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Structural Steel Design to Eurocode 3 and AISC Specifications E-Book

Claudio Bernuzzi

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Herausgeber: John Wiley & Sons
Kategorie: Wissenschaft und neue Technologien
Sprache: Englisch

Beschreibung

Structural Steel Design to Eurocode 3 and AISC Specifications deals with the theory and practical applications of structural steel design in Europe and the USA. The book covers appropriate theoretical and background information, followed by a more design‐oriented coverage focusing on European and United States specifications and practices, allowing the reader to directly compare the approaches and results of both codes. Chapters follow a general plan, covering: A general section covering the relevant topics for the chapter, based on classical theory and recent research developments A detailed section covering design and detailing to Eurocode 3 specification A detailed section covering design and detailing to AISC specifications Fully worked examples are using both codes are presented. With construction companies working in increasingly international environments, engineers are more and more likely to encounter both codes. Written for design engineers and students of civil and structural engineering, this book will help both groups to become conversant with both code systems.

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Leseprobe

Cover

Title Page

Preface

CHAPTER 1: The Steel Material

1.1 General Points about the Steel Material

1.2 Production Processes

1.3 Thermal Treatments

1.4 Brief Historical Note

1.5 The Products

1.6 Imperfections

1.7 Mechanical Tests for the Characterization of the Material

CHAPTER 2: References for the Design of Steel Structures

2.1 Introduction

2.2 Brief Introduction to Random Variables

2.3 Measure of the Structural Reliability and Design Approaches

2.4 Design Approaches in Accordance with Current Standard Provisions

CHAPTER 3: Framed Systems and Methods of Analysis

3.1 Introduction

3.2 Classification Based on Structural Typology

3.3 Classification Based on Lateral Deformability

3.4 Classification Based on Beam-to-Column Joint Performance

3.5 Geometric Imperfections

3.6 The Methods of Analysis

3.7 Simple Frames

3.8 Worked Examples

CHAPTER 4: Cross-Section Classification

4.1 Introduction

4.2 Classification in Accordance with European Standards

4.3 Classification in Accordance with US Standards

4.4 Worked Examples

CHAPTER 5: Tension Members

5.1 Introduction

5.2 Design According to the European Approach

5.3 Design According to the US Approach

5.4 Worked Examples

CHAPTER 6: Members in Compression

6.1 Introduction

6.2 Strength Design

6.3 Stability Design

6.4 Effective Length of Members in Frames

6.5 Worked Examples

CHAPTER 7: Beams

7.1 Introduction

7.2 European Design Approach

7.3 Design According to the US Approach

7.4 Design Rules for Beams

7.5 Worked Examples

CHAPTER 8: Torsion

8.1 Introduction

8.2 Basic Concepts of Torsion

8.3 Member Response to Mixed Torsion

8.4 Design in Accordance with the European Procedure

8.5 Design in Accordance with the AISC Procedure

CHAPTER 9: Members Subjected to Flexure and Axial Force

9.1 Introduction

9.2 Design According to the European Approach

9.3 Design According to the US Approach

9.4 Worked Examples

CHAPTER 10: Design for Combination of Compression, Flexure, Shear and Torsion

10.1 Introduction

10.2 Design in Accordance with the European Approach

10.3 Design in Accordance with the US Approach

CHAPTER 11: Web Resistance to Transverse Forces

11.1 Introduction

11.2 Design Procedure in Accordance with European Standards

11.3 Design Procedure in Accordance with US Standards

CHAPTER 12: Design Approaches for Frame Analysis

12.1 Introduction

12.2 The European Approach

12.3 AISC Approach

12.4 Comparison between the EC3 and AISC Analysis Approaches

12.5 Worked Example

CHAPTER 13: The Mechanical Fasteners

13.1 Introduction

13.2 Resistance of the Bolted Connections

13.3 Design in Accordance with European Practice

13.4 Bolted Connection Design in Accordance with the US Approach

13.5 Connections with Rivets

13.6 Worked Examples

CHAPTER 14: Welded Connections

14.1 Generalities on Welded Connections

14.2 Defects and Potential Problems in Welds

14.3 Stresses in Welded Joints

14.4 Design of Welded Joints

14.5 Joints with Mixed Typologies

14.6 Worked Examples

CHAPTER 15: Connections

15.1 Introduction

15.2 Articulated Connections

15.3 Splices

15.4 End Joints

15.5 Joint Modelling

15.6 Joint Standardization

CHAPTER 16: Built-Up Compression Members

16.1 Introduction

16.2 Behaviour of Compound Struts

16.3 Design in Accordance with the European Approach

16.4 Design in Accordance with the US Approach

16.5 Worked Examples

Appendix A: Conversion Factors

Appendix B: References and Standards

B.1 Most Relevant Standards For European Design

B.2 Most Relevant Standards for United States Design

B.3 Essential bibliography

Index

End User License Agreement

List of Tables

Chapter 01

Table 1.1 Mechanical characteristics of steels used for hot-rolled profiles.

Table 1.2 Mechanical characteristics of steels used for hollow profiles.

Table 1.2 Nominal yielding strength values (

) and nominal failure strength (

) for bolts.

Table 1.3 ASTM specifications for various structural shapes (from Table 2-3 of the

AISC Manual

Table 1.4 Applicable ASTM specifications for plates and bars (from Table 2-4 of the

AISC Manual

Table 1.5 Codes used for toughness requirement (Charpy V-notch).

Chapter 02

Table 2.1 Proposed values of the ψ combination coefficients (from Table A1.1 of EN 1990).

Table 2.2 Proposed values of action coefficient

for verification at ultimate limit states.

Chapter 03

Table 3.1 Maximum values of member imperfections.

Table 3.2 Value of the shape coefficient (α

shape

) for the European I beams (IPE) and European wide flange beams (HE) for steel grade S235, S275, S355, S420 and S460.

Table 3.3 Methods of analysis and associated approaches for verification checks.

Table E3.2.1 Indications of analysis type according to European codes.

Table E3.2.2 Indications of the type of analysis using an engineering approach.

Chapter 04

Table 4.1 Maximum width-to-thickness ratios for compression elements, from EN 1993-1-1: Table 5.2 (sheet 1 of 3).

Table 4.2 Maximum width-to-thickness ratios for compression elements from EN 1993-1-1: Table 5.2 (sheet 2 of 3).

Table 4.3 Maximum width-to-thickness ratios for compression elements, from EN 1993-1-1: Table 5.2 (sheet 3 of 3).

