• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.4
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• pp.83-93
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• 2007

This paper represents the development of 3-axises loadcell for measuring the side-force of suspension module of MPV(Multi Purposed Vehicle). The side force causes the failure of damper, such as leakage. The loadcell was developed using strain gauges, and the Wheastone bridge circuit to compensate for the cross-talk between the each axises and the measurement error by temperature. Structure analysis of loadcell was accomplished with FEM(Finite Element Method) to optimize the location of strain gages. The design optimization for important factors that have an effect on performance of loadcell was accomplished by using DOE(Design of Experiment). Loadcell was produced and successfully tested, showing good sensitivity and low cross-talk. The cross-talk of the developed loadcell is bellow 5%. The load history was measured at proving ground. The maximum side-force, the longitudinal force, and vertical force of MPV are 4.2 kN, 8.0 kN, and 17.0 kN, respectively, at Belgian road.

• Journal of the Korean Geophysical Society
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• v.8 no.2
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• pp.97-103
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• 2005

It is necessary, in the light of the importance of long-term slope stability problem, to develop a simple method or tool which can figure out the possible failure zone resulted from weathering effect and other factors. The FBG sensor system is used to estimate the correlations between the temperature and the slope in Yunhwajae, and to find a failure zone in slopes effectively. This research is to seek for the correlation between the soil temperature distribution and the strain distribution in a active zone by analyzing the data from the in-situ measurement so that the possible failure zone should be well defined based on the correlation. The zone of high temperature fluctuation can be regarded as one of the possible sliding zone due to the weathering effect while the constant temperature depth of the ground, if exists, would not be relatively affected by the weathering process.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1360-1364
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• 2009

Necessity of removable soil nailing has been arisen in the soil nailing system because of problem such as civil petition for geotechnical environment and invasion of the ground boundary line and payments for use besides geotechnical engineering. Removable soil nailing system is improved soil nailing system that fixed socket arranged in boring hole for increasement of skin friction. In this study, field pull-out tests are carried out more 4 times considering installed distance of fixed socket and analyze skin friction behavior characteristics in fixed socket through analysis of measurements of strain gauge attached to fixed socket. Also, to evaluate application for wedge type removable soil nailing system analyzing displacement aspects through field pull-out tests by trial construction.

• Earthquakes and Structures
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• v.3 no.5
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• pp.767-781
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• 2012

The residual capacity against collapse of a main shock-damaged bridge can be coupled with the aftershock ground motion hazard to make an objective decision on its probability of collapse in aftershocks. In this paper, a steel tower suspension bridge with a main span of 2000 m is adopted for a case-study. Seismic responses of the bridge in longitudinal and transversal directions are analyzed using dynamic elasto-plastic finite displacement theory. The analysis is conducted in two stages: main shock and aftershocks. The ability of the main shock-damaged bridge to resist aftershocks is discussed. Results show that the damage caused by accumulated plastic strain can be ignored in the long-span suspension bridge. And under longitudinal and transversal seismic excitations, the damage is prone to occur at higher positions of the tower and the shaft-beam junctions. When aftershocks are not large enough to cause plastic strain in the structure, the aftershock excitation can be ignored in the seismic damage analysis of the bridge. It is also found that the assessment of seismic damage can be determined by superposition of damage under independent action of seismic excitations.

• Journal of the Korean Society of Safety
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• v.25 no.2
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• pp.55-64
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• 2010

Since various weathered soils are encountered in many domestic construction sites, it is necessary to estimate characteristics of natural weathered soils. However, the remolded sample of weathered soils are commonly used to estimate their characteristics because it is very difficult to sample weathered soils in undisturbed states. However, it is well known that the behavior of remolded sample is different from that of the undisturbed sample particularly in the dynamic response, because the particle structure of undisturbed sample maintains its original structure from the mother rock. Thus, to evaluate the influence of sampling method and preparation method on stress-strain behavior, the resonant column tests were performed on the block, tube samples, remolded samples with static compression and remolded samples with tamping of the weathered granite soils. The shear modulus of the remolded sample with tamping is larger than the other samples presumably due to the high tamping pressure enough to induce particle breakage. The tube samples show larger damping ratios than other samples. Furthermore, one-dimensional ground response analysis was performed to compare the results qualitatively.

• Structural Engineering and Mechanics
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• v.11 no.1
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• pp.71-87
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• 2001

A frequency domain response analysis is presented for building frames passively controlled by viscoelastic dampers, under harmonic ground excitation. Three different models are used to represent the linear dynamic force-deformation characteristics of viscoelastic dampers namely, Kelvin model, Linear hysteretic model and Maxwell model. The frequency domain solution is obtained by (i) an iterative pseudo-force method, which uses undamped mode shapes and frequencies of the system, (ii) an approximate modal strain energy method, which uses an equivalent modal damping of the system in each mode of vibration, and (iii) an exact method which uses complex frequency response function of the system. The responses obtained by three different methods are compared for different combinations of viscoelastic dampers giving rise to both classically and non-classically damped cases. In addition, the effect of the modelling of viscoelastic dampers on the response is investigated for a certain frequency range of interest. The results of the study are useful in appropriate modelling of viscoelastic dampers and in understanding the implication of using modal analysis procedure for building frames which are passively controlled by viscoelastic dampers against base excitation.

