Design of masonry structures Eurocode 3 For Dummies

Design of masonry structures Eurocode 3 For Dummies This edition has been fully revised and extended to cover blockwork and Eurocode 6 on masonry structures. This valued textbook: discusses all aspects of design of masonry structures in plain and reinforced masonry summarizes materials properties and structural principles as well as descibing structure and content of codes presents design procedures, illustrated by numerical examples includes considerations of accidental damage and provision for movement in masonary buildings. This thorough introduction to design of brick and block structures is the first book for students and practising engineers to provide an introduction to design by EC6.

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Eurocode 3 for Dummies The Opportunities and

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Slides available on the web

http://www2.umist.ac.uk/construction/staff/

mccarthy/index.htm Follow the link from my home page From 21 March 2003

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Overview

n Current status

n CoveragePitfalls

n Major and minor differences with BS5950

Element Design

n Beams, StrutsCapacity comparisons

Manchester Centre for Civil & Construction Engineering

EC3 Current Status

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E-SCI News March 2003

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Eurocode terminilogy

n You can use it if you wish

prEN

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EC3 Current Published Status

DD ENV 1993-1-1:1992 Eurocode 3 Design of steel structures General rules and rules for buildings (together with United Kingdom National Application Document)

DD ENV 1993-1-2:2001 Eurocode 3 Design of steel structures General rules Structural fire design (together with United Kingdom National Application Document)

DD ENV 1993-1-3:2001 Eurocode 3 Design of steel structures General rules Supplementary rules for cold formed thin gauge members and sheeting

Other EC’s Published Status

prEN 1994-1-1:2002 Design of composite steel and concrete structures Part 1.1 General rules and rules for buildings Stage 49 Examination Document

DD ENV 1998-3:1997 Eurocode 8: Design provisions for earthquake resistance of structures Towers, masts and chimneys

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Potential pitfalls

Terminology

n Restricted vocabulary Change in symbols

n More logical symbol name conventions

n Lots of subscripts Changes in values

n Young’s Modulus etc Multiple documents

n Need to consult more than one part

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Terminology

ForceCapacity

n McDesign strength

n pyDead loadLive loadWind load

ActionResistance

n Mc,RdYield strength

n fyPermanent loadVariable loadAnother variable load

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Consistent across all Eurocodes

Easy to translate

Symbols BS5950 Eurocode

Radius of Gyrat on

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Changes in Values

Young’s Modulus

n BS - 205000 N/mm²

n EC - 210000 N/mm²Shear modulus

n BS – 79000 N/mm²

n EC - 81000N/mm²

Changes in load factors

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Axes redefined in Eurocodes

Major axis is y-yVertical axis is z-z

X direction is along the member

This is consistent with most FE and Frame analysis software

EC3 Definitions

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ε = (235/fy)0.5

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y

z

x u

φ

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n Mc = pyZeffLow shear

n Fv< 60 % Pv

Class 1 and 2

n Mc,Rd= fyWpl/γM1

n γM1= 1.05 in UK Class 3

n Mc,Rd= fyWel,min /γM1

Class 4

n Mc,Rd= fyWeff,min/γM1Low shear

n Av= tDShear buckling if

n hw/w> 72ε

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Compression Members

Pc = Ag pc from Tables 23 and 24

pc is a function of λ

BS5950 requires a large number of tables

f

1

2 2

≤

− +

=

? 0,2

? a 1

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Table 3.1: tf = 14.2mm < 40mm therefore fy=275N/mm² for S275 grade

E = 210000 N/mm² Slenderness - λzz= 600/5.2 = 115 <180 OK βa=1.0, implies λ1=π(E/fy) 0.5 = 86.8

( λzz/ λ1) βa 0.5 = 115/86.8 = 1.324

?

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1.32 0.38

Example

UC 203x203x60 of grade S275 is axially loaded and pinned at each end of its 6m length

Figure 6.3 factor, χ= 0.38

NbRd = 0.38*1.0*76.4*10²*275/1.05

= 760kN

BS5950 – 786kN

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But

EC loads are typically 5% lower than BS Scaling the capacity by this figure gives:

EC3 = 760/0.95 = 800 kN EC3 stronger than BS at 786 kN

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BS5950 - mLT for UDL

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pb from Table 16

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EC3 LTB

Same approach as for Compression

1 M y

y pl w LT Rd

LT LT

?

λ φ

)2.0(

15,

φ

1.05 1.0 For UB, UC

EC3 LTB

αLT = 0,34 for rolled UCsections

αLT = 0,49 for rolled UB sections

)2.0(

15,

EI C M

2 2

= Where C1 results from the

Wply.fy

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EC3 LTB

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Same curves as before!

1 M y

y pl w LT Rd

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Summary of LTB

BS5950 splits calculations between strength and equivalent moment EC3 combines equivalent moment and section properties to give a reduction factor

EC3 uses EXACT same buckling curves for LTB and Strut buckling

EC3 look awful but is easily programmed

in a spreadsheet

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Conclusions

They are just a little different Rationalises terminology across materials and countries

The EFTA region is 10 times bigger than UK

time

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2 What does EC3 say about effective lengths?

Ans: The EC3 guidance is not as helpful as BS5950 Table 22 EC3 gives the general approach for effective lengths in frames which results in the same values as Table 22

2 What’s in EC3 about sway, lambda crit etc?

Ans: There is a lengthy section in the prEN on frame stability On initial viewing, this looks very like the BS5950:2000 approach See Section 5

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