Assessment of Direct Displacement Based Seismic Design Philosophy for Reinforced Concrete Frame Buildings

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Date

2011-11

Authors

Alemayehu, Golla

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Publisher

Addis Ababa University

Abstract

Structural displacements and member deformations do not enjoy a primary role in the current force-based seismic load resistance design. Their absolute magnitude is of interest only for aspects considered of secondary importance for seismic performance and safety. In the main phases of current force-based design, namely that of member dimensioning for given strength demands and that of detailing, structural displacements and member deformations enter in an average sense and indirectly. Recent years have seen, however, an increased interest in absolute magnitude of displacement and deformations as the basis of seismic design. The main reason for this is the recent recognition that displacement rather than strength, demands and capacities is what determines seismic performance and safety. Since an earthquake is dynamic action, it represents for a structure a demand to withstand certain displacement and deformations, but not specific forces. In this work the recent displacement based design philosophy is assessed, examined and compared with the current traditional force-based design philosophy as applied for reinforced concrete frame buildings by taking representative frame buildings without structural wall to be analyzed using both methods so that the limitations and suitability of the recent method can be drawn as well as the parameters to be considered is examined by taking span length, story height, beam depth and number of stories as a parameter. The parametric study shows that this new design philosophy accounts parameters those affect the response of the structure directly in transparent way. Specially, the span length and beam depth have significant influence on the resulting strength requirement. It is also simple for practical application in addition to its basic on convincing and logical theoretical back ground. In this thesis work, a lot of effort have been done to introduce the world wide trend of shifting the design philosophy towards displacement-based which and also help further researchers to insight the detail researchable areas those guide for the revision of our seismic design building standard codes.

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Keywords

direct displacement based design, design displacement, substitute structure, equivalent damping

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