Civil Engineering Reference
In-Depth Information
the recommended values are
e
ud
¼
0.02 and
f
p0.lk
/
f
pk
¼
0.9. Prestressing ten-
dons in sheaths (e.g., bonded tendons in ducts and unbonded tendons) shall
be adequately and permanently protected against corrosion. Prestressing
tendons in sheaths shall be adequately protected against the effects of fire
as specified in EC2 (BS EN 1992-1-2) [
2.31
].
2.6 NONLINEAR BEHAVIOR OF SHEAR CONNECTION
2.6.1 General
Steel-concrete composite construction is used extensively in highway brid-
ges owing to its advantages in terms of saving in weight of steel, high
strength, high stiffness, high resistance to seismic and cyclic loading, increas-
ing load capacity, better fire resistance, and reduction in construction depth.
In composite beam design, shear connectors are commonly used to transfer
longitudinal shear forces across the steel-concrete interface. The shear
strength of the connector and the resistance of the concrete slab against lon-
gitudinal cracking are the main factors affecting the shear stiffness and
strength of the shear connection. Calculation of the structural behavior of
composite beams depends on howmuch slip is assumed to occur at the inter-
face between concrete and steel. Experimental push-off tests are the tradi-
tional source of knowledge about the load-slip behavior and the shear
capacity of the shear stud in composite beams.
Up to the early 1950s, steel beams were designed to act as composite
beams with solid concrete slabs of various thickness, connected to them
using a variety of types of mechanical shear connectors. However, during
this period, composite construction in buildings was generally uneconom-
ical. This was due to the significant amount of formwork and propping
required for the concrete slabs, along with the costly process in terms of time
of having the shear connectors welded to the steel beams. In a composite
steel-concrete beam, the floor slab tends to slide along the flange of the steel
beam and the importance of the shear connectors arises from preventing this
slippage. The structural behavior of a composite beam is affected by the slip
at the steel-slab interface. Practically, the assumption that this slip may be
completely eliminated cannot be ensured. Therefore, accurate calculation
methods of the structural behavior of composite girders must take into con-
sideration the effects of this slip. Push-off tests provide a convenient way to
study the behavior of shear connector without carrying an expensive full
bending test. Initially, the evaluation of the shear capacity of connectors
was the main output of these tests. After that, researchers realized that the
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