Cyclic Shear Strength and Seismic Design of Reinforced Concrete Coupling Beams

• Main Authors: Erwin Lim, 林孝勇
• Other Authors: Shyh-Jiann Hwang
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/49443692160439432252

博士 === 國立臺灣大學 === 土木工程學研究所 === 103 === Coupling beams in the coupled wall system are the “fuse” to limit the input earthquake force into building system. They are also expected to subject to very large displacement demand. So, it is important to preserve the shear strength at the Maximum Considered Earthquake (MCE) level. The requirement of the use of diagonal reinforcement layout by ACI 318-14 code design procedure has been proven effective to maintain shear strength at the MCE level and to achieve good deformation capacity, especially for deep coupling beams (clear span-to-depth ratio ln/h < 2). However, the ACI 318-14 neglects the check for flexural strength developed at the Design Based Earthquake (DBE) level, which might cause adverse effects to the system. The design procedure of ACI 318-14 is also criticized for lacking of a proper consideration of force transfer mechanism. It causes that for coupling beams with intermediate span-to-depth ratio (2 < ln/h < 4), engineers are left with options of choosing either a diagonally reinforced layout or a conventional ductile beam design, without being fully aware of the consequences. This study summarized the findings from a five-year experimental program of coupling beam specimens tested in National Taiwan University from 2010 through 2014 and identified that the major parameters influencing their seismic behavior is the shear strength at the MCE level. Following it, semi rational shear strength models and the corresponding design procedures were developed. The design procedures suggested that the flexural design of a coupling beam be the primary strength design at the DBE level. At the MCE level, by adopting a capacity design concept, the design procedure aims to provide sufficient shear capacity to resist the plastic shear demand. This study also proposes a concept of coupling beams with partial amount of diagonal reinforcement or hybrid layout, which combines the conventional and diagonal layout. This hybrid layout is suitable for coupling beams with intermediate span-to-depth ratio (2 < ln/h < 4). The use of partial amount of diagonal reinforcement (hybrid) layout would not only maintain the shear strength at the MCE level, but also ease the constructability of the coupling beams.