A nonrecoverable I/O error occurred on file after DB Shrink
After I did the following steps below, I was able to produce a database backup again.

Step 1:

use Test_DB

GO


Step 2:

DBCC CheckDB

GO


Step 3:


Right click the Test_DB database then click properties.
Choose Option page
From Restrict Access option, select Single
Click OK and Open Connections dialog will appear. Click Yes if you want to close all connection connected to the database and change the database on single user mode. 


-OR-

ALTER DATABASE Test_DB SET SINGLE_USER WITH NO_WAIT

GO


Step 4:

dbcc checkdb ('Test_DB',repair_rebuild) 

GO


Step 5:

dbcc checkdb ('Test_DB',repair)

GO


Step 6:

ALTER DATABASE Test_DB SET MULTI_USER WITH NO_WAIT

GO