• Title/Summary/Keyword: shear design

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An Comparative Study on the Method of Determining Allowable Horizontal Bearing Capacity of Piles (말뚝의 허용횡방향지지력 결정법의 비교연구)

  • Lee, Seung-Hyun;Han, Jin-Tae
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.22 no.6
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    • pp.267-274
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    • 2021
  • Among several methods for determining the allowable lateral resistances of piles, the subgrade reaction method and ultimate lateral resistance method are generally used. To determine the effects of the soil conditions, pile head restraint conditions, and pile lengths on determining the allowable lateral resistances of piles, computations of the allowable lateral resistances of piles using the two methods were executed, and the computation results were compared. For piles in soft cohesive soil, the pile design is governed by the allowable lateral resistance of a pile from subgrade soil reaction method regardless of the pile head restraints conditions and pile lengths. The allowable lateral resistance of a pile from the ultimate lateral resistance governs the design as the undrained shear strength increases. Except for the case of a short pile, which is installed in loose granular soil, the allowable lateral resistance of a pile from ultimate lateral resistance governs the design of laterally loaded piles. According to this study, computation of the ultimate lateral resistance of a pile is needed, even though some opinions suggest that the design of a laterally loaded pile is satisfied only by the subgrade reaction method. The pile width barely influences the coefficient of horizontal subgrade reaction. Realistically, the effect of the pile width can be disregarded in the condition of common pile widths of 20~90cm.

Probabilistic Risk Assessment of a Cable-Stayed Bridge Based on the Prediction Method for the Combination of Failure Modes (붕괴모드 조합 예측법에 의한 PSC사장교의 위험도평가)

  • Park, Mi-Yun;Cho, Hyo-Nam;Cho, Taejun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.4A
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    • pp.647-657
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    • 2006
  • Probabilistic Risk Assessment considering statistically random variables is performed for the preliminary design of a Cable Stayed Bridge, which is Prestressed Concrete Bridge consisted of cable and plate girders, based on the method of Working Stress Design and Strength Design. Component reliabilities of cables and girders have been evaluated using the response surface of the design variables at the selected critical sections based on the maximum shear, positive and negative moment locations. Response Surface Method (RSM) is successfully applied for reliability analyses for this relatively small probability of failure of the complex structure, which is hard to obtain through Monte-Carlo Simulations. or through First Order Second Moment Method that can not easily calculate the derivative terms of implicit limit state functions. For the analysis of system reliability, parallel resistance system consisting of cables and plate girder is changed into series connection system and the result of system reliability of total structure is presented. As a system reliability, the upper and lower probabilities of failure for the structural system have been evaluated and compared with the suggested prediction method for the combination of failure modes. The suggested prediction method for the combination of failure modes reveals the unexpected combinations of element failures in significantly reduced time and efforts compared with the previous permutation method or system reliability analysis method, which calculates upper and lower bound failure probabilities.

Effect of Sodium Bicarbonate Supplementation on Carcass Characteristics of Lambs Fed Concentrate Diets at Different Ambient Temperature Levels

  • Jallow, Demba B.;Hsia, Liang Chou
    • Asian-Australasian Journal of Animal Sciences
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    • v.27 no.8
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    • pp.1098-1103
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    • 2014
  • The objective of this study was to investigate the influence of ambient temperatures on carcass characteristics of lambs fed concentrate diets with or without $NaHCO_3$ supplementation. A slaughter study was carried on 12 male Black Belly Barbados lambs randomly drawn from a growth trial (35 weeks). The lambs were divided into four equal groups and allotted in a $2{\times}2$ factorial design. The lambs were allotted at random to two dietary treatments of a basal diet (35:65 roughage:concentrate) or basal diet supplemented with 4% $NaHCO_3$ at different ambient temperatures ($20^{\circ}C$ and $30^{\circ}C$) in an environment controlled chamber for 10 days. Lambs were slaughtered for carcass evaluation at about 262 days of age (245 days of growth trial, 7 days adaptation and 10 days of experimental period). Ambient temperature had significant (p<0.05, p<0.05, p<0.01, and p<0.001) effects on meat color from the ribeye area (REA), fat, leg and longissimus dorsi muscles with higher values recorded for lambs in the lower temperature group than those from the higher ambient temperature group. Significant differences (p<0.05) in shear force value ($kg/cm^2$) recorded on the leg muscles showed higher values (5.32 vs 4.16) in lambs under the lower ambient temperature group compared to the other group. Dietary treatments had significant (p<0.01, p<0.01, and p<0.05) effects on meat color from the REA, fat, and REA fat depth ($cm^2$) with higher values recorded for lambs in the $NaHCO_3$ supplementation group than the non supplemented group. Similarly, dietary treatments had significant differences (p<0.05) in shear force value ($kg/cm^2$) of the leg muscles with the $NaHCO_3$ groups recording higher (5.30 vs 4.60) values than those from the other group. Neither ambient temperature nor dietary treatments had any significant (p>0.05) effects on pH, and water holding capacity on both muscles. These results indicated that $NaHCO_3$ supplementation at low ambient temperatures had caused an increase in carcass characteristics leading to significant effect on meat quality.

