Simplified design of frames with V bracings

The simplified design approach for V or A bracings (called inverted V in Eurocode 8 and 'chevron' bracings in North American terminology) is different from that considered for X bracings, due to the fact that both the tension and the compression diagonals are considered

Clauses 6.7.2(1), 6.7.4(1), 6.7.3(1), 6.7.3(2), 6.7.3(3), 6.7.3(4)

in the analysis. This results in higher computed stiffness and strength of the structure with respect to an analysis ignoring the compression diagonal. This more complete model with respect to X bracings is, however, compensated to take into account the degradation of resistance in the compression diagonal, by associating frames with V bracings to a lower value of the q factor,

• q = 2.5 in DCH, instead of 4 for X bracings. Moreover, the beams should be dimensioned for:

• the action effects of all non-seismic actions without considering the intermediate support provided by the diagonals

• the unbalanced vertical seismic action effect applied to the beam by the braces after buckling of the compression diagonal, calculated assuming that the force in the brace in tension is equal to ATRd and that in the brace in compression to a buckling load equal to a fraction of Npl Rd with a recommended value of 30%.

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