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Haikou, China

Zhou H.,Hainan University | Zhou H.,APCE Design Group Ltd | Zhang J.,Hainan University
Structural Engineering and Mechanics

This paper presents detailed analysis of the internal forces of interior beam-column joints of reinforced concrete (RC) frames under seismic action, identifies critical joint sections, proposes consistent definitions of average joint shear stress and average joint shear strain, derives formulas for calculating average joint shear and joint torque, and reports simplified analysis of the effects of joint shear and torque on the flexural strengths of critical joint sections. Numerical results of internal joint forces and flexural strengths of critical joint sections are presented for a pair of concentric and eccentric interior connections extracted from a seismically designed RC frame. The results indicate that effects of joint shear and torque may reduce the column-to-beam flexural strength ratios to below unity and lead to "joint-yielding mechanism" for seismically designed interior connections. The information presented in this paper aims to provide some new insight into the seismic behavior of interior beam-column joints and form a preliminary basis for analyzing the complicated interaction of internal joint forces. Copyright © 2014 Techno-Press, Ltd. Source

Zhou H.,Hainan University | Zhou H.,APCE Design Group Ltd | Xu X.,Hainan University | Zheng F.,Hainan University | Huo J.,APCE Design Group Ltd
Advances in Structural Engineering

This paper aims to investigate into the reasons for the widespread column-end damages of reinforced concrete (RC) frame buildings caused by the 2008 China Wenchuan earthquake. A six-story office building is used as the prototype building, and ten RC frames under different combinations of Seismic Intensity and Seismic Category are designed for the prototype building in accordance with the Chinese codes. Two joints of the second floor of each frame are selected for calculating the column-to-beam flexural strength ratio (CBSR), and the effects of the following four factors on the CBSR during a strong earthquake are analyzed: (1) the detailing practice of beam longitudinal reinforcement adopted in China; (2) slab participation in beam flexure; (3) reduction of joint concrete strength; and (4) variation of column axial force. The numerical results of CBSR indicate that the code requirement for the "strong column-weak beam" design in China is not sufficient for the RC frames designed for a Seismic Intensity of 0.2 g or lower to avoid column-end damages during a strong earthquake. Suggestions are made for improving the "strong column-weak beam" design of RC frames in China. Source

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