Comparative Analysis of Structural Damage Potentials Observed in the 9.12 Gyeongju and 11.15 Pohang Earthquakes (9.12 경주지진 및 11.15 포항지진의 구조손상 포텐셜 비교연구)

  • Lee, Cheol-Ho;Kim, Sung-Yong;Park, Ji-Hun;Kim, Dong-Kwan;Kim, Tae-Jin;Park, Kyoung-Hoon
    • Journal of the Earthquake Engineering Society of Korea
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    • v.22 no.3
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    • pp.175-184
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    • 2018
  • In this paper, comparative analysis of the 9.12 Gyeongju and 11.15 Pohang earthquakes was conducted in order to provide probable explanations and reasons for the damage observed in the 11.15 Pohang earthquake from both earthquake and structural engineering perspectives. The damage potentials like Arias intensity, effective peak ground acceleration, etc observed in the 11.15 Pohang earthquake were generally weaker than those of the 9.12 Gyeongju earthquake. However, in contrast to the high-frequency dominant nature of the 9.12 Gyeongju earthquake records, the spectral power of PHA2 record observed in the soft soil site was highly concentrated around 2Hz. The base shear around 2 Hz frequency was as high as 40% building weight. This frequency band is very close to the fundamental frequency of the piloti-type buildings severely damaged in the northern part of Pohang. Unfortunately, in addition to inherent vertical irregularity, most of the damaged piloti-type buildings had plan irregularity as well and were non-seismic. All these contributed to the fatal damage. Inelastic dynamic analysis indicated that PHA2 record demands system ductility capacity of 3.5 for a structure with a fundamental period of 0.5 sec and yield base shear strength of 10% building weight. The system ductility level of 3.5 seems very difficult to be achievable in non-seismic brittle piloti-type buildings. The soil profile of the PHA2 site was inversely estimated based on deconvolution technique and trial-error procedure with utilizing available records measured at several rock sites during the 11.15 Pohang earthquake. The soil profile estimated was very typical of soil class D, implying significant soil amplification in the 11.15 Pohang earthquake. The 11.15 Pohang earthquake gave us the expensive lesson that near-collapse damage to irregular and brittle buildings is highly possible when soil is soft and epicenter is close, although the earthquake magnitude is just minor to moderate (M 5+).

Development of Additive to Modify the SDAR (Solvent DeAsphalting Residue) and Laboratory Performance Evaluation of Asphalt Mixture with Modified SDAR (고품위화 정제공정 부산물(SDAR) 활용을 위한 첨가제 개발 및 이를 이용한 아스팔트 혼합물의 실내 공용성능 평가)

