الفهرس 
RESEARCH OBJECTIVES
PARAMETRIC STUDYOnly 14 pages are availabe for public view
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Abstract
In many countries and regions in the world, earthquakes are one of the most common natural disasters, which affect human life and property. To avoid the negative effects of earthquakes(EQs), the nonlinear response of structures under dynamic loading should be accurately modelled to investigate their actual behaviour under earthquake loading to ensure safe and economic design.
Most seismic design codes today include the structure nonlinear response implicitly through a ‘response reduction/modification factor’(R). This factor allows a designer to use linear elastic force based method while representing nonlinear behaviour and deformation limits. This research focuses on estimating the actual values of this factor for reinforced concrete(RC) moment resisting frames, which were designed and detailed according to the ECP and ASCE code standards for seismic and comparing these values with the value proposed in the design code.
A total of 64 analytical models for RC frames analysis models using push over analysis and time history analysis. The models were chosen to study the effect of number of stories, and relative inertia between girders and columns on the expected R factors for RC frames. Then calculated response reduction/modification factors (R) for reinforced concrete (RC) frames will be compared to those specified in ECP and the ASCE code. The software used in this study is Seismostruct 2016.
The research was carried out over three phases. The first was a review of previous literature related to the focus of the study. This was carried out in order to have a clear and broad understanding of past findings in this field. During the second phase, a technique for reinforced concrete(RC) frames modelling was developed and the experimental results of previous studies available in literature were verified. In the final phase, a parametric study was created to study the effect of number of stories, and relative inertia between girders and columns on the expected R factors for RC frames. Then calculated response reduction/modification factors(R) for reinforced concrete(RC) frames will be compared to those specified in ECP and the ASCE code.
The results show that:
The response reduction/modification factor(R) value is sensitive to both number of stories and relative inertia between girders and columns, however variation in relative inertia between girders and columns tend to display more significant impact on R-value.
The effect of increasing number of stories on decreasing the R value is more significant, compared to the value recommended in the design codes which equal to 5 according to ECP and ASCE for intermediate moment resisting frame .
Increasing number of stories lead to lower ductility factor. And also increasing the relative inertia between girders and columns lead to lower ductility factor too.
The calculated R-values for mid-rise buildings were higher than these values in ECP code and ASCE code, which lead to a lower base shear that wasn’t considered in codes.
While the number of stories increases from(2,4,8 and 12 stories), the R factor calculated based on (Rµ=µ),tends to decrease by (11%, 36% to 52%) respectively for the relative inertia between girders and columns equals to 1:1, (14%, 46% to 58%) respectively for the relative inertia between girders and columns equals to 1:2 and (32%, 54% to 64%) respectively for the relative inertia between girders and columns equals to 1:4.
While the relative inertia between girders and columns increases from (1:1, 1:2 to 1:4), the ductility factor tends to decrease by (1.3% to 3%) respectively for 2stories analysis model,(3.7% to 26%) respectively for 4stories analysis model ,(16% to 31%) respectively for 8stories analysis model and(12.5% to 26%) respectively for 12stories analysis model.
The response reduction/modification factor(R) value, calculated based on (Rμ= √(2μ – 1) ), for 2 stories analysis models using pushover analysis is low compared to time history analysis because the ductility factor depends on the fundamental period which has a value lower than 0.5 second in pushover analysis.
The time period calculated based on ECP code doesn’t take into consideration the mass and the stiffness of the RC structures as the fundamental period calculated based on structural mechanics.
While the relative inertia between girders and columns increase, the fundamental period calculated based on structural mechanics decrease.
The R –values based on (Rµ=µ) from pushover analysis and time history analysis are approximately the same.
A number of conclusions and recommendations for future work were extracted from this study. The conclusions were related to the modelling of reinforced concrete (RC) frames and to the system level behaviour under lateral loading.