The overwhelming social and economic impacts of recent earthquakes in thernworld have resulted in an increased awareness of the potential seismic hazard andrnthe corresponding vulnerability of existing structures. Greater effort has beenrngiven to reasonable estimates, predictions and mitigation of the risks associatedrnwith these potential losses. As being one of the special reinforced concreternstructural forms, flat-slab systems need further attention. We are living in an erarnwhen flat slab construction activity is booming due to many advantages it possesrnin terms of architectural flexibility, use of space, easier formwork and shorterrnconstruction time, However the structural efficiency of the flat-slab construction isrnhindered by its poor performance under earthquake loading. This undesirablernbehavior has originated from the insufficient lateral resistance due to the absencernof deep beams or shear walls in the flat-slab system. Hence, the effectiveness ofrnflat slab structures without shear walls or other stiffening mechanisms needs to berninvestigated against seismic hazard.rnGenerally, flat-slabs can be designed by any procedure that satisfies equilibriumrnand geometric compatibility provided that every section has strength at least equalrnto the required strength (ACI-318). In this study various flat slab analysis methodsrnthat are pertinent to gravity and earthquake loading are reviewed along withrndifferent modeling techniques. Among many of flat slab analysis methods, DirectrnDesign Method, Equivalent Frame Method and The finite analysis method are thernmost commonly used methods of analysis. And finally, FEM method is used tornanalyze flat slab buildings along with the effective beam width modeling methodrnfor gravity and seismic loading respectively. The regularity of the buildings inrnterms of mass and stiffness both in plan and elevation enabled the utilization ofrnAssessment of flat slab Construction without shear walls with respect to the Effectiveness against lateral load resisting Capacity.rnAAU ,FoT, Department of Civil Engineering By :Eyob Tadesserntwo-dimensional analysis in the assessment of seismic response. Hence, in thisrnstudy, the three dimensional flat-slab building is modeled as a series of tworndimensional interconnected planar frames. For the modeling of the 2-D planarrnframes, the portion of the slab that will contribute to the frame analysis isrndetermined as well as the width of the concealed beam within this slab portion.rnIn this study different flat slab structures with different aspect ratios are modeled,rnanalyzed and designed to satisfy strength requirements and these structuresrndesigned for strength are evaluated against drift capacity. Building layout in planrnis kept constant while slab depth and building height are used as a variable byrnincreasing the number of stories up to the attainment of the largest practical slabrndepth.rnFinally, Low to medium rise flat plate structures (G+1 - G+6 ) having mediumrnspans , located in seismic zone 2 which are designed and analyzed in this studyrnfound to be effective in seismic hazards resistance. How ever, the outcome of thisrnstudy articulate that flat plate structures with more than six numbers of storiesrnconstructed in seismic zone II need to be combined with shear walls or otherrnstiffening mechanisms.