• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.03a
• /
• pp.383-393
• /
• 2006

This paper investigates strength characteristics and stress-strain behaviors of geogrid mixing reinforced lightweight soil. The lightweight soil was reinforced with geogrid in order to increase its compressive strength. Test specimens were fabricated by various mixing conditions including cement content, initial water content, air content and geogrid layer and then unconfined compression tests were carried out. From the experimental results, it was found that unconfined compressive strength as well as stress-strain behavior of lightweight soil were strongly influenced by mixing conditions. The more cement content that is added to the mixture, the greater its unconfined compressive strength. However, the more initial water content or the more air foam content, the less its unconfined compressive strength. It was observed that the strength of geogrid reinforced lightweight soil was increased due to reinforcing effect by the geogrid for most cases except cement content less than 20%. In reinforced lightweight soil, secant modulus $(E_{50})$ was increased as the strength increased due to the inclusion of geogrid.

• Journal of Ocean Engineering and Technology
• /
• v.19 no.6 s.67
• /
• pp.44-49
• /
• 2005

This paper investigates strength characteristics and stress-strain behaviors of unreinforced and reinforced lightweight soils. Lightweight soil, composed of dredged soil, cement, and air-foam, was reinforced by a waste fishing net, in order to increase its compressive strength. Test specimens were fabricated by various mixing conditions, such as cement content, initial water content, air content, and waste fishing net; then, unconfined compression tests were carried out on these specimens. From the test results, it was shown that reinforced lightweight soil had different behavior after failure, even though it had similar behavior as unreinforced lightweight soil before failure. The test results also showed that stress became constant after peak strength in reinforced lightweight soil, while the stress decreased continuously in unreinforced lightweight soil. It was observed that the strength was increased due to reinforcing effect by the waste fishing net for most cases, except high water content greater than $218\%$. In the case of high water content, a reinforcing effect is negligible, due to slip between waste fishing net and soil particles. In reinforced lightweight soil, secant modulus (E50) was increased, due to the inclusion of waste fishing net.

• Journal of the Korean GEO-environmental Society
• /
• v.2 no.2
• /
• pp.33-39
• /
• 2001

In order to utilize mass of oyster shells for a partial substitute material for reclamation, the shear characteristics of two-phase mixture soil with oyster shells were investigated with $\overline{CU}$ test. From various experiments, it was found that the increase of mixed ratio of oyster shells causes the shear strength of mixed soil. And this phenomenon not only depends on friction due to confining pressure such as pure clay but also is influenced by shaping skeleton of oyster shells. Also, it was discovered that there were many influences by clay-oyster shell mixture from the study of the secant modulus and dilatancy characteristics of mixed soil. In addition, variation of oyster shell skeleton during shearing stage is examined applying modifying coefficient concept.

• Structural Engineering and Mechanics
• /
• v.15 no.4
• /
• pp.415-436
• /
• 2003

The combination of spatial latticed structures (hereafter SLS) and flexible cables, the cable-stayed spatial latticed structures (hereafter CSLS) can cross longer span. According to variation principle, a novel geometric nonlinear formulation for 3-D bar elements considering large displacement and infinitesimal rotation increments with second-order precision is developed. The cable nonlinearity is investigated and it is taken that the secant modulus method can be considered as an exact method for a cable member. The tower column with which the cables link is regarded as a special kind of beam element, and, a new simplified stiffness formulation is presented. The computational strategies for the nonlinear dynamic response of structures are given, and the ultimate load carrying capacities and seismic responses are analyzed numerically. It is noted that, compared with corresponding spatial latticed shells, the cable-stayed spatial latticed shells have more strength and more stiffness, and that the verical seismic responses of both CSLS and CLS are remarkably greater than the horizontal ones. In addition, the computation shows that the stiffness of tower column influences the performance of CSLS to a certain extent and the improvement of structural strength and stiffness of CSLS is relevant not only to cables but also to tower columns.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.4
• /
• pp.1241-1250
• /
• 1996

The characteristics of fatigue cumulative damage and fatigue life of 8-harness satin woven CFRP composites with a circular hole under constant amplitude and 2-level block loading are estimated by Stochastic Makov chain model. It is found in this study that the fatigue damage accumulation behavior is very random and the fatigue damage is accumulated as two regions under constant amplitude fatigue loading. In constant amplitude fatigue loading the predicted mean number of cycles to a specified damage state by Markov chain model shows a good agreement with the test result. The predicted distribution of the fatigue cumulative damage by Markov chain model is similar to the test result. The fatigue life predictions under 2-level block loading by Markov chain model revised are good fitted to the test result more than by 2-parameter Weibull distribution function using percent failure rule.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.12
• /
• pp.3892-3898
• /
• 1996

