• Title/Summary/Keyword: Railway bridge

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Determination of equivalent blasting load considering millisecond delay effect

  • Song, Zhan-Ping;Li, Shi-Hao;Wang, Jun-Bao;Sun, Zhi-Yuan;Liu, Jing;Chang, Yu-Zhen
    • Geomechanics and Engineering
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    • v.15 no.2
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    • pp.745-754
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    • 2018
  • In the analysis of the effects of rock tunnel blasting vibration on adjacent existing buildings, the model of simplified equivalent load produces higher calculation result of vibration, due to the lack of consideration of the millisecond delay effect. This paper, based on the static force equivalence principle of blasting load, proposes a new determination method of equivalent load of blasting vibration. The proposed method, based on the elastic-static force equivalence principle of stress wave, equals the blasting loads of several single blastholes in the same section of millisecond blasting to the triangle blasting load curve of the exploded equivalent elastic boundary surface. According to the attenuation law of stress wave, the attenuated equivalent triangle blasting load curve of the equivalent elastic boundary is applied on the tunnel excavation contour surface, obtaining the final applied equivalent load. Taking the millisecond delay time of different sections into account, the time-history curve of equivalent load of the whole section applied on the tunnel excavation contour surface can be obtained. Based on Sailing Tunnel with small spacing on Sanmenxia-Xichuan Expressway, an analysis on the blasting vibration response of the later and early stages of the tunnel construction is carried out through numerical simulation using the proposed equivalent load model considering millisecond delay effect and the simplified equivalent triangle load curve model respectively. The analysis of the numerical results comparing with the field monitoring ones shows that the calculation results obtained from the proposed equivalent load model are closer to the measured ones and more feasible.

Prevalence and Molecular Characterization of ESBL Producing Enterobacteriaceae from Highly Polluted Stretch of River Yamuna, India

  • Siddiqui, Kehkashan;Mondal, Aftab Hossain;Siddiqui, Mohammad Tahir;Azam, Mudsser;Haq., Qazi Mohd. Rizwanul
    • Microbiology and Biotechnology Letters
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    • v.46 no.2
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    • pp.135-144
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    • 2018
  • The rapid increase in number and diversity of Extended Spectrum ${\beta}$-Lactamases (ESBLs) producing Enterobacteriaceae in natural aquatic environment is a major health concern worldwide. This study investigates abundance and distribution of ESBL producing multidrug resistant Enterobacteriaceae and molecular characterization of ESBL genes among isolates from highly polluted stretch of river Yamuna, India. Water samples were collected from ten different sites distributed across Delhi stretch of river Yamuna, during 2014-15. A total of 506 non duplicate Enterobacteriaceae isolates were obtained. Phenotypic detection of ESBL production and antibiotic sensitivity for 15 different antibiotics were performed according to CLSI guidelines (Clinical and Laboratory Standard Institute, 2015). A subset of ESBL positive Enterobacteriaceae isolates were identified by 16S rRNA gene and screened for ESBL genes, such as $bla_{CTX-M}$, $bla_{TEM}$ and $bla_{OXA}$. Out of 506 non-duplicate bacterial isolates obtained, 175 (34.58%) were positive for ESBL production. Susceptibility pattern for fifteen antibiotics used in this study revealed higher resistance to cefazolin, rifampicin and ampicillin. A high proportion (76.57%) of ESBL positive isolates showed multidrug resistance phenotype, with MAR index of 0.39 at Buddha Vihar and Old Delhi Railway bridge sampling site. Identification and PCR based characterization of ESBL genes revealed the prevalence of $bla_{CTX-M}$ and $bla_{TEM}$ genes to be 88.33% and 61.66%, respectively. Co-occurrence of $bla_{CTX-M}$ and $bla_{TEM}$ genes was detected in 58.33% of the resistant bacteria. The $bla_{OXA}$ gene was not detected in any isolates. This study highlights deteriorating condition of urban aquatic environment due to rising level of ESBL producing Enterobacteriaceae with multidrug resistance phenotype.

