Applied Loads and Stability of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 165

satiability; SERVICE II, which is load combination related to control yield-
ing of steel structures and slip of slip-critical connections due to vehicular
live load; SERVICE III, which is load combination for longitudinal analysis
related to tension in prestressed concrete superstructures with the objective
of crack control; SERVICE IV, which is load combination only to tension
in prestressed concrete structures with the objective of crack control; and
finally, FATIGUE-fatigue and fracture load combination relating to repet-
itive gravitational vehicular live load and dynamic responses under a single
design truck having specific axle spacing. As stated in AASHTO [1.23], the
load factors of various loads comprising a design load combination shall be
taken as specified in Table 3.15 . For permanent force effects, the load factor
that produces the more critical combination shall be selected from

Table 3.16 .

3.8 STABILITY OF STEEL AND STEEL-CONCRETE COMPOSITE
PLATE GIRDER BRIDGES
3.8.1 General
In order to design the components of steel and steel-concrete composite
bridges, it would helpful to review the design rules specified in the current
codes of practice. As an example, a review of the rules specified in EC3
[1.27,2.11] is presented in this section. However, it should be noted that
the main objective of this topic is to highlight the finite element analysis
and design of steel and steel-concrete composite bridges. Therefore, the
finite element analysis results can be compared with the design results
obtained using any current code of practice. According to EC3
[1.27,2.11], the internal forces and moments may be determined using either
elastic global analysis or plastic global analysis, with elastic global analysis
being used in all cases. Plastic global analysis may be used only where the
structure has sufficient rotation capacity at the actual locations of the plastic
hinges, whether this is in the members or in the joints. Where a plastic hinge
occurs in a member, the member cross sections should be double symmet-
rical or single symmetrical with a plane of symmetry in the same plane as the
rotation of the plastic hinge. Where a plastic hinge occurs in a joint, the joint
should either have sufficient strength to ensure the hinge remains in the
member or should be able to sustain the plastic resistance for a sufficient
rotation.
According to EC3 [1.27,2.11], elastic global analysis should be based on
the assumption that the stress-strain behavior of the material

is linear,