Reinforced concrete bridges - Computational Analysis and Design of Bridge Structures - page 111

A

C

E

B

D

60°

(a) Load transferred from zone C and D to E and then to the supports

C

A

E

B

D

30°

(b) Greater the skew, narrower the load-transfer strip

Area has a
higher stiffness

(c) Simplified model of load transferring

Figure 4.8 (a-c) Force flows in a skewed deck.

• Negative moment along the support line and high shear and high
torsion near obtuse corners. Sagging moments orthogonal to abut-
ment in the central region.
• At free edges, maximum moment nearer to obtuse corners rather than
at the center.
• The points of maximum delection toward obtuse-angled corners (the big-
ger the skew angle, the more shift of this point toward the obtuse corner).
• Maximum longitudinal moment and also the delection reduce with
the increase of skew angle for a given aspect ratio of the skew angle.
• As skew increases, more reaction is thrown toward obtuse-angled
corners and less on the acute-angled corner. Hence the distribution of
reaction forces is nonuniform over the support line.
• For a skew angle up to 15° and skew span-to-right width ratio up to 2, the
effect of skew on principal moment values and its direction is very small.
• For a skew angle more than 15°, the behavior of the slab changes
considerably.

Illustrated examples are provided in Sections 4.5 through 4.7.