Deformation and strength based assessment of seismic failure mechanisms for existing rc frame Buildings

Student: Ahmad Abo El Ezz
Supervisors: Dr Helen Crowley

ABSTRACT

The motivation for the presented research work is the need for a reliable and simplified assessment method for predicting the most probable side-sway failure mechanism for the existing RC frame buildings, which is a basic step in evaluating the seismic capacity of these buildings. In order to predict the most probable failure mechanism, the concept of the sway potential index is introduced. A strength based sway index, as well as a newly proposed deformation based index, are verified. The concept of the strength based index is to check whether plastic hinges occur in beams or columns by comparing the sum of the probable flexural strengths of the beams to the columns. The deformation based sway index is introduced considering the relative flexibility of beams and columns using only the geometrical properties as an indicator of potential failure mechanisms. The definition of the most probable side-sway mechanism of the frame is evaluated by comparing the yield rotation of the columns to those of the beams. The deformation based index is a measure of the dominant flexible members that are expected to control the behaviour of the frame. The present study has verified the suggested sway potential indices using a newly developed displacement based nonlinear adaptive pushover analysis method and suggests limiting values between beam sway and column sway mechanisms for bare as well as masonry infilled existing RC frame buildings. Additionally, storey strength and stiffness ratios are developed as additional information to help in the prediction of the failure mechanism, which reflects the vertical distribution of strength and stiffness along the height of the building.

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