Local-buckling analysis of lower chord member in steel truss bridge under seismic loading

The criterion of the local buckling due to JSCE (2008) is based on the average strain ε in a compressive flange over the characteristic length LC. For a box-section member, the characteristic length LC is given by

aCL i ( . ,b )(1)

where a is the distance between two adjacent diaphragms and b is the width of a flange. Min indicates that the smaller of the two values in the parenthesis shall be taken. On the other hand, the limit strain εu for an unstiffened box-section member is computed by

ε ε

y = ( )fR ( )c yN N + ( )c yN N+ ≤

0 24

2 8 20 0

.