1i,Rd = fylti i + b,ov + 2U - 4tj )/ Y5

For CHS brace: a = 0

Peff = tw + 2r + ltffyJ fyi but peff < bi+hi-2ti for T, Y, X joints and K and N gap joints and beff < bi+hi-2ti for K and N overlap joints.

b = 10 f't'b b,/,,fyth-but be ov < bi

but bw < 2ti + 10 (tf + r)

For CHS braces multiply the above resistances for brace failure by 7t/4 and replace both bi and hi by di and both b2 and h2 by d2.

* Only the overlapping brace member i need be checked. The efficiency (i.e. the design resistance of the joint divided by the design plastic resistance of the brace member) of the overlapped brace member j should be taken as equal to that of the overlapping brace member.

(6) The design internal moment M,Ed may be taken as the value at the point where the centreline of the brace member meets the face of the chord member.

(7) The design in-plane moment resistance Mip,1Rd should be obtained from Table 7.22.

(8) If stiffeners in the chord (see Figure 7.7) are used, then the design bracing failure resistance ^i,Rd for T-, X-, Y-, K-gap and N-gap joints (Table 7.22) is determined as follows:

M,Rd = 2/yi ti (¿eff + ¿eff.s) / 7M5 ••• (7.6)


beff = tw + 2r + 7 tffy0 / fyi but <bi + Ui - 2ti beff,s = ts + 2a + 7 tffy0 /fyi but < bi + Ui - 2ti beff + beff,s < bi + hi - 2ti where:

a is stiffener weld throat thickness, '2a' becomes 'a if single sided fillet welds are used; s refers to the stiffener.

(9) The stiffeners should be at least as thick as the I-section web.

Table 7.22: Design moment resistances of welded joints between rectangular hollow section brace members and I or H section chords

Type of joint

Design resistance [/ = 1 or 2, j = overlapped brace]

T and Y joints

Chord web yielding

0 0

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