• Structural Engineering and Mechanics
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• v.13 no.6
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• pp.653-670
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• 2002

In order to ensure the structural dynamic stability of moving liquid-storage containers, the flow motion of interior liquid should be appropriately suppressed by means of mechanical devices such as the disc-type elastic baffle. In practice, the design of a suitable baffle requires a priori the parametric dynamic characteristics of storage containers, with respect to the design parameters of baffle, such as the installation location and inner-hole size, the baffle number, and so on. In this paper, we intend to investigate the parametric effect of the baffle parameters on the transient dynamic behavior of a cylindrical fuel-storage tank in an abrupt vertical acceleration motion. For this goal, we employ the ALE (arbitrary Lagrangian-Eulerian) kinematic description method incorporated with the finite element method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.52-59
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• 2004

In this paper, the efficacy of the MR damper-based control systems for vibration suppression of stay cables has been experimentally investigated. The performance of the several control strategies for the semiactive control system, such as the clipped-optimal control, the Lyapunov stability theory-based control, the maximum energy dissipation and the modulated homogeneous friction, has been compared with that of the passive-type control systems employing MR dampers. To do this, the full-scale stay cable, which is the same as used for the in-service cable-stayed bridge in Korea, is considered. The acceleration and the displacement of the stay cable as well as the damping force of the MR damper are measured. The velocity of the cable at the damper location, which is needed for some control algorithms, is obtained by differentiating the measured displacement. The damping ratios of the cable system employing the MR damper, which can be estimated by the Hilbert transform-based method, shows effectiveness of each control strategy considered.

• Structural Engineering and Mechanics
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• v.20 no.3
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• pp.347-362
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• 2005

The input energy to a base-isolated (BI) building during an earthquake is considered and formulated in the frequency domain. The frequency-domain approach for input energy computation has some notable advantages over the conventional time-domain approach. Sensitivities of the input energy to the BI building are derived with respect to uncertain parameters in the base-isolation system. It is demonstrated that the input energy can be of a compact form via the frequency integration of the product between the input component (Fourier amplitude spectrum of acceleration) and the structural model component (so-called energy transfer function). With the help of this compact form, it is shown that the formulation of earthquake input energy in the frequency domain is essential for deriving the sensitivities of the input energy to the BI building with respect to uncertain parameters. The sensitivity expressions provide us with information on the most unfavorable combination of the uncertain parameters which leads to the maximum energy input.

• Wind and Structures
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• v.6 no.3
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• pp.221-248
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• 2003

The design of high-rise building is often influenced by wind-induced motions such as accelerations and lateral deflections. Consequently, the building's structural stiffness and dynamic (vibration periods and damping) properties become important parameters in the determination of such motions. The approximate methods and empirical expressions used to quantify these parameters at the design phase tend to yield values significantly different from each other. In view of this, there is a need to examine how actual buildings in the field respond to dynamic wind loading in order to ascertain a more realistic model for the dynamic behavior of buildings. This paper describes the findings from full-scale measurements of the wind-induced response of typical high-rise buildings in Singapore, and recommends an empirical forecast model for periods of vibration of typical buildings in Singapore, an appropriate computer model for determining the periods of vibration, and appropriate expressions which relate the wind speed to accelerations in buildings based on wind tunnel force balance model test and field results.

• Structural Engineering and Mechanics
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• v.9 no.3
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• pp.257-268
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• 2000

The seismic design recommendations of the Jordan Code for Loads and Forces (JC) are evaluated, based on comparisons with analytical studies and the Uniform Building Code. It was established that the overall safety ensured by the implementation of these recommendations is not consistent with the established seismic risk in Jordan and the intended objectives of the code. A new zoning map is proposed with effective peak ground acceleration values. The different period formulae of the code were studied and were found to grossly underestimate the fundamental period when compared with analytically derived values or other codes' formulae. Other factors including the dynamic, soil, importance and behavior factors are discussed. It was determined that the JC's lateral load distribution formulae clearly lead to smaller internal forces than both dynamic analysis and UBC loads, even when those loads are normalized to give the same base shear. The main reason for this is attributed to the limited allowance for a backlash force in the JC.

• Structural Engineering and Mechanics
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• v.31 no.1
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• pp.93-112
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• 2009

In this study seismic analyses of steel structures were carried out to examine the effect of ground motion characteristics and structural properties on energy demands using 100 earthquake ground motions recorded in different soil conditions, and the results were compared with those of previous works. Analysis results show that ductility ratios and the site conditions have significant influence on input energy. The ratio of hysteretic to input energy is considerably influenced by the ductility ratio and the strong motion duration. It is also observed that as the predominant periods of the input energy spectra are significantly larger than those of acceleration response spectra used in the strength design, the strength demand on a structure designed based on energy should be checked especially in short period structures. For that reason framed structures with buckling-restrained-braces (BRBs) were designed in such a way that all the input energy was dissipated by the hysteretic energy of the BRBs, and the results were compared with those designed by conventional strength-based design procedure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.971-976
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• 2006

This paper presents a design technique of steel structures subjected to static and dynamic loadings using practical nonlinear inelastic analysis software. The beam-column approach using the stability functions and the plastic hinge concept enables the software to suitably predict second-order effects and inelastic behavior of beam-columns. For dynamic analysis. the incremental from of the equation of motion is solved by the use of a step-by-step numerical integration procedure in which the assumption of constant acceleration over a small time step is employed. The accuracy of the analysis program is validated using the results of ABAQUS program and experimental tests. A user-friendly graphic interface of the software is developed to facilitate the modeling process and result interpretation of the problem. A design example of large span bridge is presented to detail the direct design process using the practical advanced analysis software.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.477-484
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• 2003

Recently, sliding mode control(SMC) method has been investigated for control of building structures under earthquake loadings. SMC keeps responses of a structure in sliding surface while the structure is stable. This control method uses both linear controller and nonlinear controller such as bang-bang controller. This paper presents vibration control of a structure using saturated sliding mode controller, whose maximum conrtol force is limited. The effectiveness of SMC method with controler saturation is investigated based on two performance evaluation criteria: root mean square(RMS) and maximum values of floor drifts and accelerations. Simulation results indicate that SMC method is effective in reduction of displacement and acceleration utilizing the saturated controller's capacity efficiently.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.631-638
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• 2006

This paper considers the nonlinear direct spectrum method to estimate seismic performance of mixed building structures without iterative computations, given dynamic property $T_1$ from stiffness skeleton curve and nonlinear pseudo acceleration $A_{1y}$ and/or ductility ratio $\mu$ from response spectrum. Nonlinear response history analysis has been performed and analysed with various earthquakes for evaluation of correctness and confidence of nonlinear direct spectrum method.

• Computational Structural Engineering
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• v.4 no.3
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• pp.107-115
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• 1991

A probabilistic-Fuzzy model for seismic hazard analysis is developed. The proposed model is able to reproduce both the randomness and the imprecision in conjunction with earthquake occurrences. Results-of this research are (a) membership functions of both peak ground accelerations associated with a given probability of exceedance and probabilities of exceedance associated with a given peak ground acceleration, and (b) characteristic values of membership functions at each location of interest. The proposed probabilistic-fuzzy model for assessment of seismic hazard is successfully applied to the Wasatch Front Range in Utah in order to obtain the seismic maps for different annual probabilities of exceedance, different peak ground accelerations, and different time periods.