Table 4.4a Width-to-thickness ratios for members subject to axial compression (from Table B4.1a of AISC 360-10).

Table 4.4b Width-to-thickness ratios for members subject to flexure (from Table B4.1b of AISC 360-10).

Table E4.5.1a Values of

y,Rk

for different

values – EC3 (S.I. units).

Table E4.5.1b Values of

y,Rk

for different

values – EC3 (US units).

Table E4.5.2a Values of

for different

values – AISC (S.I. units).

Table E4.5.2b Values of

for different

values – AISC (US units).

Chapter 05

Table 5.1 Reduction factors

for angles connected via a single leg.

Table 5.2 Shear leg factors for connections to tension members (from Table D3.1 of AISC 360-10).

Chapter 06

Table 6.1 Values of the proportionality slenderness.

Table 6.2 Values of

for the various stability curves.

Table 6.3a Guide for the selection of the appropriate stability curve for hot-rolled and welded sections.

Table 6.3b Guide for the selection of the appropriate stability curve for cold-formed sections.

Table 6.4 Values of coefficient

for design checks according to EC3.

Table 6.5 Effective stiffness coefficient

for a beam in a frame without concrete floor slabs.

Table 6.6 Reduced beam stiffness coefficients

due to axial compression.

Table 6.7 Effective stiffness coefficient

for a beam in a building frame with concrete floor slabs.

Table 6.8 Theoretical and recommended AISC values of the effective length factor (K) for isolated column.

Chapter 07

Table 7.1 Recommended limiting values for vertical deflections from ENV 1993-1-1.

Table 7.2 Eurocode recommended values for the imperfection factor

for lateral torsional buckling curves.

Table 7.3 Recommended values for the lateral torsional buckling curves using the general approach.

Table 7.4 Recommendation for the lateral torsional buckling curve selection using the approach proposed for rolled sections or equivalent welded sections.

Table 7.5 Correction factors

Table 7.6a Coefficients

and

for beams with end moments (Annex F of ENV 1993-1-1).

Table 7.6b Coefficients

and

for intermediate transverse load (Annex F of ENV 1993-1-1).

Table 7.7a Coefficients

and

for beams with end moments proposed by Boissonade

et al.

in the ECCS doc. No. 119.

Table 7.7b Coefficients

and

in case of intermediate transverse loading proposed by Boissonade

et al.

in the ECCS doc. No. 119.

Table 7.8 Historical (traditional) limits for beam vertical deflections in accordance with AISC 360-10 and ASCE 7-10.

Table 7.9

values for method 1.

Table 7.10 Evaluation of

Table 7.11

and

for ASTM A6 hot rolled sections with

= 50 ksi.

Table 7.12 Appropriate limit states for flexural strength verification (from Table F1.1 of AISC 360-10).

Table 7.13 Compute of

for case (a).

Table 7.14 Values of

in most common cases (From Table 3-1 of the

AISC

Manual).

Table 7.15 Computation of

for case (b).

Table 7.16 Computation of

for case (c) (from Figure C-F10.1 of AISC 360-10).

Table 7.17 Computation of

for case (d).

Table 7.18 Values of

for round HSS, case (g).

Table 7.19 Values of

for tees, case (h).

Table 7.20 Values of

for double angles, case (i).

Table 7.21

values for angles.

Table 7.22 Indications for the minimum geometrical characteristics of cross-sections.

Table 7.23 Value of

min

);

) for European steel grades.

Table 7.24 Indications for the minimum geometrical characteristics of cross-sections (AISC-ASD).

Table 7.25 Value of

min

);

) for ASTM steel grades.

Table E7.1.1 LTB results.

Table E7.2.1 Values for design and allowable flexural strength.

Chapter 08

Table 8.1 Position of the shear centre C (point O identifies the centroid of cross-section).

Table 8.2 Value of

for a rectangular cross-section (with a > b).

Table 8.3 Warping constants when the centroid is coincident with the shear centre.

Table 8.4 Warping constants for mono-symmetrical cross-sections.

Table 8.5 Key data for the torsional design in the case of a concentrated torsional load.

Table 8.6 Key data for the torsional design in the case of a uniform torsional load.

Chapter 09

Table 9.1 Values of

and

coefficients for bi-axial bending verification.

Table 9.2 Values for

and ∆

Table 9.3 Coefficients

for members not susceptible to torsional deformations.

Table 9.4 Coefficients

for members susceptible to torsional deformations.

Table 9.5 Coefficient

mi,

Table 9.6 Interaction factors

for members not susceptible to torsional deformations.

Table 9.7 Interaction factors

for members susceptible to torsional deformations.

Table 9.8 Equivalent uniform moment factors

in Tables 9.6 and 9.7.

Chapter 10

Table 10.1 Influence of warping on the location of the more stressed cross-section point.

Chapter 12

Table 12.1 Deflection limit ratios for structures under horizontal load according to ENV 1993-1-1.

Table 12.2 Deflection limit ratios for structures under horizontal load according to AISC.

Table 12.3 Summary of the key features of the EC3 methods of analysis for frames.

Table 12.4 Second order amplification factor as a function of

Table 12.5 Summary of the direct analysis method.

Table 12.6 Summary of the effective length method.

Table 12.7 Summary of the first order analysis method.

Table E12.1.1 Summary of verification results.

Chapter 13

Table 13.1 Additional rotation for the combined method (8.8 and 10.9 bolts).

Table 13.2a Minimum free space for tightening hexagonal screws, bolts and nuts (mm) for engineer’s wrench (single-head) and box wrench (single-head).

Table 13.2b Minimum free space for tightening hexagonal screws, bolts and nuts (mm) for slugging wrench (open end) and slugging wrench (box).

Table 13.3 Nominal clearances for bolts and pins (values in millimetres).

Table 13.4 Minimum and maximum spacing, end and edge distances (using millimetres).

Table 13.5 Categories of connections in accordance with EN 1993-1-8.

Table 13.6a Nominal holes (dimensions in inches) (from Table J3.3 of AISC 360-10).

Table 13.6b Nominal holes (dimensions in millimetres) (from Table J3.3M of AISC 360-10).

Table 13.7a Minimum edge distance (

) from the centre of standard hole (

) to the edge of connected part (dimensions in inches) (from Table J3.4 of AISC 360-10).

