There is no time restriction on reapplying for a nonimmigrant visa after a denial. If you have additional information or supporting documentation to present which is substantially different from your initial application you are encouraged to reapply.
Note: If your circumstances are unchanged and you will present only evidence which has already been reviewed recently by an officer, your chances of gaining approval on a second or third application are much lower. In such cases, it is probably better to wait until your personal circumstances have changed significantly before reapplying.
The meaning of ‘strong ties’ differs from country to country, city to city and individual to individual. Some examples of ties can be a job, a house, a family, a bank account. ‘Ties’ are the various aspects of your life that bind you to your country of residence like your possessions, employment, social and family relationships.