, and continuity plates.

Figure 7.51 Central‐plate detail of large double angles in an X brace.

Figure 7.52 Base plate with stiffening ribs on both sides.

Figure 7.53 Flexible end plate between beams of different sizes and stiffener on the opposite side.

Figure 7.54 Connection between large pipe braces and an intersecting beam; stiffeners on beam web and plates.

Figure 7.55 Column splice.

Figure 7.56 Plates welded to column flange and bolted to beam to resist an important bending moment; to help erection there is clearance between top flange and top plate; finger shims will be added during erection.

Figure 7.57 End plate between beams; beam stub welded on the opposite side.

Figure 7.58 Beam‐to‐column moment connection with continuity plates; welded stub on the left‐hand side to support a C purlin; a welded plate supports a C girt.

Figure 7.59 Secondary beam (deeper than primary) notched on both flanges and connected by all‐bolted double angles.

Figure 7.60 Double moment connection; continuity plates in the column and top and bottom stiffeners on beam flanges.

Figure 7.61 Top notched beams connected by double angles.

Figure 7.62 Apex connection between rafters and purlins on top.

Figure 7.63 Column splice – end plate to support compression and shear; external plates for bending moment.

Figure 7.64 Fin plate with notched secondary beam (deeper than supporting beam).

Figure 7.65 Extended shear tab with primary beam positioned over column.

Figure 7.66 Beam splice (single plates on web and flanges).

Figure 7.67 Channels framing into a stiffened beam.

Figure 7.68 Welded truss (bottom chord detail); double angles are interconnected through welded ties.

Figure 7.69 Symmetric connection at column – welded beam stubs are bolted by end plates with beams.

Figure 7.70 Stiffened beam leaning on column; channel brace bolted to gusset welded to column and to top end plate.

Figure 7.71 H brace flanges connected by bolted angles to the gusset welded to the horizontal beam; stiffeners added to gusset and beam.

Figure 7.72 Symmetric joints with all‐bolted double plates that connect secondary beams.

Figure 7.73 L braces connected to column weak side.

Figure 7.74 Symmetric connection with braces framing into it.

Figure 7.75 Inclined beam bolted through a moment connection to column – various stiffeners are present, including a diagonal stiffener to help web panel shear.

Figure 7.76 Another moment connection with haunch and continuity plates.

Figure 7.77 Column spliced by double‐bolted plates on flanges and web; due to the gap, the compression load is not transferred by contact.

Figure 7.78 Base plate with central stiffener on column strong side.

Figure 7.79 Bottom chord of a truss with large bolted double angles; various stiffeners inserted.

Figure 7.80 Beam‐to‐beam flexible end plate with horizontal braces in double angle also framing into it.

Figure 7.81 Central plate possible detail of X braces designed as L profiles.

Figure 7.82 Sloping beam bolted on column through a plate also serving as connection for horizontal pipe braces.

Figure 7.83 Double‐sided end‐plate connections to a primary beam also supporting a welded stub on top.

Figure 7.84 Column with beam stubs welded on the weak side that serves to splice beams (likely designed as continuous in the calculation model).

Figure 7.85 Main beam bolted to column (stiffeners added) and connecting secondary beams by all‐bolted double plates.

Figure 7.86 Horizontal double‐L braces framing into the web of a beam.

Figure 7.87 Lattice tower details.

Figure 7.88 Stiffened base plate also connecting a double‐U brace.

Figure 7.89 Connection without welds – brace, gusset, and beam are all connected through all‐bolted double angles.

Figure 7.90 On‐site welded moment connection – the web is bolted, then full‐penetration welds of flanges are executed on‐site.

Figure 7.91 Beam splice designed to maintain uniform

TOS

(

top of steel

) for a crane girder – external plate only on the bottom flange (the joint is likely in a zone where positive bending is prevalent, i.e. bottom flange has tension) and end plate (with internal stiffeners) for shear and top flange tension.

Figure 7.92 Heavy vertical brace made by quadruple angles framing into the stiffened web of a beam.

Figure 7.93 Four L braces converging into a heavy base plate realized by a double plate and a shear lug (shear key).

Figure 7.94 Braces bolted to gussets welded to an RHS column; a horizontal RHS is also bolted in the joint.

Figure 7.95 Beam‐to‐column moment connection by bolted web (also good for preassembly during erection) and field welds to beam flanges; continuity plates in the column, also supporting an additional smaller column bolted on top.

Figure 7.96 Brace central detail – the channels are bolted to a plate reinforced by welded channels to increase the available area and help the stability of the plate itself.

Figure 7.97 Stair U stringer bolted to the supporting beam by a bolted angle.

Figure 7.98 End plate for connection to column weak side; stiffeners on both sides of the column.

Figure 7.99 Large I‐shaped brace splice connected to stiffened beam.

Figure 7.100 Vertical I‐shaped brace bolted by four angles (alternatively, four double plates also possible); to allow this kind of connection, a cruciform plate assembly is welded to the column and another to the end of the brace.

