Homework 1

Department of Civil Engineering, Faculty of Engineering, Mahidol University
EGCE 406: Bridge Design
Homework 1 (Due Monday, July 2 nd 2007)
1. If you want to build a bridge to cross a river with a cross-section as shown
below. What kind of a bridge would you build? Think of two different types
and sketch it to scale. Compare the advantage and disadvantages and the
factors that you need to consider between the two.
2. For the beam shown below, find the influence line for:
a. Support Reaction at B
b. Moment at B
c. Shear at C
d. Moment at C
e. Shear to the left of D (Hint: Apply a shear release just to the left of
D)
f. Shear to the right of D (Hint: Apply a shear release just to the right of
D)
A B C D E
4 m 4 m 6 m 3 m

3. Suppose the above structure has to carry a pair of concentrated load, each 5
kN, spaced at 2 m from each other. What would be the placement of these
concentrated loads to produce the maximum effects in each of the cases
above? Determine the maximum value.
5 kN 5 kN
2 m
4. For the truck and bridge shown below. Determine the influence line for
moment at midspan. Use the Increase-Decrease Method to find the load
placement to get the maximum moment at midspan.