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In our previous paper, it is shown that story drift concentration is restraint by columns of two braced frames with pinned and fixed column bases. But embedded column bases are nearly fixed and exposed column bases are nearly pinned in the real structures. These column bases is designed as rotational springs. In this paper, the equations of the drift concentration factor for two story braced frames with columns base of rotational springs have been developed from the equilibrium conditions of the frames subjected to lateral force. This paper clarifies the relationship between drift concentration and ratio of column flexural stiffness and column rotational stiffness., 日本建築学会構造系論文集, 73(628), pp.973-982; 2008

This report shows the advantage of using high-strength steels and hysteretic dampers for low- and medium-rise buildings. In this paper, the structural members are decided by the long term stress. Seismic loads are burdened with hysteretic dampers. There are two methods to increase the yield stress of columns; one is using high-strength steels, and the other is adopting larger members. Through the investigation of time history response analysis, a method using high-strength steels has high performance not only decreasing damage of frame but also increasing the equivalent damping factor than another method.

In this paper, a stiffness-damping identification method for a building structure is proposed when the building is subjected to earthquake ground motion. The difficulty arising in the limit manipulation in the previous method is overcome by introducing an ARX model. The weakness of small SN ratio in the low frequency range is avoided by using the ARX model and introducing new constraints on the ARX parameters. The validity of the proposed method is examined through numerical examples using simulated data and actually recorded data., Transactions of AIJ. Journal of structural and construction engineering

When non-structural members are used as eccentric braces in real structures, flexural and torsional deformation of compression members may occur due to the eccentric joints to the braces. This paper clarifies the buckling behavior with web deformation for H-shaped compression members with laterally and rotationally eccentric braces. The elasto-plastic buckling stress is evaluated with the buckling curve for design codes using the modified equivalent slenderness ratio. Then the elastic buckling load with energy method is applied to the slenderness ratio. In addition, the relationship between the required rigidity and strength of braces is evaluated., 日本建築学会構造系論文集, 74(637), pp.583-591; 2009

This paper discusses the wind tunnel tests for a tall building model having either viscous or visco-elastic damper under the turbulent boundary layer flow. The wind tunnel tests are carried out either the across- or along-wind direction for the viscous and the visco-elastic damper systems, respectively. This wind test set-up includes a special measurement system to obtain the damper hysteetic loop, then the response property of damper and system are discussed by the referring to the obtained loop. In case of the severe wind speed, the response of visco-elastic system is smaller than the viscous system because the stiffness of visco-elastic damper contributes to the stiffness of system.

This paper presents the results of analytical studies in order to evaluate flexural strength demand for beam-to-column connections in earthquake-resistant design. The authors have developed a computer program based on the one-dimensional finite element method in which a generalized constitutive relationship considering isotropic hardening and kinematic hardening is incorporated. Numerical analysis of steel wide-flange beams is carried out under various loading sequences similar to seismic response. The results are summarized as a method to predict the maximum bending moments of beams, taking into account the maximum story drift angles.

This paper presents a seismic design procedure to estimate the ductility demanded of beams in strong column - weak beam steel frames. Critical parameters that control the earthquake response of steel frames are characterized and incorporated into the equivalent SDOF representation. Maximum and cumulative plastic rotations induced into beam-ends are derived in explicit forms as functions of these parameters, and accuracy of the estimated rotations is demonstrated through the comparison with numerical results.

In this paper, we propose a method of improving the deformation capacity of truss grids, without the loss of initial stiffness and load bearing capacity. Shear panels are introduced into the eccentric joint areas To investigate the behavior of the trusses, numerical analysis is carried out using X-braced models for shear panels As a result, it is cleared that such trusses show stable elasto-plastic behavior, keeping their initial stiffness and maximum strength as high as those of ordinary trusses. And the present method improves hysteresis characteristics of truss grids under cyclic loading.

In this paper a singular integral equation method is applied to calculate the variation of stress intensity factors along the crack front of a 3 D oblique semi-elliptical surface crack when the whole of the crack surfaces are in contact each other. The body force method is used to formulate the problem as a system of singular integral equations. In the numerical solutions unknown body force densities are approximated using fundamental density functions and polynomials. The calculation shows that the present method yields rapidly converging numerical results and smooth variation of stress intensity factors along crack front even when the inclination angle between the crack and the free surface is small. The mode II and mode III stress intensity factors are shown when an inclined edge crack is subjected to compressive residual stresses or Hertzian contact loads with varying the inclination crack angle and friction coefficient.

We have proposed the trusses with eccentric joints to improve the post-buckling behavior. It is confirmed that the trusses with eccentric joints show stable behavior, although their initial stiffness and ultimate strength are not so high as those of ordinary trusses. In this paper, loading tests and numerial analyses are carried out to investigate the effect of lattice patterns (warren or double-warren) on ultimate strength and plastic deformation behavior of truss beams with several types of eccentric joints. As a result, double-warren trusses with eccentric joints show stable behavior, keeping their load bearing capacity high enough.

In a previous paper, the present authors clarified that COD is a suitable parameter to interpret the fatigue damage on the basis of the fatigue crack growth in low-cycle random fatigue. Especially the COD parameter correlated well the fatigue damage counted using the rainflow method (RFM) with the crack growth life in LCF. To extend this idea to high-cycle random fatigue the present study has been done. The result showed that although the RFM is valid to evaluate total fatigue life, it is invalid to predict the crack growth life. This is due to the fact that the crack growth life is strongly affected by the effect of crack closure, which is more amplified in high-cycle fatigue than low-cycle fatigue.