Do you think pressure can create bending ( unless of course you are considering bourdon effect which is typically treated as a secondary effect analogous to thermal expansion) ? Bending is created by dead wt. of pipe along with wt. of fluid, valves, insulations etc. Honestly, do you really need to ask this question to find out how bending is created in piping systems? You should know it from a course of Strength of materials which you must have taken ( I presume you hold an engineering degree/ diploma).

My advise for you will be to:

1) Read/Brush up Strength of materials.

2) Read B31.3/B31.1 code.

3) Improve your english.

4) If you can't do the above three ,do something else other than pipe stress analysis.

Regards