Examining the Behaviour of a Reinforced Concrete System Under Horizontal Loads and Determination of Preliminary Design Reinforcement Ratios

Abstract

Minimum reinforcement ratios provided in the standards remain at very low levels especially at large systems subject to the effects of earthquakes. Thus, arranging the reinforcement ratios intended for preliminary design can provide significant ease and safety in project design phase, and speed and simplicity in the project control phase. Moreover, a more realistic limitation is thus ensured compared to general minimum reinforcement ratios given in the standards. System characteristics which may affect the reinforcement ratios can be specified by general and simple parameters. As the result of many extensive studies, expressions for reinforcement ratios intended for preliminary design which will cover systems with different parameter values can be composed. Today, thanks to the development levels of finite elements programs which can perform reinforced concrete modeling, meeting this requirement is much more possible compared to the past. Structure of parameters should neither be very special nor very general. Otherwise, reinforcement ratios intended for preliminary design will either be valid for a single system or they will remain at very low limits such as the minimum reinforcement ratios given in the standards. For this reason, in this study a route in between these two extreme conditions was followed. Today, it is possible to perform many studies on the systems with different and comprehensive inclusive parameters and to determine practical ratios which will constitute a recommendation for the project designs. For this purpose, an eight storey reinforced concrete system with single spacing whose shear wall cross-section is 25 x 250 cm, column cross-section is 25 x 30 cm, and beam cross-section is 25 x 50 cm was addressed, and its non-linear planary analyses under static earthquake loads were performed through the ANSYS finite elements program for 13 different reinforcement cases. The reinforcement ratios to be recommended for the system at hand and similar systems were tried to be revealed. The examined system was arranged so as to get the most critical and extreme values for many parameters which can be considered, but it was tried for the reinforcement ratios to be recommended to be valid not only for this system but also for the general system network with similar properties to this system. In future studies, expressions of general and inclusive preliminary design reinforcement ratios can be obtained as per the results of many studies to be made on systems with different parameter values. Thus, the tables for preliminary design reinforcements of examined systems can be created. For preliminary design, reinforcement ratios based on the values of system elements' parameters can be determined from these tables. In this case, the design process will be greatly reduced and it will be more reliable. These ratios can be called as the minimum reinforcement ratios for the preliminary design.