Figure 7.101 Horizontal roof braces connected by bolted angles to omega‐shaped purlins.

Figure 7.102 Fin plate (shear tab) with Nelson studs welded to the beam.

Figure 7.103 I brace spliced to same section stub framing into heavy base plate with shear lug.

Figure 7.104 Symmetric moment connection with haunches and various stiffeners on column web and beam web; I‐shaped purlins bolted on top.

Figure 7.105 Bolted beam‐to‐column connection where also the gusset plate supporting the brace is field bolted to beam and column.

Figure 7.106 Splice in the corner of a lattice tower – end plates connect vertical angles, also connected by external cover plates; bent plates welded to vertical angles connect diagonals.

Figure 7.107 Secondary beams connected to main member on web and flanges in order to restore secondary‐beam bending resistance.

Figure 7.108 Perfect hinge between pipe brace and stiffened beam.

Figure 7.109 Apex connection of multiple beams into a pipe column.

Figure 7.110 Cruciform column splice with end plate and external cover plates; octagonal base plate also taking a gusset plate for braces.

Figure 7.111 Haunched end‐plate apex of rafters also taking the loads of plane braces realized with pipes.

Figure 7.112 H brace connected to base plate gusset by web plates on web and angles on flanges.

Guide

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Design and Analysis of Connections in Steel Structures

Fundamentals and Examples

Alfredo Boracchini

Copyright

Author

Alfredo Boracchini, P. E.

[email protected]

Cover

Detail of a Moment Connection in a Composite Building Structure (“InterPuls spa” Building, Reggio Emilia, Italy)

Photo: Alfredo Boracchini

All books published by Ernst & Sohn are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.

Library of Congress Card No.: applied for

British Library Cataloguing‐in‐Publication Data

A catalogue record for this book is available from the British Library.

Bibliographic information published by the Deutsche Nationalbibliothek

The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at http://dnb.d‐nb.de.

© 2018 Wilhelm Ernst & Sohn, Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Rotherstraße 21, 10245 Berlin, Germany

All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form – by photoprinting, microfilm, or any other means – nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law.

Coverdesign Sophie Bleifuß, Berlin, Germany

Typesetting SPi Global, Chennai, India

Printing and Binding

Print ISBN: 978-3-433-03122-3

ePDF ISBN: 978-3-433-60606-3

ePub ISBN: 978-3-433-60607-0

oBook ISBN: 978-3-433-60605-6

Dedication

To my mom Alda

Preface

Structural Steel Connection Design is an engineering manual directed toward the engineering audience. The first section provides an introduction to key concepts, then progresses to provide a more in‐depth description for the design of structural steel connections.

A correct approach to connection design is fundamental in order to have a safe and economically sound building. Therefore, this book will attempt to explain how to set up connections within the main calculation model, choose the types of connections, check them (limit states to be considered), and utilize everything in practice.

The focal point of the book is not to closely follow and explain one specific standard; rather the aim is to treat connections generally speaking and to understand the main concepts and how to apply them. This means that, even though Eurocode (EC) and the American Institute of Steel Construction (AISC) are the most referenced standards, other international norms will be mentioned and discussed. This helps to understand that connection design is not an exact science and that numerous approaches can be viable.

Type by type, connection by connection, detailed examples will be provided to help perform a full analysis for each limit state.

An excellent software tool (SCS – Steel Connection Studio) will be illustrated and used as an aid to assist in the comprehension of connection design. The software can be downloaded for free at www.steelconnectionstudio.com or at www.scs.pe and can be installed as a demo (trial) version (limitations about printing, saving, member sizes, and reporting), see “Software Downloads and its Limitations” (page xxiv). A professional full version can also be purchased online but the demo version is enough to reproduce the examples in the book.

The book will also try to deliver some practical suggestions for the professional engineer: how to talk about bracings to the architect, how to interact with fabricators showing an understanding of erection and fabrication, and much more.

Many countries have a deeper engineering culture about concrete structures than steel structures. This manual therefore aims to illustrate to engineers that do not design steel structures daily, some concepts that will facilitate and make their design of connections for steel structures more efficient. This will be done using a practical, rather than a theoretical, approach.

Design of steel structures can become tricky when it is about stability (buckling) and joints: this second fundamental aspect of steel constructions, which is crucial for economic performance, will be examined in detail.

The text, figures, charts, formulas, and examples have been prepared and reported with maximum care in order to help the engineer better understand and set up his or her own calculations for structural steel connections. However, it is possible that the book contains errors and omissions, and therefore readers are encouraged to have standards at hand as their primary reference. No responsibility is accepted and taken for the application of concepts explained in the manual: the engineer must prepare and perform any analysis and design under his or her complete competence, responsibility, and liability.

For a list of errors and omissions found in the book and their corrections, please check www.steeldesign.info.

Finally, please use www.steeldesign.info to send comments, suggestions, criticisms, and opinions. The author thanks you in advance.