Growth Characteristics and Removal Effect of Nitrogen and Phosphorus of Salix gracilistyla Grown in Waterway Soils (하천토양에서 갯버들의 생장특성과 질소와 인의 제거효과)

  • Seo, Byung-Soo;Choi, Su-Min;Park, Chong-Min
    • Journal of Korean Society of Forest Science
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    • v.94 no.1 s.158
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    • pp.1-5
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    • 2005
  • This study was carried out to survey the growth and the photosynthesis of Salix gracilistyla, the reduction rate of nitrogen and phosphoric acid by the plant grown in waterway soil. The results were summarized as follows; I. The contents of nitrogen and phosphoric acid at waterway soils of Mangyeong river showed the highest level in the around Samrye railway bridge where was located in the downstream and livestock complex. 2. The Salix gracilistyla which grown in waterway soil showed that the growth of stem length and diameter were 170~215% and 42.3~79.3%, respectively. In addition the growth rate of Salix gracilistyla was increased with increasing nitrogen concentrations in waterway soils. 3. The rate of photosynthesis was high in waterway soil contained high nitrogen and it appeared the highest in August. 4. The nitrogen and phosphoric acid by Salix gracilistyla grown in waterway soil were removed about 14~15% and 9~11 %, respectively. The Salix gracilistyla was effective removing nitrogen more than phosphoric acid.

Parametric Study of MD Constitutive Model for Coarse-Grained Soils (조립재료에 대한 MD구성모델의 매개 변수 연구)

  • Choi, Changho
    • Journal of the Korean Geosynthetics Society
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    • v.12 no.1
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    • pp.11-19
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    • 2013
  • Coarse-grained soils are typical engineering materials commonly used in many civil engineering applications such as structural fills, subgrade and drainage fills for dam, railway and bridge. Various researches have been performed with related to constitutive laws for numerical analysis of such structures. This paper presents a parametric study for a constitutive model for coarse grained materials. The model is a kind of the bounding surface models based on critical state theory. A distinct feature of the model is to capture the response of coarse-grained materials with different void ratios and confining pressures using a single set of model parameters. The model behavior is defined with a set of elastic parameters, critical state parameters, and model-specific parameters. The parametric study was performed for the model-specific parameters. The result of parametric study shows that the model is capable to capture stress-dilatancy behavior and kinematic-hardening under non-associative plastic flow.

Study on the Influence of Stray current Between Sacrificial Anode Cathodic Protection and Impressed Current Cathodic Protection in Marine Environment

  • Jeong, Jin-A;Kim, Ki-Joon
    • Corrosion Science and Technology
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    • v.11 no.3
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    • pp.77-81
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    • 2012
  • Cathodic protection(CP) is widely used as a means of protecting corrosion for not only marine structures like ship hulls and offshore drilling facilities, but also underground structures like buried pipelines and oil storage tanks. The principle of CP is that the anodic dissolution of metal can be protected by supplying electrons to the cathode metal. When unprotected structures are nearby to CP systems, interference problems between unprotected and protected structures may be happened. The stray current interference can accelerate the corrosion of nearby structures. So far many efforts have been made to reduce the interference in the electric railway systems adjacent to the underground metal structures like buried pipelines and gas/oil tanks. During recent few decades the protection technologies against stray current induced corrosion have been significantly improved and a number of techniques have been developed. However, there is very limited information an marine environments. Some complex harbor structures are protected by two cathodic protection systems, i.e. sacrificial anode cathodic protection(SACP) and impressed current cathodic protection(ICCP). In this case, when the protection current from sacrificial anodes returns to the cathode through electrolyte, it passes through nearby other low resistance metal structures. In many cases the stray current of ICCP systems influences the function of SACP. In this study, the risk of stray current from the SACP system to adjacent reinforced concrete structures has been verified through laboratory experiments. Concrete and steel pile structures modeled a part of bridge have been investigated in terms of CP potential and current between the two. The variation of stray current according to the magnitude of ICCP/SACP has been studied to mitigate it and to suggest the proper protection criteria.

