• Journal of the Korea Concrete Institute
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• v.26 no.5
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• pp.615-625
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• 2014

Excessive long-term slab deflection caused by construction load is a critical issue for the design of concrete slabs, as long span flat plates become popular for tall buildings. In the present study, the effect of construction load causing early slab cracking on the long-term deflection was theoretically studied. On the basis of the result, a numerical analysis method was developed to predict the long-term deflection of flat plates. In the proposed method, immediate deflection due to slab cracking and long-term effect of creep and shrinkage were considered. To verify the construction load effect, long-term slab deflections were measured in actual flat plate buildings under construction. The results showed that the immediate deflection due to the construction load increased significantly the long-term deflection. The proposed method was used to predict the deflections of the buildings. The results were compared with the measurement results. The predictions agree well with the long-term deflections of flat plate affected by construction load.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.4
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• pp.469-475
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• 2019

A long-term bridge monitoring system has been introduced and is under operation for long-term safety management of the structure. However, it is difficult to assess the condition of the quantitative structural system as it only measures responses and does not measure input loads. To overcome these shortcomings, FBG (Fiber Bragg Grating)-based input load measurement sensors were developed in this paper for measuring highway bridge input loads and their validity was verified through laboratory tests.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.5D
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• pp.505-512
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• 2010

Generally, the repeated traffic loading condition should be considered to predict the long-term deformation on road foundations or foundation systems. However, it is not easy to estimate long-term deformation on multi-layered system like roads and railways. For more quantitative analysis, mechanistic-empirical approach requires proper analytical tool, material's model, and material properties of foundation geomaterials under both traffic and environmental loadings. In this study, therefore, laboratory data from the long-term repeated load triaxial tests were used to predict accumulated deformation on pavement foundations and the results were analyzed based on the nonlinear models and stress state considered. All these results are presented and verified on laboratory based scale using the finite element analysis with the deformation characteristics of foundation geomaterials at various stress states.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.189-196
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• 2005

The effects of the impulse and the magnitude of the impulsive loads to the responses of the structure are analyzed with the safety criteria established with the peak load and impulse ratio. It is shown for the loadings with short duration that the impulse is dominant factor for the damage of the structures due to the inertial effect. On the other hand the magnitude of the load is dominant factor for the load with long duration due to the duration time long enough for the loads to overcome the inertia force. It is also shown that the peak particle velocity and the peak particle acceleration of the foundation have the same influences as the impulse and the magnitude of the loads do to the structures.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.85-97
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• 2005

Despite a number of advantages of reinforced earth walls over conventional concrete retaining walls, there exist concerns over long-term residual deformation when subjected to repeated and/or cyclic loads, especially when used as part of permanent structures. In view of these concerns, in this paper time-dependent deformation characteristics of geosynthetic reinforced soil under sustained and/or repeated loads were investigated using a series of plane strain compression tests on geogrid reinforced weathered granite soil specimens. The results indicate that sustained or repeated loads can yield appreciable magnitudes of residual deformations, and that the residual deformations are influenced not only by the loading characteristics but by the mechanical properties of geogrid. It is also found that the preloading technique can be effectively used in controlling residual deformations of reinforced soils subjected to sustained and/or repeated loads.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5C
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• pp.359-368
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• 2006

After construction, time-variant seepage and long-term underground motion are representative factors to understand the abnormal behavior of tunnels. In this study, numerical models have been developed to analyze the behavior of tunnels associated with seepage and long-term underground motion. Possible scenarios have been investigated to establish causes-and-results mechanisms. Various parameters such as permeability of tunnel filter, seepage condition, water table, long-term rock mass load, size of damaged zone due to excessive blasting have been investigated. These are divided into two sub-parts depending on the tunnel type and major loading mechanisms depending on the types. For the soft ground tunnels, the behavior associated with seepage conditions has been studied and the effect of permeability change in tunnel-filter and the effect of water-table change which are seldom measurable are investigated in detail. For the rock mass tunnels, tunnel behavior associated with the visco-plastic behavior of rock mass has been studied and the long-term rock mass loads as a result of relaxation and creep have been considered.

• Journal of the Korean GEO-environmental Society
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• v.23 no.12
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• pp.25-31
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• 2022

Unlike structures installed on land, the structures installed on the offshore ground must consider long-term cyclic loads such as wave loads, wind loads and tidal loads at sea. Therefore, it is important to analyze the behavior of the ground subjected to long-term cyclic loads in order to design a structure installed on the ocean ground. In this paper, cyclic simple shear tests were performed to analyze the ground behavior for long-term cyclic loads according to the confining pressure, and a three-dimensional design failure curve was prepared that can easily check the failure characteristics according to the confining pressure. As a result of the analysis, it was confirmed that the position of the design failure curve is different depending on the confining pressure even under the same conditions of the cyclic shear stress ratio and the average shear stress ratio, and the number of cyclic loads reaching failure is affected by the confining pressure. From the created 3-D design failure curve under different confining pressure, the tendency and approximate value of the design failure curve according to the confining pressure can be estimated.

• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.5-21
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• 2007

Despite a number of advantages of reinforced earth walls over conventional concrete retaining walls, there exit concerns over long-term residual deformation when they are subjected to repeated and/or cyclic loads, especially when used as part of permanent structures. In view of these concerns, in this paper time-dependant deformation characteristics of geosynthetic reinforced modular block walls under sustained anuor repeated loads were investigated using reduced-scale model tests. The results indicated that a sustained or repeated load can yield appreciable magnitude of residual deformation, and that the residual deformations are influenced not only by the loading characteristics but by the mechanical properties of geogrid. It is also found that the preloading technique can be effectively used in controlling residual deformations of reinforced soils subjected to sustained and/or repeated loads.

• Journal of the Korean Geotechnical Society
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• v.32 no.12
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• pp.69-78
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• 2016

A suction bucket foundation has been considered to be a potential foundation type for offshore wind turbines. A suction bucket foundation is usually installed in soft soil, so the accumulated displacement of the foundation may occur under long-term cyclic loads. In this study, a series of 1-g model tests were performed to analyze the accumulated rotation of suction bucket foundations under long-term cyclic horizontal loads. The dry model ground was prepared to have two different soil densities by air-pluviation method. The model tests were performed varying the embedment depth of the suction bucket, the soil density, and the amplitude of cyclic load. A one-way horizontal cyclic load was applied over $10^4$ cycles. Test results showed that the accumulated rotation of the suction bucket foundation increased with the increase in the number of cycles and load magnitudes. Based on the model test results, a new equation was proposed to evaluate the accumulated rotation of the suction bucket foundations in dry sandy ground under long-term cyclic horizontal loads.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.3
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• pp.103-110
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• 2018

The long-term flexural behavior of reinforced concrete (RC) beams strengthened with an iron based-shape memory alloys (Fe-SMAs) by a near-surface mounted (NSM) method was evaluated. The pre-strained values of 2% and 4% and introduced prestressing force by an activation of a shape memory effect of the Fe-SMA strengthening material were considered as experimental variables. Deflections at the center of the RC beams were measured for six months after the 1 tonf concrete weight was loaded on the beam. Experimental results show that the deflections decreased because of the increased flexural stiffness of beams strengthened with the Fe-SMA strips. On the contrary, with increased pre-strained values, the deflection increased due to stiffness reduction of the strengthening material. It was confirmed that the specimens incorporating the prestressed force showed the deflection reduction of about 30%, compared to the ones without the prestressed force.