• Journal of Plant Biology
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• 제12권1호
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• pp.15-21
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• 1969

In this experiment, the litters of each five species of neadle-leaf trees and broad-leaf trees were laid on each pot soils, which had same soil conditions, is the green house and the sil fertility of each pots were determined after four years. Chemical properties among each pot soils under litters of needle-laef trees showed remarkable different values in the pH, base exchange capacity, total exchangeable base, base saturation, organic matter, available phosphorus, exchangeable potassium and calcium, and that of broad-leaf trees showed respectively significant difference. The content of chemical components, such as total exchangeable base, organic matter, total nitrogen, available phosphorus and exchanbeable potassium, between pot soils under litters of the needle-leaf trees and the broad-leaf trees were significant at the 0.01 and 0.05 levels of the statistical probability. The fertility of soil under the influence of decayed fallen leaves is the highest value in the posts of broad-leaves and next to the pots of needle-leaves and the control pots the lowest. The pH value of the soil with various kinds of fallen leaves showed little difference among themselves, but it especially approached in the broad leaves plots gradually to neutral and hte non-treated plot showed acidity. Lespedeza bicolar and Castanea crenata are supposed to contribute to the fertility of soil. Pinus rigida showed excellent exchanged properties of soi. The leaves of Robinia pseudoacacia and Pinus koraiensis did not contribute much to the promotion of fertility of soil.

• Earthquakes and Structures
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• 제14권5호
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• pp.411-424
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• 2018

This study explores the inelastic behavior of systems with flexible base. The use of a single degree of freedom system (ESDOF) with equivalent ductility to represent the response of flexible base systems is discussed. Two different equations to compute equivalent ductility are proposed, one which includes the contribution of rigid body components, and other based on the overstrength of the structure. In order to asses the accuracy of ESDOF approach with the proposed equations, the behavior of a 10-story regular building with reinforced concrete (RC) moment resisting frames is studied. Local and global ductility capacity and demands are used to study the modifications introduced by base flexibility. Three soil types are considered with shear wave velocities of 70, 100 and 250 m/s. Soil-foundation stiffness is included with a set of springs on the base (impedance functions). Capacity curves of the building are computed with pushover analysis. In addition, non linear time history analysis are used to asses the ductility demands. Results show that ductility capacity of the soil-structure system including rigid body components is reduced. Base flexibility does not modify neither yield and maximum base shear. Equivalent ductility estimated with the proposed equations is fits better the results of the numerical model than the one considering elastoplastic behavior. Modification of beams ductility demand due to base flexibility are not constant within the structure. Some elements experience reduced ductility demands while other elements experience increments when flexible base is considered. Soil structure interaction produces changes in the relation between yield strength reduction factor and structure ductility demand. These changes are dependent on the spectral shape and the period of the system with fixed and flexible base.

• 한국지진공학회논문집
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• 제19권3호
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• pp.85-92
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• 2015

Response spectra of a building are made with a SDOF system taking into account a first mode shape, even though higher modes may affect on the dynamic responses of a high-rise building. A soft soil layer under a building also affects on the responses of a building. In this study, seismic responses of a MDOF system were investigated to examine the effects of higher modes on the response of a tall building by comparing them with those of a SDOF system including the kinematic interaction effect. Study was performed using a pseudo 3D finite element program with seven bedrock earthquake records downloaded from the PEER database. Effects of higher modes on the seismic responses of a tall building were investigated for base shear force and base moment of a MDOF system including story shear forces and story moments. Study results show that higher modes of a MDOF system contribute to a reduction of base shear force up to 1/4-1/5 of KBC and base moment. The effect of higher modes is more significant on the base shear force than on the base moment. Maximum story shear force and moment occurred at the top part of a building rather than at a base in the cases of tall buildings differently from short buildings, and higher modes of a tall building affected on the base forces making them almost constant at the base. A soft soil layer also affects some on the base shear force of a high-rise building independently on the soft soil type, but a soft soil effect is prominent on the base moment.

• Earthquakes and Structures
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• 제24권5호
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• pp.345-352
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• 2023

This paper studied the effect of soil-structure interaction (SSI) on the seismic response and retrofit of a reinforced concrete structure with a soft-first story for different soil types. A 5-story structure built on a 30m deep homogeneous soil mass was considered as a case study structure, and steel column jacketing and steel bracing were chosen as seismic retrofit methods. Seismic responses of a fixed-base and a flexible base structure subjected to seven scaled earthquake records were obtained using the software OpenSees to investigate the effect of soil on seismic response and retrofit. The nonlinearBeamColumn elements with the fiber sections were used to simulate the nonlinear behavior of the beams and columns. Soil properties were defined based on shear wave velocity according to categorized site classes defined in ASCE-7. The finite element model of the soil was made using isoparametric four-noded quadrilateral elements and the nonlinear dynamic responses of the combined system of soil and structure were calculated in the OpenSees. The analysis results indicate that the soil-structure interaction plays an important role in the seismic performance and retrofit of a structure with a soft-first story. It was observed that column steel jacketing was effective in the retrofit of the model structure on a fixed base, whereas stronger retrofit measures such as steel bracing were needed when soil-structure interaction was considered.

