• Steel and Composite Structures
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• v.45 no.1
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• pp.83-100
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• 2022

Timber is one of the few natural, renewable building materials and glulam is a type of engineering wood product. In the present work, timber-based braces are applied for retrofitting midrise Special Moment Resisting Frame (SMRF) using two types of timber base braces (Timber base glulam, and hybrid Timber-Steel-BRB) as alternatives for retrofitting by traditional steel bracings. The improving effects of adding the bracings to the SMRF on seismic characteristics of the frame are evaluated using load-bearing capacity, energy dissipation, and story drifts of the frame. For evaluating the retrofitting effects on the seismic performance of SMRF, a five-story SMRF is considered unretofitted and retrofitted with steel-hollow structural section (HSS) brace, Glued Laminated Timber (Glulam) brace, and hybrid Timber-Steel BRB. Using OpenSees structural analyzer, the performance are investigated under pushover, cyclic, and incremental loading. Results showed that steel-HSS, timber base Glulam, and hybrid timber-steel BRB braces have more significant roles in energy dissipation, increasing stiffness, changing capacity curves, reducing inter-story drifts, and reducing the weight of the frames, compared by steel bracing. Results showed that Hybrid BRB counteract the negative post-yield stiffness, so their use is more beneficial on buildings where P-Delta effects are more critical. It is found that the repair costs of the buildings with hybrid BRB will be less due to lower residual drifts. As a result, timber steel-BRB has the best energy dissipation and seismic performance due to symmetrical and stable hysteresis curves of buckling restrained braces that can experience the same capacities in tension and compression.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.235-246
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• 2003

Since the study of Lee et al.(1994) there have been some case studies on the set-up effect of driven piles in Korea country. However, comprehensive examination on the analyses of the set-up effect with various testing data has not been carried out. In particular, the analysis of the influence of soil type and pile shape on the set-up effect has not been reported. It is necessary to analyse the test results of production piles in order to apply the set-up effect of driven piles for the field engineering. In this study some test piling and analyses were performed to give basic information to the piling design as well as the research on the set-up effect in sandy soils. The analyses on the set-up effect were performed with the monitoring data obtained from the high-strain dynamic loading tests. It was shown that the set-up effect of driven piles was not only affected by soil type but also by soil formation history It turned out that the set-up effect in sandy soils was considerable one that should not be ignored in the field, and that the bearing capacity increase of pile is mainly caused by the increase of shaft resistance. It was shown that the set-up effect of closed pile was larger than that of opened pile in clayey soils, while the set-up effect of opened pile was larger than that of closed pile in sandy soils.

• Journal of the Korean Geotechnical Society
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• v.39 no.5
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• pp.27-40
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• 2023

A pile is a structural element that is used to transfer external loads from superstructures and has been widely utilized in construction fields all over the world. The method of installing a pile into the ground should be selected based on geotechnical conditions, location, site status, environmental factors, and construction costs, among others. It can be divided into two types: direct hammering and preboring. The direct hammering method installs a pile into the bearing layer, such as rock, using a few types of hammer, generating a considerable amount of pile driving-induced vibration. The vibration from pile driving influences adjacent structures and the ground; therefore, quantitatively investigating the effects of vibration is inevitably required. In this study, two-dimensional dynamic numerical modeling and analysis are performed using the finite difference method to investigate the influence on the adjacent slope, including temporary supporting system. Time-dependent loading induced by pile driving is estimated and used in the numerical analysis. Consequently, large surface displacement is estimated due to surface waves and less wave deflection, and refraction at the surface. The total displacement decreases with the increase of the distance from the source. However, lateral displacement at the top of the slope shows a larger value than vertical displacement, and the overall displacement tends to be concentrated near the face of the slope.

• Journal of the Korean GEO-environmental Society
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• v.18 no.7
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• pp.37-47
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• 2017

In this study, a series of full-scale field tests on prebored and precast steel pipe piles and the corresponding numerical analysis have been conducted in order to study the characteristics of pile load-settlement relations and shear stress transfer at the pile-soil interface. Dynamic pile load tests (EOID and restrike) have been performed on the piles and the estimated design pile loads from EOID and restrike tests were analysed. Class-A type numerical analyses conducted prior to the pile loading tests were 56~105%, 65~121% and 38~142% respectively of those obtained from static load tests. In addition, design loads estimated from the restrike tests indicate increases of 12~60% compared to those estimated in the EOID tests. The EOID tests show large end bearing capacity while the restrike tests demonstrate increased skin friction. When impact energy is insufficient during the restrike tests, the end bearing capacity may be underestimated. It has been found that total pile capacity would be reasonably estimated if skin friction from the restrike tests and end bearing capacity from the EOID are combined. The load-settlement relation measured from the static pile load tests and estimated from the numerical modelling is in general agreement until yielding occurs, after which results from the numerical analyses substantially deviated away from those obtained from the static load tests. The measured pile behaviour from the static load tests shows somewhat similar behaviour of perfectly-elastic plastic materials after yielding with a small increase in the pile load, while the numerical analyses demonstrates a gradual increase in the pile load associated with strain hardening approaching ultimate pile load. It has been discussed that the load-settlement relation mainly depends upon the stiffness of the ground, whilst the shear transfer mechanism depends on shear strength parameters.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.85-93
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• 2021

The seventy percentage of Korean Peninsular is covered by the mountainous area, and the depth of west sea and south sea is relatively shallow. Therefore, a large scale land reclamation from the sea has been implemented for the construction of industrial complex, residental area, and port and airport facilities. The common problem of reclaimed land is consisted of soft ground, and hence it has low load bearing capacity as well as excessive settlement upon loading on the ground surface. The hollow concrete block has been used to reinforce the loose and soft foundation soil where the medium-high apartment or one-story industrial building is being planned to be built. Recently the earthquakes with the magnitude of 4.0~5.0 have been occurred in the west coastal and southeast coastal areas. Lee (2019) reported the advantages of hollow concrete block reinforced shallow foundation through the static laboratory bearing capacity tests. In this study, the dynamic behavior of hollow concrete block reinforced sandy ground with filling the crushed stone in the hollow space has been investigated by the means of shaking table test with the size of shaking table 1000 mm × 1000 mm. Three types of seismic wave, that is, Ofunato, Hachinohe, Artificial, and two different accelerations (0.154 g, 0.22 g) were applied in the shaking table tests. The horizontal displacement of structure which is situated right above the hollow concrete block reinforced ground was measured by using the LVDT. The relative density of soil ground are varied with 45%, 65%, and 85%, respectively, to investigate the effectiveness of reinforcement by hollow block and measured the magnitude of lateral movement, and compared with the limit value of 0.015h (Building Earthquake Code, 2019). Based on the results of shaking table test for hollow concrete block reinforced sandy ground, honeycell type hollow block gives a large interlocking force due to the filling of crushed stone in the hollow space as well as a great interface friction force by the confining pressure and punching resistance along the inside and outside of hollow concrete block. All these factors are contributed to reduce the great amount of horizontal displacement during the shaking table test. Finally, hollow concrete block reinforced sandy ground for shallow foundation is provided an outstanding reinforced method for medium-high building irrespective of seismic wave and moderate accelerations.