Table 13.7b Minimum edge distance (

) from the centre of standard hole (

) to the edge of connected part (dimensions in millimetres) (from Table J3.4M of AISC 360-10).

Table 13.8a Values of edge distance increment

–

dimensions in inches (mm) (from Table J3.5 of AISC 360-10).

Table 13.8b Values of edge distance increment

–

dimensions in millimetres (inches) (from Table J3.5M of AISC 360-10).

Table 13.9a Minimum bolt pretension (from Table J3.1 of AISC 360-10).

Table 13.9b Minimum bolt pretension (from Table J3.1M of AISC 360-10).

Table 13.10 Nut rotation from the snug-tight condition for turn-of-nut pretensioning.

Table 13.11 Nominal strength of fasteners and threaded parts, ksi (MPa) (from Table J3.2 of AISC 360-10).

Chapter 14

Table 14.1 Design of welded joints.

Table 14.2 Effective throat of partial-joint-penetration groove welds (from Table J2.1 of AISC 360-10).

Table 14.3 Effective weld throats of flare groove welds (from Table J2.2 of AISC 360-10).

Table 14.4 Minimum effective throat of partial-joint-penetration groove welds (from Table J2.3 of AISC 360-10).

Table 14.5 Minimum size of fillet welds (from Table J2.4 of AISC 360-10).

Table 14.6 Available strength of welded joints, ksi (MPa) (from Table J2.5 – part 1 of AISC 360-10).

Table 14.7 Available strength of welded joints, ksi (MPa) (from Table J2.5 – part 2 of AISC 360-10).

Table 14.8 Available strength of welded joints, ksi (MPa) (from Table J2.5 – part 3 of AISC 360-10).

Table 14.9 Available strength of welded joints, ksi (MPa) (from ACI 360-10, Table J2.5 – part 4).

Chapter 15

Table 15.1 Value of the design rotation required for some common types of loaded beams.

Table 15.2 Excerpt from

Joint in Steel Construction: Simple Joints to Eurocode 3

, by BCSA-SCI, Publication P358 (2011).

Table 15.3 End plate connections according to the

AISC Steel Construction Manual

Chapter 16

Table 16.1 Efficiency factor

Table 16.2 Maximum spacing for interconnections in closely spaced built-up or star battened angle members.

Table E16.2.1 Stress ratios for Examples E16.1 and E16.2.

List of Illustrations

Chapter 01

Figure 1.1 Typical constitutive law for structural steel.

Figure 1.2 Structural steel: (a) schematization of the uniaxial constitutive law and (b) yield surface for biaxial stress states.

Figure 1.3 Rolling process.

Figure 1.4 Intermediate steps of the rolling process for an I-shape profile.

Figure 1.5 Continuous formation of circular hollow cold-formed profiles.

Figure 1.6 Punch-and-die process for cold-formed profiles.

Figure 1.7 Cold-formation images of a stiffened channel profile.

Figure 1.8 Typical insulated element.

Figure 1.9 Example of a special ribbed decking product.

Figure 1.10 Typical steel-concrete composite floor system.

Figure 1.11 Example of a design table for a bare steel ribbed decking product.

Figure 1.12 Regions that are typically subject to local effects of wind loads.

Figure 1.13 Residual stress distribution in a hot-rolled rectangular profile during the cooling phase (temporary from a to d).

Figure 1.14 Distribution of residual stresses during the cooling phase of an I-shape.

Figure 1.15 Distribution of residual stresses in hot-rolled I-shapes.

Figure 1.16 Residual stresses in a cold-rolled plate.

Figure 1.17 Variation of the mechanical properties of the material after cold-formation.

Figure 1.18 Additional tolerance checks for I-shapes: (a) perpendicularity tolerance, (b) symmetry tolerance and (c) straightness tolerance.

Figure 1.19 Horizontal notional loads equivalent to the imperfections for a sway frame.

Figure 1.20 Imperfect column (a) and horizontal equivalent force (b).

Figure 1.21 Typical sample for rolled products.

Figure 1.22 Typical stress-strain (

σ–ε

) relationship for structural steels.

Figure 1.23 Upper and lower yielding points for structural steel.

Figure 1.24 Influence of temperature on the constitutive law of steel.

Figure 1.25 Testing of a specimen in a stub column test.

Figure 1.26 Typical components of adjustable storage pallet racks.

Figure 1.27 Charpy V-notch test.

Figure 1.28 Energy associated with the toughness test as a function of the testing temperature.

Figure 1.29 Bending test.

Figure 1.30 Hardness test: (a) durometer, (b) conical tip and (c) spherical tip.

Chapter 02

Figure 2.1 Example of the probability density function (PDF).

Figure 2.2 Probability density function and cumulate density function.

Figure 2.3 Probability density function for the weight per unit volume of the concrete and the steel.

Figure 2.4 Example of the relationship between costs and probability of an unsuccessful outcome.

Figure 2.5 Assessment of failure probability.

Figure 2.6 Safe domain in accordance with level II methods.

Figure 2.7 Safety index.

Figure 2.8 Verification in accordance with first level approaches.

Chapter 03

Figure 3.1 Building and framed system.

Figure 3.2 Three-dimensional framed system.

Figure 3.3 Planar frame model.

Figure 3.4 Common frame typologies (a–d).

Figure 3.5 Simplified models for the design of braced frames.

Figure 3.6 Cantilever beam in the initial and deformed configuration.

Figure 3.7 Example of planar braced frame with diagonal members resisting to sole tension: (a) the frame and (b) model for the structural analysis.

Figure 3.8 Typical buckling modes that are not relevant for design purposes.

Figure 3.9 Deformed configuration due to lateral frame instability.

Figure 3.10 Application of Horne’s method.

Figure 3.11 (a) Definition of the moment and of the rotation for a joint. (b) Typical moment-rotation relationships.

Figure 3.12 Domains for joint classification.

Figure 3.13 European joint classification criteria.

Figure 3.14 Example of classification of typical non-dimensional moment-rotation relationships.

Figure 3.15 Domains for US joint classification.

Figure 3.16 Influence of the degree of continuity provided by beam-to-column joints on the distribution of internal moments.

Figure 3.17 Approaches for the modelling of semi-rigid joints: equivalent beam element (a), rotational spring (b) and springs plus rigid bars (c).

Figure 3.18 Horizontal forces equivalent to out-of-straightness imperfection.

Figure 3.19 Horizontal notional loads equivalent to the imperfections to a sway frame. Imperfect frame (a) and horizontal equivalent forces (b).

