Seismic Performance Evaluation of RC Framed Buildings Designed According to Ethiopian Building Code Standard
Creators: name: Yohannes Gudeta
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2018
Subjects: RC framed building, limit state capacities, probabilistic seismic demand model, fragility curves, reliability curves, reliability index, and seismic hazard curve.

description: Uncertainties are common throughout the existence of building structures. The major<br> uncertainties include uncertainties in the material properties, structural properties, and seismic<br> hazard; and seismic performance of buildings also depends on such uncertainties. Due to such<br> uncertainties the seismic performance evaluations of buildings also require probabilistic approaches<br> rather than deterministic approaches. Deterministic approach will not always be suitable in the<br> seismic performance assessment of buildings; in such cases Probabilistic approach yields better<br> results to understand the real behaviour of buildings under seismic excitations. The objective of this<br> study is to evaluate the seismic performance of existing reinforced concrete framed buildings on the<br> Probabilistic bases taking into account the significant uncertainties inherent to the seismic<br> performance of buildings.<br> This study focuses on the existing reinforced moment resisting frame buildings which are<br> designed according to the Ethiopian Building code standard for Addis Ababa region where a<br> substantial seismic risk exists with potential high intensity earthquakes. Different existing<br> reinforced concrete framed buildings are selected as case study, and using a ground motion records<br> the structural behavior of the representative case study buildings is analyzed through nonlinear<br> dynamic time history and pushover analyses. The seismic performance of the buildings is evaluated<br> to describe the structural behavior under ground motions. This study includes the development of<br> the limit state capacities, probabilistic seismic demand model, fragility curves, reliability curve and<br> reliability index to study the Seismic behaviour of the buildings considered.<br> Characterizing the probabilistic nature of structural parameters in the present study is done<br> through the use of Fragility and reliability analysis. A fragility analysis assesses the probability that<br> the seismic demand placed on the structure exceeds the capacity conditioned on a chosen intensity<br> measure, representative of the seismic loading. Demand and capacity are assumed to follow a<br> lognormal distribution, and the probability of exceeding a specific damage state for a particular<br> component is estimated with the standard normal cumulative distribution function. Probability of<br> exceedance of a damage state by incorporating the uncertainties is studied through a fragility<br> analysis. Using detailed demand models and the corresponding capacity limits, fragility curves are<br> developed for different performance levels based on appropriate failure mechanisms for different<br> structural parameters. Latin Hypercube sampling scheme; this sampling scheme is used in this stuy<br> to incorporate the random variables and uncertainties in the material and structural properties and<br> executed in Mat lab program.<br> Reliability assessment is carried out by combining Fragility curve and seismic hazard curve.<br> From probabilistic seismic demand models and limit state capacities fragility curves are developed.<br> Nonlinear dynamic time history analysis was performed to develop probabilistic seismic demand<br> models and pushover analysis was performed to develop limit state capacities. All the analysis’s<br> was performed in SeismoStruct software which is nonlinear finite element software. Seismic hazard<br> curve, which represents probability of occurrence of earthquake, is collected from literature.<br> Reliability curves and the corresponding reliability indexes for different performance objectives are<br> developed by combining the results of fragility analysis and collected hazard curve. And the<br> achieved reliability index for each case of the buildings was cross checked with the target<br> reliabilities for different performance objectives. Finally the outcome of this work show that the<br> current Ethiopian design code provisions for the seismic design does not satisfy all the required<br> performance objectives for buildings under seismic excitations.