How High Could Buildings Made of Ribbed or Flat Slab Construction With out Shear Walls be Built? (Case Study)

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Addis Ababa University


The main objective of this thesis was to study the stability of slab-column, specifically ribbed slab-column, for high rising building frame systems with out lateral load resisting structural element. The study also tried to answer the question how the stability of ribbed slab column frames without lateral load resisting structural element determines the limit of the story number which can be built using ribbed slab column frame system in Addis Ababa and other seismic areas in Ethiopia. Computer aided analysis based on 3-dimensional model consisting reduced column and ribbed beam stiffness for case of ACI and unreduced stiffness for case of EBCS was used in the determination of stability index of a story. This can be applied for various categories of building frame and structural element sizes to carry out the study of stability. The selection of a building configuration is one of the most important aspects of the overall design; it is influenced primarily by the intended function, architectural considerations, internal traffic flow, building height, aspect ratio and to a lesser extent the intensity of loading. In this study, buildings are categorized as commercial (shops and market complex), office and apartment buildings. The arrangement or grid spacing for structural element is compatible with the international standards given from Time- Savers standards for building types and Neufert (architects’ data). The study showed that the stability index or moment ratio of a frame system should not be greater than 0.25 according to EBCS-8 1995 and 0.3 for ACI building code standard, but the building systems which were described in this thesis work have a value which is much greater than this value for eight story and above . The serviceability limit of a story is not satisfied in most analyzed ribbed slab frame systems. Therefore, the ribbed slab column frame systems are designed for gravity load, and for deformation compatibility lateral force resisting structural element should be 9 used to ensure that the system can maintain the required serviceability and ultimate limit state specified on EBCS and ACI code of practice.



Case; Study