TUTORIAL 5

FLEXURAL MEMBERS

Lateral Torsion Buckling Lateral Torsion Buckling

Summary

Summary of design process

The design process for a beam can be summarised as follows

(a) Determination of all forces and moments on critical section

(b) Selection of UB or UC

(c) Classification of section

(d) Check shear strength; if unsatisfactory return to (b)

(e) Check bending capacity; if unsatisfactory return to (b) (e) Check bending capacity; if unsatisfactory return to (b)

(f) Check deflection; if unsatisfactory return to (b)

(g) Check web bearing and buckling at supports or concentrated load; if unsatisfactory provide web stiffener

(h) Check lateral torsional buckling; if unsatisfactory return to (b) or provide lateral restraints

(i) Summarise results

STEP 1: Determine:

VEd - Design Shear Force(Reactions)

MEd - Design Bending Moment( Maximum Moment)

STEP 2: Determine Section ( UB for Beams)

Trial Section: EdM

W = Trial Section:

Classify

STEP 3: Determination of C1 value :

yfEd

y,trialW =

2

1

MM

=

21 52.04.188.1C +=

STEP 4: Calculation of Mcr(considering the section 2-3):

Lcr Distance between 2 restrained points

STEP 5: Evaluate of reduction factor :General Case( EN 1993-1-1 cl 6.3.2.2)

1

2/1

z2

t2

cr

z

w

2cr

z2

cr C*EIGIL

II

LEI

M

+=

pi

pi

LT

cr

yyLT

MfW

=

( ) ( )[ ]22.015.0 LTLTLTLT ++=

( )[ ] 11

2/12LT

2LTLT

LT +

=

STEP 5: LTB Resistance(EN 1993-1-1 cl 6.3.2.2 , eq. 6.55):

Depends of the class

STEP 6: Safety Check:

1Mf

WM yy,plLTRd,b =

M1

MM

Rd,b

Ed