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RISS 인기검색어
- 검색키워드
- 저자 : Reza Kamgar (검색결과 3 건)
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Reza Kamgar,Peyman Rahgozar 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.4
Currently, there are many lateral resisting systems utilized in resisting lateral loads being produced in an earthquake. Such systems can significantly reduce the roof’s displacement when placed at an optimum location. Since in the design of tall buildings, the minimum distance between adjacent buildings is important. In this paper, the critical excitation method is used to determine the best location of the belt truss system while calculating the minimum required distance between two adjacent buildings. For this purpose, the belt truss system is placed at a specific story. Then the critical earthquakes are computed so that the considered constraints are satisfied, and the value of roof displacement is maximized. This procedure is repeated for all stories; i.e., for each, a critical acceleration is computed. From this set of computed roof displacement values, the story with the least displacement is selected as the best location for the belt truss system. Numerical studies demonstrate that absolute roof displacements induced through critical accelerations range between 5.36 to 1.95 times of the San Fernando earthquake for the first example and 7.67 to 1.22 times of the San Fernando earthquake for the second example. This method can also be used to determine the minimum required distance between two adjacent buildings to eliminate the pounding effects. For this purpose, this value is computed based on different standard codes and compared with the results of the critical excitation method to show the ability of the proposed method.
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Reza Kamgar,Reza Rahgozar 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.1
In this paper, based on maximizing the outrigger-belt truss system’s strain energy, a methodology for determining the optimum location of a flexible outrigger system is presented. Tall building structures with combined systems of framed tube, shear core, belt truss and outrigger system are modeled using continuum approach. In this approach, the framed tube system is modeled as a cantilevered beam with box cross section. The effect of outrigger and shear core systems on framed tube’s response under lateral loading is modeled by a rotational spring placed at the location of belt truss and outrigger system. Optimum location of this spring is obtained when energy absorbed by the spring is maximized. For this purpose, first derivative of the energy equation with respect to spring location as measured from base of the structure, is set to zero. Optimum location for outrigger and belt truss system is calculated for three types of lateral loadings, i.e. uniformly and triangularly distributed loads along structure’s height, and concentrated load at top of the structure. Accuracy of the proposed method is verified through numerical examples. The results show that the proposed method is reasonably accurate. In addition, for different stiffness of shear core and outrigger system, several figures are presented that can be used to determine the optimum location of belt truss and outrigger system.
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Homa Rajaei,Parisa Yazdanpanah,Marjan Dadbin,Ali Akbar Kamgar Haghighi,Ali Reza Sepaskhah,Tahereh Eslamzadeh 한국원예학회 2013 Horticulture, Environment, and Biotechnology Vol.54 No.4
Changes in environmental conditions may lead to modifications in structural development of plant root. Effects of supplementary irrigation and soil depths (0-90 cm) on anatomical changes in xylem were investigated in rain-fed Vitis vinifera L. cv. Yaghooti-Syah Shiraz. Irrigated and control roots were prepared according to routine histological procedure. Light microscopic observations revealed the structural features of drought tolerant control roots and their changes after the treatment. Irrigated roots were characterized by the absence of starch grains in parenchyma cells, uniformity of parenchymatous pith cells, and a decrease in periderm thickness. Morphometric investigation of xylem showed that irrigated and deep roots had larger mean and maximum vessel diameter and fewer vessel number than rain-fed and shallow roots, at every soil depth of every treatment. Secondary xylem vessel diameter and number were more affected by irrigation and soil depths than metaxylem. Grape roots responded to supplementary irrigation and increasing soil depth by reducing protective and supporting tissues and increasing vessel diameter.
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