Experimental and numerical study on large-curvature curved composite box girder under hogging moment

  • Zhu, Li;Wang, Jia J.;Zhao, Guan Y.;Huo, Xue J.;Li, Xuan
    • Steel and Composite Structures
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    • v.37 no.2
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    • pp.117-136
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    • 2020
  • Curved steel-concrete composite box girder has been widely adopted in urban overpasses and ramp bridges. In order to investigate its mechanical behavior under complicated and combined bending, shear and torsion load, two large-curvature composite box girders with interior angles of 25° and 45° were tested under static hogging moment. Based on the strain and deflection measurement on critical cross-sections during the static loading test, the failure mode, cracking behavior, load-displacement relationship, and strain distribution in the steel plate and rebar were investigated in detail. The test result showed the large-curvature composite box girders exhibited notable shear lag in the concrete slab and steel girder. Also, the constraint torsion and distortion effect caused the stress measured at the inner side of the composite beam to be notably higher than that of the outer side. The strain distribution in the steel web was approximately linear; therefore, the assumption that the plane section remains plane was approximately validated based on strain measurement at steel web. Furthermore, the full-process non-linear elaborate finite element (FE) models of the two specimens were developed based on commercial FE software MSC.MARC. The modeling scheme and constitutive model were illustrated in detail. Based on the comparison between the FE model and test results, the FE model effectively simulated the failure mode, the load-displacement curve, and the strain development of longitudinal rebar and steel girder with sufficient accuracy. The comparison between the FE model and the test result validated the accuracy of the developed FE model.

The Construction of the Trans-Central Asian Railroad and Its Current Implications (중앙아시아 횡단철도의 건설과 그 현재적 함의)

  • Lee, Chai-Mun
    • Journal of the Korean association of regional geographers
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    • v.15 no.1
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    • pp.67-85
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    • 2009
  • The Trans-Central Asian Railway consists of the Trans-Caspian Railroad, the Kazalinsk Route, the Turk-Sib, and the Trans-Kazakhstan Trunk Line. Currently, one-fifth of the residents in Central Asia are living around these railroads on which 70% of the economic activities in the region depends. The construction of the railroads in Central Asia was motivated by the Russian Empire's competition 'with its maritime rival, the United Kingdom, over the Eurasian heartland in a geostrategic sense. Using the railroads, the Russian Empire aspired to connect its central industrial regions in European Russia with the remote frontier areas in the Central Asian republics and to increase economic specialization of the region. After the breakdown of the USSR, however, the rail network, which had well been linked among the regions in the former Soviet nations, has been in a deteriorated linkage with their non-Soviet neighboring nations. Despite a lot of problems to be solved, the Trans-Central Asian rail network is expected to play a crucial role as a land bridge between East Asia and Europe as well as between Russia/the Baltic sea and the Indian Ocean/the Persian Gulf in the long-term.

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Study on Fatigue Behavior and Rehabilitation of Stringer with Coped Section(I) -Experimental Study on Static and Fatigue Behavior- (절취부를 갖는 세로보의 피로거동과 보수·보강에 관한 연구(I) -정적거동 및 피로거동의 실험적 고찰-)

