Baláž Ivan & Koleková Yvona

Faculty of Civil Engineering

Slovak University of Technology in Bratislava

Slovak Republic, EU

Lateral torsional stability of

timber beams

M2D2015, Ponta Delgada, Azores, 26-30 July 2015

Lateral Torsional Buckling

Die Espe Die Birke

ASPEN BIRCH

OSIKA BRZOZA

LTB of member will occur even if it is

loaded in the plane of minor stiffness

when point of load application is too

high over shear center

This phenomenon is called „mosquito wings“ effect

.

Structure magazine, February 2008

Elastic critical moment Mcr

„fork“ boundary conditions, uniform bending moment M,

uniform nonwarping cross-section: warping stiffness EIw= 0 kNm4

L

GIEIM

tz

cr

EIz bending stiffness

GIt torsional stiffness

L span

Taking into account all influences

L

GIEIM

tz

cr

C1, C2, C3 are coefficients depending on

type of loading and boundary conditions

For symmetric cross-section to axis y-y is zj = 0

ENV 1993-1-1, ENV 1999-1-1

ENV 1993-1-1, ENV 1999-1-1

Cantilever

EN 1999-1-1 EN 1995-1-1

steel + alumunium timber

X =

X =

F at the free end of the cantilver

CONCLUSION

Harmonization and unification of rules

of metal (steel, aluminium) and timber

Eurocodes, if it is reasonable,

will be good for everybody

especially for designers in practice.

Shortening of Eurocodes is desirable.

Thank for agreeing with us