Xb if Xbrel .m < 0.75 if 0.75 < Xbrel.m < 1.4

otherwise rel.r kbcrit= 1

As kbcrit — 1, lateral torsional buckling is not relevant

Modification factor for bracing stiffness, ks

Modification factor, kf.1 (equation (9.6a) (UKNA to EC5, Table NA.6))

Load sharing factor, ksys is not relevant

Redistribution factor for a solid timber rectangular section, km ( (EC5, 6.1.6(2)))

ks 4

6. Stiffness of each bracing member

The critical design load case at the ULS will be due to the combination of permanent and unfavourable medium-duration variable action:

Design bending moment in the main beam, Md

M _ Fd ■ L i Wd ■ L1 Wbd ■ lb L1 d 4 + 8 + 2 ' 3 The mean design stabilising force in each bracing member, Nd Nd = (1 - kcrit)

Minimum stiffness of each bracing member, C C = k,

(equation (9.4); EC5, equation (9.34)) Axial stiffness of each bracing Ca =

Md h

Axial stiffness of each bracing member Caf = plus connections, Caf

0 0

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