In this study, the prediction of the fatigue life as well as the extimation of the characteristics of fatigue cumulative damage on GFRP under random loading were performed. The constant amplitude tests and the ramdom loading test were carried on notched GFRP specimens with a circular hole. Random waves were generated with a micro-computer and had wide band spectra. Since it is useful that the prediction of fatigue life ot the given load sequences is based on S-N curves under constant amplitude loading, the estimation of equivalent stress is done on every random waves. The equivalent stress wasat first estimated by Miner's rule and then by the proposed model which was based on Hashin-Rotem's comulative damage theory regarding nonlinear fatigue cumulative damage behavior. The fatigue lives were predicted from each equivalent stress evaluated. And each predicted fatigue llife was compared with experimental results. The number of cycles of random loads were counted by mean-cross counting method. The reuslts showed that the fatigue life predicted by proposed model was correlated well with the experimental results in comparison with Miner's model.

• Geomechanics and Engineering
• /
• v.11 no.1
• /
• pp.161-175
• /
• 2016

A series of experimental studies are conducted on the deformation and shear strength property of compacted loess. The results reveal that the relationships of both the initial moisture content (w) and the initial degree of compaction (K) of compacted loess with cohesion (w) and the angle of internal friction (${\varphi}$) are linear. The relationship between the secant modulus ($E_{soi}$) and K is also linear. The relationship between $E_{soi}$ and w can be fitted well by a second-order polynomial. Further, when the influences of w and K are ignored, the relationship between the confined compression strain (${\varepsilon}$) and vertical pressure (p) can be expressed by a formula. A correction formula for the deformation of compacted loess caused by a change in w and K is derived on the basis of the study results.

• Geomechanics and Engineering
• /
• v.16 no.5
• /
• pp.547-558
• /
• 2018

Studies of soil dynamic properties in Malaysia are still very limited. This study aims to investigate the dynamic properties of two selected tropical residual soils (i.e., Sandy Clay and Sandy Silt) and a sand mining trail (Silty Sand) in Peninsular Malaysia using 1g shaking table test. The use of 1g shaking table test for soil dynamic testing is often constrained to large strain level and small confining pressure only. Three new experimental setups, namely large laminar shear box test (LLSBT), small chamber test with positive air pressure (SCT), and small sample test with suction (SSTS) are attempted with the aims of these experimental setups are capable of evaluating the dynamic properties of soils covering a wider range of shear strain and confining pressure. The details of each experimental setup are described explicitly in this paper. Experimental results show that the combined use of the LLSBT and SCT is capable of rendering soil dynamic properties covering a strain range of 0.017%-1.48% under confining pressures of 5-100 kPa. The studied tropical residual soils in Malaysia behaved neither as pure sand nor clay, but show a relatively good agreement with the dynamic properties of residual soils in Singapore. Effects of confining pressure and plasticity index on the studied tropical residual soils are found to be insignificant in this particular study.

• Steel and Composite Structures
• /
• v.43 no.3
• /
• pp.293-309
• /
• 2022

Accurate design models for predicting the shear resistance of headed studs in solid concrete slabs are essential for obtaining economical and safe steel-concrete composite structures. In this study, symbolic regression with genetic programming (GPSR) was applied to experimental data to formulate new descriptive equations for predicting the shear resistance of studs in solid slabs using both normal and lightweight concrete. The obtained GPSR-based nominal resistance equations demonstrated good agreement with the test results. The equations indicate that the stud shear resistance is insensitive to the secant modulus of elasticity of concrete, which has been included in many international standards following the pioneering work of Ollgaard et al. In contrast, it increases when the stud height-to-diameter ratio increases, which is not reflected by the design models in the current international standards. The nominal resistance equations were subsequently refined for use in design from reliability analyses to ensure that the target reliability index required by the Eurocodes was achieved. Resistance factors for the developed equations were also determined following US design practice. The stud shear resistance predicted by the proposed models was compared with the predictions from 13 existing models. The accuracy of the developed models exceeds the accuracy of the existing equations. The proposed models produce predictions that can be used with confidence in design, while providing significantly higher stud resistances for certain combinations of variables than those computed with the existing equations given by many standards.

• Journal of the Korean Geosynthetics Society
• /
• v.18 no.4
• /
• pp.215-224
• /
• 2019

According to the recent civil engineering construction work site which is a complex process, development of multi-functional geotextiles is required. In this study, the characteristics of five different modified cross-section fiber yarns for the selection of wicking yarns were analyzed and yarns that can achieve target properties were selected. Experimental prototype geotextiles suitable for horizontal wicking drain property and reinforcement was developed and its tensile strength, 2% secant modulus, vertical water permeability, AOS, friction characteristics by the direct shear method, and vertical/horizontal wicking test were analyzed. These tests are conducted to verify the performance of the geotextiles with horizontal wick drain property, separation and reinforcement developed in this study. As a results of the indoor soil box test, it was confirmed that the geotextiles using the wicking yarn sufficiently exhibited the function of discharging excess pore water in the horizontal direction.