ANALYSIS ON ELASTO-PLASTIC BEHAVIOR OF AN EXISTING REINFORCED CONCRETE BUILDING RETROFITTED BY STEELFRAMED BRACES IN DIFFERENT ARRANGEMENTS AND SIMPLIFIED EVALUATION METHOD OF HORIZONTAL BEARING CAPACITY OF THE RETROFITTED BUILDING

摘要

Using analysis models of a building retrofitted with steel-framed braces, this study analyzes the effects of different brace arrangements on the elasto-plastic behavior of the retrofitted building and the states of stress in the members in the retrofit zones to determine the characteristics of elasto-plastic behavior achieved with different bracing arrangements. Then, on the basis of the effects of different bracing arrangements determined, the study proposes a seismic retrofit design method. The results and findings of this study can be summarized as follows: 1) A retrofit design calculation method and conditions for applying the method have been proposed, and usefulness and practicality of the method have been confirmed. 2) Increasing the horizontal load-carrying capacity of the upper stories is difficult in the case of multistory continuous bracing, while in the case of discontinuous bracing; the load-carrying capacity increases in proportion to the number of braces. Discontinuous bracing also makes it easy to achieve the required stiffness of each story and can be used as an effective means of reducing the earthquake response of a building. 3) Retrofit design using discontinuous bracing depends on yielding of braces and requires confirming the safety of adjoining members (e.g., lower-story columns, adjoining beams). 4) In cases where discontinuous bracing is used, it is desirable that braces be arranged more or less regularly, such as in a checkered pattern.