ANALYSIS AND DESIGN OF ROCKING STRUCTURES

Ebru Günaydın (TOY)

(Thesis Supervisors: Prof. Ayşe Edinçliler & Co- Supervisor: Prof. M.Eren Uçkan)

ABSTRACT

Due to their high dynamic seismic resistance, ancient columns survived the severe ground shaking through the ages. The high seismic resistance of ancient rigid columns standing unrestrained on a rigid base is due to the fact that these columns were designed by ancient architects based on an articulated mechanism. Due to the rocking working principle, recentering of these free-standing structures is achieved with gravity. Therefore, these “unconventional” rocking structures behave quite differently from conventional structures and may exhibit superior stability during earthquakes. In this dissertation, the dynamic response of ancient columns that are allowed uplift and rock motion when subjected to ground excitation was studied.

This thesis aimed at investigating the dynamic rocking response of rigid blocks subjected to a variety of seismic excitations by performing numerical methods and contributing to the understanding of the fundamental dynamics of rocking systems. After deriving linear and nonlinear form of differential equations of motion about pivoting points, O or O’, a set of numerical approaches were employed for the evaluation of the dynamic response of the rigid blocks. The formulation of analytical equations and numerical solution of the rigid rocking blocks to trigonometric pulses and real earthquake records is achieved using a routine adopted to the numerical computing MATLAB package. The energy loss due to the impact between the rigid block and the base during the rocking movement is included in the program as the “coefficient of restitution (COR)” as suggested by Housner (1963).

Following chapters proceeds with examining the effect of changes in ground motion forms on overturning acceleration spectra (OAS). The influence of frequency and amplitude of the ground acceleration function on the overturning thresholds of rigid bodies were investigated. With the aim to see the scale effect on overturning curve, samples with different sizes and slenderness ratios were considered. Numerical results revealed that the rocking response of rigid bodies significantly alters with amplitude and frequency content of the ground acceleration, slenderness ratio as well as the size parameter.