Figure 3.20 Horizontal forces equivalent to the imperfection. Imperfect column (a) and horizontal equivalent forces (b)

Figure 3.21 Effect of alignment imperfections of columns.

Figure 3.22 Layout of the types of structural analysis.

Figure 3.23 Simple supported beam: stress and strain distribution in the cross-section at the mid-span.

Figure 3.24 Bending moment distribution in a built-in beam (a) and typical moment-curvature relationship of the beam cross-section (b).

Figure 3.25 Bending moment diagram at the formation of the first two plastic hinges.

Figure 3.26 Bending moment distribution after the first two plastic hinges at the beam ends.

Figure 3.27 Collapse mechanism for the built-in beam.

Figure 3.28 Typical collapse mechanisms for steel frames.

Figure 3.29 Examples of local buckling of thin walled members.

Figure 3.30 Influence of the type of analysis on the response of sway frames.

Figure 3.31 Moment-curvature (M–χ) relationships for the different classes of cross-sections considered in accordance with the European approach.

Figure 3.32 Example of elastic analysis with bending moment redistribution.

Figure 3.33 Evaluation of the equivalent lateral force.

Figure 3.34 Flow-chart of the equivalent lateral force procedure.

Figure 3.35 Evaluation of the equivalent lateral force in a multi-storey frame.

Figure 3.36 Set of frames (a–c) in case of symmetry of both frame and vertical loading condition.

Figure 3.37 Set of frames (a–e) for the application of the amplified sway moment method in case of unsymmetrical structures and/or unsymmetrically distributed vertical loads.

Figure 3.38 Typical simple frame.

Figure 3.39 Typical bracing panels.

Figure 3.40 Transfer force mechanism in a K-bracing system.

Figure 3.41 Transfer force mechanism in an eccentric bracing system (a–c).

Figure 3.42 Vertical bracing in a three-dimensional portal frame.

Figure 3.43 Liability due to the absence of horizontal bracings.

Figure 3.44 Example of an efficiently braced single storey frame.

Figure 3.45 Equivalent force in the bracing system.

Figure 3.46 Types of bracings according to AISC specifications (a) column bracing and (b) beam bracing.

Figure 3.47 Example of a multi-storey braced frame and bracing models for horizontal bracings: two longitudinal and two transversal vertical bracings.

Figure 3.48 Example of a multi-storey braced frame and bracing models for horizontal bracings: one longitudinal and two transversal vertical bracings.

Figure 3.49 Example of a multi-storey braced frame with a closed (a) or open (b) concrete bracing core.

Figure 3.50 Common structural typologies for industrial buildings (a and b).

Figure E3.1.1

Figure E3.1.2

Figure E3.1.3

Figure E3.2.1

Figure E3.3.1

Figure E3.3.2

Chapter 04

Figure 4.1 Typical deformed cross-section for distortional buckling.

Figure 4.2 Internal or outstand elements.

Figure 4.3 Effective class 2 web method: compression (1), tension (2), plastic neutral axis (3) and neglected area (4) of the web.

Figure 4.4 Superimposition of the stress distribution diagram associated with a plastic web under compression and bending.

Figure 4.5 Superimposition of the stress distribution diagram associated with an elastic web under compression and bending.

Figure 4.6 Example of classification moment (

)-axial load (

) classification domain.

Figure 4.7 Stress distributions due to axial load (a) and bending (b) about a minor axis.

Figure 4.8 Gross and effective cross-sections in the case of axial load (a) and flexure (b).

Figure 4.9 Rules for the evaluation of the effective width of internal compression elements (a–c: from Table 4.1 of EN 1993-1-5).

Figure 4.10 Rules for the evaluation of the effective width of outstanding compression elements (a–d: from Table 4.2 of EN 1993-1-5).

Figure E4.5.1 Geometrical parameters.

Figure E4.5.2 Geometrical parameters for calculation of

eff,y

Figure E4.5.3 Comparison between

(AISC) and

y,Rk

(EC3) computed for various values of

Chapter 05

Figure 5.1 Connection detail for a member in tension.

Figure 5.2 Single angle connected by one leg via (a) one bolt, (b) two bolts and (c) three bolts.

Figure 5.3 Typical connection in tension with staggered holes.

Figure E5.1.1

Figure E5.2.1

Figure E5.2.2

Figure E5.3.1

Figure E5.4.1

Chapter 06

Figure 6.1 Typical global instability configurations: (a) flexural, (b) torsional and (c) flexural-torsional.

Figure 6.2 Influence of the restraints on the effective length.

Figure 6.3 Capacity domain in terms of stress (

) and slenderness (

) relationship for a compression member.

Figure 6.4 Load-transverse displacement relationship for a real compression member with initial imperfection

(a) and stress state in the mid-length section (b).

Figure 6.5 Stability curve for a compression member with or without imperfections.

Figure 6.6 Typical deformation for non-sway and sway frames.

Figure 6.7 Typical cases of buckled shapes for a single compression member.

Figure 6.8 Load conditions and corresponding values of the effective length for the compression members considered.

Figure 6.9 Stability curves for an equal-leg angle considering flexural, torsional and flexural-torsional buckling.

Figure 6.10 Shear deformation of an infinitesimal element of a beam.

Figure 6.11 Second order effects on a simply supported compression member.

Figure 6.12 Buckling length ratio

for a column in a non-sway mode (a) and distribution factor for column in a non-sway mode (b).

Figure 6.13 Buckling length ratio

for a column in a sway mode (a) and distribution factor for column in a sway mode (b).

Figure 6.14 Distribution factor for continuous columns.

Figure 6.15 Alignment chart–sidesway inhibited (no-sway frames).

Figure 6.16 Alignment chart–sidesway uninhibited (sway frames).

Chapter 07

Figure 7.1 Bending in a non-principal plane: (a) deflection in a non-principal plane and (b) principal bending moments

and

Figure 7.2 Deformed beam configurations associated with lateral torsional buckling.

Figure 7.3 Three-dimensional shell models for a steel beams: the mesh (a) and typical critical deformed shapes obtained via buckling analysis in case of wide flange HE beam (b), standard I beam (c) and wide flange beam (d) for a high mode.

Figure 7.4 Mono-symmetrical unequal flange I profiles.

Figure 7.5 Bending load cases for mono-symmetrical unequal flange I profiles.

Figure 7.6 Moment diagrams and moment values for Eq. (7.14a,b).

