Among major effects of high temperatures on structural materials include a dramatic change in thematerial behavior and a reduction in the load resistance capacity. In a structural system, the high temperatures from fire along with the changes occurredto the material properties and behavior may affect the system's integrity and capability to supportloads. As the fire persists in a building, structural components suffer a gradual degradation processthat may eventually lead to structural collapse. From the serviceability point of view, a building isconsidered a loss once fire spreads to a major portion of it regardless of whether structural collapseoccurs or not. However, the collapse prevention is especially important to the safety of fire fighterswho stay around or inside the building until the fire is completely contained. In this regard, animportant design consideration is how to treat the collapse issue in a design code. At the presenttime, fire protection coating remains as the only safeguard against fire in buildings. No specificguidelines exist to address design strategies to reduce the risk of collapse in buildings during fire.In an effort to clarify on design issues for buildings subject to high temperature arising from fire,this paper presents the results of an investigation into the behavior of structures subject to hightemperatures during fire. Floor systems made up of reinforced concrete slabs with or withoutintermediate beams were investigated under application of a loading that consisted of dead load andfire exposure. The effect of high temperature on material strength and behavior; creep and crackingin concrete; formation of localized failures; and structural degradation resulting from loss of stiffnesswere investigated using a nonlinear finite element analysis. The analysis simulated the loadingprocess and followed the step-by-step structural degradation of floor systems until a predeterminedcollapse criterion was reached. The results revealed a dramatic loss of structural stiffness after atemperature increase of about 400-500 ° C. The paper also describes the significance of fire loadsin structural analysis and design. Issues pertinent to design include: (1) prevention; and (2) designfor safe performance in a fire. These issues as related to a performance-based design code arereviewed and discussed.