• Structural Engineering and Mechanics
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• v.34 no.1
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• pp.39-60
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• 2010

In Turkey, majority of industrial facilities are composed of precast buildings. However, precast buildings have suffered extensive damage during Kocaeli and Duzce (1999) and Adana-Ceyhan (1998) earthquakes. Therefore, in this study, fragilities of existing building stock and damage probabilities of precast buildings were studied. For this purpose, building inventories were prepared and variation of structural parameters was determined by investigating the design project of 65 precast buildings constructed in Denizli, Turkey. Twelve analysis models which reflect the stiffness, strength and ductility properties of building inventory were constructed. After the definition of strain based displacement limits and corresponding damage states for buildings, displacement demands were calculated by using non linear time history analysis. During the analyses 360 strong ground motion records were used. Exceedence ratios of concerned damage limits was calculated by checking the displacement demands and then PGV based fragility curves were constructed. Efficiency of strength, stiffness and ductility properties of existing precast buildings were investigated by comparing the fragility curves. The results have shown that the most effective parameters that govern the damage probabilities of precast buildings are stiffness and ductility. It was also stated that the results of fragility analysis and damage and failure observations performed after Kocaeli and Duzce Earthquakes are compatible.

• Structural Engineering and Mechanics
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• v.69 no.3
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• pp.243-255
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• 2019

Utilization of fiber beam-column element has gained considerable attention in recent years due mainly to its ability to model distributed plasticity over the length of the element through a number of integration points. However, the relatively high sensitivity of the method to modeling parameters as well as material behavior models can pose a significant challenge. Residual drift is one of the seismic demands which is highly sensitive to modeling parameters and material behavior models. Permanent deformations play a prominent role in the post-earthquake evaluation of serviceability of bridges affected by a near-fault ground shaking. In this research, the influence of distributed plasticity modeling parameters using both force-based and displacement-based fiber elements in the prediction of internal forces obtained from the nonlinear static analysis is studied. Having chosen suitable type and size of elements and number of integration points, the authors take the next step by investigating the influence of material behavioral model employed for the prediction of permanent deformations in the nonlinear dynamic analysis. The result shows that the choice of element type and size, number of integration points, modification of cyclic concrete behavior model and reloading strain of concrete significantly influence the fidelity of fiber element method for the prediction of permanent deformations.

• Steel and Composite Structures
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• v.43 no.3
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• pp.389-401
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• 2022

This study investigated the flowability and mechanical properties of cost-effective steel fiber reinforced ultra-high performance concrete (UHPC) by using locally available materials for field-cast application. To examine the effect of mixture constituents, five mixtures with different fractions of silica fume, silica powder, ground granulated blast furnace slag (GGBS), silica sand, and crushed natural sand were proportionally prepared. Comprehensive experiments for different mixture designs were conducted to evaluate the fresh- and hardened-state properties of self-consolidating UHPC. The results showed that the proposed UHPC had similar mechanical properties compared with conventional UHPC while the flow retention over time was enhanced so that the field-cast application seemed appropriately cost-effective. The self-consolidating UHPC with high flowability and low viscosity takes less total mixing time than conventional UHPC up to 6.7 times. The X-ray computed tomographic imaging was performed to investigate the steel fiber distribution inside the UHPC by visualizing the spatial distribution of steel fibers well. Finally, the tensile stress-strain curve for the proposed UHPC was proposed for the implementation to the structural analysis and design.

• Geomechanics and Engineering
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• v.34 no.3
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• pp.303-316
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• 2023

With the development and utilization of urban underground space, the artificial ground freezing technology has been widely used in the construction of underground engineering in soft soil areas. The mechanical properties of soft clay changed greatly after freezing and thawing, which affected the seismic performance of underground structures. In this paper, a series of triaxial tests were carried out to study the dynamic response of the freezing-thawing clay under the seismic load considering different dynamic stress amplitudes and different confining pressures. The reduction factor of dynamic shear stress was determined to correct the amplitude of the seismic load. The deformation development mode, the stress-strain relationship and the energy dissipation behavior of the soft clay under the seismic load were analyzed. An empirical model for predicting accumulative plastic strain was proposed and validated considering the loading times, the confining pressures and the dynamic stress amplitudes. The relevant research results can provide a theoretical reference to the seismic design of underground structures in soft clay areas.