This publication provides introductory technical guidance for civil engineers, structural engineers and other professional engineers and construction managers interested in tie forces to prevent progressive collapse of buildings in the event of seismic or explosive incidents. Here is what is discussed: 1. TIE FORCES, 2. LOAD AND RESISTANCE FACTOR DESIGN FOR TIE FORCES, 3. FLOOR LOADS, 4. REQUIRED TIE STRENGTH, DISTRIBUTION, AND LOCATION, 5. CONTINUITY OF TIES, 6. SPLICES, ANCHORAGE, AND DEVELOPMENT OF TIES, 7. STRUCTURAL ELEMENTS AND CONNECTIONS WITH INADEQUATE TIE STRENGTH.