Study of Three Bridges and Questions Answer Key

Logon to the University of Florida truss building laboratory http://www.ce.ufl.edu/activities/cdrom/civil/sample.html

Study the following pages on this website.

Click on each bridge below and review information available at the Library of Congress American Memories website. Then answer the questions at the bottom of the page.

	The Wheeling Suspension Bridge-1849
	Delaware County Bridge No. 131
	Waterford Covered Bridge, Spanning Le Boeuf Creek, Waterford, Erie County, PA

Delaware County Bridge No. 131

1) What style of truss is used in this bridge? Refer to the University of Florida, Civil Engineering website. http://www.ce.ufl.edu/activities/trusslab/sample.html

Pratt Truss

Waterford Covered Bridge

2) Discuss the probable reasons for the designers use of criss crossed members in the construction of this bridge.

The Criss Cross design allow the members to supply not only a vertical force component but horizontal force components as well. Allowing the bridge to maintain a rigid structure and not collapse like a parallelogram.

In the "search for" box type -- Wheeling Suspension Bridge

3) The Wheeling Suspension Bridge combines elements of what two major bridge styles in its design?

True Suspension and Cable Stayed

Turn to data page 5 and 6 and read.

4) How did the bridge designers deal with expansion and contraction of the bridge cables caused by temperature change or loading of the bridge?

"The cables rested on iron rollers placed on the summits of the columns, moving back and forth slightly in response to the contraction and expansion of the metals and loads placed upon the flooring." Page 5

5) No bridge of this span had ever been built. According to this historical document what gave the designers confidence that their bridge would work?

"Ellet Assured the City Council of Wheeling that although no span of that length had ever been previously attempted, the laws governing its equilibrium were known and could be measured accurately." Page 6