• International Journal of Highway Engineering
• /
• v.11 no.2
• /
• pp.239-247
• /
• 2009

Pipe installation following excavation of pavement and underlying-soils induces settlements, cracks and bad roughness near utility cut. This study is to use PMT and LDWT in order to evaluate stiffness and/or degree of compaction of sublayers and backfill in utility cut section because no specially designed efforts for evaluating stiffness condition of the substructures below new pavement after pipe installation are offered at this time. From test results of PMT, comparable stiffness and/or degree of compaction in recompaction process is not obtained comparing to that of the existing sublayers before excavation. Thickness of the new surface layer after pipe installation must be designed thicker than that of the existing surface layer. It is verified that LDWT comparing to PMT is effective only to get stiffness and/or degree of compaction within limited depth from surface of materials, but it is not useful to evaluate stiffness of substructures in full depth in case of utility cut.

• Journal of the Korean Society for Railway
• /
• v.18 no.1
• /
• pp.53-62
• /
• 2015

LWDT was developed for use as an alternative technique to measure the stiffness of trackbed soils. In this study, numerical and theoretical analyses of LWDT's acting mechanism were performed. The effectiveness of the adapted elastic formula used for calculation of the dynamic modulus, Evd, was investigated theoretically and also numerically by running ABAQUS analysis. The minimum thickness of the upper layer is proposed based on the analysis. Correction factors for the formula of elastic modulus are also proposed in this study. In the future, following field test results and laboratory mechanical tests such as the resonant column test, a guideline for the use of LWDT as a standard test protocol in track construction sites, as a measuring tool for the degree of compaction and/or stiffness and dynamic modulus, will be proposed based on this analysis.

• Journal of the Society of Disaster Information
• /
• v.9 no.4
• /
• pp.392-399
• /
• 2013

The use of advanced composite materials in strengthening and repair of existing structures is increasing rapidly. One specific area in which the technique has been introduced lately is the strengthening of metallic structures with bonded carbon-fibre laminates. In this paper, the behaviors of composite steel-CFRP members is studied experimentally. A new type of test specimen has been developed for this purpose. By examining different combination of CFRP-laminates and adhesives, different types of fracture mode could be examined. The tested composite elements also displayed different behavior and a large difference in strength and ductility could be observed.

• Aerospace Engineering and Technology
• /
• v.9 no.1
• /
• pp.72-77
• /
• 2010

A hydraulic test on a filament wound case of Kick-Motor was conducted to evaluate the structural stiffness degradation and to confirm the burst performance. Failure criteria have been defined with bursting above 150% of MEOP(Maximum Expected Operation Pressure) and failure in the cylinder. The analysis result showed that filament fiber in the cylinder should be broken at about 2088psig. From a hydraulic test it has been verified that composite case meets the failure requirements, and that the stiffness does not decrease even after a year since the manufacturing.

• TTA Journal
• /
• s.127
• /
• pp.100-105
• /
• 2010

• TTA Journal
• /
• s.139
• /
• pp.104-110
• /
• 2012

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.2A
• /
• pp.179-186
• /
• 2008

To analyzing the validity for using the stiffness ratio in evaluating edge stiffness effect of the composite girder bridges, modification factors are analyzed with changing girder spacing. The relation between stiffness ratio, loading type, girder spacing and modification factors is analyzed. From the results of comparing modification factors analyzed from the field loading test and the established design method with the modification factor analyzed from this study, it was concluded that evaluating the edge stiffness effect using stiffness ratio is possible.

• Journal of the Korean Society for Railway
• /
• v.12 no.1
• /
• pp.55-64
• /
• 2009

Recently, concrete track is replacing ballast track for efficient and economic maintenance of track. It considerably offer less maintenance, a longer service life and reduced life-cycle costs. With the aim of achieving high-quality track construction work, of developing tools for quality assurance in new construction and for later technical inspection of material condition, a quality strategy has to be developed. For these purpose, NDT which is using the seismic wave has carried out in situ studies in the test construction section. The used NDT are SASW test, impact echo test and continuous impact echo test. The test is performed 5,353 times on 49 pre-cast concrete track panels to verify the stiffness structure and grouting efficiency of the track structure. To conclude, because of the non-homogeneous characteristic of concrete material. it is restricted to apply the elastic wave test at some aspect. However it is possible to acquisite a sufficient reliability about structural stiffness and grouting efficiency of concrete track.

• Journal of the Korean Geotechnical Society
• /
• v.16 no.5
• /
• pp.19-25
• /
• 2000

배수성과 인장강성을 가지는 복합 보강재를 사용하여 보강한 포화점성토의 거동에 선행하중이 미치는 영향을 조사하기위하여 평면변형을 시험을 수행하였다. 보강하지 않은 공시체와 보강한 공시체에 대하여 이방압밀(K=0.3, σ3'=50kPa)을 실시하고 비배수 및 배수전단시험을 일정변형율 속도를 실시하였다. 선행하중을 가한 시험의 경우는 이방압밀후 소정의 선행하중을 가하여 크리이프, 제하, 에이징 후에 비배수 전단시험을 실시하였다. 시험결과 분석한 결과 포화전성성토와 같이 연약한 토질이라도 다짐을 잘하고 보강토의 큰 배수압툭강도를 이용하여 큰 배수압축강도를 이용하여 큰 선행하중을 가하여 과압밀 상태로 함으로써 비배수 전단시에 큰 초기강성을 가지는 것을 알수 있었다. 즉, 점성토의 보강토의 경우 보강에 의한 배수강도의 증가는 큰 선행하중을 가하기 위하여 사용하는 것이 가장 효율적인 것으로 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.12 no.2
• /
• pp.205-215
• /
• 1992

Load tests for fourteen small-scale foundation models combined with geotextile, sand mat and rigid mat were conducted to study the effect of geotextile(G/T), sand mat(S/M), and foundation types on deformation of foundation soils. In addition, the experimental results were compared with those obtained from numerical analysis using a software program. The main conclusions were summarized as follows: 1. The restraint effect on G/T is more outstanding on the lateral displacement than on the vertical one. 2. The single use of S/M has better effect on the restraint of vertical displacement than lateral one. 3. The use of both S/M and G/T is required for the restraint of lateral and vertical displacement. 4. Multi-layered foundation with large rigidity shows similar tendency to that of foundation reinforced with S/M and G/T.