• 한국토양환경학회지
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• 제3권3호
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• pp.3-10
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• 1998

토양의 산/염기 완충능은 토양-오염물질-공극수로 이루어진 시스템의 pH에 직접적인 영향을 미치므로 오염물질의 토양내 거동예측시에 많은 영향을 미치는 매우 중요한 토양의 성질이다. 본 연구는 이중확산층이론과 two layer electrostatic 흡착모델을 응용하여 토양의 산/염기 완충능의 이론모델을 유도하고 이 모델의 적용절차를 제시하였다. 산-염기 적정실험을 통하여 두 종류의 카올리나이트의 완충능을 실측하고 이를 본 연구에서 개발된 모델의 예측치와 비교하였다.

• Structural Engineering and Mechanics
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• 제3권2호
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• pp.107-120
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• 1995

A soil-structure interaction formulation is used here which is based on consideration of the dynamics of the structure with a free, rather than a fixed, base. This approach is shown to give a quite simple procedure for coupling the dynamic characteristics of the structure to those of the foundation and soil in order to obtain a matrix formulation for the complete system. In fixed-base studies it is common to presume that each natural mode of the structure has a given fraction of critical damping, and since the interaction formulation uses a free-base model, it seems natural for this situation to assign the equal modal damping values to free-base modes. It is shown, though, that this gives a structural model which is significantly different than the one having equal modal damping in the fixed-base modes. In particular, it is found that the damping matrix resulting in equal modal damping values for free-based modes will give a very significantly smaller damping value for the fundamental distortional mode of the fixed-base structure. Ignoring this fact could lead one to attribute dynamic effects to interaction which are actually due to the choice of damping.

• Geomechanics and Engineering
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• 제9권1호
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• pp.39-55
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• 2015

Usually the analyses of structures are carried out by assuming the base of structures to be fixed. However, the soil beneath foundation alters the earthquake loading and varies the response of structure. Hence, it is not realistic to analyze structures by considering it to be fixed. The importance of soil-structure interaction was realized from the past failures of massive structures by neglecting the effect of soil in seismic analysis. The analysis of massive structures requires soil flexibility to be considered to avoid failure and ensure safety. Present study, considers the seismic behavior of multi-storey reinforced concrete narrow and wide buildings of various heights with and without shear wall supported on raft foundation incorporating the effect of soil flexibility. Analysis of the three dimensional models of six different shear wall positions founded on four different soils has been carried out using finite element software LS DYNA. The study investigates the differences in spectral acceleration coefficient (Sa/g), base shear and storey shear obtained following the seismic provisions of Indian standard code IS: 1893 (2002) (IS) and International building code IBC: 2012 (IBC). The base shear values obtained as per IBC provisions are higher than IS values.

• 한국환경복원기술학회지
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• 제15권6호
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• pp.61-67
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• 2012

This study was conducted to evaluate the effects of soil covering and vegetation base materials implementation on the growth of Lespedeza cyrtobotrya Miq. in abandoned coal mine land. We compared the biomass of L. cyrtobotrya at the study plots of four different soil covering depth (control, 10cm, 20cm, and 30cm) and four different compounds of vegetation base materials composed of soil conditioner (S), erosion control (E), and peat moss (P) (control, S+P, E+P, and S+E+P). The result showed that the biomass of L. cyrtobotrya was higher in the study plots implemented with soil covering than control plot, although the increase in biomass was not constant with soil covering depth. In case of the vegetation base materials treatments, the biomass was highest in S+E+P plot, and S+P and E+P plots showed higher biomass than control plot.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.40-48
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• 2010

Saemangeum reclaimed area is needed to construct much green zone to make high-quality multi-functional land such as tide embankment, lake dike, industrial complex, environmental spaces, etc. However, growth of plants is somewhat difficult because a salinity of Saemangeum soil is very high and a soil fertility, water content of soil are low. Therefore, it is essential to initial desalination of soil and continuous management for planting base. It is recommended that a group of grassland to raise the efficiency of covering should be made in the first stage and a forest by improvement of vegetation should be made in the mid and long term stage. It is recommended that the construction of vegetation base should be made with a regular thickness of soil of good quality in multi-functional area such as a shrub and wood. In case of construction of a windbreak forest, it is necessary to make a wood base of suitable depth using soil brought from another place or filling of soil. Also, it is necessary to keep a maintenance of woods in early stage. Saemangeum reclaimed land will be brand-named worldwide tourist attractions due to construction of much green zone having high quality multi-functional facilities.

• 한국지반공학회논문집
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• 제19권6호
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• pp.85-97
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• 2003

본 논문에서는 건축물 하중기준 및 해설에서 제시된 지반분류 방법으로 지반 III 또는 IV에 해당하는 지반을 대상으로 등가선형해석을 수행하였고, 해석에서 얻어진 스펙트럴 가속도 값으로 지반계수를 역산하여 국내 각 기준에서 제시하고 있는 지반계수와 비교 검토하였다. 해석결과 고유주기 0.9초 이상 고층 건물의 경우 지반 III의 경우 지반 II의 지반계수의 사용이 가능하였고, IV의 경우 지반 III의 지반계수를 사용하여도 충분하였다. 또한, 대부분의 해석에서 얻어진 지반계수의 값이 국내 내진설계기준의 값보다 상당히 작게 나타났다. 이는 내진설계시 국내 내진설계기준을 그대로 적용하면 구조물 밑면전단력이 보수적으로 산정될 수 있음을 의미한다.