Can anyone give me the exact ASTM Reference where the mechanical properties of a structural steel is reflected? I'm just new in structural engineer and would appreciate if you could help me out.
This is not a singular reference. There are about 30 ASTM plate steel standards, probably that many more for pressure vessel steel, sheet steel has around 20, and coated sheet steel again more. Within those some have as many as 30 grades each with their own properties. You're going to have to be a lot more specific in your needs.
There are also handbooks and articles from trade associations that will summarize the more common structural steel specs. You might also look for guides published by major producers of structural steel.
Maybe if you give us a specific steel. I just went to Industrial Metal Supply to buy some square tube (smaller than HSS). The guy bragged about how it met ASTM A (Whatever) and was 72 ksi steel. But he didn't know that this spec is a dimensional spec that allows steel down to 33 ksi and he had no purchase order to prove what he bought. ASTM's are tricky!
The ASTM specification for each structural steel provides this information. You can also review AWS D1.1 and find numerous structural steel specifications used and the strength thereof.