In this paper recent earthquakes in Turkey are briefly discussed. Large-scale seismic rehabilitation projects carried out by the Middle East Technical University faculty and staff on moderately damaged R/C buildings are summarized. Research at METU related to seismic rehabilitation is presented, emphasizing infilled frames, a system extensively used in Turkey.

The seismic design requirements in the Building Standard Law of Japan were revised in June 2000 toward a performance-based design framework. The performance objectives are (a) life safety and (b) damage control of a building at two corresponding levels of earthquake motions. The design earthquake motion is defined in terms of acceleration response spectrum at engineering bedrock. The amplification of ground motion by surface geology and the soil-structure interaction must be taken into consideration. The response is examined by so-called capacity spectrum method by comparing the linearly elastic demand spectrum of design earthquake motions and the capacity curve of an equivalent single-degree-of-freedom (ESDF) system. The structure as designed is reduced to an ESDF system using a nonlinear static analysis under monotonically increasing horizontal forces. Equivalent damping is used to modify the demand spectrum taking into account the energy dissipation capacity of a structure at the prescribed limit states.

The approach for seismic evaluation and guidelines for seismic retrofit in the Canadian Highway Bridge Design code are presented. A number of common seismic deficiencies found in bridge structures are discussed. The reversed cyclic loading behavior of columns with lap splices at their bases, outrigger beam-column connections and columns with hinges at their bases are discussed. Methods suitable for retrofit of a number these deficiencies are described. The responses of these elements after these retrofit strategies had been carried out are also presented.

To my friend and hero Professor $tikti Muvaffak flztimeri, a bouquet of thoughts and an invention of another hero, Professor Hardy Cross.

Professor S. M. Uzumeri and the author initiated a research program on the seismic resistance of reinforced concrete columns in mid seventies. The first phase of this work concentrated on the behavior of rectilinearly confined concrete columns under axial compression. In addition to carrying out an extensive experimental program, an analytical model for the mechanism of concrete confinement by rectilinear transverse reinforcement was developed. This was followed by an investigation of square columns under combined axial load and flexure. After identifying the important variables that affected the mechanism of confinement and section behavior, the research advanced to a study of column behavior under simulated earthquake loads. Distribution of longitudinal and lateral reinforcement, level of axial load, spacing of ties and the type of lateral support provided to the longitudinal bars were found to significantly affect the ductile performance of a column. Based on the results from extensive experimental and analytical research, a design procedure was developed in which the amount of tie reinforcement and the detailing of both longitudinal and lateral reinforcement are determined for a required ductile performance of a column subjected to a given axial load. This paper presents selected results from the work carried out over the last several years. An example demonstrating the application of the design procedure is also included.