• Title/Summary/Keyword: construction mechanics

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Cost optimization of segmental precast concrete bridges superstructure using genetic algorithm

  • Ghiamat, R.;Madhkhan, M.;Bakhshpoori, T.
    • Structural Engineering and Mechanics
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    • v.72 no.4
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    • pp.503-512
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    • 2019
  • The construction of segmental precast concrete bridge is an increase due to its superior performance and economic advantages. This type of bridge is appropriate for spans within 30 to 150 m (100 to 500 ft), known as mega-projects and the design optimization would lead to considerable economic benefits. A box-girder cross section superstructure of balanced cantilever construction method is assessed here. The depth of cross section, (variable along the span linearly), bottom flange thickness, and the count of strands are considered as design variables. The optimum design is characterized by geometry, serviceability, ductility, and ultimate limit states specified by AASHTO. Genetic algorithm (GA) is applied in two fronts: as to the saving in construction cost 8% and as to concrete volume 6%. The sensitivity analysis is run by considering different parameters like span/depth ratio, relation between superstructure cost, span length and concrete compressive strength.

A case study on perforation under Daejeon station building by Front-Jacking method (Front-Jacking공법에 의한 대전역사 하부 관통사례)

  • Kim, Yong-Il;Hwang, Nak-Yeon;Jeong, Du-Seok;Cha, Jong-Hwi;Lee, Nae-Yong
    • Proceedings of the Korean Society for Rock Mechanics Conference
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    • 2006.03a
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    • pp.195-203
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    • 2006
  • The crossing construction under railroad have two methods which are cut and cover and trenchless method. first, cut and cover method is an extremely limited method concerning non-running time. Whereas, trenchless method is free from restriction such as train speed and running time, and has the strong points of safe and rapid construction. Front Jacking method, one of the trenchless methods, is frequently applied recently due to its stability during construction and vantage of assuring schedule reliability. The procedure is that after minimizing interlocking friction with structure and earth pressure due to jacking the small steel tube, pulling the precast box manufactured at the field in the ground using PC strand and hydraulic Jack. This method is able to be applied regardless of section size and length of box and condition of ground. And that is also pro-environmental. This paper presents the case of Daejeon E. W. perforate Road Project applied with the Front Jacking method.

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Determination of Mode I Fracture Toughness of Rocks Using Wedge Splitting Test (쐐기 분열 시험을 이용한 암석의 모드 I 파괴인성 측정)

  • Ko, Tae Young;Kim, Taek Kon;Lee, Dae Hyuk
    • Tunnel and Underground Space
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    • v.29 no.6
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    • pp.523-531
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    • 2019
  • In the applications of rock mechanics or rock engineering including drill and blast, drilling and mechanical excavation, the fracture toughness is an important factor. Several methods have been proposed to measure the fracture toughness of rocks. In this study, wedge splitting test specimen which is prepared with ease and tested under compression loading was used to obtain mode I fracture toughness of rocks. The equation of stress intensity factor through numerical analysis is proposed from the stress state of crack tip considering both vertical and horizontal loads due to the vertical load acting on the wedge. The validity of the wedge splitting test method was confirmed by comparing the mode I fracture toughness values obtained by the GD and SENB test specimens.

Subjective Explanation of Pictures Considering Feelings of Objects in Pictures

  • Kato, Shigeru;Onisawa, Takehisa
    • 제어로봇시스템학회:학술대회논문집
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    • 2003.10a
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    • pp.2399-2404
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    • 2003
  • This paper aims at the construction of the system that outputs subjective and consistent linguistic expressions of some pictures. Input to this system is information on some pictures and this system outputs explanations of basic contents of pictures and consistent connective relationships between pictures. The present system consists of the explaining part of basic contents and the explaining part of connective relationship. The former part explains behaviors and feelings of objects drawn in pictures. The latter one explains the matters not drawn in pictures by guessing them from pictures. This part considers consistency of connective relationships. From the viewpoint that the interpretation of pictures is dependent on individual subjectivity, the present system has individual database for individual subjectivity. In order to confirm the usefulness of the present approach, simulation experiments are performed. In the experiments the individual databases of subjects are constructed and the outputs of the system are evaluated. Experiment results show that good evaluation is obtained.

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Net Penetration Rate of a Large Diameter Shield TBM in Hard Rock (대구경 Shield TBM의 암반층 굴착속도)

  • 박철환;송원경;신중호;천대성
    • Proceedings of the Korean Society for Rock Mechanics Conference
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    • 2001.10a
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    • pp.115-120
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    • 2001
  • In No. 1 tunnel for Kwnagju urban subway construction, net penetration rate of the shield TBM was analyzed. This tunnel of 540 m length is located in soil layers at starting and in hard rocks such as amphibolite and granitic gneiss at ending with 84 m length. The net penetration rate was dropped down to 2∼11 cm/hr in rock while 50∼80 cm/hr in soil. Theoretical penetration rate is analyzed in conditions of machine and rock in order to compare the actual net penetration rate. The relationships between net penetration rate and thrust force is also investigated in this report.