Figure 7.7 Bending moment-shear resistance domain.

Figure 7.8 Mono-symmetrical cross-section (symmetry about the minor axis).

Figure 7.9

as a function of

Figure 7.10

as a function of

Figure 7.11 Elastic and plastic stress distribution for case (c).

Figure E7.1.1

Figure E7.2.1

Chapter 08

Figure 8.1 Free warping (a) and restrained warping and (b) in a beam-to-column rigid joint.

Figure 8.2 Pure torsion shear stresses for circular (a), rectangular hollow (b) and open cross-section (c).

Figure 8.3 Torsion in an open cross-section member: the loading condition (a) considered as the sum of a symmetrical (b) and a hemi-symmetrical loading condition (c).

Figure 8.4 Distribution of stresses in the cantilever beam of Figure 8.3 due to pure torsion (shear stresses

in (a)) and to the non-uniform torsion shear stresses

in (b) and normal stresses

x,ω

in (c).

Figure 8.5 Shaded area to evaluate the sectorial area.

Figure 8.6 Distribution of

(a) and S

(b) in case of a bi-symmetrical I- and H-shaped profile.

Figure 8.7 Distribution of the shear stresses in a channel loaded on the shear centre.

Figure 8.8 Distribution for a channel section of: (a) sectorial area (

) and (b) first moment of area of the sectorial area (

Figure 8.9 Cross-section nodes.

Figure 8.10 Examples of torsional restraints: (a) simple support restraining torsion (warping is free) and (b) fully fixed restraint to torsion (warping is prevented).

Figure 8.11 Cantilever beam loaded by a torsional moment at the free end (

) with torsional restraint preventing warping at the fixed end (

= 0).

Figure 8.12 Distribution of pure and warping torsion along the cantilever beam (

x =

0 and

x = L

indicate fixed end and free end, respectively) and ratio between the rotation at generic cross-section

and the one at the free end.

Figure 8.13 Beam restrained at its ends by torsional supports and loaded at the midspan (

x = L/

2) by a torque.

Chapter 09

Figure 9.1 Typical deformed shapes for flexural buckling (a) flexural torsional buckling (b).

Figure 9.2 Typical axial force-bending moment buckling domains for different values of the end ratio moment (

Figure 9.3 Typical axial load (

)-bending moments interaction domain (

Figure E9.3.1

P-M

interaction curves; Example E9.3, LFRD verification.

Chapter 10

Figure 10.1 Displacements, internal forces and moments for bi-symmetrical cross-section members.

Figure 10.2 Displacements, internal forces and moments for mono-symmetrical cross-section members.

Figure 10.3 Example of a mono-symmetrical cross-section and distribution of the sectorial area

(a) and the static moment of the sectorial area

(b).

Figure 10.4 Example of the influence of the bimoment

on the location of the maximum normal stress in the cross-section (a–c).

Chapter 11

Figure 11.1 Example of failure due to large transverse forces on the beam web.

Figure 11.2 Different types of patch loading and buckling

coefficients: web crushing (a), web crippling (b) and web buckling (c).

Figure 11.3 Different types of patch loading and buckling

coefficients: loads applied to the flange and resisted by shear forces in the web (a), transferred through the web directly (b) and adjacent to an unstiffened end (c).

Figure 11.4 Definition of stiff loaded length.

Figure 11.5 Effective cross-section of stiffener.

Figure 11.6 Web sidesway buckling.

Chapter 12

Figure 12.1 AISC benchmark problem Case 1 (

P-δ

effects). From Figure C-C2.2 of AISC 360-10.

Figure 12.2 AISC benchmark problem Case 2 (

P-Δ

effects). From Figure C-C2.3 of AISC 360-10.

Figure 12.3 AISC 303-10 column out-of-plumbness tolerances.

Figure 12.4 AISC notional loads

Figure 12.5

coefficient.

Figure E12.1.1

Figure E12.1.2

Figure E12.1.3

Figure E12.1.4

Chapter 13

Figure 13.1 Examples of bolt (a), nut (b) and washer (c).

Figure 13.2 Finite element model for beam-to-column joints.

Figure 13.3 Typical connection in shear.

Figure 13.4 Influence of degree of tightening on the behaviour of bolted joints: relationship between the applied load and the relative displacement of plates in Figure 13.3.

Figure 13.5 Typical failure modes for a shear connection: bolt failure (a), plate bearing (b), tension failure of the plate (c) and shear failure of the plate (d).

Figure 13.6 Typical deformation holes due to a bearing.

Figure 13.7 Example of an HRC bolt.

Figure 13.8 Example of a washer used as a direct tension indicator.

Figure 13.9 Bolted connection with four bolts (a): bolt forces per shear area in the case of stiff bolts and weak plates and (b) in the cases of weak bolts and stiff plates (c).

Figure 13.10 Distribution of the stress in the plate of a bearing connection in elastic (a) and plastic (b) range.

Figure 13.11 Example of possible failure paths of different lengths.

Figure 13.12 Bearing connection with a different number of bolts per line.

Figure 13.13 Typical force distribution due to a bearing connection with eccentric shear.

Figure 13.14 Influence of the stiffness of plate and bolts of the force transfer mechanism: stiff plate and flexible bolts (a) or flexible plate and stiff bolts (b).

Figure 13.15 Connection in tension (a): relationship (b) between the applied tension force (

) and the bolt shank elongation (

∆L

) and relationship (c) between the applied tension force (

) and the axial load on the bolt shank (

Figure 13.16 Example of connection under shear and torsion (plane

) and shear and bending (plane

Figure 13.17 Symbols used to define the minimum free space.

Figure 13.18 Symbols for end distance and spacing for holes in accordance with En 1993-1-8: (a) normal holes, (b) staggered holes, (c) staggered holes for compression members, (d) tension member and (e) slotted holes.

Figure 13.19 Examples of long joints.

Figure 13.20 Single and multiple filler plates.

Figure 13.21 Example of a riveted joint in an historical bridge.

Figure 13.22 Riveting of the pin.

Figure E13.1.1

Figure E13.2.1

Figure E13.3.1

Figure E13.4.1

Chapter 14

Figure 14.1 Cracks in welds.

Figure 14.2 Typical cases of lamellar tearing.

Figure 14.3 Weld defects: (a) lack of penetration and (b) lack of alignment.

Figure 14.4 Classification based on the relative position of the elements to be joined: (a) butt joint, (b) edge joint, (c) corner joint, (d) T-joint, (e) L-joint and (f) lap joint.

