The IL Condo Act grants the board the power to levy assessments for the repair, replacement and restoration of the common elements. Often, a special assessments is required to gather the funds necessary for such repairs and replacement. The board has the authority to levy a special assessment without obtaining an owner vote.
If your bylaws indicate that an owner vote is required for a special assessment (if over a certain dollar amount, for example), that provision applies only to an addition or improvement to the property, not to any repair or replacement of existing common elements.