April 2018

Alfredo Boracchini

Reggio Emilia

About the Author

Alfredo Boracchini is a Professional Engineer in Italy, Canada, and some states of the United States. His professional experience is mainly in steel structures that he has designed and calculated for many applications and in various parts of the world. He is an active member in some international steel associations and the owner of an engineering firm with offices in Europe, Asia, and America. This allowed him to collect extensive international experience in the field of steel connection design that he shares in this manuscript with other engineers interested in this field.

Acknowledgments

The author is grateful to Giovanna Zanardi for her assiduous support and to Renzo Mazzali for his precious advice.

I also wish to express my gratitude to Antonella, Alda, Emma, Irma, Vera, and Lea for their love and for sharing daily with me, sometimes in spite of themselves, my passion for structural engineering.

List of Abbreviations

AISC

American Institute of Steel Construction

ASD

allowable stress design

AWS

American Welding Society

BS

British Standards

CG

center of gravity

EC

Eurocode

EN

European Standard

DIN

German Institute for Standardization

ECCS

European Convention for Constructional Steelwork

FCAW

flux‐cored arc welding

FEA

finite element analysis

FEM

finite element method

GMAW

gas metal arc welding

HSS

hollow structural steel

ISO

International Organization for Standardization

KISS

keep it simple stupid

LRFD

load and resistance factor design

NDP

nationally determined parameter

NTC

Italian Standard for Constructions

OSHA

Occupational Safety and Health Administration

PL

preload

PR

partially restrained

RCSC

Research Council on Structural Connections

SAW

submerged arc welding

SCS

Steel Connection Studio

SMAW

shielded metal arc welding

TOS

top of steel

UFM

uniform force method

Software Download and its Limitations

The engineer can use the book to get familiar with SCS – Steel Connection Studio, a fantastic software tool that can be used in the design of steel connections. The software (which can be downloaded from www.steelconnectionstudio.com or www.scs.pe) works in a demo version with the following limitations:

Only 90 consecutive days of usage are allowed after installation. Providing the code

Ej8Z4pn1

the demo version can be extended with no time limitation. Please send an email to [email protected] if you are interested in this offer.

File saves are not possible.

Commercial and academic usage is not possible.

Maximum dimensions of members are 254 mm/10 in. in width and 361 mm/14.2 in. in depth. The sketch cannot be printed.

The word

demo

is watermarked in the sketch.

The maximum number of reports that can be generated is 25.

For videos, tutorials, validation examples, the manual, and additional (commercial too) information, please visit www.steelconnectionstudio.com or www.scs.pe.

1Fundamental Concepts of Joints in Design of Steel Structures

Regarding joints, the first fundamental concept the engineer must be clear about when he or she starts to design is which connections will develop moment resistance and which can be executed as simple pin joints. To do this, it is necessary to clarify the lateral load resisting system.

1.1 Pin Connections and Moment Resisting Connections

1.1.1 Safety, Performance, and Costs

Steel structures should be safe, able to perform, and be cost‐effective.

They must be safe because they act as canopies, mezzanines, buildings, skyscrapers, bridges, and much more that give shelter, protect, and be welcoming to men and women. A structural collapse is extremely dangerous and likely to cause severe harm to anyone in the surrounding area.

Structures must also effectively serve their commercial purpose while efficiently and comfortably (for the users) maintaining their design features over time. These are the basic notions of serviceability limit state design specifying that, just as a nonlimiting example, deformations will not damage secondary structures or that excessive vibrations will not make users uncomfortable.

Poor performance might also decrease the structure's value and harm the property owner.

Simultaneously, the market logic requires that the structural system be economically sound and cost‐effective when compared to alternatives using different materials and design. Being economically sound is a complex matter that must take into account many factors in the building design. However, the engineer must make the structure as cost‐effective as possible without compromising safety and performance. The service and expertise that engineers are expected to deliver should include reducing costs while maintaining high standards of functionality and protection.

For the principles stated, the design of connections is a focal point and it must be well defined in the engineer's mind from the commencement of the project.

1.1.2 Lateral Load Resisting System

The choice of connections is related to the choice of the lateral load resisting system.

Taking a closer look at this key point, we consider these initial hypotheses: that the structure geometry is defined, that steel will be used as structural material, and that the design loads are provided. This means that the engineer can set up the analysis model with the finite element software available. However, before building the model wireframe, the engineer must have a clear vision of the lateral resisting system(s). This choice influences costs and architectural restraints.

Lateral load resisting systems can be diverse and variously combined among themselves. Each horizontal direction can have its own system, one that may be different from the other direction.

The basic lateral resisting systems (Figure 1.1) are as follows:

Braces (bracings)

Moment connections (portals)

Base rigid restraints (cantilever columns or inverted pendulum)

Connection to an existing structure or another ad hoc structure built with different materials (say a concrete staircase, masonry or concrete walls, etc.).

Figure 1.1 Lateral load resisting systems.