Introduction - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 31

discussed the effect of the slab deck casting sequence on the short-term and
long-term behaviors of the bridges. Three cases of sequential casting and one
case of continuous casting were investigated. The study showed that the
effect of slab casting sequence can be neglected for both short-term and
long-term behaviors as well as the resulting moments of the bridges. The
authors concluded that continuous casting for closed box sections can be
used as an easy and fast construction without any danger of increasing trans-
verse cracking. The authors recommend that continuous casting can be
applicable to open box sections used widely in many countries. However,
the study showed that the effect of drying shrinkage was most critical for the
long-term behavior of a bridge and transverse cracking, which can result in
crack development at interior supports. Steel-concrete composite girders are
analyzed using beam bending theory by utilizing the effective flange width
concept to evaluate deflections, stresses, strengths, etc. Shear lag effects can
be considered by replacing the actual slab width by an appropriate reduced
effective width. Nonlinear finite element analyses can effectively consider
the shear lag effects. However, current codes of practice provide simplified
empirical equations to evaluate effective flange width, which differ from
country to country. Ahn et al. [ 1.57 ] investigated effective flange width pro-
visions of several countries including America, Britain, Canada, Japan, and
Europe. The provisions were compared qualitatively and quantitatively by
the authors. It was shown that each specification shares common organiza-
tion in describing the effective flange width comprising basic formulation
and effective span length. In the basic formulation part, the effective flange
width of a simply supported span can be specified. For continuous girders,
the lengths of independent spans to which basic formulation can be applied
were specified in the effective span length part. It was also shown that the
way to describe the basic formulation differed from one provision to the
other following the underlying philosophy that drove the development of
each specification. AASHTO and Eurocode 4 provisions used a list of
descriptions. However, Canadian and Japanese provisions used equations;
BS 5400 used a table format. Through a numerical example of simply sup-
ported spans, it is observed that BS 5400 (interior) develops the largest effec-
tive flange width. Eurocode 4 delivered the largest effective flange width.
Effective flange widths from AASHTO varied considerably compared with
the others. Without the thickness limitation, AASHTO provisions were
similar to the values from Eurocode 4. It was concluded that the interrelation
between effective flange width, loading effects on the bridges, and design of
concrete deck (especially crack control) should be consistent.