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Nonlinear analysis of interaction between flexible pile group and soil

  • Liu, Jie;Li, Q.S.;Wu, Zhe
    • Structural Engineering and Mechanics
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    • v.20 no.5
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    • pp.575-587
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    • 2005
  • Using the nonlinear load transfer function for pile side soil and the linear load transfer function for pile end soil, a combined approach of the incremental load transfer matrix method and the approximate differential equation solution method is presented for the nonlinear analysis of interaction between flexible pile group and soil. The proposed method provides an effective approach for the solution of the nonlinear interaction between flexible pile group under rigid platform and surrounding soil. To verify the accuracy of the proposed method, a static load test for a nine-pile group under a rigid platform is carried out. The finite element analysis is also conducted for comparison purposes. It is found that the results from the proposed method match very well with those from the experimental test and are better in comparison with the finite element method.

Prediction of compressive strength of concrete based on accelerated strength

  • Shelke, N.L.;Gadve, Sangeeta
    • Structural Engineering and Mechanics
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    • v.58 no.6
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    • pp.989-999
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    • 2016
  • Moist curing of concrete is a time consuming procedure. It takes minimum 28 days of curing to obtain the characteristic strength of concrete. However, under certain situations such as shortage of time, weather conditions, on the spot changes in project and speedy construction, waiting for entire curing period becomes unaffordable. This situation demands early strength of concrete which can be met using accelerated curing methods. It becomes necessary to obtain early strength of concrete rather than waiting for entire period of curing which proves to be uneconomical. In India, accelerated curing methods are used to arrive upon the actual strength by resorting to the equations suggested by Bureau of Indian Standards' (BIS). However, it has been observed that the results obtained using above equations are exaggerated. In the present experimental investigations, the results of the accelerated compressive strength of the concrete are used to develop the regression models for predicting the short term and long term compressive strength of concrete. The proposed regression models show better agreement with the actual compressive strength than the existing model suggested by BIS specification.

Corrosion of rebar in carbon fiber reinforced polymer bonded reinforced concrete

  • Bahekar, Prasad V.;Gadve, Sangeeta S.
    • Advances in concrete construction
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    • v.8 no.4
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    • pp.247-255
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    • 2019
  • Several reinforced concrete structures that get deteriorated by rebar corrosion are retrofitted using Carbon Fiber Reinforced Polymer (CFRP). When rebar comes in direct contact with CFRP, rebar may corrode, as iron is more active than carbon. Progression of corrosion of rebar in strengthened RC structures has been carried out when rebar comes in direct contact with CFRP. The experimentation is carried out in two phases. In phase I, corrosion of bare steel bar is monitored by making its contact with CFRP. In phase II, concrete specimens with surface bonded CFRP were casted and subjected to the realistic exposure conditions keeping direct contact between rebar and CFRP. Progression of corrosion has been monitored by various parameters: Half-cell potential, Tafel extrapolation and Linear Polarisation Resistance. On termination of exposure, to find residual bond stress between rebar and concrete, pull-out test was performed. Rebar in contact with CFRP has shown substantially higher corrosion. The level of corrosion will be more with more area of contact.

Development of a DB program for the Construction of the Borehole Log Information System (시추자료 정보화를 위한 DB 프로그램 개발)

  • 송원경;박형동;유명환
    • Proceedings of the Korean Society for Rock Mechanics Conference
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    • 1999.03a
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    • pp.65-68
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    • 1999
  • 우리나라의 지반조사 전문업체는 200여 개에 이르며 연간 시추연장은 약 500 km에 달하고 있다(구호본, 1995). 한국 도로공사의 경우만 하더라도 연간 약 500공의 시추조사가 이루어지고 있다(장병욱 외, 1997). 이에 따라 국내 시추시장의 규모는 연간 약 500억원에 이르는 것으로 알려져 있다(구호본, 1995). 그러나 이러한 막대한 양의 지반정보들은 불행히도 해당 사업에서 사용되고 나면 재활용되지 못하고 공사 완료와 함께 사장되고 만다. 이에 따라 값진 수많은 지반 정보들이 재활용되지 못함으로서 잠재 가치의 손실을 초래할 뿐더러 자료의 표준화가 이루어져 있지 않기 때문에 업체간 또는 기관간 자료 공유는 더더욱 기대하기 어렵다. (중략)

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Closed-form Green's functions for transversely isotropic bi-solids with a slipping interface

  • Yue, Zhong Qi
    • Structural Engineering and Mechanics
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    • v.4 no.5
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    • pp.469-484
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    • 1996
  • Green's functions are obtained in exact closed-forms for the elastic fields in bi-material elastic solids with slipping interface and differing transversely isotropic properties induced by concentrated point and ring force vectors. For the concentrated point force vector, the Green functions are expressed in terms of elementary harmonic functions. For the concentrated ring force vector, the Green functions are expressed in terms of the complete elliptic integral. Numerical results are presented to illustrate the effect of anisotropic bi-material properties on the transmission of normal contact stress and the discontinuity of lateral displacements at the slipping interface. The closed-form Green's functions are systematically presented in matrix forms which can be easily implemented in numerical schemes such as boundary element methods to solve elastic problems in computational mechanics.