40610 Homework 4

Department of Civil Engineering, Faculty of Engineering, Mahidol University
EGCE 406: Bridge Design
Homework 4 (Due Tuesday, September 14 th 2010)
Develop an Excel worksheet to calculate the stresses in a prestressed concrete
member at initial and service stages based on AASHTO LRFD Specifications. The
worksheet must have the following features:
• Able to input material and section properties
• Able to input the prestressing force, number of strand, and eccentricity.
• Able to input (or calculate) moments due to dead load, superimposed dead
loads, and live loads on a simple-supported member.
• Able to calculate allowable stresses from the input compressive strength
according to the AASHTO specifications.
• Able to calculate stresses on the top and bottom fiber in the member for initial
(immediately after transfer) and final (service) stages.
• Able to plot a simple feasible domain for the critical section
• Able to plot prestress envelope at every 10% of the span
The example given in class may be used as a guideline and to check your results.
However, you do not need to follow it closely (you may be as creative as you want).
After successfully develop the worksheet, use this worksheet to find the number of
strands and the tendon profile for the following beam:
Assume
f’ ci = 40 MPa, f’ c = 55 MPa,
f pu = 1860 MPa, f pi = 1300 MPa,
η = 0.8, f pe = 1040 MPa
A ps (each) = 98.71 mm 2
Note that the dead load and live loads are
uniformly distributed and there are two
superimposed point loads at both ends.