Lean Construction

1
(No Transcript)
2
By Dr. Attaullah ShahSwedish College of
Engineering and Technology Wah Cantt.

• CE-407
• Lec-02
• Structural Engineering

3
The net stress in the prestressed section
The resultant stress due to the combined effect
of applied loads and pre-stress force is given
as At the ends of the beam where there is no
moment the MC/I 0 , the stress becomes
4
Example
5
Solution
6
The kern of a section is the region in which a
compressive point load may be applied without
producing any tensile stress on the cross section.
7
Shapes of pre-stressed sections

• Rectangular shape Simple and easy to pour
• I-Section and T-section Economical
• Channels and Boxes

8
Prestress losses

• The initial prestress becomes smaller with time
  due to following reasons
• A lump sum value has been recommended by ACI Code

9
Elastic Shortening
10
(No Transcript)
11
Losses due to shrinkage
12
Relaxation of creep in the tendons
13
Slippage in post tension and anchorage system
14
Friction along the duct
15
Ultimate Stress of pre-stressed section
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
Assignment No.1