Reinforced concrete bridges - Computational Analysis and Design of Bridge Structures - page 108

1000

800

Carbon FRP

600

Glass FRP

400

200

0

0 0.005 0.01 0.015 0.02 0.025

Strain

Figure 4.5 FRP uniaxial stress-strain curve for carbon and glass FRP composites in the
fiber direction.

4.3 BehavIoR oF nonSkewed/Skewed
concRete Beam-SlaB BRIdgeS

Skew effect occurs in all types of bridge. It is discussed here because the
effect is especially true and can be easily interpreted for concrete slab bridges.
Nonskewed bridges, also known as straight, normal, or right bridges, are built
with the longitudinal axis of the roadway normal to the abutment and there-
fore have a skew angle of 0°. As described in the American Association of State
Highway and Transportation Officials (AASHTO) Load Resistance Factor
Design (LRFD) Bridge Design Specifications (2013a), the skew angle of a bridge
is defined as the angle between the longitudinal axis of the bridge and the
normal to the abutment or, equivalently, as the angle between the abutment and
the normal to the longitudinal axis of the bridge as shown in Figure 4.6. Skewed
bridges are often built due to geometric restrictions, such as obstacles, com-
plex intersections, rough terrain, or space limitations (Menassa et al. 2007).
As early as 1916, design recommendations were made to avoid building
skewed bridges because of the many difficulties that arose when designing
them, such as complex geometry and load distributions. However, because
of increasingly complex site constraints, an increasing number of skewed
bridges have been built. In addition to the complex geometry and load dis-
tributions caused by the skew, the skew angle can affect the performance of
the substructure in conjunction with the superstructure, causing a coupling
of transverse and longitudinal modes because of wind and seismic loads.
Skew angles, in addition to the length-to-width ratio, also affect whether
the bridge undergoes beam bending or plate action. As the skew increases
or the length-to-width ratio of a bridge decreases, the bridge behaves more
similarly to a plate than a beam.