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RISS 인기검색어
- 검색키워드
- 저자 : Koichi Maekawa (검색결과 6 건)
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Maekawa, Koichi,Irawan, Paulus,Okamura, Hajime Techno-Press 1997 Structural Engineering and Mechanics, An Int'l Jou Vol.5 No.6
A three-dimensional constitutive modeling for reinforced concrete is presented for finite element nonlinear analysis of reinforced concrete. The targets of interest to the authors are columns confined by lateral steel hoops, RC thin shells subjected to combined in-plane and out-of-plane actions and massive structures of three-dimensional (3D) extent in shear. The elasto-plastic and continuum fracture law is applied to pre-cracked solid concrete. For post cracking formulation, fixed multi-directional smeared crack model is adopted for RC domains of 3D geometry subjected to monotonic and reversed cyclic actions. The authors propose a new scheme of decomposing stress strain fields into sub-planes on which 2D constitutive laws can be applied. The proposed model for 3D reinforced concrete is experimentally verified in both member and structural levels under cyclic actions.
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Yasuyuki Maekawa,Shosuke Miyamoto,Koichi Sawai,Yoshiaki Shibagaki,Toru Sato,Mamoru Yamamoto,Hiroyuki Hashiguchi,Shoichiro Fukao 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
Rain attenuation characteristics of the Ku-band up-link satellite signals are presented for the past four years of 2003-2006 in Japan and Indonesia, using Japan’ domestic communication satellite Superbird C that connects Research Institute for Sustainable Humanosphere of Kyoto University (RISH) to Equatorial Atmosphere Radar Observatory (EAR). Compared with the rainfall rates with the same time percentages, equivalent path lengths of the satellite signal against the rain area are shown to be reduced down to 2 km at EAR, which is remarkably shorter than those at RISH in Japan. The almost same attenuation values and annual statistics are, however, obtained from the X-band radar observations simultaneously conducted at EAR. This suggests that long-term radar observations of convective clouds are effective to estimate rain attenuation statistics of the satellite signals in the tropical regions.
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Computer aided reinforcement design of RC structures
Xuehui An,Koichi Maekawa 한국계산역학회 2004 Computers and Concrete, An International Journal Vol.1 No.1
In this study, a design process for reinforced concrete structures using the nonlinear FEM analysis is developed. Instead of using the nonlinear analysis to evaluate the required performance after design process, the nonlinear analysis is applied before designing the reinforcement arrangement inside the RC structures. An automatic reinforcement generator for computer aided reinforcement agreement is developed for this purpose. Based on a nonlinear FEM program for analyzing the reinforced concrete structure, a smart fictitious material model of steel, is proposed which can self-adjust the reinforcement to the required amount at the cracking location according to the load increment. Using this tool, the reinforcement ratio required at design load level can be decided automatically. In this paper, an example of RC beam with opening is used to verify the proposed process. Finally, a trial design process for a real size underground RC LNG tank is introduced.
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Performance Comparison of Circular and Square RC Columns under Monotonic Loading Conditions
Ahmed Mohammed Youssef Mohammed,Ali Ahmed,Koichi Maekawa 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.1
Current flexural and shear design methods for reinforced concrete members are mainly based upon the rectangular cross-sectional shape. A simplified new approach for designing circular cross sectional Reinforced Concrete (RC) members might be to convert them to equivalent area, square shapes. An experimental study was performed on reinforced concrete circular cross sections and equivalent area, rectangular cross sectional members. The RC members were tested under non linear monotonic loading conditions, under both flexural and shear controlled conditions. Furthermore, the 3D FEM package COM3D was used to simulate the nonlinear performance of circular and its equivalent area, square members. Experimental and analytical results show that the circular RC members and its equivalent square have similar nonlinear performance (load-deflection behavior) in both flexural and shear controlled failure conditions. A good agreement was found in nonlinear performance of main design criteria; initial stiffness, flexural capacity, and shear capacity of both types. Based upon these results, the proposed approach can be considered satisfactory.
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Comparative Nonlinear Behavior of Corroded Circular and Square RC Columns
Ahmed Mohammed Youssef Mohammed,Ali Ahmed,Koichi Maekawa 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.7
This paper discusses performance of the reinforced concrete structures deteriorated by corrosion on basis of numerical simulation analysis. The purpose is to preliminarily investigate the idea of performance comparison of circular and square reinforced concrete columns under corroded conditions. Previous research carried out by the authors shows that equivalent area reinforced concrete (RC) columns exhibit similar load-displacement behavior under flexural and shear controlled conditions. The two types of columns deviate from this similarity after the corrosion of steel reinforcement present in the concrete. The change in the load-displacement behavior is highly dependent upon factors including the corrosion ratio, axial load, presence of web reinforcement etc., The experimentally verified 3D finite element modelling (FEM) program (COM3D) was used to investigate the seismic performance of the circular shaped and its equivalent area square shaped RC columns. The results show that the effect of mild corrosion (around 2% corrosion) on the load-displacement behavior of square RC columns is more significant as compared to circular RC columns at without axial load and at lesser main reinforcement ratio while a similar behavior or reverse trend is observed at higher main reinforcement ratios and for cases with 10% axial load. The effect of corrosion on the web reinforcement present in square columns is more pronounced as compared to circular columns at low main reinforcement ratios.
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Ali Ahmed,Ahmed Mohammed Youssef Mohammed,Koichi Maekawa 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.5
In current design practice, mostly architectural needs govern the shape of reinforced concrete columns. There is a need to study and compare the load-deflection behavior and failure pattern of high strength reinforced concrete columns of different shapes. This paper presents a correlation between the performance of equivalent area circular and square columns subjected to shear controlled cyclic loading. Square and circular columns with equal cross-sectional area were experimentally tested in this research. Experimental results show that the maximum load, number of loading cycles and maximum deflection in case of square and circular columns were found to be close however, the final failure pattern was different. In case of columns without shear stirrups, the square column resisted 6.7% more loading cycles as compared to the circular column. However, the square column showed 19% lesser deflection at ultimate stage. In case of columns with shear stirrups, square column resisted only 9% more loading cycles as compared to circular column and exhibited similar ultimate deflection. The fatigue performance of equivalent area circular and square columns was found to be comparable in shear controlled conditions. However, the final failure pattern of circular columns shifted from shear to flexure near final failure.
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