Figure 14.5 Classification based on the location of the weld with respect to the force to be transferred: (a) longitudinal, (b) transverse and (c) inclined.

Figure 14.6 Examples of surface preparations for groove welds: (a–h) show CJP welds and (i–j) show PJP welds.

Figure 14.7 Butt joint showing the distribution of tensile stresses through the cross-section.

Figure 14.8 Effective throat dimension for various fillet shapes.

Figure 14.9 State of stress in the effective throat area.

Figure 14.10 Plates connected by longitudinal fillet welds.

Figure 14.11 Plates connected with transverse fillet welds.

Figure 14.12 Welded connection with inclined fillets.

Figure 14.13 Joint in flexure with longitudinal fillet welds.

Figure 14.14 Joint in flexure with transverse fillet welds.

Figure 14.15 Combination of longitudinal and transverse fillet welds.

Figure 14.16 Joint under torsion with transverse fillet welds.

Figure 14.17 Joint under torsion with longitudinal fillet welds.

Figure 14.18 Joint under torsion with transverse and longitudinal fillet welds.

Figure 14.19 Definition of effective throat dimension.

Figure 14.20 Effective width in an unstiffened T-joint.

Figure E14.1.1

Figure E14.2.1

Chapter 15

Figure 15.1 Example of cross-sections where locate intermediate partial-strength connections.

Figure 15.2 Typical connection detail for a pinned simply supported beam.

Figure 15.3 Examples of pinned connections.

Figure 15.4 Articulated bearing joints: contact between cylindrical (a) and spherical (b) surface, contact plate (c) and knife contact plate (d).

Figure 15.5 Most common types of contact surfaces: linear contact via cylindrical pin (a–d) and via spherical ball (e) and (f).

Figure 15.6 Typical splice for beams.

Figure 15.7 Examples of splice connections.

Figure 15.8 Examples of column splice for columns with different cross-sections.

Figure 15.9 Typical examples of beam-to-column connections.

Figure 15.10 Examples of typical beam-to-beam connections.

Figure 15.11 Stress distribution in bolted plates in shear and tension: (a) shear and bending, (b) tension and bending, (c) block tearing in plate and (d) block tearing in a coped beam.

Figure 15.12 Typical connections for horizontal bracings.

Figure 15.13 Typical connections for vertical bracings.

Figure 15.14 Example of cross bracing with an internal connection.

Figure 15.15 Typical column bases for simple frames.

Figure 15.16 Examples of anchor bolts embedded in the concrete of foundation: simple anchor bolt (a) hooked anchor bolt (b) and anchor bolt with a washer plate (c).

Figure 15.17 Typical solutions to anchor the foundation when bolts are in presence of high values of the tension force: hooked anchor bolts (a) and hammer head anchor bolts (b).

Figure 15.18 Examples of appropriate device to transfer shear load via direct contact steel-concrete.

Figure 15.19 Examples of common beam-to-concrete wall connections.

Figure 15.20 Examples of beam-to-concrete wall connection (a) and site slots of the thin plate to assemble the connection with geometrical tolerances that are too large (b).

Figure 15.21 Terms and definitions.

Figure 15.22 Classification of the nodes on the basis of the connected members.

Figure 15.23 Stress and deformations in a typical beam-to-column joint.

Figure 15.24 A typical external beam-to-column joint and the main contribution to its response.

Figure 15.25 Typical moment-rotation (

M–Φ

) relationship for a beam-to-column joint.

Figure 15.26 Moment-rotation determined via the experimental approach: (a) details of the measuring system for the connection and contribution to joint rotation (b).

Figure 15.27 The finite element model (a) to appraise the moment-rotation curve an extended end plate connection (b).

Figure 15.28 The component approach: the undeformed (a) and the deformed (b) joint configuration.

Figure 15.29 Examples of simple beam-to-column joints.

Figure 15.30 Typical design modes for simple frames.

Figure 15.31 Header plate connection: (a) contact between the beam and the column flanges and (b) moment-rotation joint curve before the contact (zone 1) and after the contact (zone 2).

Figure 15.32 Contributions to the deformation of an external rigid joint.

Figure 15.33 Forces in the column panel zone.

Figure 15.34 Examples of typical rigid joints.

Figure 15.35 A typical moment-rotation joint curve classified according to EC3 criteria.

Figure 15.36 A regular semi-continuous planar frame.

Figure 15.37 Typical collapse mechanisms for regular semi-continuous frames: (a) beam mechanism, (b) panel mechanism and (c) mixed mechanism.

Figure 15.38 Isolated beam with semi-rigid joints.

Figure 15.39 Activation of the plastic hinges at the beam ends.

Figure 15.40 Collapse mechanism.

Chapter 16

Figure 16.1 Typical arrangements for laced struts (a), the associated design model (b) and types of lacing panels (c).

Figure 16.2 Typical arrangements for struts with batten plates (a) and the associated design model (b).

Figure 16.3 Typical arrangements for buttoned struts (a) and the associated design model (b).

Figure 16.4 Examples of connections able to absorb slippage force.

Figure 16.5 Second order effects on the strut and axial load on the chords at the midspan.

Figure 16.6 Typical failure modes for a battened column: (a) overall buckling and (b) local buckling of the chord between the panels.

Figure 16.7 Example of built-up laced member (a): deformed shape of the panel due to deformation of the diagonal (b) and of the batten (c).

Figure 16.8 Example of a built-up battened member (a): deformed panel shape due to the bending of the chords (b) and due to the bending of the batten (c).

Figure 16.9 Design model (a) for uniform built-up columns with lacings (b) and battenings (c).

Figure 16.10 Single lacing system on opposite faces of a built-up member with two parallel laced planes: (a) corresponding lacing system (recommended system) and (b) mutually opposed lacing system (not recommended).

Figure 16.11 Shear stiffness of lacings of built-up members.

Figure 16.12 Moments and forces in an end panel of a battened built-up member.

Figure 16.13 Closely spaced built-up members (a) and star-battened angle members (b).

Figure 16.14 Built-up members connected with lacing and tie plates (a) and with perforated cover plates (b).