  • Hwang, Yoon Koog;Chang, Dong Il
    • Journal of Korean Society of Steel Construction
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    • v.9 no.3 s.32
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    • pp.363-375
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    • 1997
  • This study encompasses the performance of static and fatigue test for the 8 large scale test specimens to clarify the fatigue behavior of coped stringer and the effect of the repair and strengthening on the damaged stringer of the floor system in steel railway bridges. For the purpose of the research, the actual stress wave for the existing bridge was measured, the basic stress range frequency histogram was made and the equivalent stress range was calculated. Using the result from the equivalent stress range made by adjusting the stress range, the static and fatigue test was carried out by identifying the previous rehabilitation and after. As the result of the static tests, it was revealed that the level of local stress under the S1 specimen test of the real equivalent stress range was similar to tensile strength of the test material, and it was consistent with the requirement of the initiation condition of the fatigue crack. Through the various rehabilitation methods to the damaged specimens, the effects of the repair and reinforcement were analyzed. According to the results of the repair of effect, bolting the high tension bolt over the stop hole was confirmed to be more adequate method than drilling only stop hole to delay the fatigue crack growth. Futhermore, in case of the stringer subjected by bending moment, the reinforcement over the upper flange side was determined to be a useful strengthening method, and the reinforcement to the web of the stringer was not appropriate to accomodate as a adequate strengthening method. Also it was confirmed that the category of the fatigue design for the coped stringer met with the category E specified on the fatigue design criteria of the Highway Standard Specification in Korea.

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Pseudo-Static Behaviors of U-shaped PSC Girder with Wide Flanges (확폭플랜지를 갖는 U형 프리스트레스 거더의 유사정적거동)

  • Rhee, In-Kyu;Lee, Joo-Beom;Kim, Lee-Hyeon;Park, Joo-Nam;Kwak, Jong-Won
    • Proceedings of the KSR Conference
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    • 2008.11b
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    • pp.993-999
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    • 2008
  • A girder height limitation is the critical parameter for rapid construction of bridge deck and construction space limitation especially in urban area such as high population area and high density habitats. A standard post-tensioned I-shaped concrete girder usually demands relatively higher girder height in order to retain sufficient moment arm between compression force and tensile force. To elaborate this issue, a small U-shaped section with wide flanges can be used as a possible replacement of I-shaped standard girder. This prestressed concrete box girder allows more flexible girder height adjustment rather than standard I-shaped post-tensioned girder plus additional torsion resistance benefits of closed section. A 30m-long, 1.7m-high and 3.63m-wide actual small prestressed concrete box girder is designed and a laboratory test for its static behaviors by applying 6,200kN amount of load in the form of 4-point bending test was performed. The load-deflection curve and crack patterns at different loading stage are recorded. In addition, to extracting the dynamic characteristics such as natural frequency and damping ratio of this girder, several excitation tests with artificial mechanical exciter with un-symmetric mass are carried out using operational frequency sweep-up. Nonlinear finite element analysis of this 4 point bending test under monotonic static load is investigated and discussed with aids of concrete damaged plasticity formulation using ABAQUS program.

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Analytical Behavior of Concrete Derailment Containment Provision(DCP) according to Train Impact Loading (열차 충돌하중에 대한 콘크리트 일탈방호시설물(DCP)의 해석적 거동 검토)

  • Yi, Na-Hyun;Kim, Ji-Hwan;Kang, Yun-Suk
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.11
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    • pp.604-613
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    • 2018
  • In recent years, numerous train derailment accidents caused by deterioration and high speed technology of railways have increased. Guardrails or barriers of railway bridges are installed to restrain and prevent the derailment of the train body level. On the other hand, it can result in a high casualties and secondary damage. Therefore, a Derailment Containment Provision (DCP) within the track at the wheel/bogie level was developed. DCP is designed for rapid installation because it reduces the impact load on the barrier and inertia force on the steep curve to minimize turnover, fall, and trespass on the other side track of the bridge. In this paper, DCP was analyzed using LS-Dyna with a parameter study as the impact loading location and interface contact condition. The contact conditions were analyzed using the Tiebreak contact simulating breakage of material properties and Perfect bond contact assuming fully attached. As a result, the Tiebreak contact behaved similarly with the actual behavior. In addition, the maximum displacement and flexural failure was generated on the interface and DCP center, respectively. The impact analysis was carried out in advance to confirm the DCP design due to the difficulties of performing the actual impact test, and it could change the DCP anchor design as the analysis results.