DSpace コミュニティ:http://hdl.handle.net/2433/102018-03-20T13:27:46Z2018-03-20T13:27:46ZParameter optimization of tetrahedral tuned mass damper for three-directional seismic response reductionOhsaki, MakotoTsuda, SeitaHasegawa, Tomahttp://hdl.handle.net/2433/2295362018-03-09T09:03:06Z2016-11-01T00:00:00Zタイトル: Parameter optimization of tetrahedral tuned mass damper for three-directional seismic response reduction
著者: Ohsaki, Makoto; Tsuda, Seita; Hasegawa, Toma
抄録: An optimization approach is presented for design of a tetrahedral tuned mass damper called TD-TMD for three-directional seismic response reduction of structures. The mass damper consists of a viscous damper and a mass connected by springs and a rigid bar. By utilizing flexibility of the springs, movement of the mass in three-directions and elongation of the viscous damper are amplified, and vibration energy of the structure is effectively dissipated by the viscous damper. The objective function of the parameter optimization problem is the mean norm of the response displacements of the structure. The bounds of parameters are determined by solving an auxiliary nonlinear programming problem to maximize the minimum deformation of the damper against unit static loads in various directions. Approximate optimal solutions are found using a heuristic approach called simulated annealing combined with pure random search that generates efficient initial solutions. The TD-TMD is attached to a simple three-degree-of-freedom structure, and the seismic responses are compared with those with conventional single-directional tuned mass dampers.2016-11-01T00:00:00ZForce density method for simultaneous optimization of geometry and topology of trussesOhsaki, MakotoHayashi, Kazukihttp://hdl.handle.net/2433/2295352018-03-09T09:03:06Z2017-11-01T00:00:00Zタイトル: Force density method for simultaneous optimization of geometry and topology of trusses
著者: Ohsaki, Makoto; Hayashi, Kazuki
抄録: A new method of simultaneous optimization of geometry and topology is presented for plane and spatial trusses. Compliance under single loading condition is minimized for specified structural volume. The difficulties due to existence of melting nodes are successfully avoided by considering force density, which is the ratio of axial force to the member length, as design variable. By using the fact that the optimal truss is statically determinate with the same absolute value of stress in existing members, the compliance and structural volume are expressed as explicit functions of force density only. After obtaining optimal cross-sectional area, nodal locations, and topology, the cross-sectional areas and nodal coordinates are further optimized using a conventional method of nonlinear programming. Accuracy of the optimal solution is verified through examples of plane trusses and a spatial truss. It is shown that various nearly optimal solutions can be found using the proposed method.2017-11-01T00:00:00ZA comprehensive numerical simulation of steel-concrete composite beam incorporating compressive failure of concretePal, Kumar, MahendraYamashita, TakuzoMiyamura, TomoshiOhsaki, Makotohttp://hdl.handle.net/2433/2295342018-03-09T09:03:05Zタイトル: A comprehensive numerical simulation of steel-concrete composite beam incorporating compressive failure of concrete
著者: Pal, Kumar, Mahendra; Yamashita, Takuzo; Miyamura, Tomoshi; Ohsaki, Makoto
抄録: We present a high delity numerical simulation technique to analyze the non-linear behavior of a composite beam under cyclic loading. The analysis is performed by using the in-house software called E-Simulator. A constitutive model for concrete; extended Drucker-Prager model considering the compressive failure and the tensile crack has been employed and the parameters are identi ed so that compressive and tensile behavior of concrete can be reproduced. The relation between the bending moment and deflection angle of a composite beam has been analyzed and compared with experimental results. Damage propagation and sti ness degradation results of concrete slab are demonstrated.Estimation of phase delay due to precipitable water for DInSAR-based land deformation monitoringSusaki, JunichiMaeda, NaoyaAkatsuka, Shinhttp://hdl.handle.net/2433/2294982018-03-05T09:03:03Z2017-09-01T00:00:00Zタイトル: Estimation of phase delay due to precipitable water for DInSAR-based land deformation monitoring
著者: Susaki, Junichi; Maeda, Naoya; Akatsuka, Shin
抄録: In this paper, we present a method for using the estimated precipitable water (PW) to mitigate atmospheric phase delay in order to improve the accuracy of land-deformation assessment with differential interferometric synthetic aperture radar (DInSAR). The phase difference obtained from multi-temporal synthetic aperture radar images contains errors of several types, and the atmospheric phase delay can be an obstacle to estimating surface subsidence. In this study, we calculate PW from external meteorological data. Firstly, we interpolate the data with regard to their spatial and temporal resolutions. Then, assuming a range direction between a target pixel and the sensor, we derive the cumulative amount of differential PW at the height of the slant range vector at pixels along that direction. The atmospheric phase delay of each interferogram is acquired by taking a residual after a preliminary determination of the linear deformation velocity and digital elevation model (DEM) error, and by applying high-pass temporal and low-pass spatial filters. Next, we estimate a regression model that connects the cumulative amount of PW and the atmospheric phase delay. Finally, we subtract the contribution of the atmospheric phase delay from the phase difference of the interferogram, and determine the linear deformation velocity and DEM error. The experimental results show a consistent relationship between the cumulative amount of differential PW and the atmospheric phase delay. An improvement in land-deformation accuracy is observed at a point at which the deformation is relatively large. Although further investigation is necessary, we conclude at this stage that the proposed approach has the potential to improve the accuracy of the DInSAR technique.
記述: [ISPRS Geospatial Week 2017] 18-22 September, Wuhan, China2017-09-01T00:00:00Z