Guide

Cover

Table of Contents

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Structural Steel Design to Eurocode 3 and AISC Specifications

Claudio Bernuzzi

and

Benedetto Cordova

Registered OfficeJohn Wiley & Sons, Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom

Editorial Offices9600 Garsington Road, Oxford, OX4 2DQ, United KingdomThe Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom

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Based on Progetto e verifica delle strutture in acciaio by Claudio Bernuzzi.© Ulrico Hoepli Editore S.p.A., Milano, 2011. Published in the Italian language.

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ISBN: 9781118631287

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Cover image: photovideostock/Getty

Preface

Over the last century, design of steel structures has developed from very simple approaches based on a few elementary properties of steel and essential mathematics to very sophisticated treatments demanding a thorough knowledge of structural and material behaviour. Nowadays, steel design utilizes refined concepts of mechanics of material and of theory of structures combined with probabilistic-based approaches that can be found in design specifications.

This book intends to be a guide to understanding the basic concepts of theory of steel structures as well as to provide practical guidelines for the design of steel structures in accordance with both European (EN 1993) and United States (ANSI/AISC 360-10) specifications. It is primarily intended for use by practicing engineers and engineering students, but it is also relevant to all different parties associated with steel design, fabrication and construction.

The book synthesizes the Authors’ experience in teaching Structural Steel Design at the Technical University of Milan-Italy (Claudio Bernuzzi) and in design of steel structures for power plants (Benedetto Cordova), combining their expertise in comparing and contrasting both European and American approaches to the design of steel structures.

The book consists of 16 chapters, each structured independently of the other, in order to facilitate consultation by students and professionals alike. Chapter 1 introduces general aspects such as material properties and products, imperfection and tolerances, also focusing the attention on testing methods and approaches. The fundamentals of steel design are summarized in Chapter 2, where the principles of structural safety are discussed in brief to introduce the different reliability levels of the design. Framed systems and methods of analysis, including simplified methods, are discussed in Chapter 3. Cross-sectional classification is presented in Chapter 4, in which special attention has been paid to components under compression and bending. Design of single members is discussed in depth in Chapter 5 for tension members, in Chapter 6 for compression members, in Chapter 7 for members subjected to bending and shear, in Chapter 8 for members under torsion, and in Chapter 9 for members subjected to bending and compression. Chapter 10 deals with design accounting for the combination of compression, flexure, shear and torsion.

Chapter 11 addresses requirements for the web resistance design and Chapter 12 deals with the design approaches for frame analysis. Chapters 13 and 14 deal with bolted and welded connections, respectively, while the most common type of joints are described in Chapter 15, including a summary of the approach to their design. Finally, built-up members are discussed in Chapter 16. Several design examples provided in this book are directly chosen from real design situations. All examples are presented providing all the input data necessary to develop the design. The different calculations associated with European and United States specifications are provided in two separate text columns in order to allow a direct comparison of the associated procedures.

Last, but not least, the acknowledge of the Authors. A great debt of love and gratitude to our families: their patience was essential to the successful completion of the book.

We would like to express our deepest thanks to Dr. Giammaria Gabbianelli (University of Pavia-I) and Dr. Marco Simoncelli (Politecnico di Milano-I) for the continuous help in preparing figures and tables and checking text. We are also thankful to prof. Gian Andrea Rassati (University of Cincinnati-U.S.A.) for the great and precious help in preparation of chapters 1 and 13.

Finally, it should be said that, although every care has been taken to avoid errors, it would be sanguine to hope that none had escape detection. Authors will be grateful for any suggestion that readers may make concerning needed corrections.

Claudio Bernuzzi and Benedetto Cordova

CHAPTER 1The Steel Material

1.1 General Points about the Steel Material

The term steel refers to a family of iron–carbon alloys characterized by well-defined percentage ratios of main individual components. Specifically, iron–carbon alloys are identified by the carbon (C) content, as follows:

wrought iron

, if the carbon content (i.e. the percentage content in terms of weight) is higher than 1.7% (some literature references have reported a value of 2%);

steel

, when the carbon content is lower than the previously mentioned limit. Furthermore, steel can be classified into extra-mild (C < 0.15%), mild (C = 0.15 ÷ 0.25%), semi-hard (C = 0.25 ÷ 0.50%), hard (C = 0.50 ÷ 0.75%) and extra-hard (C > 0.75%) materials.

Structural steel, also called constructional steel or sometimes carpentry steel, is characterized by a carbon content of between 0.1 and 0.25%. The presence of carbon increases the strength of the material, but at the same time reduces its ductility and weldability; for this reason structural steel is usually characterized by a low carbon content. Besides iron and carbon, structural steel usually contains small quantities of other elements. Some of them are already present in the iron ore and cannot be entirely eliminated during the production process, and others are purposely added to the alloy in order to obtain certain desired physical or mechanical properties.

Among the elements that cannot be completely eliminated during the production process, it is worth mentioning both sulfur (S) and phosphorous (P), which are undesirable because they decrease the material ductility and its weldability (their overall content should be limited to approximately 0.06%). Other undesirable elements that can reduce ductility are nitrogen (N), oxygen (O) and hydrogen (H). The first two also affect the strain-ageing properties of the material, increasing its fragility in regions in which permanent deformations have taken place.

The most important alloying elements that may be added to the materials are manganese (Mn) and silica (Si), which contribute significantly to the improvement of the weldability characteristics of the material, at the same time increasing its strength. In some instances, chromium (Cr) and nickel (Ni) can also be added to the alloy; the former increases the material strength and, if is present in sufficient quantity, improves the corrosion resistance (it is used for stainless steel), whereas the latter increases the strength while reduces the deformability of the material.

Steel is characterized by a symmetric constitutive stress-strain law (σ–ε). Usually, this law is determined experimentally by means of a tensile test performed on coupons (samples) machined from plate material obtained from the sections of interest (Section 1.7). Figure 1.1 shows a typical stress-strain response to a uniaxial tensile force for a structural steel coupon. In particular, it is possible to distinguish the following regions:

an initial branch that is mostly linear (

elastic phase

), in which the material shows a linear elastic behaviour approximately up to the yielding stress (

). The strain corresponding to

is usually indicated with ε

(yielding strain). The slope of this initial branch corresponds to the modulus of elasticity of the material (also known as

longitudinal modulus of elasticity

Young’s modulus

), usually indicated by

, with a value between 190 000 and 210 000 N/mm

(from 27 560 to 30 460 ksi, approximately);

plastic phase

, which is characterized by a small or even zero slope in the σ–ε reference system;

the ensuing branch is the

hardening phase

, in which the slope is considerably smaller when compared to the elastic phase, but still sufficient enough to cause an increase in stress when strain increases, up to the ultimate strength

. The hardening modulus has values between 4000 and 6000 N/mm

(from 580 to 870 ksi, approximately).

