• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.515-525
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• 2007

In this investigation, results of laboratory tests on four reinforced concrete flat plate interior connections with elongated rectangular column support which has been used widely in tall residential buildings are presented. The purpose of this study is to evaluate an effect of column aspect ratio (${\beta}_c={c_1}/{c_2}$=side length ratio of column section in the direction of lateral loading $(c_1)$ to the direction of perpendicular to $c_1$) on the hysteretic behavior under earthquake type loading. The aspect ratio of column section was taken as $0.5{\sim}3\;(c_1/c_2=1/2,\;1/1,\;2/1,\;3/1)$ and the column perimeter was held constant at 1200mm in order to achieve nominal vertical shear strength $(V_c)$ uniformly. Other design parameters such as flexural reinforcement ratio $(\rho)$ of the slab and concrete strength$(f_{ck})$ was kept constant as ${\rho}=1.0%$ and $f_{ck}=40MPa$, respectively. Gravity shear load $(V_g)$ was applied by 30 percent of nominal vertical shear strength $(0.3V_o)$ of the specimen. Experimental observations on punching failure pattern, peak lateral-load and story drift ratio at punching failure, stiffness degradation and energy dissipation in the hysteresis loop, and steel and concrete strain distributions near the column support were examined and discussed in accordance with different column aspect ratio. Eccentric shear stress model of ACI 318-05 was evaluated with experimental results. A fraction of transferring moment by shear and flexure in the design code was analyzed based on the test results.

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.711-722
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• 2011

Beam-column gravity or Intermediate Moment frames subjected to unexpected large displacements are vulnerable when no seismic details are provided, which is typical. Conversely, economic efficiency of those frames is decreased if unnecessary special detailing is applied as the beam and column size becomes quite large and steel congestion is caused by joint transverse reinforcement in beam-column connections. Moderate seismic design is used in Korea for beam-column connections of buildings with structural walls, which are to be destroyed when the unexpected large earthquake occurs. Nonetheless, performance of such beamcolumn connections may be substantially improved by the addition of steel fibers. This study was conducted to investigate the effect of steel fibers in reinforced concrete exterior beam-column connections and possibility for the replacement of some joint transverse reinforcement. Ten half-scale beam-column connections with non-seismic details were tested under cyclic loads with two cycles at each drift up to 19 cycles. Main test parameters used were the volume ratio of steel fibers (0%, 1%, 1.5%) and joint transverse reinforcement amount. The test results show that maximum capacity, energy dissipation capacity, shear strength and bond condition are improved with the application of steel fibers to substitute transverse reinforcement of beam-column connections. Furthermore, several shear strength equations for exterior connections were examined, including the proposed equation for steel fiber-reinforced concrete exterior connections with non-seismic details.

• Journal of Korean Library and Information Science Society
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• v.53 no.3
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• pp.73-94
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• 2022

Florence is the cradle of the Italian Renaissance. It is the result of a combination of medieval humanists' exploration of ancient Greek and Roman knowledge and culture, the leadership of great monarchs and priests, patronage of the Medici family, etc., free-thinking and creativity of artists, and critical consciousness and cultural needs of citizens. However, the Florentine Renaissance could not have blossomed unless the Medici family had collected ancient manuscripts and translations, and built libraries to preserve and provide literature. Based on this logical basis, this study outlined the Florentine renaissance and historic libraries, analyzed the collection and composition of favorite books of the Medici family, and traced the architectural characteristics and metaphors of the Medici libraries, The San Marco Library (Michelozzo Library), Library of Badia Fiesolana, and the San Lorenzo Library (Laurentian Library) were the priming and birthplace of the Florentine Renaissance despite of many difficulties, including earthquake, fire, restoration, transfer, seizure, and closure. In particular, the San Marco Library, which was opened in 1444 based on the financial support of Cosimo de' Medici, Michelozzo's design, and Niccoli's private collections was the first common library in the Renaissance period. And the architectural highlight of the Laurentian Library, which opened in 1571 under the leadership of Giulio (Papa Clemente VII), is Michelangelo's staircase, which symbolizes 'from ignorance to wisdom', and the real value of the content is the ancient manuscripts and early printed books, which were collected by the humanist Niccoli and the Medici family. In short, when discussing the Florentine Renaissance, Medici's collection and historic libraries are very important points. The reason is that the ancient collections were not stuffed products, but syntactic semiotics, and the libraries are telescopes that view the history of human knowledge and culture and microscopes that create knowledge and wisdom. If records dominate memories, libraries accumulate records. Therefore, long breathing and time capsule strategies are also required for the development and preservation of retroactive books in domestic libraries with a relatively long history.