Structures may be subjected to a local loss of soil support under some oftheir footings due to several factors such ~s adjacent excavation for a newneighbor foundation, increasing the load on the surrounding soil, erosion byground water and compaction resulting from vibrations due to-pile driving,./traffic and earthquakes. The previous factors may cause excessive differentialsettlements and even failures of an existing building. ’The aim of this thesis. is to investigate theoretically and experimentallyusing finite element and photoelasticity techniques the behavior of multi storyframes supported” by continuous strip footing and resting on elastic half spacemedium when an edge loss of soil support underneath the footing takes place.Local loss of soil support may cause an increase in the internal forces inthe superstructure frames beyond the allowable values. It may also cause anincrease in the internal stresses ID the footing beyond the allowable valuesconsidered in the design, which may cause cracks, or failure of existingbuildings. Therefore analysis of soil-structure interaction with a loss of soilsupport is of fundamental importance to both structural and geotechnicalengmeenng.This thesis presents a three-dimensional finite element approach as acontribution to meet the need for treating the superstructure, foundation and thesupporting soil as parts of a single continuous system.The results for the case of no loss of soil support and the different cases ofloss of soil support will be compared. The results obtained form finite elementand photoelasticity techniques will also be compared. Curves andrecommendations which ought to be considered by designers to assure safetyof structures will be introduced.