Figure 1.1 Typical constitutive law for structural steel.

Usually, the uniaxial constitutive law for steel is schematized as a multi-linear relationship, as shown in Figure 1.2a, and for design purposes an elastic-perfectly plastic approximation is generally used; that is the hardening branch is considered to be horizontal, limiting the maximum strength to the yielding strength.

Figure 1.2 Structural steel: (a) schematization of the uniaxial constitutive law and (b) yield surface for biaxial stress states.

The yielding strength is the most influential parameter for design. Its value is obtained by means of a laboratory uniaxial tensile test, usually performed on coupons cut from the members of interest in suitable locations (see Section 1.7).

In many design situations though, the state of stress is biaxial. In this case, reference is made to the well-known Huber-Hencky–Von Mises criterion (Figure 1.2b) to relate the mono-axial yielding stress (fy) to the state of plane stress with the following expression:

(1.1)

where σ1, σ2 are the normal stresses and σ12 is the shear stress.

In the case of pure shear, the previous equation is reduced to:

(1.2)

With reference to the principal stress directions 1′ and 2′, the yield surface is represented by an ellipse and Eq. (1.1) becomes:

(1.3)

1.1.1 Materials in Accordance with European Provisions

The European provisions prescribe the following values for material properties concerning structural steel design:

Density:

= 7850 kg/m

(= 490 lb/ft

)

Poisson’s coefficient:

= 0.3

Longitudinal (Young’s) modulus of elasticity:

= 210 000 N/mm

(= 30 460 ksi)

Shear modulus:

Coefficient of linear thermal expansion:

= 12 × 10

−6

per °C (=6.7 × 10

−6

per °F)

The mechanical properties of the steel grades most used for construction are summarized in Tables 1.1a and 1.1b, for hot-rolled and hollow profiles, respectively, in terms of yield strength (fy) and ultimate strength (fu). Similarly, Table 1.2 refers to steel used for mechanical fasteners. With respect to the European nomenclature system for steel used in high strength fasteners, the generic tag (j.k) can be immediately associated to the mechanical characteristics of the material expressed in International System of units (I.S.), considering that:

j·k·10

represents the yielding strength expressed in N/mm

;

j·100

represents the failure strength expressed in N/mm

Table 1.1a Mechanical characteristics of steels used for hot-rolled profiles.

Nominal thickness

≤ 40 mm

40 mm <

≤ 80 mm

EN norm and steel grade

(N/mm

)

(N/mm

)

(N/mm

)

(N/mm

)

EN 10025-2

S 235

235

360

215

360

S 275

275

430

255

410

S 355

355

510

335

470

S 450

440

550

410

550

EN 10025-3

S 275 N/NL

275

390

255

370

S 355 N/NL

355

490

335

470

S 420 N/NL

420

520

390

520

S 460 N/NL

460

540

430

540

EN 10025-3

S 275 M/ML

275

370

255

360

S 355 M/ML

355

470

335

450

S 420 M/ML

420

520

390

500

S 460 M/ML

460

540

430

530

EN 10025-5

S 235 W

235

360

215

340

S 355 W

355

510

335

490

EN 10025-6

S 460 Q/QL/QL1

460

570

440

550

Table 1.1b Mechanical characteristics of steels used for hollow profiles.

EN norm and steel grade

Nominal thickness

≤ 40 mm

40 mm <

≤ 65 mm

(N/mm

)

(N/mm

)

(N/mm

)

(N/mm

)

EN 10210-1

S 235 H

235

360

215

340

S 275 H

275

430

255

410

S 355 H

355

510

335

490

S 275 NH/NLH

275

390

255

370

S 355 NH/NLH

355

490

335

470

S 420 NH/NLH

420

540

390

520

S 460 NH/NLH

460

560

430

550

EN 10219-1

S 235 H

235

360

S 275 H

275

430

S 355 H

355

510

S 275 NH/NLH

275

370

S 355 NH/NLH

355

470

S 460 NH/NLH

460

550

S 275 MH/MLH

275

360

S 355 MH/MLH

355

470

S420 MH/MLH

420

500

S 460 NH/NLH

460

530

Table 1.2 Nominal yielding strength values (fyb) and nominal failure strength (fub) for bolts.

Bolt class

4.6

4.8

5.6

5.8

6.8

8.8

10.9

(N/mm

)

240

320

300

400

480

640

900

(N/mm

)

400

500

600

800

1000

The details concerning the designation of steels are covered in EN 10027 Part 1 (Designation systems for steels – Steel names) and Part 2 (Numerical system), which distinguish the following groups:

group 1

, in which the designation is based on the usage and on the mechanical or physical characteristics of the material;

group 2

, in which the designation is based on the chemical content: the first symbol may be a letter (e.g. C for non-alloy carbon steels or X for alloy steel, including stainless steel) or a number.

With reference to the group 1 designations, the first symbol is always a letter. For example:

for steels to be used in reinforced concrete;

for steel sheets for cold forming;

for mechanical construction steels;

for high strength steels;

for structural steels;

for steels to be used in prestressing applications.

Focusing attention on the structural steels (starting with an S), there are then three digits XXX that provide the value of the minimum yielding strength. The following term is related to the technical conditions of delivery, defined in EN 10025 (‘Hot rolled products of structural steel’) that proposes the following five abbreviations, each associated to a different production process:

the

(

As Rolled

) term identifies rolled and otherwise unfinished steels;

the

(

Normalized

) term identifies steels obtained through normalized rolling, that is a rolling process in which the final rolling pass is performed within a well-controlled temperature range, developing a material with mechanical characteristics similar to those obtained through a normalization heat treatment process (see

Section 1.2

);

the

(

Mechanical

) term identifies steels obtained through a thermo-mechanical rolling process, that is a process in which the final rolling pass is performed within a well-controlled temperature range resulting in final material characteristics that cannot be obtained through heat treating alone;

the

(

Quenched and tempered

) term identifies high yield strength steels that are quenched and tempered after rolling;

the

(

Weathering

) term identifies weathering steels that are characterized by a considerably improved resistance to atmospheric corrosion.

The YY code identifies various classes concerning material toughness as discussed in the following. Non-alloyed steels for structural use (EN 10025-2) are identified with a code after the yielding strength (XXX), for example:

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