  • Baek, Cheolmin;Yang, Sung Lin;Hwang, Sung Do
    • International Journal of Highway Engineering
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    • v.18 no.6
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    • pp.97-104
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    • 2016
  • OBJECTIVES : The objective of this research is to develop additives for the modification of Solvent DeAsphalting Residue (SDAR) to be used as pavement materials, and evaluate the performance of asphalt mixture manufactured using the SDAR modified by developed additives. METHODS : The SDAR generally consists of more asphaltenes and less oil components compared to the conventional asphalt binder, and hence, the chemical/physical properties of SDAR are different from that of conventional asphalt binder. In this research, the additives are developed using the low molecular oil-based plasticizer to improve the properties of SDAR. First, the chemical property of two SDARs is analyzed using SARA (saturate, aromatic, resin, and asphaltene) method. The physical/rheological properties of SDARs and SDARs containing additives are also evaluated based on PG-grade method and dynamic shear-modulus master curve. Second, various laboratory tests are conducted for the asphalt mixture manufactured using the SDAR modified with additives. The laboratory tests conducted in this study include the mix design, compactibility analysis, indirect tensile test for moisture susceptibility, dynamic modulus test for rheological property, wheel-tracking test for rutting performance, and direct tension fatigue test for cracking performance. RESULTS : The PG-grade of SDARs is higher than PG 76 in high temperature grades and immeasurable in low temperature grades. The dynamic shear modulus of SDARs is much higher than that of conventional asphalt, but the modified SDARs with additives show similar modulus compared to that of conventional asphalt. The moisture susceptibility of asphalt mixture with modified SDARs is good if, the anti-stripping agent is included. The performance (dynamic modulus, rutting resistance, and fatigue resistance) of asphalt mixture with modified SDARs is comparable to that of conventional asphalt mixture when appropriate amount of additives is added. CONCLUSIONS : The saturate component of SDARs is much less than that of conventional asphalt, and hence, it is too hard and brittle to be used as pavement materials. However, the modified SDARs with developed additives show comparable or better rheological/physical properties compared to that of conventional asphalt depending on the type of SDAR and the amount of additives used.

A Study on Strength of Plat-Plate Wall-Column Connections (Wall Column을 적용한 플랫플레이트 접합부 강도발현에 관한 연구)

  • Lee, Do-Bum;Park, Hong-Gun;Lee, Li-Hyung
    • Journal of the Korea Concrete Institute
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    • v.18 no.2 s.92
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    • pp.257-266
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    • 2006
  • Flat-plate building systems are utilized extensively for construction of apartments, hotels and office buildings because of short construction period, low floor-to-floor height and flexibility in plan design. Recently, to increase lateral seismic resistance of flat-plate building systems, wall-columns are used frequently. Therefore, to estimate strength of flat-plate column connection accurately, the effect of column section shape on the behavior of flat-plate column connection should be considered properly, In the present study, a numerical analysis was performed for interior connections of continuous flat-plate to analyze the effect of column section shape. For the purpose, a computer program for nonlinear FE analysis was developed, and the validity was verified. Through the parametric study, the variations of shear stress distribution around the connection were investigated. According to the result of numerical analysis, as the length of the cross section of column in the direction of lateral load increases, the effective area and the maximum shear strength providing the torsional resistance decrease considerably. Therefore, these effects should be considered properly to estimate the strength of flat-plate connection accurately.

The Estimation Method of Empirical Formula of Strength Parameters by RMR System and Uniaxial Strength (RMR과 일축강도를 이용한 암반 강도정수 추정식의 적용방법)

  • Oh, Sewook;Ahn, Byungchul
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.1
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    • pp.13-18
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    • 2010
  • It is crucial to decide reasonably the parameters necessary for design through research on the characteristics of rock in order to analyze stability of rock structure. This article has conducted both pressure meter test, uniaxial and triaxial compression test to the areas of andesite or tuff located in local regions such as Yeosu, Gwangju, Yangsan, Busan, and Daejeon and has comparatively analyzed previously proposed estimative formulas. According to the result of estimating the deformation modulus through using the damping coefficient suggested by Nicholson & Bieniawski, when RMR is less than 60, it is desirable to use the result of the pressure meter test considering the damping coefficient. If the RMR value is over 60, however, the formula suggested by Kim Gyo-won has been proved to be the most applicable. Moreover, according to the result of comparing the RMR, adhesion, and angle of internal friction, both the adhesion and angle of internal friction best correspond to the formula proposed by Tsuchiya. Comparatively analyzing the relations between the rock deformation modulus and RMR and also suggesting the formula of calculating the shear strength parameter to use the RMR value, this study did not include the deformation modulus and shear strength parameter as factors to decide the RMR index. Since result can differ by several factors, it will be necessary afterwards to suggest practical estimative formulas applicable to the actual spots of Korea.

