• Steel and Composite Structures
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• v.17 no.6
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• pp.803-824
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• 2014

The dynamic characterization is important in making accurate predictions of the seismic response of the hybrid structures dominated by different damping mechanisms. Different damping characteristics arise from the construction of the tower with different materials: steel for the upper part; reinforced concrete for the lower main part and interaction with supporting soil. The process of modeling damping matrices and experimental verification is challenging because damping cannot be determined via static tests as can mass and stiffness. The assumption of classical damping is not appropriate if the system to be analyzed consists of two or more parts with significantly different levels of damping, such as steel/concrete mixed structure - supporting soil coupled system. The dynamic response of structures is critically determined by the damping mechanisms, and its value is very important for the design and analysis of vibrating structures. An analytical approach capable of evaluating the equivalent modal damping ratio from structural components is desirable for improving seismic design. Two approaches are considered to define and investigate dynamic characteristics of hybrid tower of cable-stayed bridges: The first approach makes use of a simplified approximation of two lumped masses to investigate the structure irregularity effects including damping of different material, mass ratio, frequency ratio on dynamic characteristics and modal damping; the second approach employs a detailed numerical step-by step integration procedure in which the damping matrices of the upper and the lower substructures are modeled with the Rayleigh damping formulation.

• Steel and Composite Structures
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• v.43 no.2
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• pp.229-240
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• 2022

The main objective of this work is presenting a mathematical model for the concrete slab with fiber reinforced polymer (FRP) layer under the impact load. Impacts are assumed to occur normally over the top slab and the interaction between the impactor and the structure is simulated using a new equivalent three-degree-of-freedom (TDOF) spring-mass-damper (SMD) model. The structure is assumed viscoelastic based on Kelvin-Voigt model. Based on the sinusoidal shear deformation theory (SSDT), energy method and Hamilton's principle, the motion equations are derived. Applying DQM, the dynamic deflection and contact force of the structure is calculated numerically so that the effects of mass, velocity and height of impactor, boundary conditions, FRP layer, structural damping and geometrical parameters of structure are shown on the dynamic deflection and contact force of system. Results show that considering structural damping leads to lower dynamic deflection and contact force. In addition, increasing the impact velocity of impactor yields to increases in the maximum contact force and deflection while the contact duration is decreased. The result shows that the contact force and the central deflection of the structure decreases and the contact time decreases with assuming FRP layer.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.276-281
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• 2008

Glass-fiber reinforced polyester(GFRP) composite material is a promising alternative to existing construction materials such as steel, concrete and wood. One of passible applications of GFRP composite material is to build temporary bridges by assembling GFRP composite decks. In this paper, we develop a system of temporary arch bridges that can be built by easy assembling of GFRP composite decks. For this purpose, several types of temporary arch bridges are suggested and verified by FE analysis.

• Earthquakes and Structures
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• v.14 no.1
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• pp.55-71
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• 2018

This paper investigates the role of the masonry infills on the correlation between widely used earthquake Intensity Measures (IMs) and the damage state of 3D R/C buildings taking into account the orientation of the seismic input. For the purposes of the investigation an extensive parametric study is conducted using 60 R/C buildings with different heights, structural systems and masonry infills' distributions. The results reveal that the correlation between the IMs and the seismic damage can be strongly affected by the masonry infills' distribution, depending on the special characteristics of the structural system, the number of stories and the incident angle.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1990.10a
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• pp.55-60
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• 1990

The objective of this study is to predict the nonlinear behavior of reinforced concrete shear walls, with the reinforcement uniformly distributed, under reversed cyclic loads. This study introduces joint Element Model which formulates the pulling out of rebars, slipping and intrusion of junction planes. The applicability of this study was experimental verfied by specimens SW1, SW2 and SW3 tested by authors, Wall1 by Paulay, SW16 and SW19 by Sheu. In almost specimen, the ratio of analytical to experimental maximum shear stress is within approximately 5%. In case of energy dissipation and maximum drift, the analytical results fully coincide with those of experiment.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.519-524
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• 2007

Recently, Fiber sheets have been used for strengthening the deteriorated reinforced concrete RC slabs because of its resistant capacity of corrosion and repairing works. The purpose of this study is to carry out the experimental studies on thirteen kinds of RC slabs and to investigate the behavior of RC slabs form the experimental results. Test parameters are the strengthening material, the number of sheet layer and strengthening direction. The behavior of strengthened He: slabs is represented by crack load-deflection curves and maximum load. And the parametric study based on the nonlinear FEM analysis are performed and its results are discussed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.4
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• pp.219-223
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• 2000

The evaluation of habitability to building vibration is conducted by the values of natural frequency, amplitude displacement, damping ratio. These values can be obtained from test or analytical results. Data acquisition through test may be possible in existing building, however, to estimate the serviceability of the building, it is necessary to evaluate those values at the stage of design. The natural frequency is important and basic factor for the evaluation of the serviceability. Calculation method of the effective stiffness in RC slab is proposed. To prove the efficiency of the proposed method, sample results of the analysis and the test are compared. These results proved that the effective width proposed to calculate the effective stiffness is proper to evaluate the natural frequency.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.4
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• pp.121-128
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• 2000

When RC beams are strengthening in flexure with steel plate, they have initial strain due to dead load. Strain of steel used in strengthening member is zero. The effect of strengthening in flexure at member changes in accordance with the quantity of initial strain. But in most cases, Quantity of reinforcement is determined without regard to the difference of initial strain when there are calculated the strengthening in flexure at beams. Such method is possible to suggest inadequate quantity of reinforcement. Thus, the object of the study is to suggest practical design equation and reinforcement proposal using comparison and analysis reinforcement efficiency about fexural strength in case with regard and without regard to the initial strain when Re beams are strengthening in flexure with steel plate.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.190-197
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• 2000

A moment-curvature relationship to simulate the behavior of reinforced concrete beam under cyclic loading is introduced. Unlike previous moment-curvature models and the layered section approach, the proposed model takes into consideration the bond-slip effect by using monotonic moment-curvature relationship constructed on the basis of the bond-slip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stress-strain relation of steel gives more exact numerical result. The advantages of the proposed model, comparing to layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures. The modification of the moment-curvature relation to reflect the fixed-end rotation and pinching effect is also introduced. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed model.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.465-472
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• 2003

In this paper, the displacement-based seismic design approaches are evaluated utilizing shaking-table test data of a 1:3 scaled reinforced concrete (RC) bearing wall structure Provided by IAEA. The maximum responses of the structure are estimated using the two prominent displacement-based approaches, i.e., the capacity spectrum method and the displacement coefficient method, and compared with the measured responses. For comparison purpose, linear and nonlinear time history analyses and response spectrum analysis are also performed. The results indicate that the capacity spectrum method underestimates the response of the structure In inelastic range while the displacement coefficient method yields reasonable values in general.