Pre-stress in concrete

 PRE-STRESS IN CONCRETE

Pre-stress can be defined as the initial stress deliberately introduced in a particular structural element by mechanical means. 

OR

It can be defined as the process of deliberately developing stress in an element is known as pre-stressing. 

However, plain cement concrete does not have any strength in tension which is why it is susceptible to crack under tension. This is why it cannot be used for economical design of structures. Because of this plain cement concrete is reinforced by embedding steel bars in tension zone. This steel embedded cement concrete is known as Reinforced Cement Concrete  ( RCC ).

Advantages of Pre-Stressing:

• Pre-stressed members can resist of impact, shock, and reversal stresses more efficiently than RCC structures hence they remain free from cracks.
• Life of pre-stressed elements is more than RCC elements reason being that reinforcement remains unaffected from external agents.
• Section of any member is considerably reduced because of which smaller sections can be used for longer spans.
• There is complete utilization of high compressive strength of concrete resulting in an economical section.

Disadvantages of Pre-stressing:

• Pre-stressing requires special equipment like jacks, anchorage, etc. This restricts the complete use of the pre-stressed member.
• Majority of the steel used is high tensile steel which is difficult to procure and costs more than plain mild steel.
• It requires expertise to exercise control during preparation of high cement concrete.