26.1. Introduction

Try these first

1. 1.

   What is the main purpose of using prestressed concrete?

   Hint

   Think about the advantages over traditional methods.

2. 2.

   Name the two methods of prestressing concrete.

   Hint

   One involves tensioning before the concrete is set.

3. 3.

   What is the primary purpose of prestressed concrete?

   • Increase weight limits
   • Reduce deflections
   • Increase material costs

   Hint

   Look for benefits of construction methods.

4. 4.

   True or False: Posttensioning occurs before the concrete is poured.

   • True
   • False

   Hint

   Consider the order of operations.

5. 5.

   A simply supported beam is prestressed using a tendon that introduces a 120 ksi initial stress. After considering creep and shrinkage, what is the effective stress left in the steel if the losses amount to 20 ksi?

   Hint

   Identify the initial stress and subtract the specified losses.

6. 6.

   Compare the performance of a 30 feet R/C beam with 5 inches of deflection to a P/C beam subjected to the same load. Assuming the P/C design reduces deflection by 50%. What would the new deflection of the P/C beam be?

   Hint

   Calculate based on the reduction percentage given.