Application of EPS Considering Long-term Durability (장기내구성을 고려한 EPS의 현장 적용성)

  • Chun, Byungsik;Jung, Changhee;Ahn, Jinhyun
    • Journal of the Korean GEO-environmental Society
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    • v.8 no.6
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    • pp.53-60
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    • 2007
  • L/EPS, manufactured in the shape of block and used for civil engineering, is a lightweight material with an excellent resistance to compression, and provides a superb self-sufficient stability. EPS is a suitable material capable of resolving the problem of settlement and lateral flow if it is applied as the soil on soft ground. The Korean Standards (KS) has not yet proposed any testing method for use of EPS as an engineering banking material. Only its testing and quality ordinance as a heat insulation material has been standardized. The design criteria for EPS has been established and applied through the trial construction of KHC (Korea Highway Corporation) and quality test of manufacturer, but most studies on them have been confined to factory products. This study is focused on comparing and analyzing long-term durability by conducting cyclic load test, freezing and thawing test, absorption rate test and others. EPS used in the test was chosen from construction sites and factory products, focusing on the long-term durability of EPS depending on the passage of time. Unconfined compression test results indicated that the strength of collected samples was lower than factory products. While the triaxial compression test results indicated that the shear strength increased in proportion to the increase of confining pressure, and factory products had declining shear strength as the confining pressure rose.

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Progressive Failure Analysis of Adhesive Joints of Filament-Wound Composite Pressure Vessel (필라멘트 와인딩 복합재 압력용기의 접착 체결부에 대한 점진적 파손 해석)

  • Kim, Junhwan;Shin, Kwangbok;Hwang, Taekyung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.11
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    • pp.1265-1272
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    • 2014
  • This study performed the progressive failure analysis of adhesive joints of a composite pressure vessel with a separated dome by using a cohesive zone model. In order to determine the input parameters of a cohesive element for numerical analysis, the interlaminar fracture toughness values in modes I and II and in the mixed mode for the adhesive joints of the composite pressure vessel were obtained by a material test. All specimens were manufactured by the filament winding method. A mechanical test was performed on adhesively bonded double-lap joints to determine the shear strength of the adhesive joints and verify the reliability of the cohesive zone model for progressive failure analysis. The test results showed that the shear strength of the adhesive joints was 32MPa; the experiment and analysis results had an error of about 4.4%, indicating their relatively good agreement. The progressive failure analysis of a composite pressure vessel with an adhesively bonded dome performed using the cohesive zone model showed that only 5.8% of the total adhesive length was debonded and this debonded length did not affect the structural integrity of the vessel.

Numerical Study on the Behavior of Fully Grouted Rock Bolts with Different Boundary Conditions (경계조건의 변화에 따른 전면접착형 록볼트 거동의 수치해석적 연구)

  • Lee, Youn-Kyou;Song, Won-Kyong;Park, Chul-Whan;Choi, Byung-Hee
    • Tunnel and Underground Space
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    • v.20 no.4
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    • pp.267-276
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    • 2010
  • In modern rock engineering practice, fully grouted rock bolting is actively employed as a major supporting system, so that understanding the behavior of fully grouted rock bolts is essential for the precise design of rock bolting. Despite its importance, the supporting mechanism of rock bolts has not been fully understood yet. Since most of existing analytical models for rock bolts were developed by drastically simplifying their boundary conditions, they are not suitable for the bolts of in-situ condition. In this study, 3-D elastic FE analysis of fully grouted rock bolts has been conducted to provide insight into the supporting mechanism of the bolt. The distribution of shear and axial stresses along the bolt are investigated with the consideration of different boundary conditions including three different displacement boundary conditions at the bolt head, the presence of intersecting rock joints, and the variation of elastic modulus of adjacent rock. The numerical result reveals that installation of the faceplate at the bolt head plays an important role in mobilizing the supporting action and enhancing the supporting capabilities of the fully grouted rock bolts.