NUMERICAL STUDY ON 2D REINFORCED CONCRETE FRAMES WITH NONDUCTILE COLUMNS USING IDA APPROACH

In recent decades, reliable seismic design of reinforced concrete (RC) structures has been of interest in both practical engineering calculations and research studies. That requires adequate information regarding the ultimate capacities of structural components to withstand the demands (i.e., columns, beams, joints, etc.). Several experimental and numerical studies have been carried out to predict the maximum lateral ductility and strength of RC columns with non-seismic detailing due to the crucial role of this type of primary structural element during earthquakes. Those resulted in developing some criteria as well as numerical models (Elwood and Moehle, 2005; Azadi and Allahvirdizadeh, 2019). The latter can be utilized in numerical simulations of RC structures either based on 1D structural elements or 3D continuum elements (Azadi and KhanMohammadi, 2018; Azadi et al., 2018). This work employs the former sort of elements for developing the numerical models since it is computationally much cheaper than another approach. The numerical models consist of nine 2D ten-story three-bay RC frames, which consider the impacts of various values for transverse reinforcement ratio (3 cases) and initial axial load ratio (3 cases) on the nonlinear seismic response of existing columns and consequently the global behavior of frames. In this regard, the columns and beams are modeled utilizing nonlinear beam-column elements. Moreover, zero-length elements defined by the uniaxial limit state material proposed by Elwood and Moehle (2005), which enhanced and extended to time history analysis by Azadi (2007), are located at the top of columns to predict the occurrence of shear and axial failure in columns. The performance of the modeling approach to capture the nonlinear behavior of such structures is already demonstrated in (Farahmand et al., 2015). The geometrydetails, mechanical properties of concrete and reinforcing steel, and the initial axial load ratios used for developing the numerical models are presented in Table 1. The height of columns and length of beams are 320 and 500 cm, respectively.

کلیدواژه ها:

Reinforced concrete ، Existing buildings ، Columns ، IDA ، Shear-axial failure